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C ‘Iu Hi .1 v \. 1.\ .‘r. “ ”v.1. Vt). _:._.______:___ : | I y .bt ‘l'..!'t'1‘.! .rigi!’ '4... ’lni.‘!.E!y’J—.llu \/ LIBRA'R Y Michigan Scat! mimic? '. THEStb ABSTRACT THE EFFECTS OF MICROWAVE HEATING ON THE PROPERTIES OF RAW UNEXTRACTED SOYBEANS FOR UTILIZATION BY THE CHICK 3? Matteas Arthur Gustafson, Jr. Soybeans contain, in addition to the high quality protein present, an excellent energy source for the chick, in the form of soybean oil. For unextracted soybeans to be efficiently utilized by the chick, they must be heated. This study was conducted to evaluate microwave heating as a means of producing an unextracted soybean product which may be satisfactorily utilized by the chick. Samples of soybeans that had been subjected to microwave heating were analyzed for urease activity and protein dispersibility to estab- lish the most effective treatments. Soybeans which had been effectively heated, as indicated by the analyses, were ground and included in an experimental chick diet for a biological analysis. Observations were made on weight gains, feed consumption, and pancreas weights. Heating soybeans with microwave energy effectively destroyed the factor(s) responsible for pancreas enlargement. Also, the feed effi- ciency levels of chicks fed microwave heated soybeans nearly equaled those of chicks fed the diets containing soybean meal supplemented with either soybean oil or animal fat. However, the weight gain of chicks fed the diet containing microwave heated soybeans was less than that of chicks fed either of the diets containing soybean meal. THE EFFECTS OF MICROWAVE HEATING ON THE PROPERTIES OF RAW UNEXTRACTED SOYBEANS FOR UTILIZATION BY THE CHICK BY Matteas Arthur Gustafson, Jr. A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Poultry Science 1969 ACKNOWLEDGEMENTS The author wishes to express his appreciation to Dr. Cal J. Flegal, Assistant Professor of Poultry Science, for his guidance and interest in this study and many helpful suggestions in the preparation of this manuscript. The author also appreciates the assistance provided by Professors T. H. Coleman, P. J. Schaible and H. C. Zindel of the Department of Poultry Science, Dr. E. J. Benne of the Department of Biochemistry, and Dr. L. E. Dawson of the Department of Food Science. Appreciation is also extended to the other members of the Department of Poultry Science and to my fellow graduate students for their assistance. Finally, the author is indebted to his wife, Nancy, for her sacrifice, patience and encouragement during this period of study and research. 11 ACKNOWLEDGEMENTS . . . . TABLE OF CONTENTS . . . LIST OF TABLES . . . . . LIST OF FIGURES . . . . INTRODUCTION . . . . . . REVIEW OF LITERATURE . . MATERIALS AND METHODS . TABLE OF CONTENTS Soybean Treatments and Analyses . . . Diet Formulation . Chick Growth Trial Statistical Procedure . RESULTS AND DISCUSSION . SUMRY O O O O C O O 0 LIST OF REFERENCES . . . iii iii iv 11 14 14 15 31 32 LIST OF TABLES Table 1 Protein, phosphorus, calcium and energy content of variable ingredients . . . . . . . . . . . . . . . . 2 Composition of diets . . . . . . . . . . . . . . . . . 3 Urease activity and PDI values of soybeans containing different moisture levels and heated for various time periOds O O O O 0 O O O O O O O O O O O O O O O O O O O 4 Urease activity and PDI values of soybeans containing an equal moisture level (14.5%) and heated for various time periOds O O O O O O O 0 0 O O O O O O O O O O O O 5 Moisture content, urease activity and PDI values of soybeans heated and incorporated into chick diets . . . 6 Effect of different protein and supplemental energy sources on broiler performance and pancreas weight . . 7 Analysis of variance of four-week chick weights . . . . 8 Analysis of variance of feed conversion . . . . . . . 9 Analysis of variance of chick pancreas weights . . . . iv 21 23 24 25 26 27 LIST OF FIGURES Page Urease activity and PDI values of soybeans containing 15.3% moisture and heated for various time periods . . . l7 Urease activity and PDI values of soybeans containing 20.8% moisture and heated for various time periods . . . l9 INTRODUCTION The soybean, Glycine max, is native to Eastern Asia. Early writings indicate that the soybean was perhaps one of the oldest crops cultivated by man and also was regarded as having many medicinal values. Early in the Nineteenth century, soybeans were first brought to America and grown primarily as a forage and pasture crop. More than a century elapsed before they were produced commercially for processing purposes. Commercial soybean meal is the major protein product utilized for livestock and poultry feeds in the United States. More than half of the soybean meal is consumed by the poultry industry via its high protein feeds. The protein quality or amino acid balance of soybean meal probably excels that of any other plant protein product available for use in animal feeds. In the commercial processing of soybeans, moisture, pressure, heat and solvents are involved in the oil removal process. The 44- and 49% protein, heated meals remaining after oil removal are the materials which are incorporated into animal feeds. In the past, the price of soybean meal has been highly corre- lated with the price obtained for soybean oil as a human food. In recent years, there has been a greater need for soybean meal and a reduced demand for soybean oil° If this trend prevails, the price of the oil may be lowered to the extent that it will not be economical to process soybeans for oil removal. 2 High energy livestock and poultry feeds have been widely accepted due to the resultant improved growth performance. Fats and tallows are frequently incorporated into these feeds as supplemental energy sources. The occasional low soybean oil prices together with the acceptance of high energy feeds has created an interest in feeding unextracted soybeans with their characteristic high oil content. Raw soybeans are poorly utilized by monogastric animals, there- fore, they are subjected to various heat treatments. Microwave.radia- tion is a revolutionary process in which heating is accomplished by direct absorption of energy. 'As the microwaves penetrate, they produce instantaneous heat, not only on the surface, but deep inside the material as well. The molecules are rapidly set in motion. Thus, heat is generated quickly and uniformly, thereby maximizing heat efficiencies. Toasting the intact soybeans with microwave radiation should produce a highly uniform product, eliminate the cost of fat extraction, and accelerate processing. The development of a method to process raw whole soybeans by microwave radiation would be of scientific interest and economic importance. The purpose of this research was to determine if microwave processing was effective in producing a heated soybean- which would perform well in chick diets. REVIEW OF LITERATURE The growth arresting effect experienced when raw soybeans are fed to monogastric animals was initially reported many years ago. In studies with rats, Osborne and Mendel (1917) reported an increase in the rate of growth when the soybean portion of the ration had been heated in comparison with a raw soybean ration. These same investi- gators demonstrated the superiority of moist heat over dry heat. Numerous investigations with unheated and heated soybeans have since been conducted. These inquiries have confirmed the beneficial effect of moist heat on the nutritive value of soybeans and soybean meal for chickens, rats, and other monogastrics (Hayward, Steenbock and Bohstedt, 1936; Parsons and Walliker, 1941; Evans and St. John, 1945; Borchers, 35 al,, 1947; Fritz, Kramke and Reed, 1947; MbGinnis and Evans, 1947 and Rackis, 1966). The unextracted soybean recently has been the subject of con- siderable interest and research as a poultry feed ingredient. In about 1959, this research was stimulated when soybean oil prices were low enough in relation to those of other feed fats to allow serious con- sideration of the oil for animal feeding. With a metabolizable energy of over 8,800 calories per kilogram, soybean oil is an excellent energy source for the young chick. It is logical to use the bean itself as a source of both protein and oil in poultry feeds rather than going to 4 the trouble of extracting the oil from the bean and recombining it with soybean meal (Nesheim, 1961). Presupposing the development of a satisfactory commercial pro- cess for producing cooked-unextracted soybean meal, several agricul- tural economists (Poats, Doty and Eley, 1961) conducted economic feasibility studies on the incorporation of this feed ingredient into poultry feeds. The analysis was made at a time when, due to the price of soybeans and soybean oil, the potential return from using soybeans as unextracted meal was attractive. These economists indicated the following advantages which would accrue to the feed mixer upon utili- zation of cooked-unextracted soybean meal which are not directly re- lated to ingredient prices: 1. The addition of fats to feeds is a problem. Availability of a granular high-fat-content ingredient (such as cooked soybeans) would circumwent the large capital requirements necessary for and costs.associated with making high energy feeds. 2. Unextracted soybean meal manufactured under quality controlled conditions would be a consistently high quality energy source. The caloric value of soybean oil exceeds that of feed grade fats and is more constant in nature. 3. Having the fat within the matrix of the feed particle rather than sprayed on its surface would permit higher energy con- tent feeds to be made. This initial feasibility study was revised and expanded upon by Doty (1965). 5 Numerous workers have reported on various means of heating un- extracted soybeans for chick rations. The methods investigated to date include steam heating at various pressures, extruding and infrared heating. It was concluded by Carew, Renner and Hill (1959) that auto- claved, flaked soybeans were at least as efficient as commercial soy- bean meal and degummed soybean oil for stimulating chick growth and improving feed conversion efficiency. A report by Renner and Hill (1960) indicated that autoclaved, ground soybeans were equally as. effective in promoting rapid growth as the combination of autoclaved, extracted soybean flakes and soybean oil, despite the lower absorb- ability of the oil supplied by the unextracted soybeans. The results of an experiment by Carew, Hill and Nesheim (1961) demonstrated that autoclaved, dehulled, unextracted soybean flakes produced a growth rate and feed efficiency equal to that obtained with the combination of soybean meal and degummed soybean oil while auto- claved, ground, unextracted soybeans were less satisfactory in this respect. The poorer results obtained with autoclaved, ground, unex- tracted soybeans was shown to be related to a reduced absorbability of the oil contained in them. Yates (1963) reported that autoclaved (248° F. for 15 minutes), ground soybeans supported significantly lower gains than did soybean meal with added corn oil when fed to chicks from age two weeks to age six weeks. Stephenson and Tollett (1959) utilized two forms of steam heating in producing heated soybean flakes. The flakes were processed in a rendering plant cooker or in a laboratory autoclave. The 6 steamrcooked soybean flakes produced gains which were comparable to those produced with soybean meal and animal fat. Combs (1960) reported on two feeding trials with broilers grown under commercial-like conditions. The broilers receiving a diet con- taining ground whole soybeans, processed at atmospheric pressure in a meat scrap cooker, weighed only slightly less than the controls at 12 weeks of age. In a second test, soybeans were processed at both atmo- spheric pressure and at 15 pounds of steam pressure for various lengths of time. Again, the controls receiving solvent extracted commercial soybean meal and feed grade fat performed slightly better than the broilers on any of the other treatments. Continuous processing of whole soybeans was carried out in a regular solvent extraction soybean plant by Runnels (1961). The soy- beans passed through the normal plant cycle, with the exception of being diverted around the extractors, and the resultant flakes were cooked similar to the method by which commercial soybean meal is pro— cessed. Also, ground and flaked soybeans were batch processed in a meat scrap cooker. The results of feeding trials with broilers approached those obtained with commercial meals. Utilizing a steam-jacketed cylinder, Rogler and Carrick (1961) heated whole soybeans with additional injected steam.and ground soy- beans without supplementary injected steam. Feeding trials yielded growth results for both experimental rations which exceeded the growth rate supported by a soybean meal ration, but less than that of a soy- bean meal ration with added soybean oil. The feed efficiency levels derived from the high energy rations were nearly equivalent. 7 It was demonstrated by Mustakas £5 21, (1964) that the rate of gain and efficiency of feed conversion for extruded full-fat soybeans equaled that of soybean meal with added oil when fed to broiler chicks. Supplementation studies suggest that the methionine and cystine in the extruded product were probably more available which could account for the higher biological values obtained for chick feeding. The high nutritive value of the extruded soybean material was attributed to the relatively high temperature -- short retention time process. Growth inhibitors were effectively destroyed; whereas, the heat-labile amino acids, vitamins and other nutrients were preserved. Featherston and Rogler (1966) employed autoclaving and infrared radiation as a means of heating unextracted soybeans for maximum utilization by the chick. When chicks were fed cracked, autoclaved soybeans the weight gain and feed efficiency achieved were statistically equivalent to that obtained with a corn-soybean oil meal ration with an equivalent amount of soybean oil added. The substitution of ground, infrared heated soybeans for soybean meal, soybean oil and a portion of the corn in the positive control diet on an isonitrogenous and isocaloric basis resulted in significantly poorer growth and feed conversion. Pancreas size of the chicks fed diets containing raw soybeans was markedly enlarged. The pancreases of chicks fed the infrared heated soybeans were much smaller than those of chicks fed the raw soybean diet but were larger than those of chicks fed the corn-soybean meal- soybean oil diets. No improvement in growth performance was observed when the moisture content of the soybeans was increased by 10% prior to infrared heating, in comparison with infrared heating dry soybeans. However, similar pancreas weights were observed in chicks fed diets 8 which contained soybeans which had been moisturized prior to infrared heating as was observed in chicks fed the control diets containing commercial soybean meal. White 35 21. (1967) evaluated the processing methods of auto— claving, extruding and infrared cooking for the production of cooked, unextracted soybeans for broiler rations. The results of this study indicate that autoclaving, extruding and infrared cooking significantly improved the feeding value of raw-unextracted soybeans to the extent that this material may replace soybean meal in broiler ratiOns. Soy- beans processed by these three methods approached the nutritional' value of extracted soybean meal and soybean oil in isocaloric- isonitrogenous rations when fed to broiler chicks from 7 to 28 days of age. Experiments were also conducted by Hull g£_§l, (1968) to evaluate infrared cooking and extrusion processing of-unextracted soybeans for inclusion in broiler diets. It was reported that diets containing extruded soybeans supported chick performance equal or superior to feeds containing solvent extracted soybean meal with soy- bean oil added; whereas, infrared cooked beans were usually inferior to solvent extracted soybean meal with added soybean oil. Rackis (1968) recommended the use of urease activity and pro- tein dispersibility tests as guides to indicate properly processed soybean meal. He suggested that if the urease activity indicated a. pH increase from 0.05 to 0.15 and if the protein dispersibility index (PDI) was from 10 to 202, the soybeans were considered to have been properly processed. MATERIALS AND METHODS Soybean Treatments and Analyses At the outset of this experiment, three variables existed -- batch size heated, moisture content of the beans and heating period. The-first variable to be standardized was the batch size heated. To accommodate the size of the oven1 and for convenience, a batch size of 1,800 grams was selected. From every trial batch heated, a minimum of one sample of approximately fifty grams was removed for an analysis of optimal heating. If the sample was too moist to grind, it was dried overnight at 40° C. in'a drying oven. Each sample was ground through a Number-10 Wiley mill screen and extracted with redistilled n-hexane in a Soxhlet extractor. The resulting meal was then desolventized overnight at 40° C. The urease activity and the protein dispersibility index (PDI) of each sample was determined following procedures outlined by the AmeriCan Oil Chemists' Society (1965). The guidelines provided by Rackis (1968) were then applied to determine the effectiveness of the heating procedure. In a pre-experiment trial, raw dry (5.9% moisture) soybeans were heated in the microwave oven. The soybeans were cooled at room temperature, but were not further dried, prior to grinding, due to 1Hotpoint Model 20 RER 1 powered by one magnetron (Raytheon QK 390) providing a frequency of 2,450 megahertz (MHz) and an.output of 0.8 kilowatts. 10 their low moisture content. Urease analysis was then conducted on several samples as outlined. The next trial was designed to assess the effects of heating beans of different moisture contents. Two identical batches of beans were soaked in water for 5 or 15 minutes, respectively. After soaking, the beans were held overnight under refrigeration in sealed containers to allow uniform moisture distribution (Renner and Hill, 1960). In- dividually, 1,800 grams of each moisturized batch were placed in the oven. After six minutes of heating, and every two minutes thereafter, the beans were removed from.the oven, stirred, sampled, and returned to the oven, until a total heating time of twenty minutes had elapsed. Each sample was cooled at room temperature, dried overnight at 40° 0., ground, extracted, desolventized and analyzed as previously mentioned. In the previous trial, in which the desirable moisture level was ascertained, the batch size decreased with heating time as the samples were removed. Therefore, it was necessary in this trial to heat batches of soybeans undiminishing in size and nearly equal in moisture content to determine the most desirable heating interval. Four batches of beans were soaked in water, each for five minutes, and refrigerated. The heating period ranged from 15 to 18 minutes. Each batch was stirred at two-minute intervals for the last ten minutes of the heating cycle. The heated beans were cooled to room temperature in shallow steel pans and a sample was removed from each batch. The heating process dried the beans considerably (to about 81 moisture), therefore, they were not further dried. Grinding, extraction, desolventizing and chemical analyses were performed as in the previous trials. 11 After having determined the correct relationships between batch size, moisture level and heating time, the next procedure was to heat several batches, employing this information, so that the chemical analyses might be substantiated by a chick growth trial. Each of 13 batches was soaked in water for five minutes and refrigerated overnight. The soybeans were then heated for 15 minutes and each batch was stirred at twoaminute intervals for the last ten minutes of the heating period. Each batch was poured into a shallow metal pan, cooled to room temperature and then sampled. The samples were of low moisture content, thus they were not further dried. Sample preparation and analysis was conducted as aforementioned. Diet Formulation In the growth trial phase of this experiment, all diets were formulated to be isonitrogenous and isocaloric. For the accuracy of the formulations to be increased, the feed ingredients which varied in amount among the diets were analyzed for protein, phosphorus and calcium. Energy values previously reported were utilized. Illus- trated in Table l are the derived protein, phosphorus and calcium values and assumed energy values applied in formulating the diets. The diets compared in this experiment contained soybean meal, microwave heated soybeans or raw soybeans. The soybean meal and soy- bean oil were commercial products; however, the microwave heated and the raw soybeans were both from the same lot (Harosoy-63 variety). The composition of the diets is given in Table 2. All diets were fed in the mash form. The microwave heated and raw soybeans were ground in a hammermill prior to inclusion in the diets. 12 Table 1. Protein, phosphorus, calcium and energy content of variable ingredients Analyzed “Assumed Protein Phosphorus Calcium MQE. Ingredient (Z) (Z) (Z) (Cal/1b) Soybean meal 49.38 .707 .238 1,100“ Corn 8.88 .310 .010 1,560“ Microwave heated soybeans 39.25 .552 .151 1,500b Raw soybeans 39.25 .552 .151 1,100c Soybean oil -- -- -- 4,100d Animal fat, stabilized -- -- -- 3,480“ (yellow grease) aFlegal and Adams, 1969. bwaldroup‘gtngl., 1969. c8111 and Renner, 1958. dYoung, 1963. 13 Table 2. Composition of diets Diet number Ingredient l 2 3 4 Corn 57.74 56.07 54.07 46.83 Soybean meal 26.11 26.41 -- -- Microwave heated soybeans -- -- 33.68 -- Raw soybeans -- -- -- 35.52 Soybean 011 3.90 -- -- 5.60 Animal fat, stabilized -- 5.27 -- -- (yellow grease) Constant ingredients“ 12.25 12.25 12.25 12.25 Total 100.00 100.00 100.00 100.00 Calculated analysis: Protein (1) 21.00 21.00 21.00 21.00 Calcium (2) .96 .96 .95 .95 Phosphorus, total (I) .78 .78 .77 .76 Phosphorus, available (1) .51 .51 .50 .50 Metab. energy (Kcal/kg) 3,172 3,174 3,174 3,174 Chemical analysis: Protein (2) 21.31 21.63 21.56 21.75 Calcium (1) .91 .89 .97 .85 Phosphorus, total (2) .79 .73 .76 .75 aSupplied 2.0: alfalfa meal (20% protein); 31 fish meal (60: protein); 2% corn distillers dried solubles (272 protein); 21 dried whey (121 protein); 0.5% salt; 1! ground limestone; 1.51 dicalcium phosphate and 0.251 vitamin-trace mineral mix (supplied the following in milligrams or units per kilogram: Vitamin A, 6,608 USP units; Vitamin D3, 1,652 IC units; Vitamin E, 2.2 IU; riboflavin, 4.4 mgs; d-pantothenic acid, 6.1 mgs; niacin, 27.5 mgs; choline chloride, 275.3 mgs; menadione sodium.bisu1fite complex, 2.2 mgs; Vitamdn.812, .0088 mgs; BHT, 124.9 mgs; manganese, 60 mgs; zinc, 27.6 mgs; iron, 20 mgs; copper, 2 mgs; iodine, 1.2 mgs; cobalt, 0.2 mgs.) 14 Chick Growth Trial One-day-old Cobb's strain White Rock broiler cockerels were placed in equalized weight groups, wing-banded, and three replications of ten birds each were randomly distributed in chick batteries. The chicks were individually weighed at weekly intervals and feed consumption per lot was recorded. After having been on the test rations 28 days, the birds were sacrificed and their pancreases were excised and weighed. Statistical Procedure Significance of variations in growth, feed conversion and pancreas weight, as a percentage of body weight, were measured by analysis of variance (Snedecor, 1956) and Duncan's (1955) multiple range test. The 0.01 level of probability provides the basis for all statements concerning statistically significant differences. RESULTS AND DISCUSSION In the pre-experiment trial the urease analysis revealed that when dry (5.92 moisture) soybeans were heated with microwaves as outlined, the desired effects were not produced. Soybeans which were soaked in water for five minutes attained a moisture content of 15.32 and those soaked for 15 minutes 20.82. The results of the chemical analyses of meals derived from this second trial, in which soybeans of the two moisture levels were heated, is shown in Table 3 and Figures 1 and 2. In Figure 1, it can be seen that soybeans which contained 15.3% moisture prior to heating, required be- tween 14 and 16 minutes of heating before both the urease and PDI levels were in their respective recommended ranges (Rackis, 1968). As can be seen in Figure 2, no such commonality of indices resulted for the 20.82 moisture soybeans. From these results, it was ascertained that approximately 152 moisture was desirable for heating. The urease activity and protein dispersibility data derived from the third trial is presented in Table 4. In this trial, four batches of soybeans containing approximately 14.5% moisture were heated. The analysis of soybeans which had been heated for 15 minutes provided urease and PDI values which both approximated their recom-. mended ranges, therefore, the desirable heating time under this set of conditions was considered to be 15 minutes. 15 16 Table 3. Urease activity and PDI values of soybeans containing dif- ferent moisture levels and heated for various time periods 15.32 moisture 20.81 moisture Heating Urease activity PDI Urease activity PDI time (pH change) (2) (pH change) (Z) Raw 2.080 86.0 2.080 92.7 12 minutes 1.145 45.4 -- -- l4 " 0.145 29.8 0.465 39.6 16 " 0.015 16.0 0.030 26.0 18 " 0.015 12.1 0.010 15.4 20 " 0.005 10.0 0.005 12.1 17 Figure 1. Urease activity and PDI values of soybeans containing 15.3% moisture and heated for various time periods. .- UREASE ACTIVITY (pH change) P D I (96) 46 44 42 4O 38 36 34 32 28 26 24 22 20 I8 l6 I4 I2 Io 18 \ \ \ \ \ \ I I I I I I I I I \ \ \ \ \ \\PDI \\\ ureos ‘ activeity \ \ / \ \ I2 I4 l6 I8 20 HEATING INTERVAL (min) 19 Figure 2. Urease activity and PDI values of soybeans containing 20.8% moisture and heated for various time periods. iv in '4: '0: UREASE ACTIVITY (pH change) 20 PDI We) 38? \ 36- \ 32 . \ 30 - \ 28 b \ 26 - I 24 - \ 22 I- \\ 20 - \ I8 - \ I6 - \ PDI '4 ' urease \ I2 - ocIIVIIy IO- I2 I4 I6 IS 20 HEATING INTERVAL (min) 21 Table 4. Urease activity and PDI values of soybeans containing an equal moisture level (14.5%) and heated for various time periods Heating Urease activity PDI time (pH change) (I) 15 minutes 0.047 20.3 16 " 0.037 15.6 17 " 0.015 13.5 18 " 0.003 10.6 22 The data resulting from the chemical analysis of each of the 13 batches heated for the feeding trial and their moisture contents prior to heating can be seen in Table 5. As will be noted in the urease values for batches l and 6, there were some slight deviations.from the suggested ranges, however, these were negligible. Thus, all 13 batches were considered acceptable for use in the chick growth trial and were. combined together. When the three soybean sources were compared in alldmash broiler diets, chicks fed the diets containing commercial soybean meal were significantly greater in body weight gained than chicks fed the diet containing microwave heated soybeans (Table 6). Chicks fed the diet containing raw soybeans grew significantly less than birds fed the diets containing commercial soybean meal or microwave heated soybeans. Feed efficiency values did not vary significantly among those chicks receiving diets containing soybean meal or microwave heated soybeans (Table 6). Birds fed the diet containing raw soybeans were, significantly less efficient in feed utilization than those chicks whose diets included soybean meal or microwave heated soybeans. Chicks fed the diet containing raw soybeans manifested a marked enlargement of the pancreas when pancreas weight is expressed as a percentage of total body weight, hereafter referred to as pancreas weight (Table 6). Pancreas weights of chicks fed diets containing soybean meal or microwave heated soybeans were not significantly dif- ferent. The analyses of variance of chick weights, feed conversion and pancreas weights are provided in Tables 7, 8 and 9, respectively. 23 Table 5. Moisture content, urease activity and PDI values of soybeans heated and incorporated into chick diets Batch Moisture Urease activity PDI number (1) (pH change) (2) 1 15.1 0.028 15.5 2 13.7 10.054 17.0 3 15.1 0.078 18.5 4 13.1 0.050 15.7 5 14.7 0.046 16.3 6 14.0 0.030 16.1 7 15.4 0.058 17.4 8 15.4 0.085 20.2 9 16.0 0.050 18.8 10 16.6 0.103 20.6 11 15.5 0.095 18.8 12 15.2 0.080 19.8 13 16.0 0.109 19.1 Average 15.1 0.067 18.0 24 Table 6. Effect of different protein and supplemental energy sources on broiler performance and pancreas weight. 28-day body Diet weight gain Feed/ Pancreas weight number Protein-energy source (gms)a gain8 (2 bodywt.)a l Soybean meal-soybean oil 652.07 A 1.708 A .257 A 2 Soybean meal-animal fat 647.54 A 1.661 A .272 A 3 Microwave heated soybeans, 575.23 B 1.850 A .285 A 4 Raw soybeans-soybean oil 341.70 C 2.320 B .602 B aMeans bearing the same superscript do not differ significantly P < 0.01; means not having the same superscript are significantly different (P < 0.01). Table 7. Analysis of variance of 25 fourdweek chick weights Source of Degree of Sum of Mean variation freedom squares square F value Total 142 2,510,762 Subclass 14 1,864,951 133,211 26.405** Treatments 4 1,818,661 454,665 90.122** Replications 2 7,360 3,680 0.729 ,. T X R (Int.) 8 38,930 4,866 0.965 A Error 128 645,811 5,045 Standard error of mean - 13.282 ** Significant at the 0.01 level of probability 26 Table 8. Analysis of variance of feed conversion Source of Degrees Sum.of Mean F variation of freedom squares. square value Total 14 1.023 Treatment 4 0.837 0.20925 T x R (Int.) 10 0.186 0.01860 11.250** Standard error of mean - 0.0787 ** Significant at the 0.01 level of probability 27 Table 9. Analysis of variance of chick pancreas weights Source Degrees of Sum.of Mean of variation freedom squares square F ratio Total 142 2.876499 Subclass 14 2.455433 0.175388 53.509** Treatments 4 2.403426 0.600857 182.63l** Replications 2 0.010607 0.005304 1.612 T X R (Int.) 8 0.041400 0.005175 1.573 Error 128 0.421066 0.003290 Standard error of mean - 0.01072 ** Significant at the 0.01 level of probability 28 The results of this chick growth trial duplicate the results reported by Featherston and Rogler (1966). They compared chick diets containing ground infrared heated soybeans, which had been moisturized prior to heating, with diets containing soybean meal and soybean oil. The pancreas weight data of this trial also indicated that the factor(s) responsible for pancreatic enlargement had been destroyed by the in- frared heating process. The chicks fed the unextracted heated soy— beans.did not grow as rapidly as the chicks fed the basal diet with added soybean oil. Feed utilization of chicks fed the diets containing the heated soybeans in some instances approached that of chicks fed the basal diet with added soybean oil. Their failure to obtain comparable growth in chicks fed unextracted infrared heated soybeans with that in chicks fed a corn-soybean meal diet with equivalent soybean oil added, and the results of published studies indicating a need for mechanical pressure in the processing of-unextracted soybeans, led them to study the effects of pelleting and flaking in addition to the infrared heating of unextracted soybeans for chicks. The results of their study indicated that the heating of unextracted soybeans by infrared radiae tion when used in conjunction with some form of mechanical pressure resulted in an unextracted soybean meal which was well utilized by the chick. However, although the differences were not statistically significant, slightly better performance was obtained with a corn- soybean meal diet with an equivalent amount of oil added than could be obtained with the soybean product of any of the processing methods employed, which included pelleting, pelleting and regrinding, and flaking. 29 In addition, Hull 25 21, (1968) reported that when a diet con- taining infrared heated soybeans was pelleted and compared with the same diet in mash form, the pelleted diet resulted in significantly greater chick body weights. No significant body weight.differences existed when the pelleted, infrared heated soybean diet was compared with a pelleted soybean meal-soybean oil diet. Pelleting did not significantly improve the feed efficiency of diets containing soybean meal-soybean oil over that of mash form, but it significantly improved the feed utilization of chicks fed diets containing infrared heated soybeans. The differences in feed efficiency which occurred when come paring pelleted soybean meal-soybean oil diets with pelleted infrared heated soybean diets were insignificant. Carew 35 51. (1961) found that by compressing cracked soybeans into very thin flakes prior to autoclaving and including them in chick diets, the availability of the soybean oil in soybeans for chicks could be markedly improved, to the extent that the absorbability of the oil present in the soybeans closely approached that of soybean oil fed as such. Autoclaved, unextracted soybean flakes were found to be equally as effective as equivalent amounts of soybean meal and soybean oil in their ability to stimulate chick growth and improve the effi- ciency of feed utilization. In contrast to results with autoclaved, unextracted soybean flakes, autoclaved, ground unextracted soybeans were less effective. The poorer results obtained with autoclaved ground, unextracted soybeans were shown to be related to a poorer absorbability of the oil present in them. These investigators indi- cated that apparently the maximum value from autoclaved soybeans as a 30 poultry feed ingredient can be obtained only if a processing method is used that will allow’maximum availability of the soybean oil present in them. Numerous other investigators have reported that maximal chick growth or feed utilization has not been obtained as a result of the feeding of heated unextracted soybeans, and have experienced a marked improvement in chick performance as a result of the use of mechanical pressure in addition to heating in the processing of soybeans (Carew gt g” 1959; Renner and Hill, 1960; Carew and Nesheim, 1962). The results of these preceding studies imply that mechanical pressure may supplement microwave heating of soybeans to improve the body weight gained and feed efficiency derived in comparison to that obtained from the feeding of ground microwave heated soybeans to chicks. It is possible that flaking the moisturized soybeans prior to subjecting them to microwave heating, rather than grinding the microwave heated beans, or pelleting the diet containing ground, microwave heated beans would increase the nutritional value of the soybeans to the chicks by causing a greater rupture of the cells with a concommitant increase in nutrient digestibility. SUMMARY This research was conducted to evaluate microwave heating as.a method of processing unextracted soybeans for inclusion in broiler diets. The-desirable soybean moisture content and heating interval were defined on the basis of chemical analyses. It was determined that microwave heating effectively reduced the urease activity and protein dispersibility of moisturized, unextracted soybeans to levels con- sidered to be desirable for chick growth performance. A diet con- taining microwave heated soybeans was compared with soybean meal diets adjusted with soybean oil or animal fat to be isocaloric and a raw soybean diet made isocaloric with soybean oil. All diets were formu- lated to be isonitrogenous. The heated soybeans replaced all the soybean protein and the soybean oil or animal fat. Chicks fed the microwave heated soybeans performed, in reference to feed conversion and.pancreas weight, equally as well as chicks fed the control soybean meal diets and better than chicks fed the raw soy- bean diet. However, chicks fed the microwave heated soybeans did not grow as rapidly as the chicks fed either of the soybean meal control diets, but grew more rapidly than chicks fed the raw soybean diet. 31 LIST OF REFERENCES LIST OF REFERENCES American Oil Chemists' Society, 1965. Official and Tentative Methods. Vol. 1, 3rd ed., revised to 1965. The Society: Chicago, Ill. Borchers, R., C. W. Ackerson, R. M. Sandstedt and L. Kimmett, 1947. Trypsin inhibitor. III. Determination and heat destruction of the trypsin inhibitor of soybeans. Arch. Biochem. and BiOphys. 12: 367-374. Carew, L. B., Jr., R. Renner and F. W. Hill, 1959. Growth stimulating effect of soybean oil and unextracted soybean flakes in chick rations. Poultry Sci. 38: 1183-1184. Carew, L. B., Jr., F. W. Hill and M. C. Nesheim, 1961. The comparative value of ground unextracted soybeans and heated dehulled soybean flakes as a source of soybean oil and energy for the chick. J. Am. Oil Chem. Soc. 38: 249-253. Carew, L. B., Jr., and M. C. Nesheim, 1962. The effect of pelleting on the nutritional value of ground soybeans for the chick. Poultry Sci. 41: 161-168. Combs, G. F., 1960. Practical broiler ration studies. Proc. 1960 Univ. of Md. Nutr. Conf., p. 71-80. Doty, H. 0., Jr., 1965. Cooked soybeans for feed. U. S. Dept. Agr., Economic Research Service No. 228, 8 pages. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics Evans, R. J. and J. L. St. John, 1945. Estimation of the relative nutritive value of vegetable proteins by two chemical methods. Featherston, W. R. and J. C. Rogler, 1966. A comparison of processing conditions of unextracted soybeans for utilization by the chick. Poultry Sci. 45: 330-336. Flegal, C. J. and R. L. Adams, 1969. Feed ingredient analysis table - 1969. Cooperative Extension Service, Michigan State University. Fritz, J. C., E. H. Kramke and C. A. Reed, 1947. Effect of heat treat- ment on the biological value of soybeans. Poultry Sci. 26: 657-661. 32 33 Hayward, J. W., H. Steenbock and G. Bohstedt, 1936. The effect of~ heat as used in the extraction of soybean oil upon the nutritive value of the protein of soybean oil meal. J. Nutr. 11: 219-234. Hill, F. W. and R. Renner, 1958. Studies of the metabolizable energy of soybean products for the chick. Poultry Sci. 37: 1212. Hull, 8. J., P. W. Waldroup and E. L. Stephenson, 1968. Utilization of unextracted soybeans by broiler chicks. 2. Influence of pelleting and regrinding on diets with infrared cooked and ex- truded soybeans. Poultry Sci. 47: 1115-1120. McGinnis, J. and R. J. Evans, 1947. Amino acid deficiencies of raw and over-heated soybean oil meal for chicks. J. Nutr. 34: 725-732. Mustakas, G. C., E. L. Griffin, Jr., L. E. Allen and 0. B. Smith, 1964. Production and nutritional evaluation of extrusion-cooked full- fat soybean flour. J. Am. 011 Chem. Soc. 41: 607-614. Nesheim, M. C., 1961. The metabolizable energy values of full-fat soybean products. Cornell Feed Service No. 54: 13-14. Osborne, T. 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Cornell Feed Service No. 56: 11. ll‘ l I |I|| I I|| Ill l0 || l1 II III III | 0 ll lull Ill Illz II ‘6 | 0 ll III II II|3 l.|| 'IIII Io IIII II 3 ll ll I‘ll l9 ||l| Illll | l IIII III | I III II || Ill l I 1 || I ll