-— -—-'v_ '———— V PROPIONIC ACID TREATMENT OF CORN SILAGE HARVESTED AT MEDIUM AND HIGH“ DRY MATTER STAGES OF MATURITY Thesis for the Degree of M. S. MICHIGAN STATE UNIVERSITY MOHAMAD SOEJONO ’ ' 1976 APR I 0 I994 ABSTRACT PROPIONIC ACID TREATMENT OF CORN SILAGE HARVESTED AT MEDIUM AND HIGH DRY MATTER STAGES OF MATURITY BY Mohamad Soejono The present experiment (Exp. 4) was conducted with corn silage harvested at 35 and 45% dry matter to evaluate the effectiveness of propionic acid in improving the preser— vation and feeding value for lactating dairy cows when fed as the sole forage. This experiment was combined with three previous studies conducted at Michigan State Univer- sity with corn silages (ranging in dry matter from 35 to 45%) which were treated with organic acids at 0.3 and 0.6%. After ensiling, whole chopped corn (35 and 45% DM) with or without 0.6% propionic acid, thermocouples were placed in centers of each silo at heights of 2.5, 5.0 and 7.5 m and temperatures were monitored daily during the first five weeks of fermentation. PrOpionic acid resulted cooler silage at all heights, both at 35 and 45% DM. Silage and total dry matter intakes were not sig- nificantly different at either dry matter level, but cows receiving propionic treated silage consumed slightly more Mohamad Soejono than the corresponding controls. Milk yields again favored groups fed propionic treated silage, even though differ- ences were not significant. Milk composition was not sig- nificantly different among groups, even though all milk constituents were slightly higher during treatment than standardization. No difference of the pH values due to the treatment were noted at 35 or 45% DM. Lactic acid pro- duction was significantly different (P < 0.05) between dry matter levels, but the propionic effect was not significant (P < 0.1). During the feeding trial, temperatures were also monitored. For all depths control silages were higher than the prOpionic silages (P < 0.05) at both levels of dry matter. Upon exposure to air, lactic acid concentrations were decreased in all silages and no difference between treatments were detected for the rates of decrease. The pH values of all silages increased during refermentation, differences between controls and treatment were not sig- nificant, but there was a trend toward higher pHs for untreated silages. The number of fungal colonies during refermentation was significantly decreased (P < 0.01) by propionic treatment of 45% DM silage. Initial fungi of untreated silages were also higher for 45% than 35% DM. Visual fungal growth were present on days 6 and 10 for 35% DM control and treated_silages, respectively, and on days 7 and 14 for the respective high dry matter silages. Mohamad Soejono Propionic treatment also resulted in slightly cooler silage during refermentation, but differences were not significant. Pooling of animal data from experiments 2, 3 and 4 showed that propionic acid treatment increased silage dry matter intakes 12% (P < 0.01), total intakes 6% (P < 0.05) and milk persistency 5% (P < 0.05). PROPIONIC ACID TREATMENT OF CORN SILAGE HARVESTED AT MEDIUM AND HIGH DRY MATTER STAGES OF MATURITY BY Mohamad Soejono A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Dairy Science 1976 ACKNOWLEDGMENTS The author very sincerely wishes to express his deepest appreciation to Dr. J. T. Huber for the excellent guidance, encouragement and invaluable assistance through- out his graduate program toward the completion of this thesis. The author would also like to express his appreci- ation to Dr. C. E. Meadows and Dr. M. B. Tesar as members of his graduate committee, for their assistance, advice, suggestions, and participation in his graduate program. The author wishes to thank Dr. C. A. Lassiter and Dr. Russ Erickson for making the facilities at Michigan State University and the Michigan Agricultural Experiment Station available for this research. Appreciation is also extended to Dr. Roger Neitzel, Judy Ball, Carol Roney, Becky Winters, and Tim Middleton for their assistance with this research. The author wishes to extend his sincere gratitude to his wife, Sri Kadarsih, daughter, Arianti, and son, Radityo Djati, for their sacrifices, patience and encourage- ment throughout his graduate program. ii Last, but not least, the author wishes to express his appreciation to the Government of Indonesia, the Midwest Universities Consortium for International Activ- ities, Inc. (MUCIA) and Gadjah Mada University for pro- viding the leave of absence and the financial support for his graduate program. iii TABLE OF CONTENTS LIST OF TABLES . . . . . . . . . . . . . . . . . . . LIST OF FIGURES . . . . . . . . . . . . . . . . . . INTRODUCTION . . . . . . . . . . . . . . . . . . . . LITERATURE REVIEW . . . . . . . . . . . . . . . . . Effect of Corn Plant Maturity on Silage Quality Dry Matter Yields Per Acre (hectare) . . . . Feed Intake 0 O I O O O I O O O O O O O O 0 Production and Composition of Milk . . . . . Gain 0 O O O O O O O O O O O O O O O O O O O Controlling Silage Fermentation . . . . . . . . Lactic Acid Production . . . . . . . . . . . Temperature . . . . . . . . . . . . . . . . Organic Acids for Preserving Grains and Forages Organic-Acid-Treated High Moisture Grains . Animal Performance . . . . . . . . . . . Preservative Effects . . . . . . . . . . Organic Acid-Treated Forages . . . . . . . . Animal Performance . . . . . . . . . . . Preservative Effects . . . . . . . . . . Significance of Fungal Contamination of Feeds . . . . . . . . . . . . . . . . . . Summary of Literature Review . . . . . . . . . . iv Page vi ix .5 OxlU'luh 10 10 12 13 13 16 22 23 28 33 35 Page MATERIALS AND METHODS . . . . . . . . . . . . . . . . 37 1970-1971 Experiment (Experiment 1) . . . . . . . 37 Silage Treatments . . . . . . . . . . . . . . 37 Animal Trials . . . . . . . . . . . . . . . . 38 1971-1972 Experiment (Experiment 2) . . . . . . . 39 Silage Treatments . . . . . . . . . . . . . . 39 Animal Trials . . . . . . . . . . . . . . . . 40 1972-1973 Experiment (Experiment 3) . . . . . . . 4O Silage Treatments . . . . . . . . . . . . . . 41 Animal Trials . . . . . . . . . . . . . . . . 41 Present Experiment (Experiment 4) . . . . . . . . 42 Ensiling Techniques and Temperature Measurements . . . . . . . . . . . . . . . . 42 Animal Trials . . . . . . . . . . . . . . . . 43 Refermentation Trial . . . . . . . . . . . . . 44 Chemical Analyses . . . . . . . . . . . . . . 44 Milk Analyses . . . . . . . . . . . . . . . . 46 RESULTS . . . . . . . . . . . . . . . . . . . . . . . 48 Animal Performance . . . . . . . . . . . . . . . . 48 Experiment 1 . . . . . . . . . . . . . . . . . 48 Experiment 2 . . . . . . . . . . . . . . . . . 51 Experiment 3 . . . . . . . . . . . . . . . . . 55 Experiment 4 . . . . . . . . . . . . . . . . . 55 Pooled Data . . . . . . . . . . . . . . . . 59 Preservative Effects . . . . . . . . . . . . . . . 62 Experiment 1 . . . . . . . . . . . . . . . . . 62 Experiment 2 . . . . . . . . . . . . . . . . . 64 Experiment 3 . . . . . . . . . . . . . . 64 Experiment 4 . . . . . . . . . . . . . . . 64 DISCUSSION . . . . . . . . . . . . . . . . . . . . . . 87 SUMMARY . . . . . . . . . . . . . . . . . . . . . . . 93 LITERATURE CITED . . . . . . . . . . . . . . . . . . . 94 LIST OF TABLES Table Page 1. Influence of organic acids and urea addition to medium dry matter corn silage (35-39%) on dry matter intakes of lactating cows (Experiment 1) . . . . . . . . . . . . . . . . 49 2. Influence of organic acids and urea additions to medium dry matter corn silage (35-39%) on milk yields and body weight gains of lactating cows (Experiment 1) . . . . . . . . 50 3. Influence of organic acids and urea addition to medium dry matter corn silage (35-39%) on milk composition of lactating cows (Experiment 1) . . . . . . . . . . . . . . . . 52 4. Influence of organic acids and urea addition to high dry matter corn silage (44-46%) on dry matter intakes and body weight gains of lactating cows (Experiment 2) . . . . . . . 53 5. Influence of organic acids and urea addition to high dry matter corn silage (44-46%) on milk yields of lactating cows (Experi- ment 2) . . . . . . . . . . . . . . . . .'. . 54 6. Influence of propionic acid and water additions to high dry matter corn silage (44%) on dry matter intakes and body weight gains of lactating cows (Experiment 3) . . . . . . . . 56 7. Influence of prOpionic acid and water additions to high dry matter corn silage (44%) on milk yields of lactating cows (Experiment 3) . . . 57 8. Influence of propionic acid addition to medium and high dry matter corn silage (35 and 45%) on dry matter intake and body weight gains of lactating cows (Experiment 4) . . . . 58 vi Table Page 9. Influence of prOpionic acid addition to medium and high dry matter corn silage (35 and 45%) on milk yields of lactating cows (Experiment 4) . . . . . . . . . . . . . . . . 60 10. Influence of propionic acid addition to medium and high dry matter corn silage (35 and 45%) on milk composition of lactating cows (Experiment 4) . . . . . . . . . . . . . . . . 61 11. Influence of propionic acid addition to high dry matter corn silage (44-46%) performance of lactating cows for the three experiments . 62 12. Influence of organic acids and urea additions to medium dry matter corn silage (35-39%) on pH and lactic acid production (Experi- ment 1) . . . . . . . . . . . . . . . . . . . 63 13. Influence of organic acids and urea addition to high dry matter corn silage (44%) on lactic acid production (Experiment 2) . . . . 65 14. Influence of propionic acid and water additions to high dry matter corn silage (44%) on temperature (Experiment 3) . . . . . 66 15. Influence of propionic acid addition to medium and high dry matter corn silage (35 and 45%) on pH and lactic acid production (Experi- ment 4) . . . . . . . . . . . . . . . . . . . 67 16. Influence of propionic acid addition on mean temperature of 35% corn silages during first five weeks of fermentation (Experi- ment 4) . . . . . . . . . . . . . . . . . . . 68 17. Influence of propionic acid addition on mean temperature of 45% corn silages during first five weeks of fermentation (Experi- ment 4) . . . . . . . . . . . . . . . . . . . 76 18. Influence of propionic acid addition on mean temperatures of low and high dry matter corn silage (35 and 45%) during the feeding-out period (Experiment 4) . . . . . . . . . . . . 80 vii Table Page 19. Influence of propionic acid addition on lactic acid concentration (% of DM) of low and high dry matter corn silage (35 and 45%) during refermentation (Experiment 4) . . . . . . . . . . . . . . . . 81 20. Influence of prOpionic acid addition on pHs of medium and high dry matter corn silage (35 and 45%) during refermentation (Experiment 4) . . . . . . . . . . . . . . . . 82 21. Number of fungal colonies (per 9/105) during refermentation of medium and high dry matter corn silage (35 and 45%) treated with and without propionic acid (Experiment 4) . . . . 84 22. Number of days until fungi were noted and complete spoilage on medium and high dry matter corn silage (35 and 45%) treated with and without prOpionic acid during refermentation (Experiment 4) . . . . . . . . 85 23. Influence of propionic acid addition on mean temperatures of medium and high dry matter corn silage (35 and 45%) during refer- mentation (Experiment 4) . . . . . . . . . . . 86 viii Figure 1. LIST OF FIGURES Temperature development of control and propionic corn silage (35% DM) during fermentation at a height of 7.5 m (top) (Experiment 4) . . . . . . . . . . . . . . ‘Temperature development of control and propionic corn silage (35% DM) during fermentation at a height of 5.0 m (middle) (Experiment 4) . . . . . . . . . . . . . . Temperature development of control and propionic corn silage (35% DM) during fermentation at a height of 2.5 m (bottom) (Experiment 4) . . . . . . . . . . . . . . Temperature development of control and propionic acid corn silage (45% DM) during fermentation at a height of 7.5 m (top) (Experiment 4) . . . . . . . . . . . Temperature development of control and propionic acid corn silage (45% DM) during fermentation at a height of 5.0 m (middle) (Experiment 4) . . . . . . . . . Temperature development of control and propionic acid corn silage (45% DM) during fermentation at a height of 2.5 m (bottom) (Experiment 4) . . . . . . . . . Temperature development during the feeding trial of control and propionic acid treated corn silage (35 and 45% DM) at a depth of 10 cm (Experiment 4) . . . . . Temperature development during the feeding trial of control and propionic acid treated corn silage (35 and 45% DM) at a depth of 20 cm (Experiment 4) . . . . . . ix Page 70 71 72 73 74 75 77 78 Figure Page 9. Temperature development during the feeding trial of control and propionic acid treated corn silage (35 and 45% DM) at a depth of 30 cm (Experiment 4) . . . . . . . . 79 INTRODUCTION Silage is a basic roughage constituent of cattle feeding systems in the United States. Over the past 15 years, in areas of the United States and Canada suited for corn production, there has been almost a doubling in the use of corn silage for dairy and beef cattle (Huber, 1974). This increase in corn silage production can be attributed to (1) greater energy yields per acre when harvested as corn silage over shelled corn or any other grain, (2) consistently high digestibilities of corn silage, (3) increased feed efficiency over other type of feedstuffs and (4) mechanically handling of harvesting, storage and feeding, thus minimizing labor requirements (Geasler and Henderson, 1969; Hemken and Vandersall, 1967; Huber, 1974). Due to the high proportion of total forage on dairy farms that is corn silage, attention should be given to the stage of maturity or time of harvest which will result in the most efficient use of land, labor, storage facilities and equipments. Gordon et a1. (1968) comparing normal and late harvested of corn for silage found that high quality silage could be produced with late harvesting but it would be impractical due to high field losses. Similar results were obtained by Marx (1969). However, corn silage, as known today is not the ultimate material to be fed. The chopped corn plant is a more desirable feedstuff than the ensiled material, due to fermentation changes (Wilkinson et al., 1976) and losses. Much of the materials involved in these losses could be utilized by the beef animal (Geasler and Henderson, 1969), but at present there is no method by which these losses can be totally prevented. Therefore, we have turned to investigation of methods which will minimize these losses and still produce the most desirable fermentation. Many problems of efficient feed storage are directly or indirectly related to growth of aerobic micro— organisms (especially fungi) when forages are stored between 25 and 50% moisture and grain between 14 and 40% moisture (Goering and Gordon, 1973). Traditionally, these problems have been minimized by either reducing moisture content below critical amounts or keeping the moisture con- tent high enough to more easily obtain an anaerobic con- dition. It would be a great convenience, and in many cases an economy, if storage systems could be develOped for grains and forage that would allow aerobic storage within a medium moisture range without fear of losses from fungal growth. Several chemicals have been identified as having fungistatic or fungicidal properties (Britt et al., 1975; Candlish et al., 1973; Fellows, 1971; Forsyth et al., 1970; Goering and Gordon, 1974; Huber et al., 1972; Sleiman et al., 1972). Storing and feeding high moisture corn treated with organic acids have been reported by several research workers (Christensen, 1973; Goering and Gordon, 1974; Sleiman et al., 1972; Lessard et al., 1970). Also storing and feeding organic acid treated corn silage have been done by research workers (Huber et al., 1972; Sleiman, 1972; Waldo et al., 1975). A large part of the corn silage crop is harvested late in the season when dry matter is too high for good preservation. Consequently, much of the silage fed from such silos has gone through excessive fermentation or has molded, carmelized and is of poor nutrient value (Huber, 1974). Also, inhibition of normal fermentation with propionic or other acids might improve the nutritive value of silage harvested at optimum dry matter by inhibiting proteolysis and acid production to depress silage intakes and efficiency of nutrient utilization. The objectives of this thesis were to determine the effectiveness of organic acids in improving the preservation of corn silage harvested at varying dry matter levels (35 to 45%). Also to assess the feeding value of organic acids treated corn silage for lactating dairy cows when harvested at two stages of maturity. LITERATURE REVIEW Effect of Corn Plant Maturity on Silage Quality Harvesting at the prOper stage of maturity assures the maximum content of protein, minerals and vitamins, and the higheSt digestibility and the best preservation. Several research workers have studied the effect of stage of maturity of the corn plant at time of harvest for silage on its yields, acceptability and digestibility. Dry Matter Yields Per Acre (hectare) Henderson (1969) showed that the dry matter yield per acre increases until it reaches approximately 35% or until the first killing frost. It will then level off for 5-10 days (depending upon the extent of frost, wind and rain) and then begin declining at a rapid rate. Huber (1974) found that total dry matter in the corn plant increases until accumulation of starch in the kernels is complete. At this maturity the greatest nutrient yields per acre are obtained and total plant dry matter content ranges between 34 and 38%. If the harvest is delayed after this optimum stage, there is a decrease in yield of nutrients primarily due to falling of ears from the plants. 4 Caldwell and Perry (1971) stated that for both years of their experiments, the maximum yield of dry matter per hectare occurred at the time when the whole plant contained 33% dry matter. Various criteria have been used to determine the proper time of harvesting corn silage. Maximum yield of dry matter (Johnson et al., 1966) and of digestible energy (Johnson and McClure, 1967) have been reported between the dent and glaze stages. Gay (1966) and Keeney et a1. (1967) found that the late dent-hard, dough state gave maximum dry matter yields. However, Pratt et a1. (1964) measured no differences in dry matter yield between the late milk, early dough and the well-dented stage. In addition, Geasler et a1. (1967) reported a decrease in dry matter yield with increasing maturity when 28, 45 and 60% dry matter silages were compared. Obviously, highest yields would have occurred between 33 and 37%. Feed Intake Huber et a1. (1965) reported the effect of maturity of corn silage on intakes of lactating cows. The corn was harvested at soft, medium and hard dough and the silage was fed ad libitum to 18 lactating cows as the only forage in two trials. Each trial consisted of two periods. During one period cows received soybean meal as the only supple- mental feed. A concentrate mixture (containing 16% crude protein) was fed a 1 kg per 3.5 kg milk during the other period. Dry matter content of the respective maturities averaged 25.4, 30.3 and 33.3%. Dry matter intakes of silage were significantly increased with advancing maturity and were probably responsible for higher milk production. Differences due maturity were greater when cows were supplemented with only soybean meal. Gay (1966) also found that the maximum dry matter intake was in the hard dough stage. In contrast, Noller et a1. (1963) harvested two different stages of maturity of corn plant for silage fed to Holstein steers. They found the maximum dry matter consumption occurred with very early dent stage compared to late dent. Bryant et a1. (1965) compared corn plant harvested at milk (21.7% DM) and medium hard dough (31.8% DM) stages of maturity for silage and found that dry matter consumption was higher at medium hard dough than milk, so it could be concluded that dry matter consumption increased with increasing maturity. The same result was stated by Geasler et al. (1967). Another study was conducted by Marx (1969) who harvested corn plant material for silage at two different stages of maturity. The first harvest was called early cut with 31% dry matter and the second harvest was late cut with 51.9% dry matter. The difference between two stages of maturity was six weeks and he found that dry matter intake of early cut silage was significantly lower than late cut silage. With gas-tight silos Gordon et a1. (1966) observed slightly higher intakes of silage containing 27% dry matter compared to 55%, but the difference was not significant. The above studies support the summary of Boman (1975) which showed that intake of corn silage increased linearly up to about 35-37% dry matter, plateaued to 43-45% and then gradually declined. Production and Composition of Milk Montgomery et a1. (1974) harvested corn plants in three successive years at the early dough, late dough and mealy endosperm stages. Differences among years in date of harvest and dry matter content of the silage were due to the time at which the corn was planted in the spring and to variability in growing seasons and moisture con- ditions at harvest time. The silages, cut at three stages of maturity were fed to Jersey cows, with concentrate at 1 kg/3 kg of fat corrected milk. No significant differ- ences in milk production were detected between treatments. Byers and Ormiston (1964) harvested corn for silage at 31.5% DM (control) and 54.9% DM (mature) and fed these ad libitum to lactating dairy cows. Also, limited alfalfa hay, and about 1 kg of grain to 2.5 kg of milk were fed. Milk production on a two silages was not A significantly different. It was suggested that mature corn silage can be used as a forage extender but that extra care in making the silage is needed to insure a fine chop and air tight storage by packing well in the conventional tower silos. Huber et a1. (1965) found that when corn plant was harvested at soft, medium and hard dough and fed ad libitum to three groups of lactating Holstein cows as the only forage, milk yields increased significantly with dry matter content of the silages. No significant effect due maturity of silage was noted in milk composition and efficiency of milk production. Virginia studies (Bryant et al., 1965) revealed an advantage in daily milk yields from cows fed a particular corn variety harvested for silage in the hard dough compared to the milk stage. A 5 to 10% improvement in milk yields was associated with an increase in dry matter intake of 10-20%. Similarly, Owens et a1. (1967) harvested corn for silage at three different stages of maturity (low--25—29% DM, medium--36-39% DM and high-- 54-73% DM) and reported that milk production was highest for cows fed high dry matter silage with no difference in milk fat or solids-—not fat percentages. In this experi- ment (Owens et al., 1967) high dry matter silages were ground with a hammer mill using a 3.8 cm screen before ensiling and silages were stored in gas-tight units. In 1969, Marx noted that milk fat and solids—-not fat per- centages were not significantly different between groups of lactating cows fed early out silage (31% DM) or late cut silage (51.9% DM). Gain In studies with fattening beef cattle (Geasler, 1970), cattle gains were higher from silage harvested at 28% DM compared to 48% or 60%. Silage dry matter intakes were slightly higher for the two drier silages, but efficiency of gain was greater at 28% DM. Chamberlain et a1. (1971) harvested corn plants for silage at four stages of maturity: (1) late milk (approximately 90% of the kernels were in the late-milk stage), (2) early dough (approximately 90% of the kernels were dented), (3) late dough (when all kernels were dented) and (4) mealy endosperm (approximately 35% moisture in the grain). These silages were fed ad libitum to growing heifers together with 0.9 kg hay and 0.7 kg cottonseed meal per head per day. Result indicated that corn plant maturity between late milk and late dough did not affect the average daily gain. There was a significant reduction in average daily gain at the mealy endosperm stage. No significant effect due to maturity of silage was noted in body weight gains by Byers and Ormiston (1964) or Huber et a1. (1965). 10 Controlling Silage Fermentation The feeding value of corn silage is determined almost entirely by the degree and type of fermentation it undergoes and many factors that regulate fermentation can be controlled. Lactic Acid Production Products of silage fermentation are the metabolic end products of bacterial life and the bacteria per se. The most important points in bacterial control of silage fermentation are associated with production of lactic acid. The production of lactic acid occurs in the rumen from the fermentation of ingested food and in the silo from the fermentation of ensiled materials. Silage is an important source of lactic acid for domestic ruminants (Mackenzie, 1967). Sugar, hemicellulose and organic acids in the ensiled materials are fermented anaerobically to lactic acid by bacteria. The main species involved are £3252: bacillus, Peddicoccus, and Streptococcus (Langston et al., 1962). Smaller quantities of the other acids (formic, acetic, propionic, butyric, and succinic) are also produced (Archibald, 1953; Ekern and Reid, 1963; Gordon et al., 1963; Miller et al., 1962). The lactic acid content of silage varies due to differences in composition of ensiled material and to variations in the ensiling process (Klosterman et al., 1961; Shearer and Cordukes, 1962). Generally, lactic acid comprises from 2 to 10% of dry 11 matter content of good quality silage (Archibald, 1953; Elliot et al., 1957; Geasler and Henderson, 1969; Kloster- man et al., 1961; Shearer and Cordukes, 1962), but it can range from less than 1% to more than 16% (Mackenzie, 1967). According to Barnett and Duncan (1954), poor quality silages are high in VFA content and low in lactic acid. To prevent the formation of butyric acid, they recommended compressing the materials to make the silo more air tight. Temperature Silage temperature affects the bacterial activity and the resulting level of lactic acid produced during fermentation, as well as preservation of the protein and energy in the silage. Lactic acid producing bacteria are most active at temperatures of approximately 43°C. Bac- terial activity is slowed down in direct relationship to the reduction in temperature below 43°C and fermentation virtually ceases at temperatures below 15°C. With increasing temperatures, bacterial activity is again slowed down and virtually ceases above 54°C (Henderson, 1973; Man, 1953; Wieringa, 1959). With good packing and oxygen free storage, silo temperatures will not normally exceed 43°C. Langston et al. (1960) observed that aerated silages showed higher temperatures and were of poorer quality than the sealed silages. The sealed silages which 12 were trampcd and weighed gave little temperature increase. They also found that aerated silages had high pH values with increased butyric acid and NH3-N. Ohyama et a1. (1973) studied the effects of temp— erature and glucose addition on grass silage fermentation. They found that when no glucose was applied, silages held at 30°C were without exception of very poor quality, while those kept at 15°C were generally of fairly good quality. The addition of 2% glucose at ensiling resulted in excel- lent quality silage at both 15°C and 30°C. At 30°C, lactic acid was produced rapidly, pH decreased and silage reached a stable state in a short time. On the other hand, at 15°C, though the lactic acid formation was not so rapid in the early stages, the final products contained large amount of lactic acid and little acetic with a low pH value. Thus, the effects of glucose addition are related to the silage temperature, and its addition can overcome the deteriorating effect of-the higher tempera- ture. Organic Acids for Preserving Grains and Forages Organic acids recently have become available for preserving grains and forages. Various acids are used, such as: sulfuric, hydrochloric, phosphoric, formic, acetic, propionic, butyric, or mixtures of these. 13 Organic-Acid-Treated High MOisture Grains Since the late 19605 when British Petroleum Ltd. announced the usefulness of propionic acid for the long term preservation of high moisture grain under practical conditions, the use of volatile fatty acids (VFA) for improving the storage life and enhancing the nutrient value of high moisture grains has been widely accepted (Anonymous, 1968). Animal Performance There has been an increasing interest in the use of corn, sorghum grain, barley, wheat and oats as high moisture grains for various classes of livestock. The storage of high moisture grains in sealed silos or bins has been relatively successful, but mold spoilage occurs when these structures are Opened and grains are exposed to air (Ingalls et al., 1974). Recently, interest has developed in the application of several kinds of organic acids or their mixtures to high moisture grains. These decrease microbial activity (mainly fungi) and allow grain storage under conditions similar to those required for dry grain. In 1970, Jones et a1. fed high moisture shelled corn (66.7% DM) preserved with 1.5% propionic acid as part of the ration for 12 lactating dairy cows and seven growing dairy heifers. Ensiled high moisture shelled corn 14 was fed to control groups. Fat-corrected milk yield, persistency of milk production, milk fat and protein per- centage in lactating cows, and rate of gain in dairy heifers were not significantly different between rations. Mold counts were 1 and 1200 colonies/g, respectively, for the propionic treated and ensiled, untreated corns. There were no adverse effects of propionic acid treatment upon animal health or performance. In another experiment, Forsyth et a1. (1972) har- vested shelled corn at approximately 70% CM, sprayed with propionic acid at a rate of 1.5% by weight and stored on a barn floor. Crossbred steers and lactating dairy cows were utilized in a feeding trial to compare high moisture corn preserved with propionic acid to dry corn. Acid-treated, high moisture corn was more efficient for weight gains than dry corn. There was no significant difference in milk production or milk composition, but a slight drop in milk fat percent with the treated corn ration was noted. Jones (1973) preserved 34% moisture shelled corn with 1.5% propionic acid, stored on a concrete barn floor, and subsequently mixed into a concentrate ration. He found no adverse effect of treatment on animal health. Feeding value of high moisture shelled corn treated with propionic acid at harvest equalled that of dry shelled or ear corn 0 15 McLeod et a1. (1974) compared for dairy cows dry shelled corn, high moisture shelled corn (24% moisture) treated with 0.95% prOpionic acid or a 40-60 mixture of acetic-propionic acid (1.15%). Actual and solids corrected milk, milk fat, protein and forage dry matter intakes were not significantly different between groups fed the three types of corn. Moreover, rations had no apparent effect on body weight changes or animal health. They concluded that corn preserved by either acid treatment was equal in feeding value to dried shelled corn for lactating dairy cows. Similar results were reported by Chandler et a1. (1975) and Clark et a1. (1975). McCaffree (1968) and Larsen (1972) found no significant difference in milk yields, dry matter intakes or milk fat percent between cows fed propionic treated or untreated high moisture ear corn. In apparent contrast, Rook et a1. (1965) observed a depression in milk yields and milk fat percent after intraruminal infusion of propionic acid. Several studies have been conducted on the effect of corn preserved with propionic acid when fed to pigs. Young et a1. (1970) treated high moisture corn containing approximately 76% DM with 1.5% propionic acid and stored the material in bins open to air. Pigs fed treated corn gained at a similar rate and had equal or better feed efficiencies than pigs fed dry corn (90% DM). Witting (1974) found that pigs tolerated a high concentration of 16 propionic acid in their feed. Moreover, he reported high digestibilities for treated maize and that pigs fattened better on moist maize preserved with propionic acid than on dried maize. Jones et a1. (1970) reported that propionic acid treated shelled corn (66.7% DM) resulted in greater gains by pigs than untreated corn. Preservative Effects Although the antifungal properties of organic acids have been known for many years (Byrde, 1969) and a number of recent articles have alluded to their preser- vation of moist grain, published reports verifying such activity are few (Hertig and Drury, 1974). Cameron reported in 1945 that the addition of butyric acid to water used to condition grain samples effectively supressed mold growth. Jones (1971) reported preservation of high moisture corn (72.1% DM) with a mixture of acetic, propionic and butyric acids. The preservative containing a high proportion of acetic acid appeared equal to one high in propionic acid. Seven days after treatment with VFA, there was no detectable heating of the treated corn sam- ples but heat, mold formation and an off-smell were detected in the untreated corns. However, the presence of butyric acid in the preservative may not be desirable due to its objectionable odor. Marion et a1. (1972) observed that moist grain (70% DM) treated with 2% propionic acid, and stored in 17 open barrels did not heat or show visible mold growth after it was ground and mixed with the ration. The ration containing untreated moist grain heated within eight hours and was moldy and fermented in four days. Sauer (1972) conducted an experiment with yellow corn harvested at 22% moisture content (78% DM) and treated with 0.4% propionic acid or 0.8% acetic acid. He found that there was no detectable mold growth by six months at 25°C. Lower levels of acid prevented molds growth for shorter periods. Types of fungi which grew in grain treated with insufficient amounts of acids were similar to those in untreated grain, but the species diversity was not as great as in treated grains. Jones (1973) noted that there was no visible deterioration of high moisture shelled corn (66.5% DM) treated with 1.5% propionic acid, stored for 19 months on a concrete barn floor. Propionic acid was added to moist cereals to inhibit microbial and enzymic breakdown (Furner, 1974). The mold content of corn containing initially 32% moisture (68% DM) and stored for five months was progressively reduced by adding 0.5 or 1.1% propionic acid. The amount of preservative needed depended on the initial moisture content of the cereals (ranging from 16 to 45%) and the intended length of storage. For long term preservation 18 (more than six months) the maximum amount of proPionic acid used was about 2.45% of the corn grain. Bothast et a1. (1975) harvested yellow dent corn at 27% moisture content and added ammonia, ammonium isobutyrate, isobutyric acid or propionic-acetic acids at 0.5, 1.75, 1.5 and 1.2%, respectively. Treated corn was stored in partially open wooden bins. Harvestore and barrel storage of untreated corn were included as controls. Temperature and microbiological changes were evaluated throughout six months of storage. All of the chemicals showed preservative properties for certain lengths of time. All reduced or eliminated molds, yeasts, bacteria and actinomycetes at the time of application. However, the acids controlled bacterial growth and temperature, and reduced actinomycetes better than ammonia or ammonium isobutyrate. Harvestore storage of control corn resulted in growth of bacteria and yeasts, while barrel storage enhanced proliferation of all classes of microorganisms. Miller (1971) reported the amount of propionic acid needed for preservation was directly proportional to the moisture content of the grain. For high moisture corn at 25% moisture, 1% propionic acid was sufficient; while at 30% moisture 1.25% was necessary. Britt and Huber (1974) compared the following preservatives for shelled corn harvested at 27% moisture: propionic acid (1.2%), 80% propionic and 20% acetic acid 19 (1.2%), aqua ammonia (0.54% NH3), a commercial ammonia solution (0.63% NH3) or no additive. Compared to the control, all additives reduced fungal counts 30 minutes after treatment, counts after 28 days for the aqua ammonia were significantly higher than for other treatments. During late storage both ammonia treatments increased in fungal colonies, but they occurred earlier and were of greater magnitude for aqua ammonia, which was added at a lower concentration than the ammonia solution. After 60 days of storage, corn treated with aqua ammonia heated to 50°C, while ammonia solution and propionic treated corn remained at ambient temperature. Mrvic and Zdravkovic (1974) confirmed that propionic acid was an effective preservative for moist maize grain. Preserved maize was stable during storage and no chemical or biological changes were observed. Propionic acid has been studied as a preservative of high moisture soybeans by Alexander (1972). Soybeans of 18 and 22% moisture were treated and stored by adding 0.75% propionic acid. No heating was observed in the acid treated beans during the lO-week storage period. Mold counts of the treated samples were much lower than the controls. The lack of fungal activity suggests that myco- toxin production during storage was very low. Propionic acid treatment almost eliminated germination of the boy- beans. Oil quality did not deteriorate after treatment 20 with propionic acid. They concluded that propionic acid can be successfully used to preserve high moisture soy- beans. Also Singh-Verma (1974) reported that propionic acid or a propionic-acetic acid mixture successfully pre- served soybeans. Anti-fungal activity of various volatile fatty acids on different grains was studied by Herting and Drury (1974). Grains used were corn, grain sorghum, wheat, oats, barley and soybeans. Acids tested were formic, acetic, propionic, butyric, isobutyric and mixture of these. Treated or untreated grains with various moisture contents were stored for four weeks or more at 30°C. All acids showed fungicidal properties, with isobutyric acid the highest. Most binary and tertiary mixtures of the acids were synergistic in action. The level of a formu- lation required for protection increased as the moisture content of the grain increased. Protection often lasted for periods of a year or more. Herting et a1. (1974) also investigated the effect of water dilution on the antifungal activity on grains of volatile fatty acids. The VFA's considered were acetic, propionic, butyric and isobutyric acids. All aqueus dilutions were effective fungicides. Activity of blends corresponded to the degree of dilution. Blends of acids with 50% or more water were synergistic in their activity and aqueous formulations were effective antifungal agents 21 on barley, corn, grain sorghum, oats and wheat. Their data also indicated that the amount of acid required for protection again increased as the moisture content of the grain increased. Christensen (1973) showed that sorghum at 19% moisture which was treated with 0.1 and 0.2% propionic acid became heavily molded in 16 days after storing at 27°C. Treatment of sorghum (16-17% moisture) with 0.2, 0.4 or 0.8% prOpionic acid kept it free of molds for 483 days when held at 12°C. Corn (19-20% moisture) treated with 0.5% pr0pionic acid and stored at 25°C was free of fungi after 54 days, while a 30% moisture sample treated with 1.0% propionic acid and acetic acid (60:40) was free of molds after 140 days when held at 20°C. Samples treated with enough acid to prevent molding had zero germination. In 1972, Arends et a1. treated 27% high moisture corn (HMC) with 1.5% acetic and propionic acid (60:40). Control corn was dried to 12% moisture. Mold-spore counts of the untreated dried corn were 4.6 x 105/9, while counts 2 and of the treated dried and treated HMC were 6.0 x 10 23, respectively. Goering and Gordon (1973) treated ground shelled corn (30% moisture) with sodium chloride or propionic acid at 0.2, 0.4, 0.6, 0.8 and 1.0% and sodium propionate in amounts equimolar to proprionic acid. Also formalin 22 (37% w/w formaldehyde) was added at 0.1, 0.2, 0.3, 0.4 and 0.5%. The results showed that sodium chloride had little value in delaying the onset of mold which developed within three to six days after storage on all NaCl treat— ments. Both propionic acid and formalin were effective and 0.6% of either additive was required to eliminate mold growth for the 62-day observation. Sodium propionate was 50% as effective as propionic acid or formalin. Organic Acid-Treated Forages Acid treatment of high moisture silage (< 20% DM) has been a widespread practice in Europe for several years, aiding in production of high quality silage without wilting. In Norway during 1968 to 1970, about 70% of all silage was treated with formic acid (Drysdale, 1968; Castle and Watson, 1970). Excessive heating and carmelization often decrease the nutritive value and depress cattle intake of corn silage harvested at too high dry matter levels. Studies conducted at Michigan State showed that formic acid addi- tion at ensiling increased intakes and resulted in higher milk yields of cows consuming 44% DM silage as the only forage treatment had little effect on untreated silage (Huber, 1970). It was theorized that propionic acid might be better than formic acid in protecting high dry matter 23 silage, because of stronger properties as a mold inhibitor and spoilage retardant (Huber, 1974). Animal Performance In 1970, Castle and Watson conducted an experiment with grass silages harvested in June and in September, from the same field. The silages were fed ad libitum with barley and groundnut cake to 12 Ayshire cows in a l6—week winter feeding experiment. One of the silages harvested in June and one in September had been treated with a half gallon of formic acid per ton of herbage when cut; whereas, the other two silages were untreated. Digestible organic matter in the silage DM made with and without acid was 67.4 and 63.8%, respectively, for the June silages, and 66.1 and 62.7% for the September silages. The intakes of silage and total DM were higher for the acid-treated than untreated silages. The mean daily milk yields from cows fed on the silages made with and without additive were 36.3 and 33.8 lb., respectively, for silages made in June; and 35.4 and 34.1 lb. for those made in September. The solid-not-fat contents of the milk averaged 8.60 and 8.50% respectively, from the silages with and without the additive. It was concluded that silages treated with the formic acid were superior to the untreated as feed for dairy cows. Waldo et al. (1969) reported studies where forage (orchard grass) was harvested and preserved as hay or 24 stored in a tower silo as unwilted silage with 0.5% formic acid added at the blower. The two forages were fed to Holstein heifers. Mean daily grains for heifers fed formic silage were 692 9 versus 620 g for those fed hay. The digestibility of energy from the formic acid silage was 67.1, while that for the hay was 59.4. They observed that dairy heifers consumed a similar quality of digestible energy but made greater weight gains when fed formic acid silages than when fed hay. This implies that conservation method influences the efficiency of utili- zation of digestible energy. Fisher et a1. (1971) found that milk yields were significantly higher on silages made from direct cut sorghum-sudan grass treated with 0.5% formic acid compared to wilted silages stored without formic acid. The acid- treated silage had lower fiber and energy digestibilities but efficiency of energy utilization for milk production and body weight gains were greater. Lessard et a1. (1970) found DM intakes, DM digestibility and milk fat test were reduced by treating direct cut sudan-sorghum silage with formic acid, but milk yields were maintained slightly better with the treated than untreated silage. Wilted, untreated silage resulted in performance similar to the direct cut, formic acid- treated silage. 25 Candlish et a1. (1973) studied the effects of acid treatment of chopped barley when ensiled at 35-40% DM. Barley was harvested, chopped and treated with the follow- ing at time of ensiling: no acids, 0.41% formic acid, 0.43% formic acid-formaldehyde mixture, 0.43% formic acid- acetic acid mixture, 0.34% of an 80% propionic, 20% acetic acid mixture. The silages were fed to sixty grow- ing beef calves during 154 days to study intakes and weight gains and to eight sheep during 16 weeks to determine digestibility. Acid treatment of barley tended to reduce soluble nitrogen of the silages. Neither feed intake nor digestibilities of dry matter, energy and organic matter were different among treatments. Treatment of silage with formic acid-formaldehyde resulted in reduced protein digestibility compared to control and the propionic-acetic treated silages. A11 silages were readily eaten by beef and sheep and no advantage to adding acids was noted. Bolsen et al. (1973) added aureomycin, sodium hydroxide, ammonium isobutyrate and a mixture of acetic and propionic acids to forage sorghum. They concluded that the feeding value of forage sorghum silage was not significantly improved by any of the additives. Waldo et al. (1969) fed either unwilted alfalfa silage preserved with 0.5% formic acid or untreated silage as the sole ration for 63 days to twenty Holstein heifers. Results showed that mean daily weight gains were increased 26 by formic treatment (817 vs. 429 g). Mean daily intakes (kcal DE/kg3/4 ) were also higher (300 vs. 228). In 1970, Waldo et a1. fed thirty Holstein heifers either direct cut (25% DM) alfalfa silage preserved with 0.5% formic acid or an untreated, wilted (35% DM) silage as the sole ration for 74 days. The results again showed an improvement in mean daily gains (763 vs. 653 g) and intakes (2.58 vs. 2.66% of bodyweight) from acid addition. Formaldehyde (Waldo et al., 1973) and paraformal- dehyde (Waldo and Keys, 1974; Waldo et al., 1975) were equal to formic acid in improving feed intakes, gain and feed conversion of in heifers fed direct-cut grass silages. In fact, treated silages produced over twice as much as gain as control silage. Derbyshire and Gordon (1969) studied the utiliza- tion of formic acid silages by milk cows. First cutting orchardgrass forage was wilted (35% DM) and treated with 0.8% or no formic acid. A third treatment was direct cut material (18% DM) treated with 0.5% formic acid, silages were fed ad libitum to 18 milking cows. Fat corrected milk was not different between treatments, but silage dry matter consumption, as percent body weight, was signifi- cantly greater for wilted silage treated with acid than for direct cut or untreated, wilted silage. In an additional study by Derbyshire and Gordon (1970), first cutting orchard grass was wilted (47% DM) 27 and treated with or without 0.5% formic acid, or unwilted (20% DM) and treated with 0.4% formic. Silages were fed ad libitum to 18 milking cows. Addition of formic acid to wilted or unwilted forages resulted in increased dry matter and energy intakes and higher milk production. Sflmilar results were also found by Derbyshire et a1. (1971) by treating wilted (36% DM) orchard grass with or without 1.1% formic acid. Norwegian experiments demonstrated that formic acid treated silage was equal to artificially dried grass and better than untreated silage or hay when fed in mixed rations for milk production and growth (Saue and Breirem, 1969). Huber (1970) studied formic acid treatment of urea corn silage harvested at different maturities. Corn plants were treated at ensiling with 1.75% kg urea per 100 kg DM. The two factors studied were maturity at harvest (28 vs. 44% DM) and formic acid addition (0 vs. 1.6 kg/100 kg DM). Silages were fed ad libitum and a 13% crude protein con- centrate was fed at 1 kg/3 kg milk. The formic acid treatment resulted in an 8% improvement (P < 0.05) in milk yields of cows fed 44% DM silage. Dry matter intakes of mature corn silage increased 11% due to acid treatment and accounted for the higher milk yields. It was demon- strated that through acidification with formic acid, high 28 dry matter corn silage can be treated with urea without depressing animal performance. Barker et a1. (1973) treated wilted or unwilted alfalfa-bromegrass with formic acid or a formic acid- formalin mixture. The silages were fed to dairy cows and crossbred beef bulls. Silage DM intakes, solids corrected milk yields, body weight gains and carcass composition were not significantly affected by treatment. Sleiman (1972) treated rye with 0.4% formic acid and ensiled in conventional, upright silos. Milk production and persistency and milk composition were not different for cows fed formic rye, control rye or alfalfa haylage. Although forage intakes were not significantly different, slightly higher consumption was observed on the formic treated rye compared to control. Preservative Effects Poor quality silages, characterized by low amount lactic acid, high butyric and acetic acids, high ammoniacal nitrogen and a pH of 4.8 or above reSult in high dry matter losses and unsatisfactory nutrient preservation (Barnet and Duncan, 1954; Langston et al., 1958). Better packing and sealing to exclude air improves silage quality, but inhibiting or slowing down secondary fermentation with organic acids has also been studied. Organic acids, especially propionic, has the ability to inhibit mold growth in forages. Daniel et a1. 29 (1970) demonstrated a reduction in temperature rise in ensiled forage treated with propionic acid. These German workers ensiled grass with and without propionic acid and observed decreased dry matter losses with the propionic silage. Carbon dioxide production was lower and tempera- ture rise was reduced with the propionic compared to con- trol silage. Gross (1969) also observed a reduction in ensiling losses when organic acids were added as preser- vatives to silage. In 1969, Carpintero et al. treated lucerne with 0.85% formic acid and found this level was sufficient to achieve an immediate pH fall to 4.2. Acetic acid pro- duction and chlostridial activities were inhibited by formic acid. Lopez et a1. (1970) showed a greater pH value for corn silage harvested at low (25%) and high (52%) compared to medium (30%) dry matter. Lactic acid declined signifi- cantly with advancing maturity, and total organic acids decreased from 11.94% at 25%IDM to 3.14% at 52% DM. Waldo et a1. (1969) reported that silages treated with formic acid were lower in pH, butyric acid, acetic acid and ammoniacal nitrogen and higher in lactic acid than untreated silages. Wilkins and Wilson (1960) treated grass with formic silage acid at the rate of one half gallon/ton and found an immediate drop in pH. Lactic acid in the treated silage was also low. 30 Huber et a1. (1972) treated 25% DM corn silage with formic, acetic, propionic and lactic acids at 0.13 to 0.85% and ensiled in 220 1 experimental silos. Acetic acid levels in resulting silages were higher than control when 0.17, 0.34 and 0.57% formic acid was added, but 50% of the control at 0.85%. Acetic acid treatment increased silage acetate when 0.68 and 0.85% was added; whereas propionic and lactic acid additions decreased acetate to about 50% of the controls. Lactic acid production was depressed by formic acid, unchanged by acetic and increased at higher levels of propionic and lactic acid. Wilson and Wilkins (1973) studied the effect of formic acid as a silage additive. kThey ensiled cockfoot and perennial ryegrassin test tube silos after three treatments; unwilted without additive, unwilted after addition of 0.23% formic acid and wilted (30% DM) without additive. The addition of formic acid resulted in reduc- tion in pH of the ensiled material. Barker et a1. (1973) compared the effect of formic acid or formic acid-formalin mixture as silage additives. They ensiled alfalfa-bromegrass mixture and treated with: wilted--nothing, direct cut--85% formic acid at 0.5%, and direct cut--formic-forma1in mixture at 0.5%. The results showed that wilted silage was significantly higher in pH and soluble N than the direct cut silages which had been treated with either additive. The formic-formalin 31 treatment produced significantly more total acids, butyric acid and propionic acid than the wilted or direct cut silage treated with formic acid. Candlish and McKirdy (1973) treated chopped corn plants prior to ensiling with formic acid, propionic acid, propionic:acetic acid, or Hay Savor at 0.75% or 1.5% of the fresh weight. They observed that formic acid addition lowered the pH to a greater extent than the other acids. Treatments did not severely alter lactic acid production. Goering and Gordon (1973) evaluated the effective- ness of several chemicals as mold inhibitors for forages. They treated a wilted grass-clover mixture (35-50% mois- ture) ensiled in small snow-fence stacks with propionic acid, propionic:acetic acid, and ammonium isobutyrate. Ammonium isobutyrate and propionic:acetic acid produced less temperature rise than propionic acid which showed lower heat production than the control stacks. Ammonium isobutyrate was the most effective in preventing mold growth and forage shrinkage. Sleiman (1972) treated chopped rye with nothing, 1% formic acid or a mixture of 60 acetic:40 propionic and placed the uncompacted forage in Open experimental silos (220 1). Silage temperatures, recorded daily for four weeks, averaged: 47.8, 34.8 and 35.7 C for the respective treatments. Spoilage of silage and pH were also higher for control than acetic-propionic and formic. At 3, 4 32 and 9 days after storage, mold was detected in the respec- tive treatments. In another study, Sleiman (1972) treated whole chopped corn with various mixtures of formic, acetic and propionic acids. All acids reduced temperature increases in silos with propionic most effective. Days until mold- ing were lowest for control and highest for propionic. Dry matter discarded because of spoilage was lowest for the acetic plus propionic and highest for acetic treat- ments. In a comparison trial, it was shown that propionic addition resulted in less top spoilage of upright and bunker silos than the other acids, but all acid treatments were superior to controls. It was concluded that of those treatments compared, the most effective retardant of spoilage for unprotected forage was propionic acid added at a minimum of 1% of the fresh weight. Britt (1973) treated whole chopped corn (35% DM) with either propionic, formic, propionic plus formic or propionic plus acetic acids at 0, 0.5, 1.0 or 2.0% of the fresh weight. A11 acid treatments reduced the average temperatures with propionic more effective than formic. Lactic production was totally inhibited by all acids at the 2% addition but at 1.0 and 0.5%, formic silages were lower in lactic acid than those treated with propionic. Days until complete spoilage was increased by acid treat- ments with pr0pionic more effective than formic. All 33 acids significantly decreased fungal colonies within two days after addition. During refermentation all treatments at the 1% level or lower exhibited a rapid increase in number of colonies, however, propionic-treated silages showed a slower increase in fungi than those treated with ~formic. The proportion of yeast was greatest at initiation of fermentation and decreased at day 40. During refer- mentation, yeast growth again started. Geotrichum were maximized at day 40 of fermentation but plateaued there- after. Aspergillus was significantly higher at days 40 of fermentation and 36 of refermentation than at other times. No significant amounts of Penicillium were detected at any date. Significancejpf Fungal Con- tamination of Feeds Fungi are common throughout nature; however, the important factors that influence mold development are: (1) degree of aeration, (2) moisture content, (3) tempera- ture, and (4) length of storage. Christensen and Kaufman (1969) indicated that molds will develop in stored grain when the grain moisture content exceeds 18-20% and ambient temperatures are sufficiently high. The most rapid growth of molds will occur at 30 to 32 C. It has been suggested that at least 1% of the world's grain supply was lost due to molding in the late 19408 (Warden, 1969). The value of grain losses due to fungal contamination in the 34 late 19608 in the United States alone exceeded 50 million dollars, with corn and wheat being particularly suscep- tible. The critical moisture levels for these two grains are l4.5-14.7% for whole grain and 12.3-13.0% when ground (32 C, 70% relative humidity) (Jones et al., 1974). Christensen and Kaufman (1969) indicated that the major alterations in stored grain that can be attributed to fungal invasion include: (1) decreased germinability, (2) discoloration of either the germ, embryo, the entire seed, or kernel, (3) heating and mustiness, (4) potential production of harmful toxins, (5) biochemical changes) within the grain, and (6) loss in weight. These changes may occur before the mold becomes visible to the naked eyes. Fungi of greatest concern include Aspergillus‘ flavus, Fusarium and Penicillium (Christensen and Kaufman, 1969). Jones et a1. (1974) stated that a 3-5% invasion of grain by Aspergillus flavus could result in a potentially toxic feed. The organism can be found in corn when moisture content exceeds 18-20% and the temperature is sufficiently high for the growth. If fed to milking cows, some of the toxins can be secreted in milk. Fusarium is a common cause of corn blight and decay and is not uncommon in cribbed corn in the Midwestern United States. 222$? cillium has been observed in moist corn (Jones et al., 1974). 35 Tuite and Christensen (1955) found Fusarium was common in seeds prior to harvest while Aspergillus and Penicillium appeared after harvest. Christensen (1949) found that Fusarium was the common field fungi, while Aspergillus and Penicillium were the predominating storage fungi growing best at about 30 C. Christensen and Gordon (1948) observed that mold caused the temperature of grains to rise within a few degrees of the maximum that the molds could endure. In 1963, Gregory et a1. harvested wet hay (60% DM) and found that actinomycetes and bacteria grew during the first heating with increases in acidity. The pH rose to 7.0 or above when fungi grew. Summary of Literature Review After reviewing the literature it becomes apparent that addition of organic acids, such as formic, acetic, propionic, butyric or a mixture of these can aid in better preservation of grains and forages. There has been much interest in their use for high moisture grains for retarding spoilage during storage, but information on forages (particularly corn silage) is limited. When dry silages undergo excessive heating, molding or carmelization, there is often a decrease in their nutrient value and a depression in animal performance. It was theorized that organic acid addition might protect high dry matter corn silage from these detrimental effects. 36 Even though formic acid has been shown beneficial for treating direct cut, high moisture silage, propionic acid should be more effective in retarding spoilage of high dry matter silage. Therefore, further research on pre- servation of high dry matter corn silage treated with prOpionic and formic acids is needed. MATERIAL AND METHODS This study covers four experiments with hybrid corn harvested as silage from 35 to 45% dry matter treated with various organic acids on Michigan State University dairy farms. The silages were fed lactating dairy cows as the principal forage and concentrate was fed according to milk production. 1970-1971 Experiment (Experiment 1) This was a study of organic acid treatment of urea-silages for lactating cows. The objectives of this study were to determine which acid (formic, acetic or propionic) added to corn silage at ensiling time is most effective in its nutritive value for lactating cows and to compare two levels of formic and propionic acids. Silage Treatments Silage containing 35-40% dry matter was treated at ensiling with the following additives: (1) control plus urea, (2) formic acid (0.6%). (3) formic acid (0.6%) plus urea, (4) formic acid )0.3%) plus urea, 37 38 (5) propionic acid (0.3%) plus urea, (6) propionic acid (0.3%) plus urea, (7) acetic acid (0.6%) plus urea, (8) formic acid (0.3%) plus propionic acid (0.3%) plus urea. Urea was added at 0.6% (5.4 kg/ton). During emptying the silages were sampled three times weekly. Weekly composite samples were frozen for subsequent analyses. Dry matter, lactic and pH were determined as described in Experiment 4. Animal Trials Cows averaging about 25 kg milk daily were alloted to the treatments in a randomized block design. Groups were alloted according to milk yields during a 3-week pre- liminary period and were balanced for stage of lactation, age and breeding groups. There were seven cows per group and duration of treatment was six weeks. During stand- ardization the cows were fed corn silage ad libitum, haylage at 4.5 kg/day and concentrate (containing urea) at 1 kg/3 kg of milk. During treatment cows were fed the treated corn silages ad libitum, haylage at4.5 kg/day and concentrate formulated to provide isonitrogenous rations at l kg/3 kg milk. Body weights of cows were taken twice for two consecutive days one week after the cows were on treatment and twice during the final week of treatment. Milk was sampled twice during standardization 39 and at biweekly intervals during treatment. Milk was analyzed for fat, protein and for total solids as described for Experiment 4. 1971-1972 Experiment (Experiment 2) Formic and propionic acid additions to high dry matter corn silage treated with and without urea were studied. The objectives of this study were to determine the effect of organic acids on preservation and the nutritive value of mature corn silage (in excess of 45% dry matter) fed high producing dairy cows, to compare propionic and formic acids as preservatives agents and also to determine the effect of organic acids on the nutritive value of mature corn silage treated with urea. Silage Treatments Mature corn silage was ensiled in six (3 x 13 m) silos at 44-46% and treated at the time of ensiling with the following: Silo 3 - A - nothing Silo 4 - B - 0.5% formic acid Silo 5 - C - 0.5% propionic acid Silo 6 - D - 0.6% urea Silo 7 -'E - 0.6% urea plus 0.5% formic acid Silo 8 - D - 0.6% urea plus 0.5% propionic acid. During emptying silages were sampled three times weekly. 40 weekly composite samples were frozen and subsequently analyzed for dry matter and lactic acid as described for Experiment 4. Animal Trials Forty two high producing dairy cows, averaging not less than 22 kg milk daily were alloted to six treatment groups (balanced for milk production during a 21-day standardization period, during which all cows were fed 22 kg/day of control corn silage, 4.5 kg haylage and a urea-containing concentrate at l kg/3 kg of milk). Then the cows were fed one of the silages as the only forage for ten weeks. Concentrate was fed according to milk. production (1 kg/3 kg milk). Daily milk yields and feed intake were taken during standardization and treatment periods. Body weights were determined and milk was sam- pled similarly to the Experiment 1. 1972-1973 Experiment (Experiment 3) The addition of water and two levels of propionic acid were compared in high dry matter corn silage. The objectives of this study were to confirm the beneficial effect of propionic acid as'a preservative of high dry matter corn silage, to ascertain the minimum effective level of propionic acid under field conditions and to compare water and propionic acid effects on preservation and animal performance. 41 Silage Treatments Four upright silos at the MSU Dairy Research Center were filled with mature corn silage (44% DM) and treated at the time of ensiling with the following: Silo 9 - water (10%) Silo 10 - 0.3% propionic acid Silo ll - 0.6% propionic acid Silo 12 - Nothing. During emptying the silages were sampled three times weekly. Weekly composite samples were frozen for dry matter analyses as described Experiment 4. Tempera- tures were monitored in the silos during the five-week feeding period at depths of 15 and 45 cm. Also, 40 kg lots of the different silages were removed from the silos and placed in open 220 l barrels. Temperatures of silages in the open barrels were monitored daily for seven days after removal. Animal Trials Thirty two lactating cows, averaging not less than 22.5 kg milk/day, were fed the normal herd ration for three weeks which consisted of 18 kg/day of control corn silage, haylage ad libitum and herd concentrate at 1 kg/ 3 kg of milk. Cows were alloted to treatment groups on the basis of standardization production and experimental rations were fed for five weeks. Milk yields, feed 42 intakes, and body weights were determined and milk was sampled as in the two previous experiments. Present Experiment (Experiment 4) Ensilinngechniques and Temperature Measurements Whole corn plant was field chopped on September 25 or October 11, 1974, transported to the Michigan State University Dairy Cattle Research Center in self unloading wagons and weighed prior to ensiling in four vertical, concrete stave silos (3 x 13 m). The fresh material, containing 35% or 45% dry matter, was ensiled with and without the addition of 1.7% propionic acid (on a dry matter basis). On each date, two silos were filled simul- taneously from alternate wagon loads until each silo contained approximately 15,000 kg of dry matter. At the time of ensiling, samples of the green chopped corn were taken from each load prior to entering the blower. Composites for every load were placed in a plastic bag and frozen at -20 C for future analysis. A plastic container (30 1) equipped with faucet connected to a plastic tube was used for application of propionic acid.1 For each load a weighed amount of pro- pionic acid was dribbled onto the plant material as it 1Furnished through courtesy of Union Carbide Corporation, 270 Park Avenue, New York, N.Y. 43 entered the blower from the unloading wagon. The flow of propionic acid was controlled by a clamp on the plastic tube which was adjusted during the emptying of each load depending on the flow rate of plant material and level of acid in the container. Three thermocouples were placed in the centers of each silo at heights of 2.5, 5.0 and 7.5 m (after the leveling and tramping). Exteriorized leads from the thermocouples were connected to a portable potentiometer1 for monitoring temperature during fermentation. This equipment was also used to measure silage temperatures. (at 10, 20 and 30 cm depth) three times per week during the ten week feeding period. Animal Trials Eight lactating dairy cows producing over 22.5 kg milk/day were assigned to each of the four corn silage treatments in a randomized block design. Blocks were based on milk production during a 14 day standardization period, in which control silage was fed ad libitum and an 18% crude protein concentrate was fed at l kg/3 kg milk. Milk weights and total feed intakes were recorded during standardization. Composite (AM and PM) milk samples were taken from each cow at biweekly intervals. Samples of 1Brown Portable Potentiometer Model 126 W2, Minneapolis, Honeywell Regulatory Co., Philadelphia, PA. 44 silages were taken on Mondays, Wednesdays and Fridays of each week, composited weekly and frozen at -20 C for future analysis. Bodyweights of the cows were taken for two consecutive days 7 days after the beginning and at the end of the experimental period. Refermentation Trial During the feeding trial, 68 kg portions of corn silage were removed in duplicate from each silo and placed in unsealed 200 1 steel barrels (lined with polyethylene sheeting) to test the effectiveness of the acid in pre- venting spoilage when silages were exposed to air. Temp— eratures in barrels were monitored by using the portable potentiometer three times per week for 30 days. Also, samples were taken on days 1, 7, 14, 21 and 28, and deter- mined for dry matter and number of fungi. Chemical Analyses Dry matter of corn silage samples was determined in duplicate by placing approximately 40 g of material in a forced-air oven at 90 C for 24 hours. Total nitrogen as determined by macro Kjeldahl. Silages were prepared for pH, lactic acid, volatile fatty acids (VFAs) and number of fungi by homogenizing 20 g of silage and 180 l of distilled water in a Sorvall Omni-Mixer1 for three minutes with the cup immersed in ice. The homogenized 1Ivann Sorvall, Inc., Newton, Conn. 4S material was used for measuring the pH with a Sargent pH meter1 and for plating to estimate fungal population. Extracts from the material were strained through two layers of cheesecloth, deproteinized with sulfosalicylic acid (15 ml of the filtrate was added to 1.5 m1 of sulfo- salicylic acid), and centrifuged2 at 15,000 rpm for ten minutes. The supernatant was removed and frozen at -20 C until analyzed for lactic acid and VFAs. Colorimetric procedures of Barker and Summerson (1941) were used to determine lactic acid. Volatile fatty acids were determined by injecting 3 ul of the depro- teinized samples into a Hewlett-Packard F and M gas chromatograph3 using a glass column packed with chromosorb 101 (80/100 mesh).4 The injection port temperature was set at 340 C, the column temperature at 285 C, and the flame detector at 320 C. Nitrogen was used as the carrier gas and flow rate was 30-40 ml per minute. Sample VFA concentrations were calculated by comparing peak heights with a standard solution made with known weights of anal- ytical grade acids in a stock solution and diluted until a concentration comparable to the samples was reached. E. H. Sargent and Co., Chicago, Ill. Sorvall-Superspeed, RCZ-B. Hewlett-Packard, F and M Scientific Co., Model 402. bUNH Johns-Manville, Celite Div., Denver, Colorado. 46 Concentrates were determined for dry matter and nitrogen as described for silages. Fungal population was determined by transferring (with a sterile pipette) 1 ml aliquots of the freshly homogenized silage sample into a dilution bottle filled with 99 m1 of sterile, distilled water. The sample was thoroughly mixed and serially diluted until the proper concentrations of fungal spores and mycelia were reached. Either l or 0.1 ml of the diluted sample was then dispensed into sterile plastic petri dishes. Enough potato dextrose 2 which had been agar1 (with 100 mg per liter of novobiocin melted and cooled to 45 C) was then added to cover the bottom of the petri dish and swirled to insure complete mixing of the agar and silage homogenate. After cooling, the plates were sealed and placed in the dark at 20 C for 5-7 days at which time the plates were removed and colonies were counted using a colony counter.3 Milk Analysis Total solids were determined by drying 2 ml of milk for two hours in a forced-air oven at 90-100 C. Butter fat was determined by the Babcock method. A portion of each sample was placed in plastic vial and frozen at -20 C, 1BBL, Cockeysville, Maryland. 2Upjohn Co., Kalamazoo, Michigan. 3Fisher Scientific Co., New York, N.Y. 47 and at the end of the trial it was analyzed for nitrogen by micro Kjeldahl. RESULTS Animal Performance Experiment 1 None of the acid additions had a significant effect on animal responses. Daily intakes of cows fed medium dry matter (35-39%) corn silages treated with different organic acids are shown in Table 1. There were no signifi- cant differences in silages and total dry matter intakes due to treatment by any of the acids. Highest silage consumptions were noted for the high propionic treatment and lowest for low propionic, but these differences were probably due to chance. As shown in Table 2, milk persistencies were high for all groups (> 90%), but were lowest for the group fed silage treated with only formic acid. This agrees with fattening cattle (Henderson et al., 1971) who also showed a slight depression in body weight gains when formic acid (0.6%) was added to medium dry matter corn silage. Some improvement in both milk yields and fat cattle gains (Henderson et al., 1971) were noted by urea addition to formic acid silages. The increase in body weight for all groups receiving acid-treated silages 48 .wo.o «:Oflufioom MOHDO .Amo.o v my pamowuwcmwm mum monsoHGMMAo on“ NO ocozo .mxoos me How usefiumouu\mzoo co>wmm 49 as.~ om.H oe.o : + lwm.oc .douo + 1mm.ov oaeuom om.~ h~.H mm.e a + lao.oo oauood Hm.~ o~.H Hm.s s + 1am.oc cacoaeouo mm.~ .oe.H mm.m a + Awo.o oecoeeoum oe.~ o~.a Hm.m o + lam.ov casuoe Ho.~ H~.H «5.5 a + lwo.ov oeeuom mo.m m~.H mm.o lao.ov oesuoe ~o.~ m~.H mH.o on + Homecou. oxoucmzmnmamuoe meuwH so omoaamommww ecosuomue omoaem m.AH unoEHummxmv mzoo mcwumuoma mo mmxmucw nouume who so Awmmummv wooden cuoo Houume map spaces on :ofluwoom won: one moflom owcomuo mo mucosamsunu.a manna .00H x A.osoum\ucmauuouuv.uaocounwmuom .wm.o «cofluwoom mono .Amo.o v mo mofioo Add one» Hosoa unmowuwcmwm Houucooo o .Amo.o v m. usmoauwcmwm mum moocouomuwo 0:» mo 0:02 .mxoo3 awn How ucoauoouu\n3oo co>omm n 50 mm.o mo.~ mound .oum mm.o+ oa.~o om.a- mo.m~ on.m~ a + 1am.ov .mouo + Aan.ov oeeuom om.o+ oe.oo Hm.H- om.m~ ma.m~ a + xao.ov oauooc mm.o+ ma.so ms.o- ck.v~ ec.m~ a + 1am.oc oacoadouo ma.o+ oo.~o oo.a- mm.- oe.c~ a + Aao.oa oacoeeouo m~.o+ ~m.ao m~.~u sc.m~ os.m~ a + 1am.oo oaeuoa m~.o+ mo.mo va.o- co.m~ o~.o~ a + Aao.oa oaeuom em.o+ mc.om eo.~- mm.- ~o.m~ Aao.oa oeeuom mo.o- mm.oo Ho.o- o~.m~ om.o~ on + souucoo osoo\ox a nsoc\ox soc\ms soo\mx mcwmo .umfimuom omcmnu .ummue .ocmum unevenness wouawm unoaoz soon enemas xaaz n.AH usuawuomxuv msoo msaumuooa mo magma unmwos Soon can moaoau gags so Aommumm. wooden :Hoo Hounds who suaoos ou msOAuwoom nous use mowed oassouo mo doomsaucnun.~ ounce 51 averaged 0.32 kg/day while a slight decrease in weight was noted for the group on the control silage. The overall effect of the acid on weight gains of the lactating cows was significant (P < 0.05), as shown in Table 2. Similar to data for feed intakes and milk yields, acid treatment of silages had no effect on changes in milk composition, as shown in Table 3. Experiment 2 Daily intakes and body weight gains of cows fed high dry matter corn silage (44%) treated with different organic acids and .rea are shown in Table 4. Silage intakes were higher (P'< 0.1) for cows fed the propionic treated silages than for other groups. However, due to the large variation between individuals, differences only approached significance (P < 0.1).. A similar trend was noted for total intake. Average daily gains did not differ between treatments and all groups gained weight during treatment. The control groups produced less (P < 0.05) milk than those fed propionic treated silage with formic groups intermediate (Table 5). Urea had no significant effect on production but tended to increase yields on control silage and decrease them when propionic was added. .ao.o "coaufiooo nouoo .Amo.o v my ucoowmecmwm mum moocouommwo ucoauoouu on» we 0:02 o .mM003 unfim HON UC§fl0H9\m3OU GO>0mM oa.o- mm.ma mo.o+ oa.m o~.o- em.m a + lam.oo .mouo + 1am.oa oaeuoe ma.o+ om.ma mo.o- mo.m mo.oy mm.m a + lao.oo oauooa oo.o- oo.~a mo.o+ m~.m no.o- em.m a + lem.ov oacoaeoao ea.o- av.ma ~o.o+ mH.n m~.o- mm.n a + lao.os oacoamouo oo.o+ em.~a oo.o+ mfl.m oH.o- om.m a + 1am.oo oaeuom ea.o- AH.NH mo.o+ ma.m Ha.o- oo.m : + loo.os oaeuom oo.o- oo.~a oo.o+ m~.m ma.on mc.m lao.oo oaeuoe oo.o- oo.aa HH.o+ ea.m oo.o- om.m on + Homecoo nwmcmno w w ammcono a a newsman a a unoauooua ommHam mofiaom Hmuoa awououm Hum .AH acosauomxmv msoo mcauuuomH mo coauuaomsoo sees no Ammmummv wooden cuoo nouuua asp spaces on noduwooo noun can moaoo owcomuo no oocoaaucuul.m «Home 53 .AH.o v my ucmoamw:m«m 0u03 m0os0u0mmwo 0:» mo 0:02 o .Aoa.o v mv 00:00wmw:mflm o0nomoummm m0m0me 0fl:0wmoum 0:0 douu:oo 0:» :00zu0n m0uamo0a 0xmusw Ham :w 000:0u0mmwoo .ao.o no none can em.o so cocoa need a .mx003 COD. HON HGGEMOHU\M3OU Em>0mm mc.o mv.o «v.0 ov.o mm.o mm.o Asoc\mxv m:flmw 9:0«03 woo: om.~cH o>.oma oa.ovfl oa.aoa om.ova oo.ama .c\m3m mx\mv mm.~ Ho.m me.~ cm.~ me.~ mm.~ , as: we H~.ma mo.oa oo.ea oa.ea cm.ea om.oa .lsooxmxs o0xmucw 20 Hmuoa ca.em om.mm cm.om oo.om oo.mm oe.>e AV\mzm mx\ov ck.H em.a mo.a ce.a He.H om.H is: my NH.HH ce.HH om.oa mm.oa ,hm.oa mv.m Aaoc\mxa 00x0uce so 0mmem :uoo H.mv c.mv o.Hv >.mv c.0v H.c¢ a + .mouo .moum a + .suom oasuom a + .uucoo .uucoo z: omcawm nu:0su00ua0mmaem N.Am u:0fi«u0mxmv 0300 m:eu0uowa mo u:wmm unme03 moon on: 00:09:“ u0uuua Sup :0 Aamvnvev 0moafln :uoo u0uuma who saw: 0» :oauwoom 00H: 0:0 nowoo ow:muwo mo 00:09am:Hul.v 0Hn08 .Amo.o v m. u:0u0muwo hau:mowua:mwm 0H0 umauumu0msm :oasoo 0 o:«uo:m no: m0sao> Hoao«>«o:u0 .mo.o v m um u:0ofimw:mwm .uoomm0 poo: .00H x Ao:oun\u:0au00uuv ">0:0umfinu0m .oo.o oo oooo oco om.o oo ooooo oaoo .u:00fiuw:own yo: no: uoomm0 00H: 0 o .00H0> menu :0 o0mon m:00au0maoo Hmowumououmo a M“ .mx003 :0» now u:0su00uu\msoo:0>0mm . . . . . . >0:0 mamu0 0o~o mm 0mm mm 005$ mm own Hm omm om omm ha 0 u . m Hm.Hn om.on Hm.HI ma.mu om.NI om.~: Ahoo\mxv.0o:mgu em.mm on.mm ma.v~ on.~m vm.m~ hm.H~ «umo\mxv 0:0Eu00ua wh.mm oo.om oo.om mm.v~ o~.oN om.¢N Ahoo\mxv osmo:oum H.mv m.mv o.Hv >.nv o.ov H.v¢ D + .moum owcowmoum D + .suom owsuom D + .uu:oo Houu:ou 2o 0moafim 9:06uo0ua 0mwawm a Aaovuvv. 0mmafim :uoo .fl .Am u:0sau0mxmv 0300 o:wuouooa no moaodm xaaa :0 u0uuua mun sue: on :oHuHooo 00H: 0:: mode: oa:omuo no 00:0sau:HII.m 0Hn09 55 Experiment 3 As shown in Table 6, silage dry matter intakes were again stimulated by propionic acid addition. Cows fed corn silage (44% DM) treated with 0.6% propionic acid consumed slightly more than those fed 0.3%. Cows fed con- trol silages (with and without added water) were lower in dry matter intakes than those fed silages treated with 0.3 and 0.6% propionic acid (P < 0.05). The superiority of propionic acid treatment to water addition is obvious. Total dry matter intakes were not significantly different between treatments. However, total intakes of cows fed silages treated with 0.3 and 0.6% propionic acid were slightly higher than controls. Body weight gains did not differ between treat- ments, and averaged 0.81, 1.06, 0.85 and 0.74 kg/day, respectively, for control, control + water, 0.3% propionic and 0.6% propionic. A Cows fed the 0.6% propionic acid silage were most persistent in maintaining milk yields, but they were only slightly higher than controls, as shown in Table 7. Experiment 4 Average daily intake of silage and total dry matter, and average daily gains are shown in Table 8. Silage dry matter intake were not significantly different among groups. However, cows receiving propionic treated 56 .Amo.o v my mac: ow:owmoum mm.o o:0 m.o :05» H03OH u0u03 0:0 Houu:oo n .mxmws O>Hm HON ucmfiummuu\m3oo unmwmm ee.o mo.o oo.H Ho.o Asooxmxv :fimm unmw03 hoom om.maa oo.HoH oe.oma om.oma lo\mzm ox\oc eo.~ Ho.~ Ho.~ oo.~ lam as ao.oa oo.ea mm.oa pe.oa Asooxmx. oxooce so Hoooe oa.mo oo.mo oe.ae om.os onmzm ox\o. He.a mo.a mo.a mm.H 13m as oH.HH Ho.oa oa.o o~.o isooxoxv n0x0u:w 2o 0mmem :uou . . . . kum3 + mono we o mono mm o Houu:oo Houu:ou 9:0Eu00ue 0ooawm 0.Am u:0fiwu0mxmv 0300 m:fi»ouood no.0:fiom unmw03 Soon o:o moxou:w u0uuos who :0 gave. 0ouawm :uoo u0uuos ago now: on 0:0auwooo u0u03 o:o own: 0H:oflmoum mo 00:0:HH:HII.o odoma 57 0003 000:0M0MMHO 0gp mo 0:0z .OOH x Ao:0um\ucoeu00uuv ">0:0umwmu0m .Aa.o v we ucoowmw:owm n .mx003 0>wm Mom u:0Eu00uu\m3oo usmflm0 ao.oo oe.~o om.~o oe.mo asceoooeouoo oH.m- om.o- Hm.o- om.m- Asooxexc oocoau mo.o~ eo.a~ oa.o~ ~m.a~ Asooxoxc ocoeoooue Ha.e~ om.o~ no.e~ Ha.m~ Asoo\mxc coeoooaouoocoum . . . . MODES + none mm o mono an o Houu:owI Houu:oo (#:08000HB 0mwawm 0.Am u:0e«u0mxmv 0300 m:«u0uo0a «0 moaoo» seas co loves omoaao :000 000008 >00 nae: ou 0:0fiuwoo0 H0u03 0:0 owo0 ow:owmoum mo 00:00Hu:Huu.n 0Ho09 .H0uu0e >H0 :5fi00e u so: «H0uu0e hu0 now: u so: .AH.o v my 0:00flmw:mem 0:03 000:0u0mmw0 0:» mo 0:020 .wo.o ":0HOH000 0w:0flmoumn .mx003 :00 How #:08000Hu\m300 uamwm0 58 oo.o ao.o am.o om.o isooxoxo :H0m unmw03 woom mh.v om.mma om.hma o~.vva . om.nma Av\m3m mx\mv ma.o om.~ mh.~ hm.~ en.~ 53m my oa.~ me.ea oo.oH em.oe se.»: isoo\ox. ooxooce so Hoooe Hm.v om.mm oo.mm om.mm om.mm A¢\mzm ox\mv oa.o hm.H vn.a ow.a mn.a Asm av se.: oa.aa He.oa oo.aa oo.HH Asoo\oxo 00x0u:fl 2o 000awm :uoo ma.mm mm.mm mm.mv H . v . . so: A so: 2:: . 2:: m m 0m:0Hmoum Houu:oo 0m:owmoum Houu:ou 2o 0m0awm nu:0&u00ua 0m0HHm 0.xv 0:0Ewu0mxmv 0300 m:w00u00a mo 0:H0m 0:0w03 >00: 0:0 0x0u:a 000005 >u0 :o Awme 0:0 mmv 000Hw0 :uou M00005 >00 :mfl: 0:0 Esw00a 00 :oflufi000 0w00 0H:oflmonm mo 00:00Hm:HII.m 0Ho0a 59 silage (both at medium and high dry matter) consumed slightly more than corresponding controls. Intakes of silage dry matter (kg/day) were slightly greater for high than medium dry matter groups (11.08 vs. 10.71), but the same when based on % of BW (1.73 vs. 1.74). A similar trend was observed for total dry matter intakes. All groups gained weight during the experiment and weight changes were not significantly affected by treat- ment. However, gains of cows fed 35% dry matter silage were slightly higher than those fed the 45%. As shown in Table 9, milk yields again favored groups fed propionic treated silages, even though the differences were not significant. Milk composition was not significantly different among the groups, as shown in Table 10. Percent of almost all milk constituents were slightly higher during treatment than during standardization. Because Pooled Data Because intakes and milk persistencies were con-_ sistently higher for the three experiments (Experiment 2, 3 and 4) where propionic acid was added to high dry matter corn silage (43-46%) and no year x treatment interaction was detectable, pooling of the data for statistical anal- yses was possible. Forithe three experiments, propionic acid treatment increased silage dry matter intakes 12%, total intakes 6% and milk persistency 5% (Table 11). 60 .ooa x A0:000\0:0500000v “>0:00000000 .Aa.o v my 0:00000:000 003 000:0000000 0:0 00 0:020 .wm.o “:0000000 00:00m00mn .00003 :00 000 0:0800000\03o0 unmflm0 no.m oo.om 00.00 om.vm om.0m 000000000000 mm.ou oo.0- 0~.0- oo.0- isooxoxv oocoao e~.o~ h~.o~ me.o~ mo.a0 Asoo\oxo ocoEoooue ~0.0~ 0m.0~ oo.0~ 0o.0~ isooxoxc coHooo0oooocoom mewmm INMDMMI mo.mo Hm.mm .m.m 00:wmmo0m Howmmoo 00:Mmmo0m Howmmmm 2o 0m0H00 #:0800009 0m0awm 0.Av 0:08000mxmv 0300 0:000000H mo 00H00> xuwfi :0 Rome 0:0 mmv 000H00 :000 00000: S00 :00: 0:0 5:000: 00 :0000000 0000 00:00m00m mo 00:0:Hu:Hun.m 0Ho0a 61 .00.o v my 0:00000:000 0003 000:0000000 000.00 0:020 .mm.o “:0000000 00:000000 0 .0x003 :00 000 0:0200000\0300 0000m0 n 0:0500009 000000 o~.o+ 00.o+ 0~.o 00.o+ oloocoao my mo.m0 0o.~0 ee.~0 o~.m0 10c oo0Hoo Hoooe ~m.o+ He.o+ oo.o+ ~0.o+ oiomcoao we. mv.m oa.m mm.m ao.m a». c0ooooo 00.o+ oo.o- mo.o+ om.o+ oloocooo we mo.m No.m oo.m 00.0 10V 0o: ~0.om INMhmml. 00.00 00.40 00:”MM000 00Wmmow 00:”MM000 00WMMOU so 000000 0.00 0:05000mxmv 0300 0:0000000 00 :0000000800 000: :o Awmv 0:0 mmv 000000 :000 000008 000 :00: 0:0 E50005 00 :0000000 0000 00:000000 00 00:0:00:Hlu.o0 0000B 62 Table 11.--Inf1uence of propionic acid addition to high dry matter corn silage (44-46%) performance of lactating cows for the three experiments. Dry Matter Intake Milk Yield Silage Treatment (% BW) _i Persistency Silage Total % Control 1.62 2.73 88.5 0.6% prop. acidb l.81** 2.90* 92.9* Difference (%) 12 6 - 5 aMeans for 23 cows. bSignificantly higher: **p < 0.01; *p < 0.05. Differences between cows fed control and propionic treated silages were all significant. Preservative Effects Experiment 1 As shown in Table 12, the lowest pH values were shown for treatment with formic acid alone, but urea addition to the formic treated silage resulted in the highest and most variable pH values. Formic acid greatly depressed lactic acid production during ensiling. Pro- pionic and acetic had a less depressing effect than formic on silage lactic acid. Addition of 0.6 and 0.3% propionic acid to 35-39% DM corn silage resulted in slightly lower lactic acid than in control silage, but the depression was not as great as for formic acid. Differences in lactate 63 .00.o ":0000000 000D0 mo.~ om.e 0.0m a + 10m.ov .0000 + 10m.ov 002000 00.0 00.0 0.00 . 0 + 100.oc 000000 00.0 00.0 0.0m D + awn.ov 00:000000 o>.N 00.0 0.00 D + Awm.ov 008000 m~.0 mm.m 0.00 D + 000.0V 008000 m0.0 no.0 0.0m Amm.ov 008000 0m.m mm.0 0.0m _ on + 0000000 00wm WM0W0A me so 0W0000 0:0800009 000000 .00 0:08000mxmv :000000000 0000 000000 0:0 mm :o Awmmlmmv 000000 :000 000008 000 850008 00 0:0000000 000: 0:0 00000 00:0000 mo 00:0:00:0II.~0 0000B 64 production between propionic treated silages and the con- trol were not significant. Experiment 2 Addition of 0.6% propionic acid to high dry matter (44-46%) corn silage did not diminish the normal preser- vative power as indicated by lactic acid content (% of DM) of 3.6 for control and 5.3 for the propionic treatments (Table 13). Experiment 3 As shown in Table 14, both propionic and water treatments resulted in cooler silage during the feeding trial (after fermentation was complete) and also when silages exposed to air (during 3 Moreover, the 0.6% propionic acid treatment was more effective than 0.3% or water. Experiment 4 The average pH and lactic acid (% DM) of silages are shown in Table 15. There was no significant differ- ence between groups. The pH of control 35% DM was slightly higher than that of treated silages (4.17 vs. 4.02), but no difference due to treatment was noted at 45% DM (4.18 vs. 4.20). Also, pH values for control silages were not as affected by dry matter (4.17 vs. 4.18), as they were for treated silages (4.02 vs. 4.20). 65 00.0 0m.m 00.0 0m.m v0.0 00.m .2o 00 «V 0000 000000 0.00 0.00 0.00 0.00 0.00 0.00. so 000000 D + .0000 00:000000 D + .8000 008000 D + .0:ou 0000:00 0:0800009 000000 .AN 0:08000mxmv :00005000m 0000 000000 :0 vavv 000000 :000 000008 >00 :00: 00 :0000000 000: 0:0 00000 00:0000 mo 00:0:00:H||.m0 0000B 66 .0900 00 00 "000000 00000000800 0800:000 0000080 m.mm 0.00 0.00 0.00 0000000 8000 80 N.mm 0.00 0.00 0.00 080 000 0.00 0.00 0.00 0.00 080 00v 00000 80:003 00 0 0 0 0 0 0 0 m 8 0 0 a 0 0 8 0.00 000 El Imhlmwrl . . 00003 + 000000000 00 0 000000000 00 0 0000000 0000000 20 000000 000800009 000000 .00 00080000xmv 00000000800 :0 00000 000000 0000 000008 >00 :00: 00 080000000 00003 000 0000 000000000 00 0080000:01t.00 0000B 67 .Aa.o v mv pamoflmwcmfim no: mm3 pommwm UHGOHQOMQ “Amo.o v mv 29A v 20mg .mm.o "cofluwcnm oflcoflmoumm m~.m ha.m mw.m Hm.¢ QAEQ my Odom owuumq No.q na.q o~.¢ mH.q ma ma.mm IthMWI mm.me uhbhwwl EDA Sag Sam Sam ED mmmHHm oacowmoum Houucou omconoum {Houucou mucmEumeB mmmawm .Av unmeummxmv :oHuonuoum oaom cauoma can mm :0 Ammv can mmv mmmaam cuoo umuume haw swan can asfiwme ou cowuwwvm cwom cacoflmoum mo wocmsHmcHlu.mH manna 68 Lactic acid production was significantly different (P < 0.05) between control medium dry matter and control high dry matter (6.17 vs. 4.81% DM); also between treated medium dry matter and treated medium dry matter and treated high dry matter (5.28 vs. 3.66% DM). Propionic treatments caused a slight decrease in lactate content at both dry matter levels, but difference was not significant. Average temperatures of control and propionic treated silage (35% DM) during first five weeks of fer- mentation are shown in Table 16. Propionic treatment resulted in cooler silage at all heights during fermenta- tion. There were no significant differences among heights in control, but mean temperatures of the top silage were higher than middle and bottom silages, averaging 34.3, Table l6.--Influence of propionic acid addition on mean temperature of 35% corn silages during first five weeks of fermentation (Experiment 4). Silage Treatmenta Control LDM Propionic Lfifi Silage on 35.54 36.12 mean temperature °C Height 2.5 mb 32.1 ‘ 26.7 5.0 mb 31.5 24.7 7.5 m 34.3 33.3 aPropionic addition: 0.6%. bSignificantly different (P < 0.05). Ambient day-time temperature ranged: —3 to 22°C. 69 31.5 and 32.5°C, respectively. In treated silages, there was a significant difference (P < 0.05 between depths with the temperature of top silage again higher than the middle or bottom (33.3 vs. 24.7 and 26.7°C, respectively). There was no significant difference between top control and treated silages (34.3 vs. 33.3°C), but the overall effect of treatment on temperatures of silages was significant (P < 0.05). Figures 1, 2 and 3 show how temperatures changed with time of ensiling. Greatest heating was noted during week 1 and temperatures plateaued thereafter. Differences due to propionic treatment (at 2.5 and 5.0 m) were main- tained for the entire measuring period. Table 17 shows the average temperatures of 45% DM control and propionic treated silages during first five weeks of fermentation. Propionic treatment again resulted in cooler silage (P < 0.05). Unlike the 35% DM compari- sons, all locations (2.5, 5.0 and 7.5 m) showed decreased heat production due to propionic treatment. Unlike 35% DM silage, depth had no significant effect on mean temperatures. Figures 4, 5 and 6 show changes in mean temperatures of 45% silages with time of fermentation. Patterns were somewhat different than for 35% DM silage with maxima occurring at about two weeks. Lower initial temperatures may have reflected a slower fermentation in the drier silages. Even though the 45% 50 40 30 Temperature ('C) 20 10 7O Week o-——o Control °---' Propionic b Fig. l.--Temperature development of control and propionic corn silage (35% DM) during fermentation at a height of 7.5 m (top) (Experiment 4). 71 o-—-o Control o---o Propionic o—a Ambient Temperature ('C) 10%- L, I 1 l 1 0 l 3 4 5 Week Fig. 2.--Temperature development of control and propionic corn silage (35% DM) during fermentation at a height of 5.0 m (middle) (Experiment 4). 72 Temperature (' C) o——o Control °""" Propionic II---a Ambient fi4}—_ ‘4D“‘-~_—1> L--—*—_.__ -o-u—._.____._. 20 - 10 ~ I l l I I 0 1 2 3 4 5 Fig. 3.--Temperature development of control and propionic corn silage (35% DM) during fermentation at a height of 2.5 m (bottom) (Experiment 4). 73 o+——o Control 0"". Prop ionic 9...; Ambient 40 - U C 20 . Temperature (’C) 10 - Week Fig. 4.--Temperature development of control and propionic acid corn silage (45% DM) during fermentation at a height of 7.5 m (top) (Experiment 4). 40 Lu 0 Temperature (°C) 10 74 o——o Control o--- Propionic H Ambient Week Fig. 5.--Temperature development of control and propionic acid corn silage (45% DM) during fermentation at a height of 5.0 m (middle) (Experiment 4). 75 ° ° Control """'" Propionic D——OAmbient Temperature (‘ C) 10" Fig. 6.--Temperature development of control and prOpionic acid corn silage (45% DM) during fermentation at a height of 2.5 m (bottom) (Experiment 4). :‘llill ‘ 76 Table 17.--Inf1uence of propionic acid addition on mean temperature of 45% corn silages during first five weeks of fermentation (Experiment 4). Silage Treatmenta Control HDM Propionic HDM Silage DM 44.81 43.63 mean temperature "C Height: 2.5 mb 27.4 24.6 5.0 mb 30.1 26.5 7.5 mb 31.1 26.6 aPropionic addition: 0.6%. bSignificantly different (P < 0.05). Ambient day-time temperature ranged from -4 to +22°C. silage was harvested later in the season than 35% DM, ambient temperatures were similar and were not the cause of the different patterns. Table 18 shows the average temperatures of corn Silages during feeding trial. All of the temperatures at all depths (10, 20 and 30 cm) for control silages were higher than for the pr0pionic treat- ment (P < 0.05). This was true for both the low and high dry matter comparisons. During the first weeks of feeding, temperatures were significantly different (P < 0.05) between treatments (Fig. 7, 8 and 9) with control-HDM the highest and prOpionic-LDM the lowest. Thereafter, differences between treatments were negligible. in: .10 ' I} I? 77 “.535 Sam..co«moum zom .Houucou 2oz..conoum so: .Houusou .0- 0'0 ..v usmEaummxm. 80 ca «0 numwv m an axe wmv can mm. mmmawm :Hoo panama» vwon owconoum can Houucoo mo Hawk» weapomu on» mswusp unweaon>0p ousuuummfimaul.h .mwm j cm (3,) aznnaxadma; L. 4’ iv. 21"!" .. 78 ..v acoawuomxm. an on no snoop a an .:o mmv 0cm mm. omuaan :uoo pounouu vwou oasofimoum can Houuaoo mo Haws» mswpoou on» mcwusc unusaoao>wo ousuuuomaaauu.m .mflh unmanea sax ..coaaoua new .Houucoo zoz..cowmoum so: .Houucoo 0.0-0; .' '-I. .NH 0H 0N (3.) ainnezadma; .1..1"I‘x. 79 .Av uaoafiummxm. so on no canon m um .30 «me can mm. mumafiu cuoo powwow» pwom ow:0wmoum can Houucoo mo Amway mcwpmom on» mswuso ucoEQOHm>mo musumuomsuanl.m .mwm . NI. OH ucmHnE< ou:!uo . . Na 28.. .6368... TI: :0: .Houucoo cllllx Snafcoaaoum 2.!!- so: .Houucoo culls . I 3 (3.) aznnezadmal :- 80 Table 18.--Influence of propionic acid addition on mean temperatures of medium and high dry mattern corn silage (35 and 45%) during the feeding-out period (Experiment 4). Silage Treatmenta fl Control PropiOnic Control Propionic HDM HDM MDM MDM Silage DM 44.81 43.63 35.54 36.12 mean temperatures °C b Depths 10 cm 6.8 5.2 6.4 4.6 20 cm 7.1 5.9 6.8 5.4 30 cm 7.4 6.2 7.0 5.5 aPropionic addition at 0.6%. bPropionic effect was significant (P < 0.1). Ambient day-time temperature ranged from —5 to +12°C. Upon exposure to air lactic acid concentrations were decreased in all silages. As shown in Table 19, no meaningful difference between treatments were detected for the rates of decrease. By 14 days after exposure most silages were devoid of lactate. This decrease corresponds with an increase in pH and susceptibility to fungal contamination. The pH values (as shown in Table 20) of all silages increased during refermentation. As mentioned, these increases are related to the decrease in lactic acid content. Differences between controls and treatment were not significant, but there was a trend towards high pHs of .86". .’, . "I‘: 81 .mmumowamsp 03» mo momuw>m on» ma msam> comma .wm.o usOwuwpom OHCmeoumm o om.o o mm.m oa.m .zo «mm. cacoaaoum o ca.o o m¢.o om.m .zo wmm. Houucoo o o~.o om.o mm.o om.H .zo wms. uncommoum o o o Na.. 4~.m .26 wmv. Houucou mm .m 43 s H .ucmsummua mmmHHm coflumucmEummmm mo mama .Av ucmeummxm. soflumusmeummmu mGHHSO Awmv can mm. mmmaflm cuoo nmuums mun nos: can Edwpme mo QAEQ «o w. :oflumuucmosoo owom ofiuoma so msoHuflppm Uwom owsoflmoum mo monogamcHnu.mH manna ‘4'}.- .w" .. I ’4 r I! 82 .ommHHm mo momawomm mwumoflpsfl wsam> mcflmm«20 .moumoaamso 03» mo ommnm>m on» ma msam> nommn .ww.o "coauappm oasoflmoumm NH.m mo.m mm.q mm.¢ 4H.¢ .zo smm. oncoaaoum os.¢ .mo.m om.m mm.q m~.¢ .za wmm. Houucoo sm.s m..m NH.m mm.v mm.m .zo ”ms. uncommoum o ma.m ~¢.m mo.v am.m .26 «m4. Houucoo mm am as a H ucmsummue mmmaam coflumusoEummmm «0 made ..v unmafinmmxm. cowumucosummmu msfiHSU .mmv can mm. mmmafim suoo umuume amp swan ppm Epsoms mo nmmm so ms0auwppm oaom cacoflmoum mo moswsHmanl.om wanna 83 control silages during the latter stages of refermentation (before complete spoilage). The number of fungal colonies in silages is shown in Table 21. Significant differences between 45% DM con- trol and treated silages were noted (P < 0.01). Also it was found that there was a significant difference between 45 and 35% DM controls (P < 0.05), where the 45% DM con- trol was higher initially than in the 35% DM control. Visual fungal growth was present on days 6 and 10 for 35% DM control and treated silages, respectively; and on days 7 and 14 for the respective high dry matter silages. Complete spoilage was seen on days 15 and 17 for 35% DM control and treated silages; and on 14 and 21 for 45% con- trol and treated silages (Table 22). Again, as shown in Table 23, propionic treatment resulted cooler silage during refermentation; but differ- ences were not significant. Ambient temperatures during refermentation changed from 15 to 23°C. A complete identification of fungal species was not made, but several slides that were made showed that Penicillium and Aspergillus were predominant. These species were also found in corn silages by Britt (1973) and Christensen and Kaufman (1969). 84 .wsamb mswwmwzo .ww.o "cowuwopm ow:0amoumn .moumoflamsp 03» mo monum>m may aw osam> gamma m~ mm om an ca .29 «mm. cacoamoum o NMH om mm 4H .26 “mm. Houuaoo am a. on on om .so «m4. oaqoamoum om. ms. mmfl om ow .26 “we. Houuaoo mm Hm «a h H usmfiumwua mmmem cowumucmEummmm mo ammo .Av ucmEauomxm. Odom oa:0wmoum usonufl3 0cm suw3 pmumouu .mmw can mm. mmmawm :Hoo Houuma who swan can finance mo cowumucoEummmH dawnsc .moa\m mom. 6 mmficoHoo Hmmssm mo HmnEsZII.H~ magma 85 Table 22.--Number of days until fungi were noted and com- plete spoilage on medium and high dry matter corn silage (35 and 45%) treated with and without propionic acida during refermentation (Experi- ment 4). . Days until visual Days until Silage Treatment fungal growth complete spoilage Control (45% DM) 7 14 Propionic (45% DM) 14 , 21 Control (35% DM) 6 15 Propionic (35% DM) 10 17 aPropionic addition: 0.6%. 86 _..H.o v m. unmowmacmflm mums moosmHmMMflp 0:» mo mcozn .mm.o “sowuwoom UHGmeoumw H.mm m.m~ o.- ¢.v~ so on naummo pd «H.6m sm.mm mm.mv 4m.¢¢ so mmmaam 2oz ZOE 2am Sam oflcofimonm Houucoo oasowmoum Houusou mucmEummHB mmmHfim .cOAumucmsummmu mcwusp .wmv can mm. womawm suoo Hmuume map pawn can Esfipme mo monsumumm80u saws so GOAuwppm ofiom oasonoum mo cosmsHmcHul.mN manna DISCUSSION The emphasis of these studies was to evaluate the effects of feeding corn silage treated with propionic acid on performance of lactating cows and its effects as a pre-r servative. Dry matter levels of corn silage ranged between 35 and 45% and added propionic acid between 0.3 and 0.6%. Experiment 1 showed no significant difference in silage and total DM intakes due to addition of 0.3 and 0.6% propionic, formic or acetic acids to medium dry matter (35-39%) corn silage; however, intakes were slightly higher for the 0.6% propionic treatment. Experiment 4, which also compared 35% dry matter silages (with and without propionic acids) again showed slightly higher intakes of cows consuming the treated silage. In experiment 2, 3 and 4 treatment of 45% DM silage with propionic resulted in increased silage and total DM intakes. Only in experiment 2 did intake differ- ences approach significance (P < 0.1). However, pooled data from the three studies comparing the control and 0.6% propionic acid treatment showed significantly higher (P < 0.05) dry matter intakes. Even though no previous studies were found where propionic acid was added to corn 87 88 silage for dairy cows, results on addition of formic acid have been reported. For example, higher intakes (11%) of dairy cows fed corn silage treated with formic acid than untreated silage were reported by Huber (1970). Derbyshire and Gordon (1969 and 1970) also found increased intakes when they treated grass silage with formic acid. Also, Candlish (1973) reported benefit from adding formic acid to barley silage (35-45% DM). No effect on intakes of silage was reported by Barker et a1. (1973) when they fed alfalfa silage treated with formic acid to dairy cows. In all four experiments, milk yields on treated silages were higher than on control silages (both at 35 and 45% DM) but only differences in experiment 2 were significant. However, pooling of the 45% DH treatments from experiments 2, 3 and 4 (as was done for intakes) showed that application of 0.6% propionic acid to high dry matter corn silage increased (P < 0.05) milk yields about 5%. The relatively short duration of feeding was probably insufficient for the differences in energy intake between treatments to be fully reflected in milk production. The reason of the higher milk production appeared due to higher dry matter intakes of silages treated with prOpionic acid. The relatively greater effects on intake and milk production of propionic treat- ment at 45 than 35% dry matter might be related to more difficulty in packing and excluding oxygen in the drier 89 silage. Higher milk yields were reported by Fisher et a1. (1971) when they fed grass silage treated with formic acid to dairy cows which was attributed to a higher efficiency of energy utilization for milk production. Derbyshire and Gordon (1970) and Waldo (1971) showed higher milk yields in cows fed grass silage treated with formic acid than in cows fed controls silages. Huber (1970) reported that milk yields increased 8% when cows were fed corn silage treated with formic acid. Inferior nutrient preservation has been associ- ated with poor quality silage (Barnet and Duncan, 1954; Langston et al., 1958). Poor quality silages were char- acterized by low lactic acid, high acetic and butyric acids and a pH of 4.8 or above. In these studies, lactic acid production was usually lower for propionic treated silages than controls, but the depression was not as great as for silages treated formic acid. Data in experiments 1 and 2 suggest a greater effect on intake and milk yields from adding propionic acid to medium and high dry matter silages than results from addition of formic acid. This superiority might be explained by the work of Britt et a1. (1975) who showed that propionic acid was a more effective fungicide than formic acid when applied to corn silage. However, differences in lactic production between propionic treated and control silages were not significant. Hence, it can be concluded that the addition of 0.6% propionic 9O acid to medium or high dry matter silage did not diminish its normal preservation potential. On the contrary, the refermentation data from experiment 4 show that propionic acid markedly improved preservation of corn silage as indicated by lower heat production and fungal counts of treated compared to control silages after exposure to air. Huber et a1. (1972) reported that lactic acid production was less in formic treated silage than control. Similar results were found by Lopez et a1. (1970) and Wilkins and Wilson (1969), when they treated grass silages with formic acid. LOpez et al. (1970) noted that lactic acid production declined with the maturity. This effect was also shown in experiment 4, with 35% DM higher than 45%. The pH of silages was related to the production of acids. Experiment 4 showed that pH was slightly less in treated silage than the control at 35% DM, but slightly higher than the control at 45% DH. In experiment 1, the pH was higher in propionic treated than control silage. Waldo (1969) found that pH was lower when grass silage was treated with formic acid. Similar results were found by Wilson and Wilkins (1969 and 1973), and Candlish and McKirdy (1973). In experiment 1, the lowest pH value was shown for treatment with formic acid alone. The reason for a greater decrease in pH from formic than propionic treatment was because formic is a stronger acid. 91 In all experiments propionic treatments resulted in cooler silage than controls. This applied to all heights and at both 35 and 45% DM. The decreased heating was due to inhibition of growth of both bacteria and fungi as reported by Daniel et al. (1970) for grass silage treated with propionic. Also, Goering and Gordon (1973) found that treatment of 35-50% DM grass silage with pro- pionic or ammonium isobutyrate resulted in lower tempera- tures than control silages. Propionic treatment also resulted in cooler silage while feeding out which was again due to inhibiting growth of organisms. The higher intakes of silages treated with propionic acid may have been partially due to its effect on silage stability during feeding. When silages were exposed to air in experiments 3 and 4 (refermentation), propionic treatment again retarded heating, fungal development and days until complete spoil- age, which was related to the antimicrobial activity of the additive. From these data it can be concluded that treatment of high dry matter (45-50%) corn silage with 0.6% propionic acid results in a cooler fermentation and more stable silage, which stimulates dry matter intakes and increases milk production, but the critical question is its pro- fitability. At present prices the cost of added propionic acid would be about 11¢ per cow daily and higher intakes 92 (12% of silage DM) would increase feed cost about 8¢/ day. If an increase of 5% milk production were realized (as observed from pooled data), then a cow producing 25 kg of milk daily would yield 1.25 kg more milk if consuming .treated silage. The value of this milk (at $10.00/cwt) would be 28¢. Hence, the profit from the practice might be calculated at 9¢/cow daily. SUMMARY Lactating Holstein cows were used to evaluate the nutritive value of corn silages treated with organic acids. Initially (experiment 1), propionic, formic and acetic acids were applied to medium dry matter silage with little effect on intakes or milk yields. In experiment 2 propionic treatment of high dry matter silages increased animal performance and was more effective than formic acid. Experiments 3 and 4 also showed trend toward higher intakes and milk yields on propionic than control silages. Decreasing dry matter from 45% silage to 35% with added water had no effect on intakes or milk yields when com- pared to 45% DM control silage. Pooled data for experi- ments 2, 3 and 4 showed significantly (P < 0.05) higher intakes and milk yields from propionic treatment. Superior preservation was suggested by decreased temperatures and fungal counts. Normal concentration of lactic acid and normal pH values result from propionic treatment. The higher milk yields resulting from propionic treatment to high dry matter silage was calculated as a profitable practice at present prices. 93 LITERATURE CITED LITERATURE CITED Anonymous. 1968. To market propionic acid for moist grain protection. Feedstuffs, p. 1. September. Archibald, J. G. 1953. Sugar and acids in grass silage. J. Dairy Sci. 36:385. Arends, L. G., R. D. Wyatt, M. H. Gehle, and P. B. Hamilton. 1972. Preservation of high moisture corn with volatile fatty acids. Glst Ann. Meeting of Poultry Sci. Assn. 91. Abstr. Barker, R. A., D. N. Mowat, J. B. Stone, K. R. Stevenson, and M. G. Freeman. 1973. Formic acid or formic acid-formation as a silage additive. Can. J. Anim. Sci. 53:465. Barnet, A. J. G., and R..E. B. Duncan. 1954. Volatile fatty acids in laboratory and field silages. J. Sci. Food Agric. 5:120. Bolsen, K. K., J. G. Riley, and J. D. Hoover. 1973. Four forage sorghum silage additives evaluated. KSU Cattleman's Day Research Report. Boman, R. 1975. 'Influence of source and level of non- protein-nitrogen additions on the nutritive value of corn silage. Ph.D. thesis, Michigan State University. Bothast, R. J., G. H. Adams, E. E. Hatfield, and E. B. Lancaster. 1975. Preservation of high moisture corn. A microbiological evaluation. J. Dairy Sci. 58:386. Britt, D. G. 1973. Effect of organic acids and non protein-nitrogen on fungal growth, nutritive value, fermentation, and refermentation of corn silage and high moisture corn. Ph.D. thesis, Michigan State University. 94 95 Britt, D. G., and J. T. Huber. 1974. High moisture corn treated with NPN and acid. J. Anim. Sci. 39:233. Britt, D. G., J. T. Huber, and A. L. Rogers. 1975. 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Organic acid deter- mination on treated and untreated corn silage. Can. J. Plant Sci. 53:105. Carpintero, M. G., A. J. Holding, and P. McDonald. 1969. Fermentation studies on lucerne. J. Sci. Food Agric. 20:677. Castle, M. E., and J. N. Watson. 1970. Silage and milk production, a comparison between grass silage made with and without formic acid. J. Brit. Grassl. Soc. 25:65. Chamberlain, C. C., H. A. Fribourg, K. M. Barth, J. H. Felts, and J. M. Anderson. 1971. Effect of maturity of corn silage at harvest on the perform- ance of feeder heifers. J. Anim. Sci. 33:161. 96 Chandler, P. T., C. N. Miller, and E. Jahn. 1975. Feeding value and nutrient preservation of high moisture corn ensiled in conventional silos for lactating dairy cows. J. Dairy Sci. 58:682. Christensen, C. M. 1949. Deterioration of stored grains by fungi. Botanical Rev. 23:108. Christensen, C. M. 1973. Tests with propionic and acetic acids as grain preservatives. Feedstuffs. February:36. Christensen, C. M., and D. R. 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