I... A. . 0 ' hl an a 2 (0 milnfirersiw This is to certify that the thesis entitled EFFECTS OF FEEDING DISTILLER’S GRAIN WITH SOLUBLE ON FAT DEPOSITION IN FEEDLOT CATTLE presented by BARBARA ANNE CASEY has been accepted towards fulfillment of the requirements for the Master of Science degree in Animal Science ...+l.-— /7 7 Jjjkkvew l (W Major Professor’s Signature ‘7’ ~ 3 (a -/ 0 Date MSU is an Affinnative Action/Equal Opportunity Employer PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 5/08 KzlProleocaPresIClRCIDateDtnjndd EFFECTS OF FEEDING DISTILLER’S GRAIN WITH SOLUBLE ON FAT DEPOSITION IN FEEDLOT CATTLE By Barbara Anne Casey A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Animal Science 2010 ABSTRACT EFFECTS OF FEEDING DISTILLER’S GRAIN WITH SOLUBLE ON FAT DEPOSITION IN FEEDLOT CATTLE By Barbara A. Casey The effects of modified-wet distiller’s grain with soluble (MDGS) on partitioning of fat between depots was studied in two experiments. Treatments were 0, 20, or 40% MDGS (DMB), replacing high-moisture corn in both experiments. In Exp. 1, crossbred cattle (n = 168) were used in a randomized complete block design (n = 7 pens/treatment). Ultrasound scans were taken every 56 d and cattle were harvested when the average 12th rib fat thickness (SF) was estimated to be 1.02 cm. Feeding MDGS had no effect on DMI and ADG. Dressing percent, G:F, calculated yield grade, and IMR (IMF :SF ratio; IMF = intramuscular fat) tended to increase with MDGS. Feeding MDGS resulted in fewer USDA Choice carcasses, but more yield grade 3 and Select. The ultrasound IMR was lower (P < 0.01) in cattle fed MDGS vs. the control. Color, tenderness and proximate analysis of LM were not affected by diet. Within depot, FA composition was altered with MDGS. Exp. 2 evaluated the effects of feeding MDGS on metabolism with ruminally- fistulated steers (n=6) in a 3 X 3 Latin square design. The amount of N and P retained, P excreted, and digestibility of N, P, ADF and NDF increased with MDGS level. Levels of VFA’s were similar among treatments with the exception of valeric which increased linearly (P < 0.02) with MDGS. Including MDGS in the diet may affect energy partitioning between IMF and SF. Feeding MDGS tended to improve G:F and increased SF with minimal effects on IMF, and no effect on color and tenderness. ACKNOWLEDGEMENTS I wish to express my sincere gratitude to numerous people, whom without this research would not have been possible. First and foremost I would like to thank Dr. Steven Rust for serving as my major advisor. He also served as a mentor for my research and encouraged me to strive for success in all of my endeavors. I extend my thanks to my thesis committee members: Drs. Dan Buskirk, Jeannine Schweihofer, and Glynn Tonsor. To them I am forever grateful for their guidance throughout my Master’s program. There are many people to whom I owe my gratitude for all of their encouragement and friendship. A special thanks to Dr. Steve Bursian for his willingness to always listen. I am forever indebted to the employees at the Beef Cattle Teaching and Research Center, namely Ken Metz, Phil Summer, Fred Openlander, and the student workers who assisted with my research. I would also like to thank Kenny Wells for performing the ultrasound scans and Lee Denzer of Blackhawk College and his students for assisting with carcass data and sample collections. For assistance with all of my work in the Meat Lab, I would like to extend a special thanks to Tom Forton and Jennifer Dominguez. Thank you to Lei Zhang, Dave Main, and Dewey Longuski for their assistance in the lab. Also, many thanks go to Kim Kammes, Tyler Yingst, Krysten Johnson, and my fellow graduate students who were always willing to lend a helping hand. This project would not have been possible without the help of these people. I am forever grateful to my parents Sam and Eggy Casey, my brother Robbie, and the remainder of my family and friends for their unconditional love and encouragement. Thank you for always believing in me and supporting me throughout this endeavor, I could not have done this without you. TABLE OF CONTENTS LIST OF TABLES ......................................................................................................... vi LIST OF FIGURES ..................................................................................................... viii LIST OF ABBREVIATIONS ........................................................................................ ix CHAPTER 1: INTRODUCTION ................................................................................... 1 CHAPTER 2: REVIEW OF LITERATURE ................................................................. 4 Distiller’s Grain with Soluble ....................................................................................... 4 Wet versus dry co-product use in feedlots ............................................................... 4 Limitations ............................................................................................................... 6 Effects on fat depots ................................................................................................. 8 Muscle and Meat ........................................................................................................ 12 Consumer demand ................................................................................................. 12 Color ...................................................................................................................... 12 Tenderness ............................................................................................................. I3 Adipose Tissue ........................................................................................................... 15 Subcutaneous Fat ................................................................................................... 18 Intramuscular Fat ................................................................................................... 19 KPH and Other Depots .......................................................................................... 22 Ultrasounding ............................................................................................................. 23 Technique ............................................................................................................... 23 Measurements ........................................................................................................ 24 Accuracy ................................................................................................................ 25 Acetate and Propionate ............................................................................................... 26 Acetate and propionate production from distiller's grain with soluble .................. 26 Acetate ................................................................................................................... 27 Propionate .............................................................................................................. 28 A:P Relationship .................................................................................................... 29 CHAPTER 3: MATERIALS AND METHODS .......................................................... 31 Feeding Trial .............................................................................................................. 31 Metabolism Trial ........................................................................................................ 39 CHAPTER 4: RESULTS AND DISCUSSION ............................................................ 45 Feeding Trial .............................................................................................................. 45 Metabolism Trial ........................................................................................................ 65 CHAPTER 5: SUMMARY AND CONCLUSIONS .................................................... 75 Interpretive Summary ................................................................................................ 75 Future Work ............................................................................................................... 80 APPENDICIES ................................................................................. , ............................. 8 2 LITERATURE CITATIONS ......................................................................................... 88 LIST OF TABLES Table 2.1 Action or recommended concentrations of mycotoxins in animal feeds (Imerman, 2009) ................................................................................................................ 11 Table 3.1 Formulated ration ingredients and composition ............................................... 34 Table 3.2 Formulated composition of supplements .......................................................... 35 Table 4.1 Effects of feeding modified-wet distiller’s grain with soluble on cattle performance ....................................................................................................................... 47 Table 4.2 Effects of feeding modified-wet distiller’s grain with soluble on carcass traits .................................................................................................................................... 48 Table 4.3 Comparison of ultrasound versus carcass measured carcass traits ................... 53 Table 4.4 Effects of feeding modified-wet distiller’s grain with soluble on color of lean tissue from the longissimus muscle ................................................................................... 57 Table 4.5 Effects of feeding modified-wet distiller’s grain with soluble on tenderness and composition of the longissimus muscle ...................................................................... 58 Table 4.6 Effects of feeding modified-wet distiller’s grain with soluble on fatty acid composition of subcutaneous fat..........' .............................................................................. 62 Table 4.7 Effects of feeding modified-wet distiller’s grain with soluble on fatty acid composition of intramuscular fat ....................................................................................... 63 Table 4.8 Effects of feeding modified-wet distiller’s grain with soluble on fatty acid composition of kidney, pelvic, and heart fat (KPH) ......................................................... 64 Table 4.9 VFA concentrations, rumen fluid FA composition, and ammonia values ........ 69 Table 4.10 Effects of feeding modified-wet distiller’s grain with soluble on rumen evacuation results ............................................................................................................... 71 Table 4.1] Effects of feeding modified-wet distiller’s grain with soluble on fecal output results ................................................................................................................................. 72 Table 4.12 Effects of feeding modified-wet distiller’s grain with soluble on urine output results ................................................................................................................................. 73 vi Table 4.13 Digestibility of nutrients as effected by diet ................................................... 74 Table A] Nutrient composition of ration ingredients ...................................................... 82 Table A2 Animals removed from trial ............................................................................. 82 Table A3 Diet treatment assignments identified by percent modified-wet distiller’s grain with soluble by period for the metabolism study ...................................................... 83 Table A.4 Effects of drying on N content in total mixed rations ...................................... 85 Table A.5 Effects of feeding modified-wet distiller’s grain with soluble on intake ......... 86 Table A6 Influence of Sire (KSU Venom 101M) on Marbling Score .............................. 87 vii LIST OF FIGURES Figure 4.1: Effects of feeding modified-wet distiller’s grain with soluble on ratio of subcutaneous fat and intramuscular fat measured by ultrasound ..................................... 49 Figure 4.2: Effects of feeding modified-wet distiller’s grain with soluble on calculated yield grade ........................................................................................................................ 51 Figure 4.3: Effects of feeding modified-wet distiller’s grain with soluble on quality grade ................................................................................................................................. 52 Figure 4.4: Effects of feeding modified-wet distiller’s grain with soluble on ratio of subcutaneous fat and intramuscular fat measured in the carcass ..................................... 54 Figure 4.5: Results of pH measurement across a 24 hr period ....................................... 70 V Figure A.1: Comparison of drying at 55°C and 105°C on N content of the ration ........ 84 viii A:P ADF BW CLA cm CP DG DGS DDGS DM DMB DMI DRC EE FA G:F HMC IMF IMR LIST OF ABBREVIATIONS acetate to propionate ratio acid detergent fiber average daily gain body weight conjugated linoleic acid centimeter (s) crude protein distiller’s grain distiller’s grain with soluble dry distiller’s grain withsoluble dry matter dry matter basis dry matter intake dry rolled-corn ether extractable lipid fatty acid gram (3) kg of weight gain per kg feed consumed high moisture corn intramuscular fat, marbling IMF/SF LDL LMA MDGS MU FA NDF OM PEM PUFA QG SF SFA UFA VF A WBSF WDGS YG kilogram (s) kidney, pelvic, and heart fat low-density lipoproteins longissimus muscle area modified-wet distiller’s grain with soluble millimeter (s) monounsaturated fatty acid neutral detergent fiber organic matter Bovine Polioencephalomalacia, “Polio”, a disease of cattle polyunsaturated fatty acid USDA quality grade rump fat subcutaneous fat saturated fatty acid totally mixed ration unsaturated fatty acid volatile fatty acid Warner-Bratzler shear force wet distiller’s grain with soluble USDA yield grade CHAPTER 1 INTRODUCTION Two major factors affecting profitability of beef cattle are changes in cattle markets and feed costs. This thesis addresses the feed costs and evaluation of a feedstufi', corn distiller’s grain with soluble (DGS), which potentially lowers the feed cost of gain. The livestock industry has seen a significant increase in the price of corn since 2005. This increase is due to many factors including higher oil prices, increased demand for ethanol, and a lower supply of corn. As a result, there is an increased supply of ethanol co-products which are available to producers at a lower price than corn. Corn distiller’s grain with soluble, a co-product of the corn ethanol industry, provides a popular alternative feed that is high in protein, energy, and fat. Distiller’s grain with soluble can be marketed as a dry or wet product. Many ethanol plants limit the amount of drying due to the high cost of fuel required. The process of distilling removes most of the starch, but concentrates the other nutrients found in corn. After distillation, the mash is centrifuged yielding solid, DGS and liquid fractions (syrup or distiller’s soluble; Stock et al., 2000). The most common method of marketing the syrup is by adding a portion of it back to distiller’s grain with soluble, which makes a product called modified-wet distiller’s grain with soluble (MDGS) at 50% DM, wet distiller’s grain with soluble (WDGS) at 30% DM or dry distiller’s grain with soluble at 90 % DM (DDGS). Although DGS has been used for years, the recent increase in use has raised questions regarding the effects on carcass composition and palatability. Recent research suggests that inclusion rates that are greater than 33% of distiller’s co-products results in greater subcutaneous fat (SF) deposition with a decrease in marbling at greater than 23% DGS inclusion (Reinhardt et al., 2007). Subcutaneous fat in excess of 0.64 cm is trimmed from the carcass and sold as a waste product (USDA, 2007). Decreased marbling with a resulting decrease in USDA quality grade (QG) has been attributed to a decrease in starch within the diet (Smith and Crouse, 1984). This decrease in starch content is apparent in diets containing DGS. An increase in protein levels and fat levels are also seen in DGS diets. These two factors may result in lower marbling scores (Gunn et al., 2009). Marbling is very desirable as it increases palatability and ease of cooking for consumers (Menkhaus et al., 1993). Therefore, increasing SF without a concomitant increase in marbling is undesirable. The effect of DGS on marbling is very important to both producers and consumers. Nearly half of the cattle fed within the United States are marketed based on quality grades (Lundeen, 2007). Consumers have expressed a willingness to pay more for beef that has higher marbling content (Platter et al., 2005). However, the consumer also desires less total fat in the beef. More marbling results in greater flavor for the consumer, fulfilling one of the three desired traits in meat: flavor, tenderness, and juiciness (Resurreccion et al., 2004). Additionally, the increase of SF present on the beef carcass results in a decrease in percentage of trimmed retail cuts. A 0.25 cm change in adjusted fat thickness over the ribeye alters yield grade by 25% (U .S.D.A., 2007). This can mean additional deductions and less profit to the producer. The increased grain prices relative to those prior to the recent expansion in ethanol production have further encouraged beef cattle producers to seek less expensive feedstuffs. One option is DGS. Distiller’s grain with soluble is usually priced at 70- 100% of the value of corn by the plant, which makes it an attractive alternative. Pricing is relative to other energy and protein sources, moisture content, and handling and transportation costs. Additional research is needed to determine the effects of feeding DGS on fat partitioning, which is the main objective of this study. Diets containing DGS have been shown to have a lower acetate:propionate ratio within the rumen when compared to com-based diets (Anderson et al., 2006). It has been implied that acetate is a precursor to SF production and propionate for intramuscular fat deposition (marbling or IMF). This study attempts to define the acetate to propionate ratio of a diet with DGS fed at various levels and its relationship with fat deposition. The expectation is that increased inclusion of DGS results in decreased propionate production, decreased marbling, and increased SF deposition. Objectives 1. To determine the effects of feeding DGS on feedlot performance, carcass quality, and muscle attributes. 2. To determine the effects of feeding DGS on fat deposition and composition of various fat depots. 3. To determine the effects of feeding DGS on volatile fatty acid (V FA) concentrations within the rumen. CHAPTER 2 REVIEW OF LITERATURE Distiller’s grain with soluble Wet versys dry co-product use in fizedlots Over the past decade the use of modified-wet distiller’s grain with soluble (MDGS) and wet distiller’s grain with soluble (WDGS) has become more common in beef feedlots across the United States (DiLorenzo and Galyean, 2009). This is largely due to increased production and availability of WDGS, along with the high cost of fuel to produce dry distiller’s grain with soluble (DDGS). Cost to the feedlot has been favorable relative to corn prices and the majority of large feedlots have storage facilities to maintain a wet co-product for feeding purposes. The effects of feeding WDGS in the feedlot on performance and carcass characteristics have been variable. Wet DGS has been available for more than 20 years as one of the first research trials evaluating WDGS was reported in South Dakota by 8D. Farlin et al. in 1981. Distiller’s grain with soluble has moderate NDF levels, but cannot replace all fiber in the diet. A few meta-analyses have been performed (Ham et al., 1994; Jones, 2007; Klopfenstein et al., 2008) to compare wet versus dry DGS and various levels of inclusion. A meta-analysis of 9 experiments using the same feedlot facilities and a total of 1,257 steers fed WDGS was recently completed (Klopfenstein et al., 2008). Average daily gain (ADG) and DMI were most efficient at an inclusion level of 30%. Maximal G:F was expressed in the range of 30 to 50 % MDGS. The results also indicated an overall increase in carcass fatness, rib fat, and quality grade, given equal days on feed. In recent studies, DMI with equal days on feed were similar (Gunn et al., 2009; Leupp et al., 2009b). The inclusion of 30 % DDGS showed no differences in ADG; G:F; final BW; longissimus muscle area (LMA); 12th rib fat thickness; kidney, pelvic, and heart fat (KPH); yield grade (Y G); and marbling (Leupp et al., 2009b). However, a study by Vander Pol et al. (2009) showed an increase in feed conversion efficiency with the inclusion of WDGS up to 40 % DM. Previous research showed that feeding 40% WDGS increased feed efficiency by 14%, and WDGS inclusion had 35% higher feeding value when compared to corn (Larson et al., 1993; Ham et al., 1994; Stock et al., 2000). Similarly, cattle fed WDGS and DDGS in past research have shown higher gains, while those fed WDGS consume less feed and are more efficient than those fed DDGS (Ham et al., 1994; Jones, 2007). Some of the attributes that affect consumer perceptions of beef include color, tenderness, and composition reflecting flavor. A lower occurrence of liver-like off-flavor in meat from distiller’s grain-fed cattle has been reported (Jenschke et al., 2007b). Results from that study indicate that WDGS can be fed to beef cattle without causing detrimental sensory effects, but does result in higher yield grades (Y0) and carcass weights. Research has shown that the liver-like off-flavor is a result of Na, palmitoleic acid (C16: 1), vaccenic acid, eicosadienoic acid (20:2n6), and di-homo-gamma-linolenic acid (C20z3n6). These FA’s account for 46% of the variation of the liver-like off—flavor. Other components previously reported as causing the liver—like off-flavor; iron, heme iron, and pH had no effect in this study (J enschke et al., 2007a). In a feeding study comparing dry-rolled corn (DRC) and high-moisture corn (HMC), a corn processing x WDGS interaction was observed for ADG and G:F (Corrigan et al., 2009). It was hypothesized the reduced performance may result from a decreased ruminal A:P in diets containing 40% WDGS with either DRC or HMC. Average daily gains increased quadratically and G:F increased linearly in steers fed HMC. In this study, Corrigan et. al. (2009) found that steers fed 40% WDGS had greater DM, organic matter (OM), NDF and EE intake. Total tract digestibility of DM and OM was less with WDGS and tended to be greater for BB. Limitations There are several limitations to the use of DGS in beef cattle feedlot diets. These limitations include, but are not limited to, concentrated nutrient levels of S and P compared to those of corn, and contamination with mycotoxins (NRC, 2000; Klopfenstein et al., 2008; Wu and Munkvold, 2008). Because of the starch removal during ethanol production, the remaining portion contains more concentrated levels of nutrients such as N, which is reflected in the higher level of crude protein. Distiller’s grain with soluble typically consists of 30% CP on a dry matter basis (NRC, 2000). Gunn et al. (2009) suggests that the elevated fat and CP of diets containing up to 50% DDGS cause negative effects on performance, marbling, quality grade (QG) and color stability at the higher inclusion rates. The increased levels of S and P created added challenges to proper disposal of the resulting manure. Sulfur is not only concentrated during starch removal, but also added to the product in the plant to control pH and clean the equipment. A critical concern with high S content is the increased susceptibility to Bovine Polioencephalomalacia (PEM). This is a disease caused by feeding levels of S over the maximum recommended level of 0.4% of the diet (NRC, 2000). A meta analysis by Klopfenstein et al. (2008) suggests DGS contains a range of S from 06-1 .0% DM. Total sulfur intake must be considered when formulating diets using DGS. Sulfur intake from the water must be accounted for as well as that from the diet. Provision of dietary thiamin may minimize the presence of PEM when high levels of DGS are fed. Elevated S intake also increases S released into the environment in feces, urine, and expired air. Recent research has also shown WDGS fed up to 60% inclusion increased intake and excretion of S. This is followed by increased H28 emissions and other odor causing compounds, resulting in additional air contamination (Van Horn et al., 1996; Varel et al., 2008; Spiehs and Varel, 2009). Phosphorus is more concentrated in DGS than corn, as are other nutrients at approximately a 3-fold increase (NRC, 2000). Due to the higher amount of P in the diet, it is necessary to increase the Ca in order to ensure the proper Ca:P and prevent metabolic complications. High P also causes an environmental concern for cattle producers and those in the surrounding areas as more P is contained in the manure of cattle consuming increased levels of P in DGS diets compared to those on high corn diets. Government agencies have been regulating amounts of nutrients added to the soil, resulting in more cautious fertilization by livestock and crop producers (Van Horn et al., 1996). A recent study indicated increased amounts of P in the WDGS diet results in increased fecal P content. This study also found similar results for N and S with additional ammonia excretion. Leaching of the manure and water from cattle production facilities leads to additional soil and ground water contamination (Spiehs and Varel, 2009). Mycotoxins are toxic chemicals produced by fungi, which is frequently found growing on corn in North America. Crops are predisposed to mycotoxin contamination when damaged via insects, non-rotational planting methods, high temperatures and a high moisture environment during growth or storage (Leung et al., 2006). Some of the mycotoxin species that may be harmful to bovine include: fumonisin, aflatoxin, deoxynivalenol (DON or vomitoxin), zearalenone, and ochratoxin. When consumed by animals or humans they can cause adverse health issues which vary by animal and fungi species. Cattle are less susceptible to most mycotoxins than other species such as swine and horses (Osweiler et al., 1993). At high levels in cattle diets, some mycotoxins may decrease feed intake, increase weight loss, cause vomiting and kidney damage, and death when fed at high concentrations (Wu and Munkvold, 2008). The effects of mycotoxins are further specified in Table 2.1 (Irnerrnan, 2009). Fermentation of starch into ethanol does increase the level of mycotoxin threefold greater than in corn. Methods for detection of mycotoxins in DGS have not been approved by the United States Department of Agriculture (USDA). The current approved methods for corn are being used on DGS and have often overestimated and underestimated the levels (Schaafsma et al., 2009). In this same study, only 87% of mycotoxins were detectable in DGS. Effects on fat depots Feeding high concentrate diets to cattle has been shown to increase accretion of subcutaneous (SF) and intramuscular fat (V asconcelos et al., 2009). Loza et al. (2010) showed a trend in increasing rib fat with WDGS. In their study, the highest fat thickness occurred with 30% WDGS and then decreased for the 60% treatment. The control (0% WDGS) had the least amount of 12th rib fat thickness. This study also reported a greater 1 yield grade (P < 0.01), for cattle fed WDGS. These results were supported with the 9 studies summarized by Klopfenstein et al. (2008). In a study by Mello et al. (2007), feeding WDGS at levels of 0, 15, and 30% of the diet DM resulted in no significant effect on total lipid content, unsaturated fatty acids (UFA), and saturated fatty acids (SFA) in the intramuscular fat (IMF) depot. However, increasing levels of WDGS increased the amount of linoleic acid and omega 6:3 ratio in the uncooked ribeye muscle, while decreasing vaccenic acid (C18: ln7) levels, which contributes to off flavors in the meat. This study also showed an increase in polyunsaturated fatty acids (PUFA) which increases oxidation and therefore, can have a negative effect on color and rancidity of the meat. Recent research by Gill et al. (2008) has shown feeding WDGS and DDGS increased omega 6:3 ratio, trans-vaccenic acid (C1821 H l), PUFA:SFA ratio, and one CLA (C18z2t-10, c-l2) in steaks. However, the authors concluded the small changes had little impact on overall sensory attributes. Trans-vaccenic acid is an intermediate in the biohydrogenation process within the rumen and is formed from linoleic acid (Griinari et al., 2000). It is then either reduced to stearic acid or used to synthesize CLA. Increased levels of CLA may enhance the nutritional value of beef, as it has been shown that products containing a particular CLA (Cl8:2 t- 10, c-12) are effective in decreasing lipogenesis when consumed by humans (McGuire and McGuire, 2000). Results similar to those seen in WDGS were seen in previous research utilizing corn oil in the diet (Gillis et al., 2004, 2007). Supplementation of 4% corn oil in a high concentrate diet was shown to have no effect on CLA isomer c-9, HO and total CLA contents of the ribeye steak, but increased total PUF A with minimal changes in lipid oxidation or sensory attributes. The addition of corn oil in this study provided a similar amount of lipid as 25% WDGS in a diet (Depenbusch et al., 2008). It leads one to speculate the changes observed in fat depots with DGS are being driven by the oil content. 10 Table 2.1 Action or recommended concentrations of mycotoxins in animal feeds Qmerman, 2009). Mycotoxin Commodity Animal Concentration Aflatoxin Corn, peanut products Finishing (feedlot) beef, 300 ppb cattle Breeding beef cattle, 100 ppb breeding swine, mature poultry Finishing swine >100 lb 200 ppb Corn, peanut products, Immature animals 20 ppb other animal feeds or feed ingredients, excluding cottonseed meal Cottonseed meal Beef, cattle, swine, poultry 300 ppb (regardless of age) All feeds or feed Dairy animals, animal 20 ppb ingredients species not listed above, uses not listed above, intended use unknown Fumonisin Corn & corn by- Equine (horses) 5 ppm products (<20% of diet) Swine & catfish 20 ppm (<50% of diet) Breeding ruminants, 30 ppm breeding poultry, lactating (<50% of diet) dairy animals, laying hens Ruminants >3 months old, 60 ppm raised for slaughter (<50% of diet) Poultry raised for 100 ppm slaughter (<50% of diet) All other species or classes 10 ppm of livestock or animals (<50% of diej Vomitoxin Grain & grain products Swine 5 ppm (deoxynialen (<20% 0f diet) 0] DON) Ruminating beef and 10 ppm feedlot cattle > 4 months, (<50% of diet) chickens Dairy cattle & other 5 ppm (<40% of diet) Zearalenone Diet Prepubertal gfls < 1 ppm Sexually mature sows, <3 ppm bred sows Young boars <20 ppm Mature boars <200 ppm Virgin heifers <10 ppm ll Muscle and Meat Consumer demand Today it is apparent across the United States that the perception of cattle and their meat products is very different depending on the segment of the cattle industry one is referring to. The producer, packer, and consumer all have different ideas of how cattle should be produced, what the end product is and how it should look (Menkhaus et al., 1993; Barham et al., 2003). In a production system like beef, the end-user or consumer has ultimate influence on the types and value of products sold. This acts as a domino effect, demanding particular cuts of meat along with tender, flavorful, juicy and desirably colored meat from the packer. Consumers are more likely to buy if the steak had a high marbling score or low WBSF value (Platter et al., 2005). One of the trade-offs the producer must make is whether to use anabolic implants to get improved gains, larger carcass weights, and more net returns. However, this may lead to less tender meat. The packer strives to provide products demanded by the consumer and maintain their profit margin. To accomplish this task, the packer must send a message to the producer of the types of cattle that are profitable for his plant. This signal is sent via pricing mechanisms to direct the pr0per mix of cattle for harvest. @191 Color of fresh meat is perceived by the consumer as a measure of freshness (Faustrnan and Cassens, 1990). A more red color is the most desirable (Resurreccion, 2004). Because of this, more interest has been stressed on feeding strategies and color of the meat (Faustrnan and Cassens, 1990). Visual perception of steaks range in color from 12 bright to dark and red to purple to brown. The color indicated by spectrophotometer is broken down into 3 values, L*, a*, and b*. These indicate darkness to lightness, redness, and yellowness respectively. Higher values on all indicate lighter, more red, and more yellow color of the meat (AMSA, 1991). Roeber et al. (2005) showed differences in redness with different levels of WDGS in the diet. However, the 2 experiments conducted in this study were not consistent and resulted in no difference in color of strip loin steaks. Steers fed steam-flaked corn had lower L*, but greater a* values in a recent study on strip loins (Roeber et al., 2005). However, it was also determined that feeding 15% DGS from either corn or sorghum as either a wet or dry co-product had no effect on beef sensory attributes (Gill et al., 2008). Conversely, feeding 30% DDGS lowered a* during the finishing period in a study performed by Leupp et al. (2009a). A recent study using DDGS showed a negative effect on color when DDGS was increased from 25 to 50% of the diet. The authors attribute this response to elevated fat, protein, and the combination within the diet (Gunn et al., 2009) From a limited research summary above, one can discern contradicting viewpoints on the effects of DGS on color attributes. It has been shown that feeding increased levels of alpha-tocopheryl acetate, also known as Vitamin E, can minimize the reduction in shelf-life when DGS is fed (Zerby et al., 1999). Tenderness A past survey concluded that carcasses would receive up to $76 premium when guaranteed tender versus tough meat (Miller et al., 2001). Several factors have been 13 shown to affect the tenderness in beef cattle steaks measured via slice shear force or Warner-Bratzler shear force (WBSF). Consumers panels have identified steaks with WBSF values of < 3.0 are tender and those > 4.9 are tough (Miller et al., 2001). One management strategy that has an influence on tenderness is implanting. Steaks from implanted steers and heifers result in higher WBS values and less marbling (Boles et al., 2009). Anabolic implanted steers were rated less desirable by the consumer taste panel regarding tenderness, flavor and juiciness (Roeber et al., 2000). However, this can be altered by feeding increased levels of alpha-tocopheryl acetate, also known as vitamin E (Zerby et al., 1999). Matching the proper implant strategy with the nutritional and genetic background of the cattle will alleviate some of the detrimental effects of implants on tenderness and consumer acceptability (Barham et al., 2003). Aging the meat after harvesting has also been shown to affect the tenderness values of beef. Extending aging for 12, 26, or 40 d continually decreased tenderness values in slice shear force, indicating that longer aging results in greater tenderness among steaks not tenderized prior to aging (King et al., 2009). In a study that fed DDGS to heifers, a linear increase in tenderness was seen with increasing levels up to 75% DDGS in the diet (Depenbusch et al., 2009). Although feeding DDGS at 30% inclusion rate indicated a decrease in steak tenderness (Leupp et al., 2009a), another study showed no difference in tenderness when fed up to 50% WDGS in Holstein steers (Roeber et al., 2005). One difference between these two studies is the moisture level in the DGS and this may explain some of the difference. However, it has been shown that there are no differences in tenderness values between corn and sorghum distillers grain, and between DDGS and WDGS fed up to 15% 14 inclusion (Gill et al., 2008). With the conflicting research appearing, it is necessary to evaluate the effects of feeding WDGS at various levels on tenderness as determined by the most accepted method WBSF. Adipose Tissue Adipose tissue has been identified as the primary site for FA synthesis in ruminants, unlike non-ruminants where the primary site is the liver (Vernon et al., 1981). Beitz et al. (1985) noted the ability of adipose tissue to grow through hypertrophy is determined by the amount of cells available for triglyceride accretion. Once hyperplasia stops or plateaus, hypertrophy then takes place. At this point, nutrients are absorbed more rapidly and deposition of adipose tissue increases at a higher rate. Several management strategies have been developed that may alter lipid metabolism. Propionate production increases with monensin inclusion and may promote insulin secretion and suppress lipolysis (Burrin et al., 1988). High chromium inclusion'in the diet is suggested to promote lipogenesis and suppress lipolysis (Sumner et al., 2007). Cattle fed a com-based diet showed a 60-90% decrease in lipogenesis in long-fed versus short-fed cattle (Chung et al., 2007). This study also suggested that acetate generated lipogenesis decreased over time and forage fed steers did not have sufficient acetate contribution to drive both SF and IMF deposition. These results contradict those presented by Smith and Crouse (1984), which suggest acetate is the main precursor to SF deposition. Adipose tissue differs by site in several aspects including composition, adipocyte number and adipocyte diameter. Adipocytes have a lesser volume in IMF versus SF 15 (May et al., 1995). There are also more saturated fatty acids (SFA’s) in SF and KPH than in IMF (Sturdivant et al., 1992; May et al., 1993). A study by Cianzio et al. (1985) suggests that the adipocyte diameter in cattle, at 17 months of age, decreases by depot site in cattle fed a diet consisting of 72% com. The sites in decreasing order are as follows: KPH, mesenteric, SF, interrnuscular, intramuscular (IMF), and brisket fat. Following 17 months of age, fat growth is mainly comprised of hypertrophy, growth in cell size of adipocytes. Amount of adipocytes within adipose tissue doubles between 2.5 weeks and 5 months of age in beef calves (Martin et al., 1999). At the same time, there is a 20-fold increase in adipocyte volume. These are indicative of adipocyte hyperplasia during this period. Lipogenesis is not significant until post-weaning periods. As cattle age, concentrations of monounsaturated fatty acid (MUFA) increase, polyunsaturated fatty acid (PUFA) slightly increase and SFA decrease. This trend is much more dramatic in Bos indicus cattle, Herefords and crossbred cattle as adipocytes become more unsaturated following weaning (Huerta-Leidenz et al., 1996). This supports the fact that genetic predisposition also has an effect on lipid deposition. Steers developed fi'om the 1980’s genetic pool had smaller adipocytes in both IMF and SF than adipocytes found in steers developed from 1960’s genetics which had a greater amount of adipocytes (May et aL,1995) Previous research has shown that there is a significant difference between the type and amount of lipid fed and the resulting composition within fat depots (Dryden et al., 1973). Smith and Crouse (1984) were the first to determine that lipid precursors differ depending on depot. Feeding DGS showed an increase of the following in steaks: omega 6:3 ratio, trans-vaccenic acid, PUFA:SFA ratio, and C18:2,t-10, c-12 (Gill et al., 2008). 16 However, the authors concluded there was no overall significance in sensory attributes. Trans-vaccenic acid (C18:], t-l l) is an intermediate in the biohydrogenation process within the rumen and is formed from linoleic acid (Griinari et al., 2000). It is then either reduced to stearic acid or used to synthesize CLA. Consumers prefer a healthy product for consumption, especially meat products such as beef. When compared to other sources such as olive oil and butter fat containing products, beef lipids were more beneficial to health in middle-aged men than butterfat containing products (Denke and Grundy, 1991). This was reflected in lower concentrations of low-density lipoproteins (LDL) in blood serum of middle-aged men consuming products containing these lipid sources. The LDL measurement often used to evaluate blood cholesterol levels as a precautionary measurement for risk of heart disease. This research suggests that beef lipids are healthier to have in the diet than products containing butterfat. Grass contains Cl 8:3 FA, known as a-linolenic acid, and consumption by ruminants results in a good source of omega-3 FA within grass-fed beef (Wood et al., 2004). Also synthesized from a-linolenic acid are long chain, omega-3, PUFAs (C20- C22) which are found in beef. The omega-6 and omega-3 FA must be supplemented in the human diet as they are not created in the body and are considered unsaturated essential fatty acids. It has also been confirmed that products containing Cl8:2, t-10, c-l2 are effective in decreasing lipogenesis when consumed by humans (McGuire and McGuire, 2000). A study by Weibe et al. (1984) suggested that a diet containing over half of the protein supplied by beef products did not result in high cholesterol in healthy young men. 17 Subcutaneous Fat In general, subcutaneous adipose tissue is composed of greater amounts of SF A and MUFA than other fat depots (Sturdivant et al., 1992; May et al., 1995; Pavan and Duckett, 2007). Subcutaneous fat provides insulation under cold environmental conditions and protects the meat and organs from physical damage (I-Iossner, 2005). It is also used as storage reserve for energy and is the first to be expended when dietary energy is not sufficient for the animal’s needs. Steers were also shown to have greater SFA in SF than that of heifers (Terrell et al., 1969). Dietary management is the greatest factor effecting SF composition in beef cattle. When cattle are fed increased levels of oleic acid, there is a decrease in palmitic acid with a small, but insignificant increases in oleic and linoleic acid in SF (St. John et al., 1987). This study indicated that a change in dietary lipid composition had minimal effects on SF composition. Increasing amounts of CLA’s are present in adipose tissue of cattle fed grasses and forages instead of a high concentrate diet (Pavan and Duckett, 2007; Fincharn et al., 2009). However, a recent study showed that feeding additional dietary lipid or rumen protected CLA did not affect FA composition in tailhead fat and SF, with only minor differences in CLA content (Gillis et al., 2004). Previous research (Huerta- Leidenz et al., 1991) where cattle were fed whole cottonseed at 15 and 30% of diet DM, which contributed 3.3 and 6.6% additional dietary lipid, respectively, showed only minor effects on FA composition of SF in beef cattle. Time on feed has been shown to increase the concentration of unsaturated fatty acids (U FA) in the adipose tissue (Duckett et al., 1993). 18 Cattle fed ad libitum concentrate diets containing corn have shown increased SF accretion rates (V asconcelos et al., 2009). These results were not related to differences in glucose concentration or changes in insulin regulation. Acetate has proven to be the more prevalent precursor to acetyl units in SF (Smith and Crouse, 1984; Nafikov and Beitz, 2007). While SF is not the latest developing depot (Cianzio et al., 1985), time on feed increases the amount and rate of SF deposition (Duckett et al., 1993). After 180 d on a finishing diet, the diameter and amount of SF adipocytes per gram of lipid were not different due to diet (Schoonmaker et al., 2004). Steers fed an ad libitum, high concentrate diet had greater SF depth as a result of increased diameter of adipocytes in SF at slaughter. In summary, SF is comprised of greater amounts of SFA than UF A and differs from other adipose depots in that sense. The magnitude of changes in FA composition of SF can be altered depending on diet, gender, anabolic implant strategy, and environmental management. The amount of SF deposited also depends on several factors, including age, diet, and time on feed. Intramuscular Fat Diet affects the amount of marbling found in beef carcasses. Corn grain diets increase the MUFA:SF A ratio, which is especially evident in IMF depots (Smith et al., 2009). Feeding DGS increases the omega-6zomega-3 ratio in steaks, and one study showed greater Cl8:2, t-lO, c-12 with DGS inclusion as compared to steam-flaked corn diets (Gill et al., 2008). Supplementation of 4% corn oil in a high concentrate diet was shown to have no effect on C1 8:2c-9, t-l 0 and CLA contents of the ribeye steak, but 19 increased total PUFA with minimal changes in lipid oxidation or sensory attributes (Gillis et al., 2007). This discrepancy in IMF composition may reflect a difference in methodology as Gillis et al. (2007) ground an entire ribeye steak without specifying the removal of external fat. Pavan and Duckett (2007) clearly stated that 48 h following harvest, a ribeye facing was taken, external fat was removed and only the ribeye was ground. Another study removed IMF samples by hand from the ribeye directly following slaughter (Cianzio et al., 1985). Studies also vary in the muscle fi'om which they extract the IMF which could alter IMF results (Eichhom et al., 1985). For example, LM contained 6-10% less UF A than the sernitendinosus and triceps brachii muscles. The sernitendinosus muscle also contained 6% more PUFA than the phospholipids extracted fi'om the LM. Eichhom et al. (1985) suggested that increased marbling accounts for an increase in myristic (Cl4:0) and pentadecanoic acids in the muscle. Intramuscular fat contained increased amounts of PUFA as a result of additional corn oil or rumen protected CLA (Gillis et al., 2004). This depot numerically contained the lowest percent of Cl 8:2c-9, t-l 1, total CLA, C18:1c-9, Cl 8:1t-10, and trans-vaccenic acid in cattle supplemented with corn oil or rumen protected CLA (Gillis et al., 2004; Pavan and Duckett, 2007). Feeding dry distiller’s grain with soluble increases linoleic acid in steaks compared to diets containing WDGS (Gill et al., 2008). In another study, steaks from steers fed DGS had higher quality grades, less tenderness, less connective tissue, and more intense off-flavor ratings than control steers (J enschke, 2007b). Intramuscular fat and brisket fat depots are later developing than the other fat depot sites (Cianzio et al., 1985). They also found marbling score to be better predicted by the number or mass of IMF than the cell diameter. In IMF, lipogenic enzymes have 20 increased activity when cattle are between 16 and 18 months of age (Smith and Crouse, 1984). It has been shown that glucose, rather than acetate, is a more prevalent lipogenic precursor to acetyl units leading to IMF. Other factors that affect the percent IMF include breed, implant strategy, and other environmental factors. Intramuscular fat is influenced by breed (Dinh et al., 2010), particularly the percentages of SFA and PUFA. Across the 3 breeds studied, MUFA was the same regardless of breed. The Romosinuano breed had the greatest amount of PUFA followed by Angus and then Brahman cattle which had the least. Angus cattle showed the most SFA in IMF as compared to the other two breeds. In that study, IMF contained higher proportions of MUFA and less PUFA. Dinh et al. (2010) also suggested that palmitic (Cl6:0) and oleic acids (C1821) are the most abundant FA in IMF, within the longissimus muscle. Various implant strategies are used in beef cattle management, most of which affect the rate of fat deposition. Steaks from implanted steers and heifers had higher WBSF values and less marbling (Boles et al., 2009). This is consistent with previous research (Roeber et al., 2000; Scheffler et al., 2003; Gruber etal., 2006). Environmental and management factors have also been proposed to influence deposition of IMF. However, the mechanisms for these factors are a mystery and have yet to be proven in research. One of the factors influencing deposition is the amount of time cattle are on feed, which also increases the amount of UFA (Duckett et al., 1993). Additional research is needed to further elucidate the impacts of deposition rate and precursors on IMF development. 21 KPH and Other Depots Limited research has been done to efficiently evaluate the kidney, pelvic and heart (KPH) fat depots compared to more common SF and IMF depots. Other fat depot sites that warrant additional research include, but are not limited to mesenteric, intermuscular, and the brisket area. Past research suggests that IMF and brisket fat depots are later developing than the majority of other fat depot sites (Cianzio et al., 1985). Eichhom et al. (1985) suggested that 60% of KPH is comprised of SFA. They showed KPH had the highest amount of SF A, lowest amount of PUFA and PUFA:SFA ratio when compared to SF, IMF and fat within muscle tissues. In ovine, KPH consisted of significantly less palmitoleic acid than SF depots (Barber et al., 2000). In a more recent study, KPH was shown to contain higher percentages of SFA and MUFA when compared to SF depots (Oka et al., 2002). Feeding whole cottonseed at 30% of diet DM showed an increase in linoleic and PUFA of kidney fat (Huerta-Leidenz et al., 1991). No differences were seen in MUFA or SFA. Subcutaneous fat was higher in UFA but lower in C18:0 and Cl 8:1 than kidney fat samples of cattle fed greater dietary fat from whole cottonseed. Adipose tissue from cattle fed corn grain had a greater MUFA:SFA ratio, as opposed to forage-based diets (Chung et al., 2007). This difference was most pronounced in IMF than other fat depots. Additional research is needed to thoroughly examine KPH and other internal fat depots. Adipose tissue deposition in general is effected by gender, age, time on feed, diet, and depot site. Producers and consumers appear most concerned with SF and IMF, as they have more influence on profit, cost and dietary health factors. Past research has struggled to obtain consistent results on factors effecting both fat deposition rates and FA 22 composition. It is clear from the studies cited above that additional research is needed to clearly define how these factors effect deposition, especially in IMF and KPH. Ultrasounding T echnigue Live ultrasound measures can be used as a viable tool for predicting future carcass composition (Wall et al., 2004). Correlation statistics show a positive relationship between ultrasound and carcass measurements for rib fat, longissimus muscle area (LMA), and intramuscular fat (IMF), assuming the final ultrasound is performed within 7 d prior to slaughter. It has been found in a study encompassing several years that ultrasound, carcass fat, and LMA had correlation coefficients of 0.89 and 0.86 respectively (Greiner et al., 2003c). However, carcass fat was underestimated by 0.06 cm and LMA was overestimated by 0.71 cmz. Leaner animals were underestimated and fatter were overestimated for carcass fat. Leaner animals were also more accurately measured for fat and LMA than fatter animals. This study indicates that the differences in accuracy were small and accuracy is maximized when measurements are taken by a well-trained and experienced ultrasound technician. Other research also indicates variation in results by technician as well as machine, indicating again that highly trained technicians are required to accurately perform ultrasound measurements and assess results (Herring et al., 1994). Becoming a certified technician requires that the person must be skilled at identifying individual muscles as well as the skeletal structure of the animal and be able to produce consistent results. 23 Measurements There are several measurements that are routinely taken via ultrasound, most of which are used to predict carcass measurements. The three most important ultrasound measures to predicting carcass value include rib fat (SF), IMF, and rump fat (RF). To cut down on variance in interpretation of results, it is common for technicians to send raw data to a central lab for processing in order to obtain the most accurate data. Fat depth is measured most consistently over the 12th rib (Wilson etal., 1998; Wall et al., 2004). This is referred to as rib fat or subcutaneous fat (SF). This is measured perpendicular to the 10, 11, and 12th ribs. It is important in both SF and IMF scans that the transducer be placed over the thoracic vertebrae and not the lumbar vertebrae to ensure correct placement. Correct placement will scan the longissimus dorsi and spinalis dorsi muscles as a reference point. Intramuscular fat is a measurement taken between the 12th and 13‘h ribs (Wilson et al., 1998; Wall et al., 2004). The transducer is placed parallel with the ribs to get an accurate scan of the cross section of the longissimus dorsi muscle. This is the same location that will be scored for marbling on the carcass. Technicians are capable of measuring within 0.8 to 0.9% of the predicted IMF percentage and multiple scans must show consistent images. Previous research indicates there is a positive correlation between ultrasound IMF and marbling scores (Wilson et al., 1998; Wall et al., 2004). When measuring this value, technicians obtain three images which will be analyzed and the average taken. This is due to the difficult image analysis and variation for IMF. Rump fat is often used in prediction equations for carcass composition and is often highly correlated with yield grade (YG) and amount of retail product. This 24 measurement is taken between the hook and pin bones, making sure to include the biceps femoris and gluteus medius muscles and the seam between the muscles. Certified technicians can measure this value within 0.10 to 0.13 cm (Wilson et al., 1998). Accuracy Accuracy is one of the most crucial values in ultrasound scanning technique. In order to produce accurate results, the technician must be well-trained and the machine must be consistent. The more concerning issue to researchers, producers, and packers is the accuracy in predicting carcass measurements with ultrasound technique. Ultrasound measurements have been used to estimate carcass composition based on prediction equations. Previous research has reported correlation coefficient ranges of 0.20 to 0.91 for IMF, and 0.02 to 0.94 for LMA between ultrasound and carcass measurements (Houghton and Turlington, 1992). This study does acknowledge more accuracy for rib fat and rump fat measurements than IMF. More recent research has indicated that both live animal and ultrasound measurements are accurate estimates of actual carcass composition (Realini et al., 2001; Greiner et al., 2003a, b). The combination of final live animal weight with ultrasound results intensifies the accuracy further. These studies further indicate a greater accuracy in predictions when the ultrasound measurements for rump fat and gluteus medius depth were included in yield equations. Crews et al. (2002) stated that measurements taken between weanling and yearling age accurately predict the final carcass traits. While the majority of research and field use has been done prior to harvest, some research has been done on the accuracy of ultrasounding the carcass postmortem. Griffin et al. (1999) concluded that the ultrasound measurements taken postmortem and prior to 25 dehiding were less accurate than those taken prior to harvest and were deemed an insufficient predictor of actual carcass measurements. In contrast, Rhoades et al. (2009) suggested the ultrasounding technique is an accurate measurement to predict carcass values if performed within 7 (1 prior to slaughter. Nevertheless, scans up to 120 (1 prior to harvest have been shown to be accurate predictors of endpoint carcass composition. It is uncertain which measure of carcass traits, ultrasound or physical measurement is more accurate. There is a debate with differing opinions on which measure is more accurate, ultrasound or postmortem carcass measurements. During processing in the harvest facility, some fat is lost due to trimming and hide removal. This warrants additional observation, research, and technology improvement of the ultrasound measuring and carcass measuring processes. Acetate and Propionate Acetate and propionate production jam distiller ’s grain with soluble Acetate and propionate are important VFA’s produced in ruminants. However, it is how these VF A’s are metabolized and how they affect production when feeding DGS that is puzzling. In a study performed with Holstein cows, Kleinschmit et al. (2006) found that diets containing DDGS were similar to the control when considering ruminal acetate and propionate, while ruminal ammonia concentrations decreased with the inclusion of DDGS. In a recent feedlot study, DDGS was fed up to 60% of diet DM and resulted in similar microbial efficiency, ruminal propionate and butyrate concentrations (Leupp et al., 2009). They reported that DDGS inclusion increased pH, but ammonia did not change between treatments. Ham et al. (1994) reported similar total VFA 26 concentration and ruminal pH when DDGS was added to a conventional feedlot diet. They reported, however, feeding distiller’s soluble had a tendency to reduce pH and the acetate to propionate ratio. Wet distiller’s grain with soluble contains an average of 1.6 times more energy than corn (Larson et al., 1993). Past studies have indicated an increase in NEg with up to 40% WDGS, and contributed this increase to several factors including a dietary increase in lipid concentration, decrease in starch content, and increased feed efficiency due to decreased subacute acidosis (Firkins et al., 1985; Larson et al., 1993). The variability in co-product composition warrants additional research to evaluate the effects of feeding WDGS on ruminal VFA concentrations in feedlot cattle. More importantly, the effects of a changing rumen environment due to diet alterations on beef cattle performance and carcass composition needs to be further investigated. AM Acetate is typically hydrolyzed in order to facilitate the formation of acetyl-CoA, utilized in the first step of the tricarboxylic acid (TCA) cycle. This cycle provides precursors to synthesize the breakdown of carbohydrates and other energy sources to C02 and water. Cellulolytic and saccharolytic microorganisms’ within the rumen primarily produce acetate (Baldwin and Allison, 1983). Because of these microbes’ preference to produce acetate, it is suggestive that diets containing less starch and more fiber will result in higher acetate production than propionate or other VFA’s. It has been anticipated that this is the case when feeding WDGS due to the starch removal during the ethanol production process. While some studies have established that acetate is one of the main sources of carbon for FA synthesis, others have contradicted that by distinguishing 27 different precursors with varying fat depots (Nafikov and Beitz, 2007). Smith and Crouse (1984) showed that 70 to 80% of acetyl groups were a result of acetate production in lipogenesis of subcutaneous fat although acetate contributed only 10 to 25% of the acetyl groups for intramuscular fat. Past studies have shown that diets including WDGS result in increased propionate, decreased acetate, and decreased A:P (Firkins et al., 1985; Larson et al., 1993). However, Ham et al. (1994) suggests that there is no effect on VFA concentration when feeding WDGS. This warrants additional research involving the effects of diets on VFA and their relationship to fat deposition. Propionate Propionate is the primary precursor of glucose in ruminants. Succinate is produced by cellulolytic organisms in the rumen and is further converted to propionate. However, amylolytic microorganisms in the rumen produce considerably more propionate than cellulolytic microorganisms (Baldwin and Allison, 1983). Because of this, an increase in starch content of the diet and starch fermentation in the rumen results in greater conversion by the rumen microbes to products which are easily converted to propionate. This includes greater conversion of lactate to propionate through the acrylate pathway instead of the conversion from succinate. Propionate is extensively metabolized in the liver with very little net metabolism of acetate in ruminant animals (Allen, 2000). Cattle rely on hepatic gluconeogenesis from propionate to produce glucose to meet their needs (Nafikov and Beitz, 2007). Increased amounts of carbohydrates and starch in the diet resulted in increased propionate levels (Young, 1977; Allen et al., 2009; Leupp et al., 2009). While hormones regulate intake and lipogenesis, propionate has been implicated 28 as a regulator via receptors in the rumen and liver (Allen et al., 2009). Monensin has been shown to increase propionate production in the rumen, while in turn, creating better feed efficiency and increasing gluconeogenesis (Young, 1977). While propionate is often converted to glucose via gluconeogenesis, it can also be oxidized via the tricarboxylic acid cycle (Aiello and Armentano, 1987; Knapp et al., 1992). A cetate:Propionate Relationship There are many aspects of the diet which could have an effect on the relationship of acetate:propionate (A:P). While the individual VF A concentrations are important, the A:P is of greater concern when considering the efficiency of production for beef cattle and the resulting carcass composition. It has been a concern that the feeding of ionophores may affect VFA production within the rumen and in turn, effect fat deposition. Previous reports on the influences of DGS on VFA’s have shown that ruminal A:P was lower with diets containing high inclusion of WDGS and also minimize the ability of ionophores to generate glucose from propionate (Russell and Strobel, 1989; DiLorenzo and Galyean, 2009). In vivo results by Corrigan et al. (2009) show a decreased ruminal pH with WDGS. These researchers also suggest that feeding monensin with up to 15% DGS has no effect on VFA production (DiLorenzo and Galyean, 2009). Their review suggested that this is a result of the ionophores ability to cause a repartition of nutrients. A recent study showed that feeding WDGS up to 40% increased ADG quadratically, while diets containing HMC with or without WDGS increased G:F linearly (Corrigan et al., 2009). Experiment 2 of their study suggested a corn processing by 29 WDGS interaction for ADG and G:F which may be a result of decreased ruminal A:P with diets containing 40% WDGS along with DRC or HMC. They also found steers fed 40% WDGS had greater DM, OM, NDF and EE intake. In addition, they reported total tract digestibility of DM and OM was less with WDGS and tended to be greater for EE. Based on a recent review by Allen et al. (2009), it can be suggested that a diet with higher fiber and less starch would be indicative of less propionate production and a higher A:P. Decreasing starch decreases the proportion of propionate to the total VFA’s absorbed, Causing an increase in acetate as a percent of total VF A production. Since acetate is assumed to be a precursor of subcutaneous fat, more research is needed to evaluate the effects of feeding MDGS on ruminal VFA concentrations and the relation to fat deposition. 30 CHAPTER 3 MATERIALS AND METHODS Feeding Trial This research was approved by the Michigan State University Animal Care and Use Committee (AUF # 01/08-008-00). A feeding trial was conducted with feeder cattle to determine the effects of feeding varied levels of modified-wet distiller’s grain with soluble (MDGS) on performance, carcass, and meat quality traits. Cattle originated from the Michigan State University Upper Peninsula and Lake City Experiment Stations located in Chatham, and Lake City, Michigan, respectively. After arriving at the Michigan State University Beef Cattle Teaching and Research Center (BCTRC), East Lansing, MI, cattle (n=168) were monitored for approximately 30 d for injury and illness prior to immunization. Vaccinations for Clostridial infections (U ltraBac 7, Pfizer, New York, NY), common respiratory diseases, (Bovishield 5 Gold, Pfizer, New York, NY), and internal parasites (Dectomax injectable, Pfizer, New York, NY) were administered 3 weeks post-arrival at BCTRC. At this time, steers received a Synovex S and heifers a Synovex H implant. Cattle were on feed for 94 d before the study initiation. Cattle were weighed on two consecutive d and the average weight was used to allocate the cattle to pens and served as the initial weight. The design was a randomized complete block design. Within the steer and heifer groups, cattle were allocated to blocks to equalize gender, origin, and weight differences. Treatments were randomly allocated to pens (n=21) within a block (n=7). Treatment diets consisted of 0, 20, and 40 percent of the total ration DM as MDGS, replacing high-moisture corn (Tables 3.1, 3.2). For ingredient nutrient composition see appendix Table A. 1. Cattle were fed once daily and had ad 31 libitum access to water. Feed remaining in bunks was weighed every 28 d and average dry matter intake (DMI) was calculated by pen. All cattle were fed a 30% MDGS diet prior to start of the trial. Those receiving the 20% MDGS treatment were fed a 30% MDGS diet on d lto 6 of the trial. Those receiving the control treatment were fed a 30% MDGS diet on d 1 to 3, then 20% MDGS for d 4 to 6, and MDGS was removed from the control diet on d 7. Revalor S or H implants were administered on d 28 of the trial, 100 (1 following the previous Synovex implants. Five cattle were removed during the trial due to illness or weight gain less than three standard deviations below the average for their respective pen (see Appendix Table A2). One animal died from bloat in the control treatment. Three animals were removed within the 20% treatment; one animal died from natural causes (trachea tumor), one due to bloat, and one animal was identified to be a stag. Within the 40% treatment, one animal was removed due to significant weight loss and illness. Ultrasound and Carcass Evaluation Cattle were weighed every 28 d and ultrasound measurements were performed every 56 (I. At each ultrasound measurement, data were collected by a Centralized Ultrasound Processing (CUP)-certified technician. Hair was clipped to facilitate the ultrasound technology. At each ultrasound date, each animal was scanned once for subcutaneous fat (SF) thickness over the 12th rib, once for rump fat (RF) thickness, and three times for percent of intramuscular fat (IMF), taken between the 12m and 13m rib. Images were sent to Centralized Ultrasound Processing Lab in Des Moines, IA for analysis. A ratio of IMF:SF was calculated and termed IMR. 32 Cattle were fed for 139 d, and were harvested when the cattle had an average ultrasound SF of approximately 1.02 cm, averaged across all pens. The resulting ultrasound SF estimate prior to harvest was 1.05 cm. One hundred sixty-three animals were harvested at Tyson Foods in Joslin, III, a commercial packing plant. Immediately following harvest, hot carcass weight was taken. Twenty-four h post-harvest, quality grade, longissimus muscle area (LMA), 12th rib SF thickness were measured. Kidney, pelvic, and heart fat (KPH) percentage was estimated, yield grades were calculated and marbling scores assigned. Yield grades were calculated using the following equation: YG = (2.5 + (2.5 * adjusted fat thickness) + (0.2 * KPH) + (0.0038 * HCW) — (0.32 * REA)). Kidney, pelvic, and heart fat samples were taken with a sharp knife in the kidney region and placed in Whirlpak bags. A 5 to 7.5 cm portion of the 12th rib section was removed from the carcass and placed in a Ziploc bag. Samples were immediately placed in a cooler with ice and transported to the Michigan State University Meat Laboratory. Upon arrival, ribs were immediately placed in a cooler at 2°C. 33 Table 3.1 Ration ingredients and composition. . % MDGS Ingredients, DMB 0 20 40 High moisture corn, % 78.5 62.9 43.4 MDGS, % ‘ - 20.3 40.2 Corn silage, % 12.3 12.3 12.1 Soybean meal, % 3.3 - - DGS supplement, % 2 - 4.4 BFSSO supplement, % 2 5.6 - - Urea, % 0.3 - - -—-—-----Calculated composition---------- NEm, Meal/kg 2.16 2.09 2.07 NEE, Meal/kg 1.47 1.43 1.39 8, %DM 0.07 0.27 0.49 -- Analyzed composition, %DM Dry Matter 64.1 60.7 57.3 Crude Protein 13.52a 14.83b 19.34c Ash 4.04a 4.97b 556° Starch 55.73a 43.22b 36.23c NDF 12.49a 14.72b 18.89c ADF 5.22a 5.47“ 6.84b Lipid 4.12a 5.27b 6.760 Calcium 0.71a 1.08b 1.08b Phosphorus 0.253 0.35b 046° lModified-wet distiller’s grain with soluble 2See table 3.2 abCMeans within a row with unlike superscripts differ (P < 0.05) 34 Table 3.2 Composition of supplements. Supplement Name lggredients, % As-F ed BFSSO DGS Akey TM Premix #4“'* 1.4 2.4 Limestone 24.95 71 .5 Soybean meal, 48% N 48.3 — Rumensin'” 80 0.3 0.4 TM Salt 9.6 18.0 Vitamin E, 5% 0.2 0.1 Urea, 45% N 9.55 7.6 Potassium chloride 5.1 - Selenium 90 0.7 — *Akey TM premix #4 composition: 9% Mg, 4% S, 0.02% Co, 1% Cu, 0.09% I, 2% Fe, 4% Mn, 0.03% Se, 4% Zn, 4,400,000 IU vitamin A, 550,000 IU vitamin D, and 5,500 IU vitamin E/kg (Akey Inc., Lewisburg, OH) 35 F orty-eight h postmortem, the rib sections were deboned and SF was removed and saved for further analysis. The rib was then faced from the anterior end and allowed to bloom for 30 min to allow for oxygenation of the myoglobin. Instrumental color (L*, a*, and b*) of the lean was measured using a Hunter Miniscan XE Plus (Model 45/0-L, Restin, VA). The colorimeter was set to D65 illuminant and has a 25 mm diameter aperture with a 100 standard observer. The facing was trimmed of surrounding fat and connective tissue so that only the muscle remained, cut into approximately 2.54 cm cubes and frozen at -20°C for proximate analysis. The remaining rib section was vacuum packed and placed posterior side down, stored at 2°C and aged until 14 d postmortem. Ribs were then frozen at -20°C. Frozen ribs were removed from vacuum packaging and a 2.54 cm thick rib steak was cut from the posterior side with a band saw (Model 3334, Biro Manufacturing Co., Marblehead, OH). These samples and remaining rib steaks were vacuum packed and continued to be stored at -20°C for tenderness and proximate analysis. Tenderness Frozen steaks were thawed in open bags and covered with plastic wrap in a cooler at 2°C for 24 h. Steaks were cooked on a clam shell grill (Model Q824; Taylor Co., Rockton, IL) with a 2.16 cm gap between the upper and lower plates. Steaks were cooked to 70°C (+/- 15°) as measured with thermocouples (Model 660 Omega Engineering Inc, Stamford, CT) inserted to the approximate geometric center of each steak. Following cooking, steaks were immediately weighed for cooking loss, placed into loosely closed Whirlpak bags to allow additional heat loss, covered with plastic 36 wrap, placed on trays in the cooler at 2°C and stored for 24 h. Tenderness was estimated with the Warner-Bratzler shear force (WBSF) procedure (AMSA, 1995; Wheeler et al., 1997). Six 1.27 cm diameter cores were removed from the longissimus dorsi muscle via a drill press (Model 137.248080, KCD IP, LLC; Hoffman Estates, IL) fitted with a sampler. The cores were taken parallel to the muscle fiber at random locations within each steak. Each core was sheared with a WBSF attachment perpendicular to the muscle fiber using a TAHDi texture analyser (Texture Technologies Corp, Scarsdale, NY) with a IO-kg load cell. The average force of the six cores was calculated and represented the WBSF value for each steak. Proximate Analysis Previously cubed and frozen steak facings were removed from the freezer and manually pounded to break samples into smaller pieces before grinding. A Waring blender (Model 3 l BL46 Dynamics Corp. of America, New Hartford, CT) was used to powder samples in a cooler at 2°C. First the chamber was filled one-quarter full of dry ice, followed by grinding the sample for approximately two minutes or until the sample was a fine powder. Samples were then placed into Whirlpak bags, loosely closed and returned to the freezer at -20°C to allow evaporation of the dry ice for 24 h. Bags were then closed and remained frozen until proximate and fatty acid (FA) composition analyses were performed. Moisture, crude protein (CP), and lipid contents were determined in triplicate from the powdered samples. Moisture content was determined after samples were placed in a forced air oven at 100°C for 24 h using method 950.76 (AOAC, 1995). The same 37 samples used for determining moisture content were used for determining ash content. Ash was determined by placing 2.5 to 3 g samples in a muffle furnace for 12 h or until sample was completely ashed (AOAC, 2000). Crude protein was determined using combustion method 992.15 (AOAC, 2000; Leco F P-2000, Leco Corp., St. Joseph, MI). Lipid content was determined via ether extraction performed with a modified Soxhlet method 960.39 (AOAC, 2000). Samples were placed in filter paper, folded, closed with a paper clip and placed in a Soxhlet apparatus for 24 h. The sample was then removed and ether was allowed to evaporate under a hood for approximately 2 h prior to drying for 8 h at 100°C. Lipid content was determined by calculating the weight difference on a dry matter basis (DMB). Fat Depot Analysis Subcutaneous fat and KPH fat samples were finely chopped with a knife and mixed well. All SF, KPH and intramuscular fat (IMF) contained within the rib samples were weighed and composited by pen, which is the experimental unit, while frozen. Subcutaneous fat and KPH samples were further homogenized mechanically with a Polytron (Model PT 10/35, Kinematica Inc., Switzerland). Composited samples were then analyzed for FA analysis in triplicate. The samples were first homogenized by adding equal ratios of ethanolzhexane to clean culture tubes with the fat sample. In order to do so, 4:4 ml was added to 4 g IMF, 3:3 ml was added to 1 g SF, and 2:2 ml was added to 1 g KPH. Some of the samples had greater amounts of ethanol: hexane in order to ensure the sample was immersed for mechanical homogenization. Samples were then extracted and methylated following the procedures of Woodward (2005). Samples were 38 then transported to Michigan State University Diagnostic Center for Population and Animal Health for FA analysis via gas chromatography (Perkin Elmer Clarus 500, U.S.A.). Metabolism Trial A metabolism trial was conducted to determine the effects of feeding MDGS on volatile fatty acid concentrations within the rumen, specifically acetate and propionate. This trial consisted of 6 ruminally fistulated steers in a 3 x 3 Latin square design, which was not balanced for carryover effects. The research was approved by the Michigan State University Animal Care and Use Committee (AUF #12/08-019-00). The trial was conducted for 63 d and utilized the treatments from the previous feeding trial. Each period within the trial was 21 d in length and each steer was offered one of three treatments per period so that each animal received each treatment (see Appendix Table A3). Steers were offered feed at 0800 h daily and feed was removed at 0700 h daily to measure orts. Steers were allowed 14 d to adapt to their diet. Total fecal and urine collection took place throughout d 14 to 17 for digestibility estimations (fecal phase). Rumen fluids were collected for VF A analysis beginning on d 18 and took place every 9 h for a total of 72 h (rumen phase). This represented the VFA levels every 3 h in a given 24 h period. Following the completion of VFA collection on d 20, a rumen evacuation was performed at 2 h post-feeding and 2 h prior to feeding (d 21). The measurements were averaged to determine rumen volume. 39 Feed Sampling Individual feed samples were taken on (I 14-21 and frozen immediately at -23°C. Two daily total mixed ration (TMR) samples were taken d 14 t021 prior to feeding each steer. Orts weights were recorded and a 1/8 representative sample was taken on d 15 through d 21. All feed samples were immediately frozen. Upon thawing, a subsample was taken from the combined daily TMR samples for each animal and immediately ground with dry ice in a Wiley mill (Arthur H. Thomas, Philadelphia, PA) fitted with a 1mm screen, and refrozen. The remaining TMR sample, individual feedstuffs, and orts samples were dried in a forced air oven at 55°C for 72 h. Weights were taken before and after drying to determine the DM content. Samples were ground in a Wiley mill fitted with a 2 mm screen followed by a 1 mm screen. Dry matter tests were performed on all samples at 105°C and composited on a DMB for laboratory analysis. Individual feeds were composited in equal amounts into one sample per period. Total mixed ration samples were composited in equal amounts to result in a sample for each fecal and rumen phase within periods. Orts were composited on a daily percentage of total orts collected basis for each steer within the fecal and rumen phases for each period. Sample analysis was then performed on the composited samples. Feces and Urine Collection On (I 14, fecal bags were placed on the 'steers at 0800 h. Urine was collected in plastic bags attached to rubber mats. The anterior end of the mat was elevated to allow flow of urine into the bags attached to the posterior end of the mat. For each fecal and urine collection day, all urine bags were removed at 0700 h followed by fecal bags being 40 removed one animal at a time. Animals and stall mats were rinsed, fecal bags were immediately placed on the animal and urine bags were re-attached to the mats. Fecal bags were weighed daily and total urine volume measured. Feces were subsampled and a 10% aliquot was placed in a forced air oven at 55°C for 72 h. Samples were ground in a Wiley mill (Arthur H. Thomas, Philadelphia, PA) fitted with a 2 mm screen followed by a 1 mm screen. Daily fecal samples were composited for each animal as a percentage of the total collected during the 4 d period. Each urine bag contained 20 mL of 6 N HCl on day one of the first period. For each urine collection day following this, each bag contained 100 mL of 6 N HCl to prevent as much volatilization as possible. Urine was subsampled and a 1% aliquot saved daily. The aliquot was adjusted to pH < 4 by testing with litmus paper and adding 6 N HCl when needed. Daily samples were combined to produce a composite sample per animal for each period. Urine samples were fi'ozen at -23°C immediately following compositing. Volatile Fatty Acid Collection Volatile fatty acid (VFA) collections were performed by utilizing the following methods. Five 250 mL representative samples were taken from different areas of the rumen; one sample near the bottom of the cranial pillar fold in the ventral sac, one sample directly below the cannula at the bottom of the ventral sac, one sample from the caudo- ventral blind sac, one sample fiom the caudo-dorsal blind sac and another sample anterior to the cannula at the top of the rumen mass. These samples were combined, solids and liquids were separated with a screen and a 100 mL liquid sample was saved for analysis. 41 Remaining solids and liquids were returned to the rumen. The pH of each liquid sample was taken immediately with a portable pH meter (Hanna Instruments Inc., Woonsocket, RI) and the sample was placed in a refrigerator. Within 1 h, samples were frozen at - 23°C for later compositing. Volatile fatty acid samples were thawed and composited according to procedures outlined by McPeake (2008) resulting in one sample for each animal per period. Composite samples were refrozen for later analysis. Rumen Evacuation Rumen evacuations were performed manually through the cannula. All rumen contents were removed and a 10% aliquot saved for sampling. Total volume and weight were recorded. Of the saved aliquot, solids and liquids were separated, weighed and two 500 mL subsamples were taken from each. A 100 mL liquid subsample was taken for later VFA analysis and pH was recorded. All samples were immediately frozen at -23°C. The remaining ruminal contents were immediately returned to the rumen. Steers were rinsed with cold water following each rumen evacuation to maintain cleanliness. Sample Analysis All feedstuff, TMR, ort, and fecal samples were tested for nutrient content which included DM, N, starch, ether extract, ADF, NDF, ash, Ca, and P. Composited samples were analyzed for DM by drying in a forced air oven at 105°C for at least 8 h, N (Leco, 1988), starch (Karkalas, 1985), NDF and ADF (Ankom Technology, Macedon, NY) with procedures described by Ankom Technology (1998). Ca and P were measured alter microwave digestion via procedures described by Hill et al. (2008). Ash was determined 42 by igniting the sample at 500°C for 6 h or until completely ashed. Wet TMR samples were only analyzed for N content (Leco F P-2000, Leco Corp., St. Joseph, MI) utilizing total combustion methods outlined by AOAC 992.15 (2000). Urine samples were thawed for approximately 12 h and analyzed for N, Ca, and P content using the methods listed above. Nutrient intakes were calculated by multiplication of net DM intake by nutrient concentration. Apparent digestibility and retention estimations were calculated using the intake, fecal, and urine nutrient values. Composited ruminal fluid samples were thawed and analyzed for DM as well as NH3 concentration (Broderick and Kang, 1980); absorbance was determined using a microplate reader (SpectraMax 190, Molecular Devices Corp., Sunnyvale, CA). VFA samples were processed with the procedures outlined by Oba and Allen (2003) with a minor modification. In brief, samples were centrifuged at 26,000 x g for 15 min, and supernatant (900 pl) was mixed with 300 pl Ca(OH)2 and 150 pl of CuSO4 containing crotonic acid as an internal marker in 1.7 ml microcentrifuge tubes. Samples were centrifirged at 12,000 x g for 10 min, and supernatant (1000 pl) was taken and mixed with 28 pl of H2804 in 1.5-ml microcentrifuge tubes. Samples were frozen and thawed twice, and centrifuged at 12,000 x g for 10 min to precipitate and remove protein thoroughly. Supernatant was transferred to HPLC vials. Concentrations of VFA of the supernatant were determined by HPLC (Waters 2695 Separations Module) with a Bio-Rad HPX-87H column (Bio-Rad Laboratories, Richmond, CA) as described by Dado and Allen (1995). Briefly, 0.005N sulfuric acid was used as the mobile phase. Detection was performed by using a differential refractometer (Waters 410, Millipore Corp., Milford, MA). Calibration and quantification was done by using an external standard solution. 43 Statistical Analysis Data were analyzed using SAS (Version 9.1.3, SAS Institute, Cary, NC). Feeding trial data were analyzed as a randomized complete block design with pen as the experimental unit. The model included diet, block and a random effect of pen. Ultrasound data were analyzed for the final measurement as well as over time using repeated measures. The model included diet, block, and a random effect of pen. The Proc Corr procedure of SAS (Version 9.1.3, SAS Institute, Cary, NC) was utilized to establish relationships between ultrasound and carcass data. Proc Mixed was used along with a chi-squared test to differentiate between treatments for QG and YG statistics which were discontinuous data. Metabolism trial data were analyzed as a 3 x 3 Latin Square design using the Proc Mixed procedure. The model included diet, period, diet x period interaction, and a random animal effect. Estimates of linear and quadratic effects were also evaluated. Statistical analyses were deemed significant with a P < 0.05. Parameters with P = 0.06 to 0.10 were considered trends in the data. 44 CHAPTER 4 RESULTS AND DISCUSSION Feeding Trial Cattle Performance, Ultrasound, and Carcass Evaluation Overall, live cattle performance was acceptable with no effect of diet on ADG, DMI, final weight, or feed conversion efficiency (Table 4.1). Several recent studies support this finding (Gunn et al., 2009; Leupp et al., 2009; Vander Pol et al., 2009), however, other studies showed a concomitant increase in DMI with higher MDGS and percentage lipid inclusion rates (Klopfenstein et al., 2008). It is important to note that all cattle were fed 30% MDGS prior to the start of our trial (refer to chapter 3 for details). This may have altered the composition of the cattle prior to the start of our trial. All cattle were transitioned to their respective treatment diets, which may have altered their growth and composition in the beginning months of our trial. In contrast to the results in this study, Ham et al. (1994) indicated an increase in ADG as DGS increased in the diet. After adjustment to a constant dressing percentage, feed conversion efficiency increased quadratically (P = 0.01) with 20% MDGS inclusion as compared to the control, the same was true for ADG (P = 0.01). Final ultrasound scans indicated a quadratic increase in subcutaneous fat (SF) with 20% MDGS when compared to the control (P = 0.01; Table 4.2). The 40% MDGS inclusion showed similar levels of SF as the other treatments. The final ultrasound showed a linear increase (P = 0.04) of rump fat (RF) accretion with the inclusion of MDGS, with a quadratic tendency (P = 0.07) with increasing MDGS inclusion. A linear decrease (P = 0.05) was seen with ultrasound intramuscular fat (IMF). The ultrasound 45 determined ratio of IMF to SF (IMR) decreased linearly (P < 0.01) and quadratic tendency (P = 0.08) with the addition of MDGS, but there was no significant difference in the IMR of the two diets containing MDGS. Figure 4.1 shows the final ultrasound correlation of IMF to SF, with a tendency (P = 0.06) for a positive correlation (r = 0.73) when the control diet was fed and a significant correlation with 20% MDGS (r = 0.80; P = 0.03). There was no significant correlation with 40% MDGS (r = -0.10; P = 0.83) between IMF and SF. Carcass measurements were affected by MDGS inclusion in the diet. Hot carcass weight increased quadratically (P = 0.04) and 12th rib fat increased linearly with addition of MDGS (P = 0.03). There were tendencies for MDGS to alter dressing percent (P = 0.07) with a quadratic response (P = 0.03). Dressing percent was greater for cattle fed MDGS diets, and cattle fed 20% MDGS tended to have a greater dressing percent than those fed 40%. Calculated yield grade (P = 0.02), and IMR (P = 0.02) increased linearly with MDGS addition. Figures 4.2 and 4.3 illustrate the distribution of calculated yield grade and quality grades, respectively, across treatments. More USDA yield grade 3 scores were shown with the inclusion of MDGS. Additionally, more cattle graded USDA high Select and fewer cattle graded low Choice when fed at the 40% inclusion rate. These results are supported by recent research reviews in which WDGS was fed (Jones, 2007; Klopfenstein et al., 2008; Loza et al., 2009). Marbling measured by ether extraction was similar between treatments (P = 0.40). 46 Bane maromcogm 85:: 53> 38 a £53» £80an mmwd 3 £303 £88 mo commie 05 .3 wocmgowou was» coca—=23 05 5 wow: Emmy») Bum 633.3% mmmocaom 5mm .38 hammocks u OQ< 2th 08 Sonwsoht :03 w mm mo mootom 0:5 96 $0ch can dog .3 woBmmoE_ 86 $6 sod wood usmfio nmgd ammfio mac fluoamzn—ca $330 as as who .256 $3 83 was anguish—“£5 m3 as who moo m; a; 8.” Sue. .EE :3 as :3 85 as? as: “m2 we. .97.. ".2. $25 MS 86 23 85 a: a: Gs as. 654 :85 a3 36 who one Em E Sm 9. .315...— go m2 3o 8.: 4mm 3 42 us. .2» Ex..— .I I- -i I- \t n N. 2.2. no .eZ mm mm mm 2:8 a 52 82.5.5 .325 2.32m 2mm 2. an a mum: .x. ._oo=afi.8.«..om 2:3 .3 399—6 9333 5?: 39% mas—=38 83605—58 wagon a: vacuum— 3. «Bah. 47 5&6 matombqsm 8.2:: .23 38 a £53» 882% 8:25 u 8m .8233 .1. 84m cod .3 :5 P»: ESL mix—9:2: ,3 uoEESow 33 H3 25 €25 £36 .3 3» $8.80 wEEZc 3 633330 we? 3» =25 683:5 mmmoueom as ea; Ea 228 x83 1 Eu as SEE u e2: was adv Sov :6 seem has “as. as: 48 36 mod . mod 26 nmoé page at; .x. .3. 3.33822: Bod vod mod mod haw—.— nh _ ._ «VOA Eu #5 GEE“ as is :3 :3 an: 9...: «as .5 .3 an Se :2 as 2: 53 new new We .8... %an 53m 223...: 3.3 .257 as Se 86 3 em 3. 3. .x. gamma: 3:28 as one as 35 am as am .522. :5. 93 8d 2; :5 his am? as: as: is as «so 2: 22. To. _ m 38 no.8... 3.532 as who 93 3o 8.: 3: 32 as .x. .5. a; 86 mod 85 am? has “2: so .5 .5. as Ed as as as new 2.» "so so: :22 so So So 85 has as: ~me one” 2...: 8.2.5.6 86 $6 36 and new”. 3 noodo ham. 8 «cums-59.2. 338.... sue—5 mod mmd Ed ”Nd nanmdm 92.8 «Qdm «“5520.— ”£395 a; Rs 3o 3.: £3.ch %on «mom... a: .2» £28 8: one So ”2 3.2 E E Sm 9. .E as..— Qmm t3 t2 Bouts: co .2 2.8.53 :25 3.2.x 2% e. 2 a mom: .x. :33... @323 no GOG—5 935—8 .53 amfiwmioafie Stigma—SE wag—doom no 83am Na. 03:. :5 .3 as 52 ova omé 34 SA 00a omd owd mom: :9. aoaa . ..... .. 8 m moo: x8 sou: . l u Sm men: so ass: i mom: :9. s. M mom: :2 I H mom: so 8 1\ % I 0 ohm 8s .22 Ease $3 a 53 u a 53- u e 8:288 assuage 8 5E .33 u 4 M23 u a mom: :8 2a 63 u m a; u e assess: 65:8 2.: FEB coufloboo 328a m 88me 338% .58 65522:: :3: 2: .3 62:23:. 0:25 «a 3153895.: was as a: a": E 38532.: a 2.: .3 Among 22.8 a? saw {25% 33.358... wage as soon...— E. 2:5 49 Figure 4.4 shows the correlation of IMF to SF measured post-harvest at the time of grading, in which a positive correlation (r = 0.93) was only indicated in the control diet (P = 0.003). These results may have shown greater statistical power if cattle were fed individually and the analysis was done on an individual basis. The data points were scattered, and it is difficult to show a positive correlation with only 9 pens evaluated. This warrants additional research focusing on the relationship between IMF and SF when MDGS is fed. The IMR is different when the comparison is made between the ultrasound derived and carcass measured ratio. Regardless of whether ultrasound or carcass measured variables is the most accurate, the trend line is the same in both, indicating more SF relative to IMF. There were some differences in the carcass values between the final ultrasound scan and the post-harvest measured values (Table 4.3). A positive correlation was shown between the ultrasound IMF and carcass IMF for the control (r = 0.79; P = 0.04) and 20% MDGS (r = 0.95; P = 0.001), but not for the 40% MDGS diet (r = -0.23; P = 0.62). However, this could be a result of SF thickness measurements altered due to hide removal and trimming at the harvest facility, inaccurately assigned marbling score, or an error in LM image scanning. Marbling scores were taken via image grading, but were altered by USDA graders if they felt the mechanical reading was inaccurate. Previous research has indicated a small margin of error in the ultrasound scans due to experience of the technician, but carcass measurements for SF may be less accurate than ultrasound (Brethour et al., 1992; Greiner et al., 2003). 50 3:20 23> v m N H m m m . a m 802....qu 1i 1 S w a w 892.83 , 2 M a\ \ In mum—250! 1 ON 0 la - m 2 mm m Om 3 mm w 9V .83. u 5 5E. 33.89.33 3:15 .23..” 22.» wean—=23 no awn—5 035—8 .53 59% mas—=35 33.3538 Mum—58 no 3985— N6 unaut— 51 Figure 4.3 Effects of feeding modified-wet distiller’s grain with soluble (MDGS) on quality grade. Unlike superscripts differ (P < 0.01). 40 35 30 25 20 15 Number of Cattle 10 b _ , A! 1-- i l a ”3.-” é .. l? j ~1- a .3 ”A a a i991 » . g i [1 L SE- SE+ CH- Quality Gradel WW-_.__.__J 0% MDGS D 20% MDGS [340% MDGS lQuality grades: DC/NR = dark cutter or no roll; SE- = low Select; SE+ = high Select; CH' = low Choice; CH0 = mid Choice; CAB = Certified Angus Beef 52 é 338585.55 n m3: 808 9A3... n . .59. u. . . Go I 3. w mOQE $8 I o m 3 852 .5. . . 5% 52.32.. 62. n 1.3.5 u a won: .59. Ea 9.2. n m .35 n .. nKEN Hm nomafioboo «gowflfiwmm om mm}, 0.55 Hu>v>>on Amood H K “mad H b «Gogaub 3.555 05 E fiozsma fiOUflPfi—oo 9::QO < .5358 H 000 “Ed imam H com anzm H 00? mo 0.50m MGSQHE < flan-3.50 an: Hm flung—muon— AOHOQm Mam—Shana: «an ha—flumflagflm 2:. ca 5. 53 E 38:855.... 5 5:... E. @652. .22.... £3 a...» {25% 53.2.5.5... “558. 5 53.5. v... 2.5.5 54 Color of Lean, Tenderness and Proximate Analysis The color of lean was similar among treatments (Table 4.4). These results indicated similar a* (P = 0.91; redness), b* (P = 0.17; yellowness), or L* (P = 0.17; brightness) values of the uncooked LM. The L* (P = 0.07) and b* (P = 0.08) values tended to be greater for the 20% MDGS treatment compared to the other two. The results of a*/b* ratio (P = 0.01) and hue angle (P = 0.01) were quadratically significant and were altered only at the 20% MDGS inclusion. This was similar to those reported by Depenbusch et al. (2009). The differences in values were so minute that a visual difference in meat color appearance would be difficult to detect. Table 4.5 illustrates the results on tenderness (P = 0.14), cooking loss (P = 0.54), and proximate analysis. All of the attributes investigated under these categories were similar among treatments in our study. Cooking loss results were numerically 3 to 4% lower than other research performed on the clam shell grill (Scheffler et al., 2003). This difference can be ‘ attributed several aspects including the lower cooking endpoint (70 vs. 72°C). Also, our study measured the weight of steaks immediately following removal from the grill, while Scheffler et al. (2003) allowed steaks to cool to room temperature prior to obtaining final cooking loss weights. Warner-Bratzler shear force (WBSF) results for tenderness are in agreement with those of Roeber et al. (2005) who found no difference in 25% and 50% WDGS or DDGS diets. The results are similar to others where it has also been shown that sensory attributes and tenderness were not affected with the inclusion of 15% DGS (Gill et al., 2008). Results from our study suggests there is no effect of feeding WDGS up to 40% of the diet DM on color, tenderness, and the proximate analysis of the LM as measured from the 11th and 12th rib section. 55 Fat Depot Composition The diet by fat depot interactions on FA composition were not significant (P > 0.05), although there were differences between depot; therefore the individual depots are reported in Tables 4.6, 4.7, and 4.8. Subcutaneous fat, IMF, and KPH composition results are shown in these tables, respectively. While not present in all depots investigated, the following FA were present in IMF samples: decanoic acid (C10), lauric acid (C12), C2021n9c, C20:3n6c, C20:3n3c, C22z4n6c, C22z5n3c, and one CLA (C18z2n7t9c). Other studies have also seen these FA in IMF measured in a similar manner (Gill et al., 2008; Dinh et al., 2010). Saturated FA appeared to be increased in the SF and KPH depots when compared to IMF. The SFAzUFA ratio was similar among treatments. The differences in SFA and UFA between different fat depots were expected and similar to those shown in other studies (Terrell et al., 1969; Zembayashi et al., 1995; Smith et al., 2009). 56 gutsy manombazm 83:: 63> 32 a £532 £8023 mg 85 ”no Go 3.2 2.2 3.2 3:: 2:25am :3 as 85 85 “8.8 53.? ES 2»: 2.: So 53 So So «3.2 am? as: 2:: 2:3 3o Ed 25 :5 2.8 3: 8.: .2 $6 03 So 2d 3.sz Sam 9..sz ,3 So 23 :5 :3 3.3 8.; 8.3 3 - - - - Q8 Q2 Q3 225...: .3 52 2.23% .325 3:5 2mm 3 3 .5: men: .x. 6.8::— mafimflwg— a... 8?: 25m: :3— ..c .839 no EGG—‘6 0333. 5?» 5a..» 9.8:sz 83605—52 mam—38 no floor—H v... 033—. 7 5 Emu—«.8 5.. 2:3 wean—omen. 3 co Emmi/v 8.5.. .80.... .o_N.m..m-..oEw3 a? 3.5802. 58 mad mod 36 mod ow... o:V om... 2G .x. £2... 35 .md omd o..o 3.2 312 am. SO .x. immezz mmd and 2.6 cod cod. .3... RM. 2m— .x. J...— mwd 36 mm... :d 3:? Swan mod... .x. 3.5.32 2d Ed 36 ood mud mod on.m .wx .Emmzc mmoEocaoh 36 26 Ed cod MEN. SN. owd. .x. £8. wan—ecu - - - - QR SN .3 225.38 .o .2357. 3.9.62.0 .32.: o=_a>.m Sam 3 :N e .5: mOG—z .x. ...c_._8._83 E... E35065. .5 @092. 035.8 .53 5....» 38:35. 3360512.. magnum he magnum m... 03:. Intramuscular fat had lower (P = 0.04) MU F A concentrations in the 40% MDGS treatment than the control or 20% MDGS (Table 4.6). Also in the 40% MDGS treatment, the percent of the following FA were decreased: C15 (P = 0.004), C17 (P = 0.04), and C18:1n7c (P = 0.01) compared to the other treatments. Stearic acid increased with 40% MDGS (P = 0.001) while C17: ln7c showed a linear decrease as MDGS increased (P = 0.04). A linear increase was seen for Cl6zln7c to be lower (P = 0.02) in the MDGS diets. A previous study has shown a similar decrease in C18:1n7c and C16zln7c when MDGS was fed, which has been associated with off-flavors in meat (Mello et al., 2007). Our study used the entire steak for extraction of lipids for analysis of IMF. Some researchers use this method of IMF extraction as opposed to removing the IMF for more accurate analysis of the fat depot and not muscle phospholipids, however this is rarely performed in the industry. In our study, the FA identified with liver-like off-flavor (J enschke et al., 2007) were similar among treatments. These FA include palmitoleic acid (C16zl), vaccenic acid, eicosadienoic acid (20:2n6), and di-homo-gamma-linolenic acid (C20:3n6). The level of these FA are minute and not of great concern within this study. While consumers typically desire a healthier product with more omega-3 and omega-6 FA in the diet, levels for the three treatments were similar in this study. However, C18z2n7t9c was increased with the 40% level of MDGS (P = 0.01), which may assist in lowering cholesterol of those who consume meat from animals fed a similar diet (Wiebe et al., 1984) Two fatty acids (FA) were different in SF when MDGS was fed. Margaric acid (C1720) showed a linear decrease (P = 0.05) with increased levels of MDGS (Table 4.7). 59 However, a linear decrease was seen (P = 0.01) in C17:1n7c in the MDGS diets. The SF depot also showed numerically less SFA than IMF and KPH depots. KPH values showed a linear decrease in C14 (P = 0.001) and C17 (P = 0.01) when MDGS was included in the diet (Table 4.8). Levels of C14 and C17 were significantly lower (P < 0.05) with 40% MDGS than the other treatments. The linear increase in (P = 0.01) long chain FA (2 C18) in the KPH would include both saturated (SFA) and unsaturated fatty acids (UFA) as MDGS increased in the diet. These results confirm findings by Gillis et al. (2004) which suggest long chain fatty acids are increased by adding lipid to the diet. Based on the results from this study, the FA concentration of SF, KPH, and IMF are only marginally affected by including MDGS in the diet. Subcutaneous fat had less SFA (P < 0.001) as a percent of the total composition than KPH and IMF. Higher concentrations of MUFA were found in IMF depots of cattle fed 40% MDGS. Subcutaneous fat contained similar FA composition across all treatments. A decrease in myristic acid was seen in KPH when 40% MDGS was fed, while the remainder of FA were similar among diets. These results indicate that there were only marginal changes in FA composition due to the inclusion of MDGS in the diet, indicating that MDGS has similar wholesomeness as beef produced from more traditional com-based diets. The atherosclerotic index (Al) has been proposed as a measure of the propensity of the human diet to influence the incidence of coronary heart disease (U lbright and Southgate, 1991). The equation predicts a likelihood a specific consortia of fatty acids that is more healthy and wholesome than another (AI=[12:0 + (4* 14:0) + l6:0]/(l6:1c7 + 18:1c9 + 182n6 + l8:3n3)). For instance, an A1 of “x” is less likely to cause coronary 60 heart disease than “y”. The Al for the three treatments in this study were 0.93, 0.97, and 0.94 for the 0, 20, and 40% MDGS diets, respectively. Those treatments with the lower AI would be better for the consumer to eat for the prevention of heart disease (Ulbright and Southgate, 1991 ). Based on that study and the results from this study, it could be suggested that cattle fed diets without MDGS would be healthiest for consumers, although MDGS fed at 40% would be close in Al when compared to the 20% MDGS diet. 61 Table 4.6 Effects of feeding modified-wet distiller’s grain with soluble (MDGS) on fatty acid composition of subcutaneous fat. No. %MDGS Fatty acid of P- % Obs. 0 2° 4" SEM value Linear Quadratic C14 9 3.72 3.95 3.68 0.17 0.52 0.90 0.28 C14: 1n5c 9 1.12 1.18 1.07 0.11 0.61 0.64 0.40 C15 9 0.74 0.70 0.59 0.03 0.06 0.03 0.42 C16 9 25.70 25.00 24.82 0.58 0.58 0.35 0.73 C16 :ln7c 9 4.28 4.11 3.60 0.19 0.08 0.04 0.44 C16 :ln7t 9 0.31 0.30 0.32 0.01 0.74 0.66 0.55 C17 9 1.59 1.42 1.20 0.10 0.11 0.05 0.86 C17 :ln7c 9 114a 1.01ab Q79b 0.04 0.01 0.01 0.51 C18 9 11.66 11.65 12.13 0.32 0.52 0.34 0.55 C18 :ln7c 9 1.66 1.53 1.46 0.06 0.16 0.07 0.65 C18:ln9c 9 32.23 32.67 32.74 0.86 0.87 0.65 0.84 C18: ln9t 9 10.12 10.19 10.66 0.68 0.73 0.49 0.77 C18: 2n6c 9 237a 1693b 3_22b 0.15 0.01 0.01 0.01 C18 :3n3c 9 0,108 0.16“ (nob 0.03 0.09 0.04 0.73 Unknowns 9 2.76 3.44 3.47 0.30 0.09 0.06 0.23 MUFA' 9 50.87 50.99 50.65 0.63 0.93 0.81 0.78 PUFA' 9 2.96a 2.85a 3.46b 0.16 0.01 0.01 0.02 Omega 3 9 0.14 0.15 0.17 0.05 0.92 0.72 0.87 SFA' 9 42.90 42.75 42.87 0.87 0.98 0.98 0.86 SFAMFAI 9 0.42 0.42 0.42 0.01 0.99 0.93 0.99 2C18 9 29.73 29.96 30.76 0.33 0.18 0.09 0.52 < C18 9 19.57 19.16 18.36 0.34 0.14 0.07 0.66 1MUFA= monounsaturated fatty acids; PUFA: polyunsaturated fatty acids; SFA = saturated fatty acids; UFA = unsaturated fatty acids bc . . . . . . a Means w1th1n a row w1th unl1ke superscnpts dlffer 62 Table 4.7 Effects of feeding modified-wet distiller’s grain with soluble (MDGS) on fatty acid composition of intramuscular fat. No. %MDGS Fatty acid 0f 0 20 40 P- Linear Quadratic % Obs. SEM value C10 9 0.04 0.04 0.05 0.002 0.12 0.05 0.91 C12 9 0.06 0.06 0.06 0.002 0.12 0.07 0.27 C14 9 3.05 3.30 2.89 0.12 0.16 0.40 0.09 C14:1n5c 9 0.62 0.66 0.50 0.06 0.23 0.21 0.22 C15 9 0.588 0.61111 0.48b 0.01 0.004 0.004 0.01 C16 9 25.66 25.49 24.67 0.41 0.14 0.07 0.41 Cl6:ln7c 9 3.27a 3.208 2.64b 0.12 0.04 0.02 0.19 Cl6zln7t 9 0.16 0.20 0.21 0.01 0.14 0.07 0.41 C17 9 1.69a 1.633 1.33b 0.07 0.04 0.02 0.21 C17:1n7c 9 1.218‘ 1.10b 083° 0.02 0.001 0.0002 0.04 C18 9 13.39a 13.50a 15.36b 0.25 0.001 0.001 0.01 C18:ln7c 9 1.52a 1.46a 1.34b 0.02 0.01 0.01 0.30 C18:1n9e 9 33.20 32.27 32.53 0.46 0.41 0.36 0.35 C18:1n9t 9 8.02 9.00 8.25 0.50 0.41 0.75 0.22 C18:2n6c 9 3.80a 3.61a 4.51b 0.19 0.05 0.05 0.07 C18:3n3c 9 0.21 0.22 0.22 0.02 0.95 0.77 0.94 C20:1n9c 9 0.138 0.12b 0.138 0.004 0.09 0.97 0.04 C20:3n6c 9 0.13 0.12 0.16 0.01 0.20 0.23 0.16 C20:4n6c 9 0.56a 0.44b 0.58a 0.03 0.04 0.67 0.02 C22:4n6c 9 0.03 0.05 0.05 0.01 0.39 0.22 0.62 C22:5n3c 9 0.12a 0.09b 0.12a 0.004 0.01 0.93 0.003 CLA- a b c C18:2n7t9c 9 0.06 0.07 0.10 0.003 0.002 0.001 0.26 Unknowns 9 2.4951‘ 2.76ab 2.99b 0.08 0.03 0.01 0.80 MUFA‘ 9 48.13a 48.00a 46.44b 0.22 0.01 0.003 0.04 PUFA' 9 4.92a 4.61a 5.74b 0.22 0.04 0.05 0.05 Omega 3 9 0.34 0.33 0.38 0.03 0.58 0.47 0.48 SFA] 9 44.61 44.76 44.56 0.34 0.88 0.91 0.64 SFAzUFA' 9 0.85 0.85 0.85 0.01 0.93 0.85 0.77 2C18 9 30.973 30.90a 32.15b 0.34 0.05 0.04 0.11 Hun: .x. 03a>i ........... 0...... 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Implications The objective of this study was to evaluate the effects of modified-wet distiller’s grain with soluble (MDGS) on partitioning of fat between various depots, and to determine the effects of feeding MDGS on volatile fatty acid concentrations within the rumen, specifically acetate and propionate. Experiment number 1 was organized to determine the effects of feeding MDGS on feedlot performance, carcass quality, and muscle attributes. Another target was to determine the effects on fat deposition and composition of various fat depots. The second experiment was conducted to evaluate the effects of feeding MDGS on volatile fatty acid (V FA) concentrations within the rumen. This study attempted to define the acetate to propionate ratio of a diet with MDGS fed at various levels and its relationship with fat deposition. 75 m‘ “3 Our hypothesis predicted increased levels of subcutaneous fat (SF) deposition without a significant effect on marbling, which would be similar to some previous studies feeding DGS. It has been implied that acetate is a precursor to SF production and propionate for intramuscular fat deposition (marbling or IMF). The expectation was that increased inclusion of DGS results in decreased propionate production, decreased marbling, and increased SF deposition. Inclusion of MDGS had no effect on DMI, ADG, and final weight when cattle were fed to a constant 12th rib subcutaneous fat thickness endpoint. Contrary to the results of the current study, others found enhanced DMI and ADG when MDGS was fed (Gunn et al., 2009; Leupp et al., 2009; Vander Pol et al., 2009). This may be in part due to differences in endpoint as the current study fed the cattle to a constant SF endpoint whereas the other studies fed to a constant number of days on feed. Often it is found that increased days on feed results in greater final weight, SF deposition, marbling, and yield grades. Feeding cattle to a constant BW may result in greater variance due to the differences by genetics and frame size. Cattle in this study also consisted of both heifers and steers, whereas other studies have consisted of only one sex as a constant to prevent differences due to gender related effects on carcass composition. This study, as well as other recent studies, has shown similar tendencies for MDGS to increase feed conversion efficiency, dressing percent, and yield grade. Feeding MDGS resulted in more yield grade 3, more USDA QG Select plus and less low Choice, which was similar to recent research that fed WDGS. In this study, however, less than half graded USDA Choice or higher. It has been suggested that a portion of the lower quality grade could be traced to a particular Simmental sire (KSU Venom 101M), which 76 influenced 47.6% of the pens and 20.3% of the cattle in our study, see appendix Table A6. Number of pens which were influenced were evenly distributed among treatments. A young bull with a pedigree-derived EPD for marbling was used, but as the actual offspring driven EPD was developed, it dropped significantly. His marbling EPD in 2006 was 0.49 and dropped to a current EPD of -0.12 with 0.51 and 0.60 accuracy, respectively. This is one of the hazards of using unproven bulls. While the final ultrasound results were similar to carcass results, the difference in correlation statistics indicate there must be measurement error in either the ultrasound or carcass measurements. Previous research has indicated a slight margin of error in the ultrasound scans depending on the experience of the technician, but carcass measurements for SF are less accurate than ultrasound. This is a debate that needs additional research to accurately evaluate measurements. All color of lean, tenderness, and proximate analysis results were similar to recent reports on feeding DGS to cattle. The significance of the cooking loss results appeared quite high considering the differences in quality grade. Cooking loss was measured slightly different from other studies which lowered the measurements. However, this study was consistent with all proximate analysis data showing no differences. Based on the results from this study, the FA concentration of SF, KPH, and IMF are only marginally affected by inclusion of MDGS in the diet. Although, the diet >< fat depot interaction was not significant, numerically SF appeared to have less SFA as a percent of the total composition than KPH and IMF. Higher concentrations of MUFA were found in IMF depots of cattle fed 40% MDGS. Monounsaturated fatty acids have been attributed to off-flavors in meat. However, meat with increased amounts of UFA is 77 desired as it is reported to be a healthier product for consumers. In SF, results are similar with previous reports in that it has lower SF A than IMF and KPH. There was a tendency for increased long chain FA (2 C: 1 8) and UFA in KPH with MDGS. Even though UFA increased with MDGS feeding, SFA were still numerically higher than those in the IMF depot. Subcutaneous fat contained similar composition across all treatments. A decrease in myristic acid was seen in KPH when 40% MDGS was fed, while the remainder of the FA were similar among diets. These results indicated that there were only marginal changes in FA composition due to the inclusion of MDGS in the diet. Inclusion of MDGS into the diet may shift the proportion of fat stored toward SF and away fiom IMF. Feeding 20 or 40% MDGS may result in improved G:F, and greater SF deposition with minimal effects on marbling and no effect on muscle attributes examined within this study. Improved feed conversion efficiency may be due to greater fiber and decreased particle size in MDGS diets, along with no change in ADG and increased overall digestibility. Increased SF deposition may be a result of increased dietary lipid intake with MDGS and similar amounts of energy. This would partition lipid energy sources, as compared to energy sources from starch, to produce increased SF fat since it is the primary storage depot for excess energy intake. Levels of VFA’s were similar among treatments with the exception of valeric acid, which increased linearly with the addition of MDGS. We would expect this due to the increase in protein and decrease in starch and urea nitrogen in the MDGS diets. This may also be attributed to increased microbial growth in the rumen, which warrants further investigation. Inclusion of MDGS in the diet had little effect on acetate and propionate concentrations, A:P or ruminal fluid NH3 concentration. Acetate and propionate 78 concentrations did not support our original hypothesis that increased acetate would be produced with MDGS resulting in a A:P increase. Due to previous research in fat deposition, we hypothesized the opposite trends, as acetate is a precursor to SF. Further research with greater statistical power should be done to evaluate this more extensively and the relation to fat deposition. Nitrogen concentrations on samples analyzed on an as-is or dried sample basis for the total mixed rations (TMR) yielded similar values, indicating no significant nitrogen loss in the drying process. Therefore, the N results analyzed for all dried samples should be acceptable for the majority of research trials. When sensitive balance studies are conducted, it may be beneficial to freeze dry samples. Fecal ether extract tended to increase linearly with the inclusion of MDGS, which is in agreement with most of the reported literature on feeding DGS. Increased P excretion was seen with the addition of MDGS, along with increased digestibility as a percent of DM for N, ADF, and NDF. Retention of N and digestibility all numerically increased with greater MDGS inclusion rates. This observation was contrary to results reported by Spiehs and Varel (2009). Because of this inconsistency additional studies should be conducted to further investigate N digestibility and retention in diets containing MDGS. Fecal, urinary, digestibility, and retention results for Ca increased numerically with higher MDGS inclusion. Calcium digestibility and percent retained were negative values, but total amount retained was positive for the control treatment. This may be explained by a range of positive and negative numbers influencing the average. For example, the two lowest measurements for Ca digestibility were -143. l 7 and -68.11, 79 while the highest measurements included 52.60 and 45.35. Percent calcium retained ranged from —144.83 to 52.15. These results support the premise of increasing digestibility with increased intake suggested by Varner and Woods (1972) However, that study included lower concentrations of Ca than current beef cattle rations. Clearly, additional research needs to be performed to explain the inconsistent results in this study as well as reported studies in the literature Future Work Overall, the carcass results of this group of cattle were not at, what I would consider, a satisfactory level. This trial could be duplicated with a closer look into genetic impact on the grading of the cattle. It would also be beneficial to make the diets isocaloric and/or isonitrogenous and perform a study with animal as the experimental unit rather than pen. This would also warrant additional research focusing on the correlation of IMF to SF in both ultrasound and carcass results. It would be beneficial to have whole carcass fat dissemination to more accurately partition fat depot size. The IMF samples taken in this study are a reflection of the entire steak analysis, including IMF. Some researchers use the entire steak to extract FA for IMF analysis as opposed to removing the IMF for more accurate analysis of the fat depot. Future research could remove IMF samples as well as longissimus muscle samples and analyze them separately for FA composition to better differentiate between IMF and muscle phospholipids. Due to the variability in urine output and results that debate previous studies for N output, as well as the previous stated digestibility concerns, it would be appropriate to 80 further investigate the digestibility of MDGS in beef cattle. When conducting this study, NDF and ADF results were variable and require additional repetition to obtain more consistent results. In the filture, these analyses should be performed using a method from Van Soest rather than the Ankom procedure to obtain better precision and accuracy. Van Soest methods have been used previously in this lab with better precision and more consistent results. Acetate, propionate, and A:P showed only numerical differences. With no dramatic differences in any of these three factors or diet X depot interactions, a new question arises. Is there actually a relationship of FA intake to fat deposition when MDGS is fed? 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