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Performance of Lactating Cows Fed Alfalfa Ensiled with Grain1
Performance of Lactating Cows Fed Alfalfa Ensiled with Grain 1 W. L. SHOCKEY, 2 B. A, DEHORITY, and H. R. CONRAD Departments of Dairy and Animal Science Ohio Agricultural Research and Development Center Ohio State University Wooster 44691
ABSTRACT
field (13). Hibbs et al. (12) ensiled alfalfa (Medicago sativa L.) with agrain mix of ground shelled corn. This process allowed the forage to be chopped at high (< 40% dry matter) moisture, which minimized field losses. The addition of the grain mix with high dry matter (> 85% dry matter) at ensiling reduced the moisture content of the ensiled mass (> 45% dry matter) and minimized fermentation and seepage losses. Further, proper formulation of the grain mix resulted in a complete ensiled diet that was adapted easily to mechanized feeding. The purpose of this experiment was to examine effects of ensiling alfalfa with grain mix of ground shelled horn on resulting silage fermentation and on performance of lactating dairy cows fed the silage.
Effects of ensiling alfalfa w i t h a grain mix of ground shelled corn on fermentation characteristics of silage and on performance of lactating dairy cows fed the silage were examined. Two b o t t o m unloading silos were filled with alternate loads of alfalfa (Medicago sativa L.) wilted to 45% dry matter. For one silo, grain mix was applied to the top of loads of forage (grain:forage 1:5, wet basis). Each of two groups of four lactating dairy cows was fed the alfalfa ensiled with grain or alfalfa ensiled alone plus an equivalent amount of grain for 4 mo. Cows fed the complete ensiled diet consumed less dry matter and produced less milk, fat, and protein than cows fed conventionally. Reduced consumption of dry matter was attributed to higher concentrations of lactic acid, ammonia, and nonprotein nitrogen in the complete ensiled diet. Day to day counts of silage anaerobes were highly variable. Presumptive identification of anaerobes indicated that Lactobacillus spp. dominated the populations that developed in both silages.
MATERIALS AND METHODS Silo Filling
INTRODUCTION
Hay crops generally are wilted in the field prior to ensiting to inhi/Sit growth of putrefactive bacteria in the resulting silage and to prevent seepage losses (2). However, long wilting is associated with high losses of dry matter in the
Received July 23, 1984. l Salaries and research support provided by State and Federal Funds appropriated to the Ohio Agricultural Research and Development Center, The Ohio State University. Journal Article No. 113-84. 2USDA-ARS-NCR, Ohio Cluster Program, US Dairy Forage Research Center. 1985 J Dairy Sci 68:755-759
Two identical oxygen-limiting silos (6.1 X 9.1 m) (A. O. Smith, Arlington Heights, IL) were'filled with alternate loads of third cutting alfalfa that was cut at late bud stage, wilted to about 45% dry matter, and chopped to 2- to 4-cm lengths. For the silo receiving alfalfa with added grain, each load of alfalfa was weighed and the grain mix applied to the top of the load at a ratio of 1:5 grain to forage (wet basis). The other silo received forage only. Compositions of forage and grain mix are in Table 1. Animal Production
Each of two groups of four (eight total) lactating dairy cows (Holstein) balanced for age (lactation number = 3.0, SD = 1.0) and stage of lactation (mean lactation day = 231, SD = 71) were fed the ensiled alfalfa and grain mix (CED) or the alfalfa ensiled alone plus an equivalent amount of grain mix added at feeding time (STD) for 4 mo. At the end of the 2nd mo, diets were switched so that each cow was assigned each of the diets for 2 mo. The
755
756
SHOCKEY ET AL.
TABLE 1. Chemical analysis of forage and grain.
% Dry matter % Crude protein 3 Nonprotein nitrogen 4 Acid detergent insoluble nitrogen 4 % Acid detergent fiber 3 pH
Forage ~
Grain mix 2
46.6 17.8 17.1 6.9 34.8 5.6
87.4 16.8 1.9 7.9 9.2 ...
aComposite of four samples. 2Composition of grain mix was 80% ground shelled corn, 18% soybean meal, 1% trace mineral salt, .9% BiofosTlvl (International Mineral and Chemical Corp., Skokie, IL), and .1% selenium premix. 3Dry matter basis. 4As percent of total nitrogen.
feeding trial was designed as a crossover; lactation number and day of lactation were covariates. Dry matter intake, milk, fat, and protein production were measured. Silage was sampled three times each week and composited by week. Microbiological Studies
Total numbers of anaerobic bacteria were determined on 20 silage samples collected during the 4 mo. One-kilogram samples were taken from the silo, mixed, and a 100-g subsample was chopped to .5- to 1-cm lengths in a food processor (Sunbeam Corporation, Chicago, IL). A 20-g subsample then was added to 180 ml of anaerobic dilution solution (ADS) and blended for 3 rain under a stream of O2-free CO2 (3). Cultural methods, preparation of media, and serial dilutions were in (9). The medium used for roll tubes was the basal medium of Grubb and Dehority (11) with the concentration of ruminal fluid reduced to 10% and the following additions: .025% each of glucose and cellobiose and .05% soluble starch; .2% trypticase, .45% volatile fatty acid mixture of Caldwell and Bryant (5); .05% yeast extract; and .1% of .1% hemin solution. Numbers of acid tolerant bacteria were counted in the same medium except it was prepared and tubed under nitrogen gas and buffered to pH 4.5 with acetic acid-sodium acetate buffer. The procedure for medium preparation was modified so that all ingredients except buffer and cysteine were
added, pH was adjusted to 4.5, and the medium was reduced and autoclaved under N2. After the medium was autoclaved, sterile buffer and cysteine were added, and the medium was tubed anaerobically and aseptically. Unless designated otherwise, methods for characterization of isolates were in (8, 9). Characteristics for presumptive identification were Gram stain, motility, morphology, anaerobiosis, temperature sensitivity, and end product analysis. Chemical Analysis
All chemical analyses were on freeze-dried or frozen material. Dry matter (DM) was determined by dryinl~ overnight in a forced-air oven set at 100-C. Nitrogen determinations were by Kjeldahl method. Nonprotein nitrogen (NPN) was estimated by tungstic acid precipitation (19) and acid detergent fiber (ADF) and acid detergent insoluble nitrogen (ADIN) by the method of Goering and Van Soest (10). Ammonia nitrogen (NH3-N) was measured in aqueous extracts with a Technicon AutoanalyzerTM (Technieon Instruments Corp., Tarrytown, NY) with the alkaline phenol, hypochlorite reaction. Silage pH was measured with a standard pH meter (14) on frozen material, and total energy was determined by bomb calorimetry on lyophilized samples (< 1.2% energy loss due to lyophilization). Organic acids were determined on aqueous extracts, volatile fatty acids by gas chromatography (4), and nonvolatile acids by high pressure liquid chromatography (17).
757
PRODUCTION TECHNICAL NOTE
Statistical
Animal production data were analyzed by least squares analysis of variance, and differences between means were separated by single degree of freedom comparisons (15). Microbiologic data were analyzed by Student's t test. RESULTS A N D DISCUSSION Animal Production
The CED diet contained lower (P<.I) ADIN concentrations and higher (P<.05) lactic acid, NH3-N, and NPN concentrations when compared with the STD diet (Table 2). Some inhibition of the oxidative process immediately after ensiling may have occurred in the silo containing forage plus grain, possibly by a more densely packed mass that could have excluded oxygen more efficiently, reduced heating, and resulted in lower ADIN concentration. Lactic acid (3.1 vs. 2.3% DM), NH3-N (13.3 vs. 15.3% of total N), and NPN (30.4 vs. 35.7% of total N) concentrations in the material removed from the silos (CED vs. STD) were similar; however, grain added at feeding time diluted these chemical components in the STD diet. As a
result, concentrations of lactic acid, NH3-N, and NPN were higher (P<.05) (Table 2) in the CED compared to the STD diet as presented to COWS.
Dry matter intake was lower (P<.001) for cows consuming CED compared with those consuming STD, which apparently resulted in depressed animal performance as measured by milk, fat, and protein production (Table 3). These results are similar to those of Hibbs et al. (12), who found that when concentrate was mixed with forage at ensiling, dry matter intake was lower compared to mixing the same a m o u n t of concentrate at feeding. Depressed feed intake in this experiment may have been caused by higher concentrations of lactic acid, NH3-N, and NPN in the CED compared with the STD (1, 6). Even though ADIN concentrations were higher ( P < . l ) in STD vs. CED, suggesting depressed nitrogen digestibility (16, 18), there was no apparent effect of heat damage of the forage on cow performance. The predictive equation for net energy for lactation of Conrad et al. (7) suggests that the net energy available for milk production changes little for ADIN concentrations in the range in this experiment. Also, any effect of heat damaged protein
TABLE 2. Chemical analysis of diets fed to lactating dairy cows. 1
% Dry matter % Crude protein 2 Nonprotein nitrogen3,* Ammonia nitrogen 3,,. Acid detergent insoluble nitrogen a'* % Acid detergent fiber 2 Energyz'4 pH % Lactic acid2,*** % Acetic acid 2
Complete ensiled diet (CED)
Grain added at feeding (STD)
SE
50.0 17.2 30.4 13.5
47.4 16.6 20.6 10.9
4.6 .3 5.0 2.5
13.3 32.5 4.45 4.8 3.1 .9
16.7 31.3 4.51 4.7 1.6 .8
4.1 4.6 .08 .3 .3 .3
Least squares mean, n = 10. 2Dry matter basis. 3As percent total nitrogen. 4Calories/gram. *Means differ P<.10. differ P<.05. * * *Means differ P<.0001. **Means
Journal of Dairy Science Vol. 68, No. 3, 1985
758
SHOCKEY ET AL.
TABLE 3. Performance of lactating dairy cows fed alfalfa ensiled with grain or alfalfa silage and grain added at feeding. 1 Complete ensiled diet (CED) Dry matter intake 2 , , , , Milk yield 2,tt 4% Fat-corrected milk yield s, * • • Fat yield3,t t Protein yield 3,tt % Milk fat % Milk protein
Grain added at feeding (STD)
16.9 16.8
17.6 18.3
15.8 607 524 3.7 3.2
16.9 637 583 3.8 3.2
SE .1 .2 .1 6 5 .2 .0
1Least squares mean, n = 8. 2Kilograms/day. 3Grams/day. * **Means
differ P<.001.
ttMeans differ P<.0001.
o n t h e p e r f o r m a n c e o f cows c o n s u m i n g STD m a y have b e e n m a s k e d b y t h e d e p r e s s e d DM intake o f cows c o n s u m i n g CED.
Silage M icrobiology As m e a s u r e d b y t o t a l and acid t o l e r a n t b a c t e r i a and b y p r e s u m p t i v e species identification, t h e r e were no significant d i f f e r e n c e s in m i c r o b i o l o g y o f silages (Table 4). High
s t a n d a r d deviations o f t h e m e a n s indicate high variation o f the d a y to day n u m b e r o f m i c r o organisms. The n u m b e r o f acid t o l e r a n t anae r o b e s t e n d e d to be higher in t h e silo c o n t a i n i n g forage plus grain, w h i c h m i g h t indicate diff e r e n c e s in t h e m e t a b o l i c characteristics o f the microbial p o p u l a t i o n s t h a t d e v e l o p e d in t h e silages. P r e s u m p t i v e i d e n t i f i c a t i o n o f 16 ana e r o b e s isolated f r o m each silo, h o w e v e r , i n d i c a t e d little d i f f e r e n c e in t y p e s o f m i c r o -
TABLE 4. Presumptive identification of anaerobic microorganisms isolated from alfalfa ensiled with or without grain. Colony forming units per 10 - s g of "wet silage Alfalfa ensiled with grain
Total anaerobes (n=20) Acid tolerant anaerobes (n=8) Presumptive identification Lactobacillus plantarum (HL) 2 Lactobacillus brevis (HT) Streptococcus spp. (HL) Nonmotile Gram (--) rod (HL) Motile Gram (--) rod (HL) Motile Gram (+) rod (HL) Motile Gram (+) rod (HT) 1Number of isolets. 2HL = Homolactic, HT = Heterolactic. Journal of Dairy Science Vol. 68, No. 3, 1985
2.46 1.03
Alfalfa ensiled alone
SD
X
SD
1.14 .62
2.24 .57
1.24 .35
5 4
7 6
3
1
2 1
2
1 1
PRODUCTION TECHNICAL NOTE o r g a n i s m s t h a t p o p u l a t e d t h e s e silos. T h e m a j o r i t y o f t h e m i c r o b e s isolated were L a c t o bacillus spp. o f w h i c h a p p r o x i m a t e l y h a l f were h o m o f e r m e n t a t i v e lactic a c i d - p r o d u c i n g organisms. CONCLUSIONS
Use o f a c o m p l e t e ensiled diet, u n d e r t h e c o n d i t i o n s r e p o r t e d in this e x p e r i m e n t , increased c o n c e n t r a t i o n s of lactic acid, N H a - N , a n d NPN a n d decreased c o n c e n t r a t i o n s o f A D I N in feed p r e s e n t e d t o t h e cows c o m p a r e d w i t h alfalfa silage and grain fed c o n v e n t i o n a l l y . Cows c o n s u m i n g t h e c o m p l e t e ensiled diets p r o d u c e d less milk, fat, a n d p r o t e i n t h a n cows c o n s u m i n g t h e diet fed c o n v e n t i o n a l l y . P r e s u m a b l y this e f f e c t was t h e r e s u l t of d e p r e s s e d feed i n t a k e caused b y h i g h e r acid a n d NPN c o n c e n t r a t i o n s in t h e c o m p l e t e ensiled diet. T h e r e were n o a p p a r e n t d i f f e r e n c e s in t h e anaerobic microbiological populations that d e v e l o p e d in t h e s e silages. T h e e c o n o m i c s of using a c o m p l e t e ensiled diet, w i t h r e s p e c t to n u t r i e n t loss caused b y field wilting, n e e d s t o be d e t e r m i n e d . REFERENCES
1 Baile, C. A., and W. H. Pfander. 1966. A possible chemosensitive regulatory mechanism of ovine feed intake. Am. J. Physiol. 210:1243. 2 Beck, T. 1978. The microbiology of silage fermentation. Fermentation of silage - A review. Natl. Feed Ingred. Assoc. 3 Bryant, M. P., and L. A. Burkey. 1953. Cultural methods and some characteristics of some of the more numerous groups of bacteria in the bovine rumen. J. Dairy Sci. 36:205. 4 Byers, F. M. 1980. Effects of limestone, monensin and feeding level on corn silage net energy value and composition of growth in cattle. J. Anita. Sci. 50:1127. 5 Caldwell, D. R., and M. P. Bryant. 1966. Medium
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without rumen fluid for nonselective enumeration and isolation of rumen bacteria. Appl. Microbiol. 14:794. 6 Conrad, H. R., C. A. Baile, and J. Mayer. 1977. Changing meal patterns and suppression of feed intake with increasing amounts of dietary nonprotein nitrogen in ruminants. J. Dairy Sci. 60:1725. 7 Conrad, H. R., W. P. Weiss, W. O. Odwongo, and W. L. Shockey. 1984. Estimating net energy lactation from components of cell solubles and cell walls. J. Dairy Sci. 67:427. 8 Dehority, B. A. 1966. Characterization of several bovine tureen bacteria isolated with a xylan medium. J. Bacteriol. 91:1724. 9 Dehority, B. A. 1969. Pectin-fermenting bacteria isolated from the bovine rumen. J. Bacteriol. 99:189.
10 Goering, H. K., and P. J. Van Soest. 1970. Forage fiber analysis. Agric. Handbook No. 379. US Dep. Agric., Agric. Res. Serv. 11 Grubb, J, A., and B. A. Dehority. 1976. Variations in colony counts of total viable anaerobic rumen bacteria as influenced by media and cultural methods. Appl. Environ. Microbiol. 31:262. 12 Hibbs, J. W., H. R. Conrad, and R. W. VanKeuren. 1979. Effects of different forages and methods of feeding concentrate on dry matter intake and milk production in dairy cows fed complete diets. Ohio Agric. Res. Dev. Ctr. Res. Cir. No. 248. 13 Noller, C. H. 1973. Grass-legume silage. Forages. 3rd ed. The Iowa State Univ. Press, Ames. 14 Parker, R. B. 1978. Methodology for determining quality of silage. Natl. Feed Ingred. Assoc. 15 Steel, R.G.D., and J. H. Torrie. 1960. Principles and procedures of statistics. McGraw-Hill Book Company, Inc., New York, NY. 16 Thomas, J. W. 1976. Recent research on role of heating and preservatives in haylages and silages. Proc. Dist. Feed Res. Counc. 31:22. 17 Turkelson, V. T., and M. Richards. 1978. Separation of the citric acid cycle acids by liquid chromatography. Anal. Chem. 50:1420. 18 Van Soest, P. J. 1970. The chemical basis for the nutritive evaluation of forages. Page 6 in Proc. Natl. Conf. Forage Eval. Util,, Univ. Nebraska. 19 Winter, K. A., R. R. Johnson, and B. A. Dehority. 1964. Metabolism of urea nitrogen by mixed cultures of rumen bacteria grown on cellulose. J. Dairy Sci, 47:793.
Journal of Dairy Science Vol. 68, No. 3, 1985
ABSTRACT
field (13). Hibbs et al. (12) ensiled alfalfa (Medicago sativa L.) with agrain mix of ground shelled corn. This process allowed the forage to be chopped at high (< 40% dry matter) moisture, which minimized field losses. The addition of the grain mix with high dry matter (> 85% dry matter) at ensiling reduced the moisture content of the ensiled mass (> 45% dry matter) and minimized fermentation and seepage losses. Further, proper formulation of the grain mix resulted in a complete ensiled diet that was adapted easily to mechanized feeding. The purpose of this experiment was to examine effects of ensiling alfalfa with grain mix of ground shelled horn on resulting silage fermentation and on performance of lactating dairy cows fed the silage.
Effects of ensiling alfalfa w i t h a grain mix of ground shelled corn on fermentation characteristics of silage and on performance of lactating dairy cows fed the silage were examined. Two b o t t o m unloading silos were filled with alternate loads of alfalfa (Medicago sativa L.) wilted to 45% dry matter. For one silo, grain mix was applied to the top of loads of forage (grain:forage 1:5, wet basis). Each of two groups of four lactating dairy cows was fed the alfalfa ensiled with grain or alfalfa ensiled alone plus an equivalent amount of grain for 4 mo. Cows fed the complete ensiled diet consumed less dry matter and produced less milk, fat, and protein than cows fed conventionally. Reduced consumption of dry matter was attributed to higher concentrations of lactic acid, ammonia, and nonprotein nitrogen in the complete ensiled diet. Day to day counts of silage anaerobes were highly variable. Presumptive identification of anaerobes indicated that Lactobacillus spp. dominated the populations that developed in both silages.
MATERIALS AND METHODS Silo Filling
INTRODUCTION
Hay crops generally are wilted in the field prior to ensiting to inhi/Sit growth of putrefactive bacteria in the resulting silage and to prevent seepage losses (2). However, long wilting is associated with high losses of dry matter in the
Received July 23, 1984. l Salaries and research support provided by State and Federal Funds appropriated to the Ohio Agricultural Research and Development Center, The Ohio State University. Journal Article No. 113-84. 2USDA-ARS-NCR, Ohio Cluster Program, US Dairy Forage Research Center. 1985 J Dairy Sci 68:755-759
Two identical oxygen-limiting silos (6.1 X 9.1 m) (A. O. Smith, Arlington Heights, IL) were'filled with alternate loads of third cutting alfalfa that was cut at late bud stage, wilted to about 45% dry matter, and chopped to 2- to 4-cm lengths. For the silo receiving alfalfa with added grain, each load of alfalfa was weighed and the grain mix applied to the top of the load at a ratio of 1:5 grain to forage (wet basis). The other silo received forage only. Compositions of forage and grain mix are in Table 1. Animal Production
Each of two groups of four (eight total) lactating dairy cows (Holstein) balanced for age (lactation number = 3.0, SD = 1.0) and stage of lactation (mean lactation day = 231, SD = 71) were fed the ensiled alfalfa and grain mix (CED) or the alfalfa ensiled alone plus an equivalent amount of grain mix added at feeding time (STD) for 4 mo. At the end of the 2nd mo, diets were switched so that each cow was assigned each of the diets for 2 mo. The
755
756
SHOCKEY ET AL.
TABLE 1. Chemical analysis of forage and grain.
% Dry matter % Crude protein 3 Nonprotein nitrogen 4 Acid detergent insoluble nitrogen 4 % Acid detergent fiber 3 pH
Forage ~
Grain mix 2
46.6 17.8 17.1 6.9 34.8 5.6
87.4 16.8 1.9 7.9 9.2 ...
aComposite of four samples. 2Composition of grain mix was 80% ground shelled corn, 18% soybean meal, 1% trace mineral salt, .9% BiofosTlvl (International Mineral and Chemical Corp., Skokie, IL), and .1% selenium premix. 3Dry matter basis. 4As percent of total nitrogen.
feeding trial was designed as a crossover; lactation number and day of lactation were covariates. Dry matter intake, milk, fat, and protein production were measured. Silage was sampled three times each week and composited by week. Microbiological Studies
Total numbers of anaerobic bacteria were determined on 20 silage samples collected during the 4 mo. One-kilogram samples were taken from the silo, mixed, and a 100-g subsample was chopped to .5- to 1-cm lengths in a food processor (Sunbeam Corporation, Chicago, IL). A 20-g subsample then was added to 180 ml of anaerobic dilution solution (ADS) and blended for 3 rain under a stream of O2-free CO2 (3). Cultural methods, preparation of media, and serial dilutions were in (9). The medium used for roll tubes was the basal medium of Grubb and Dehority (11) with the concentration of ruminal fluid reduced to 10% and the following additions: .025% each of glucose and cellobiose and .05% soluble starch; .2% trypticase, .45% volatile fatty acid mixture of Caldwell and Bryant (5); .05% yeast extract; and .1% of .1% hemin solution. Numbers of acid tolerant bacteria were counted in the same medium except it was prepared and tubed under nitrogen gas and buffered to pH 4.5 with acetic acid-sodium acetate buffer. The procedure for medium preparation was modified so that all ingredients except buffer and cysteine were
added, pH was adjusted to 4.5, and the medium was reduced and autoclaved under N2. After the medium was autoclaved, sterile buffer and cysteine were added, and the medium was tubed anaerobically and aseptically. Unless designated otherwise, methods for characterization of isolates were in (8, 9). Characteristics for presumptive identification were Gram stain, motility, morphology, anaerobiosis, temperature sensitivity, and end product analysis. Chemical Analysis
All chemical analyses were on freeze-dried or frozen material. Dry matter (DM) was determined by dryinl~ overnight in a forced-air oven set at 100-C. Nitrogen determinations were by Kjeldahl method. Nonprotein nitrogen (NPN) was estimated by tungstic acid precipitation (19) and acid detergent fiber (ADF) and acid detergent insoluble nitrogen (ADIN) by the method of Goering and Van Soest (10). Ammonia nitrogen (NH3-N) was measured in aqueous extracts with a Technicon AutoanalyzerTM (Technieon Instruments Corp., Tarrytown, NY) with the alkaline phenol, hypochlorite reaction. Silage pH was measured with a standard pH meter (14) on frozen material, and total energy was determined by bomb calorimetry on lyophilized samples (< 1.2% energy loss due to lyophilization). Organic acids were determined on aqueous extracts, volatile fatty acids by gas chromatography (4), and nonvolatile acids by high pressure liquid chromatography (17).
757
PRODUCTION TECHNICAL NOTE
Statistical
Animal production data were analyzed by least squares analysis of variance, and differences between means were separated by single degree of freedom comparisons (15). Microbiologic data were analyzed by Student's t test. RESULTS A N D DISCUSSION Animal Production
The CED diet contained lower (P<.I) ADIN concentrations and higher (P<.05) lactic acid, NH3-N, and NPN concentrations when compared with the STD diet (Table 2). Some inhibition of the oxidative process immediately after ensiling may have occurred in the silo containing forage plus grain, possibly by a more densely packed mass that could have excluded oxygen more efficiently, reduced heating, and resulted in lower ADIN concentration. Lactic acid (3.1 vs. 2.3% DM), NH3-N (13.3 vs. 15.3% of total N), and NPN (30.4 vs. 35.7% of total N) concentrations in the material removed from the silos (CED vs. STD) were similar; however, grain added at feeding time diluted these chemical components in the STD diet. As a
result, concentrations of lactic acid, NH3-N, and NPN were higher (P<.05) (Table 2) in the CED compared to the STD diet as presented to COWS.
Dry matter intake was lower (P<.001) for cows consuming CED compared with those consuming STD, which apparently resulted in depressed animal performance as measured by milk, fat, and protein production (Table 3). These results are similar to those of Hibbs et al. (12), who found that when concentrate was mixed with forage at ensiling, dry matter intake was lower compared to mixing the same a m o u n t of concentrate at feeding. Depressed feed intake in this experiment may have been caused by higher concentrations of lactic acid, NH3-N, and NPN in the CED compared with the STD (1, 6). Even though ADIN concentrations were higher ( P < . l ) in STD vs. CED, suggesting depressed nitrogen digestibility (16, 18), there was no apparent effect of heat damage of the forage on cow performance. The predictive equation for net energy for lactation of Conrad et al. (7) suggests that the net energy available for milk production changes little for ADIN concentrations in the range in this experiment. Also, any effect of heat damaged protein
TABLE 2. Chemical analysis of diets fed to lactating dairy cows. 1
% Dry matter % Crude protein 2 Nonprotein nitrogen3,* Ammonia nitrogen 3,,. Acid detergent insoluble nitrogen a'* % Acid detergent fiber 2 Energyz'4 pH % Lactic acid2,*** % Acetic acid 2
Complete ensiled diet (CED)
Grain added at feeding (STD)
SE
50.0 17.2 30.4 13.5
47.4 16.6 20.6 10.9
4.6 .3 5.0 2.5
13.3 32.5 4.45 4.8 3.1 .9
16.7 31.3 4.51 4.7 1.6 .8
4.1 4.6 .08 .3 .3 .3
Least squares mean, n = 10. 2Dry matter basis. 3As percent total nitrogen. 4Calories/gram. *Means differ P<.10. differ P<.05. * * *Means differ P<.0001. **Means
Journal of Dairy Science Vol. 68, No. 3, 1985
758
SHOCKEY ET AL.
TABLE 3. Performance of lactating dairy cows fed alfalfa ensiled with grain or alfalfa silage and grain added at feeding. 1 Complete ensiled diet (CED) Dry matter intake 2 , , , , Milk yield 2,tt 4% Fat-corrected milk yield s, * • • Fat yield3,t t Protein yield 3,tt % Milk fat % Milk protein
Grain added at feeding (STD)
16.9 16.8
17.6 18.3
15.8 607 524 3.7 3.2
16.9 637 583 3.8 3.2
SE .1 .2 .1 6 5 .2 .0
1Least squares mean, n = 8. 2Kilograms/day. 3Grams/day. * **Means
differ P<.001.
ttMeans differ P<.0001.
o n t h e p e r f o r m a n c e o f cows c o n s u m i n g STD m a y have b e e n m a s k e d b y t h e d e p r e s s e d DM intake o f cows c o n s u m i n g CED.
Silage M icrobiology As m e a s u r e d b y t o t a l and acid t o l e r a n t b a c t e r i a and b y p r e s u m p t i v e species identification, t h e r e were no significant d i f f e r e n c e s in m i c r o b i o l o g y o f silages (Table 4). High
s t a n d a r d deviations o f t h e m e a n s indicate high variation o f the d a y to day n u m b e r o f m i c r o organisms. The n u m b e r o f acid t o l e r a n t anae r o b e s t e n d e d to be higher in t h e silo c o n t a i n i n g forage plus grain, w h i c h m i g h t indicate diff e r e n c e s in t h e m e t a b o l i c characteristics o f the microbial p o p u l a t i o n s t h a t d e v e l o p e d in t h e silages. P r e s u m p t i v e i d e n t i f i c a t i o n o f 16 ana e r o b e s isolated f r o m each silo, h o w e v e r , i n d i c a t e d little d i f f e r e n c e in t y p e s o f m i c r o -
TABLE 4. Presumptive identification of anaerobic microorganisms isolated from alfalfa ensiled with or without grain. Colony forming units per 10 - s g of "wet silage Alfalfa ensiled with grain
Total anaerobes (n=20) Acid tolerant anaerobes (n=8) Presumptive identification Lactobacillus plantarum (HL) 2 Lactobacillus brevis (HT) Streptococcus spp. (HL) Nonmotile Gram (--) rod (HL) Motile Gram (--) rod (HL) Motile Gram (+) rod (HL) Motile Gram (+) rod (HT) 1Number of isolets. 2HL = Homolactic, HT = Heterolactic. Journal of Dairy Science Vol. 68, No. 3, 1985
2.46 1.03
Alfalfa ensiled alone
SD
X
SD
1.14 .62
2.24 .57
1.24 .35
5 4
7 6
3
1
2 1
2
1 1
PRODUCTION TECHNICAL NOTE o r g a n i s m s t h a t p o p u l a t e d t h e s e silos. T h e m a j o r i t y o f t h e m i c r o b e s isolated were L a c t o bacillus spp. o f w h i c h a p p r o x i m a t e l y h a l f were h o m o f e r m e n t a t i v e lactic a c i d - p r o d u c i n g organisms. CONCLUSIONS
Use o f a c o m p l e t e ensiled diet, u n d e r t h e c o n d i t i o n s r e p o r t e d in this e x p e r i m e n t , increased c o n c e n t r a t i o n s of lactic acid, N H a - N , a n d NPN a n d decreased c o n c e n t r a t i o n s o f A D I N in feed p r e s e n t e d t o t h e cows c o m p a r e d w i t h alfalfa silage and grain fed c o n v e n t i o n a l l y . Cows c o n s u m i n g t h e c o m p l e t e ensiled diets p r o d u c e d less milk, fat, a n d p r o t e i n t h a n cows c o n s u m i n g t h e diet fed c o n v e n t i o n a l l y . P r e s u m a b l y this e f f e c t was t h e r e s u l t of d e p r e s s e d feed i n t a k e caused b y h i g h e r acid a n d NPN c o n c e n t r a t i o n s in t h e c o m p l e t e ensiled diet. T h e r e were n o a p p a r e n t d i f f e r e n c e s in t h e anaerobic microbiological populations that d e v e l o p e d in t h e s e silages. T h e e c o n o m i c s of using a c o m p l e t e ensiled diet, w i t h r e s p e c t to n u t r i e n t loss caused b y field wilting, n e e d s t o be d e t e r m i n e d . REFERENCES
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Journal of Dairy Science Vol. 68, No. 3, 1985