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Straw in Different Proportions as Sole Roughage in Diets for Cows in Mid-lactation1,2
Straw in Different Propodions Cows in Mid-loctation 1'2
os
Sole Roughage in Diets for
A. HALEVI, H. NEUMARK, and S. AMIR Agricultural Research Organization, The Volcani Center Department of Animal Science, P.O.B. 6, Bet Dagan, Israel Abstract
cows which were to be fed large amounts of concentrates. Rations with straw as the sole roughage depressed milk fat percentage and were of low efficiency when the percentage of straw was low (2, 12). A high intake of straw was achieved in trials where whole pelleted rations were fed (2, 12, 14). This procedure seems to be the only way of feeding an appropriate ratio of straw-concentrate for highproducing cows whereas a sufficient intake of straw could be achieved for cows in mid-lactation by chopping the straw. This trial was designed to examine the effect of different percentages of chopped straw in the diet fed to cows in mid-lactation on the yield and composition of milk, feed value, and relative proportions of volatile fatty acid (VFA) formed in the rumen.
A complete switch-back trial was designed for 12 cows in mid-lactation; they received three different rations of chopped wheat straw (Triticum aestivmn) and concentrates - 45:55 (A), 30:70 (B), and 15:85% (C). Milk yield and composition in all three treatments were similar; milk fat was relatively low although the molar percentage of ruminal acetic acid was high in all groups. Concentration of plasma glucose was similar in all three groups whereas plasma free fatty acids of group B were higher than for the two others. Differences in the composition of plasma free fatty acids were not significant. Digestibility of dry matter decreased slighly with increasing percentage of straw in the ration; metabolizable energy per gram dry matter was equal in rations B and C and lower in ration A. Cows in group C showed a higher gross efllciency in using metabo]izable energy for milk production.
Methods
Introduction
Straw as a by-product of grain production is of low nutritional value and low protein content and rich in crude fiber. It is used mainly for bedding and fed only occasionally to cattle of low production. The use of straw as a major supplier of crude fiber for rations of dairy carte could enable the farmer to obtain higher profits from part of his land by changing from growing fodder crops to growing a cash crop. Straw can be fed successfully to high-producing dairy and beef cattle instead of conventional roughage (2, 7, 12, 14). Amir et al. (2) assumed that it would be difficult to achieve a high intake of long straw for high-lactating Received February 16, 1973. a Contribution from the Agricultural Research Organization, The Volcanl Center, Bet Dagan, Israel. 1973 Series, No. 117-E. =Supported by a grant of the USDA (P.L. 480).
Twelve adult Israeli-Friesian cows in midlactation with a milk yield of 17 to 21 kg milk/day were in this experiment. The animals were allotted to three treatments (A, B, C) in a complete switch-back design (8) with three periods of 38 days. Statistical analysis was on the last 3 wk of each period. The ration contained chopped wheat straw (length of straw 6 cm) and concentrates. In treatments A, B, and C the ratio of straw to concentrates was 45:55, 30:70, and 15:85%. Concentrates of different amounts of protein were prepared to ensure equal protein per unit of dry matter (DM). Milking was three times daily and feeding was four times daily. Food was weighed before each feeding, and refused feed was weighed once a day. Every l0 days the cows were weighed on 2 consecutive days. Three weeks prior to the beginning of the experiment, all cows were fed the ration of treatment B. During this pre-experimental period they were fed 20% above requirement to provide a gradual change from higher farm feeding to the lower feeding of the experiment. Energy requirement for each cow was calculated according to milk yield and body weight at the end of the preliminary period; for the
1424
STRAW T H E SOLE
TABLE 1. Average feed requirement, chemical composition, and calorie value of the rations fed in three treatments. Factor
Treatment A
Feed requirement - - ( Straw 6.32 Concentrates 7.74 Metabolizable energy a - Per kg DM 2.38 In the ration 33.5 Component - Crude protein 12.5 Crude fiber 20.2 N-free extract 57.9 Fat 2.0 Minerals 7.4
B
C
kg DM ) ~ 3.66 1.69 8.59 9.29 (Meal) - 2.62 2.86 32.1 31.4 ( % DM ) 12.3 12.9 14.7 9.5 64.3 69.4 2.3 2.6 6.4 5.6
~Nutritional values according to NRC standards ( i l ) . DM = dry matter. various diets the cows were to receive, this feeding was kept unchanged during the whole experimental period without taking into account changes in milk yield or body weight. All calculations for energy requirements, except for maintenance, were based on metabolizable energy as recommended by the ARC (1), For maintenance, 100 kcal/kgW .r~ were allowed instead of the 85 kcal/kgW -~3 recommended by the ARC. Table 1 presents the composition of the rations fed to the animals in the three treatments. Gl,ucose and free fatty acids (FFA) in plasma. On the 26th and 36th days of each period, 1 h after the first meal of the day, blood samples were drawn from the Vena iugularis by vacutainer tubes. The quantitative and qualitative determination of the FFA blood plasma was done by first separating the FFA by thin-layer chromatography according to the method of Storry and Cfuckly (13). Then, the FFA were eluted from the gel by chloroform and prepared for gas chromatography by methylation with diazo-methane according to Luddy et al. (9). For gas-liquid chromatography a Perkin-Elmer F l l apparatus was used. A glass column of about 1.63 m length and an internal diameter of 4 mm was filled with Gas chrom P as support, coated with 10% ethyl-glycol-succinate. Temperature of oven was 175 C and of injector, 210 C. The plasma glucose content was measured colorimetrically by Biochemia Test Combination s based on specific oxidation of glucose by glucose oxidase. Rumen volatile fatty acids (VFA ). Samples of rumen liquor were taken immediately after
1425
ROUGHAGE
drawing of the blood samples, and the VFA content of the rumen liquor was determined by gas-liquid chromatography according to the method of Cottyn and Boucque (6). The pH of the tureen liquor also was measured. Milk fat and total solids were determined in samples of two consecutive days. Six milk samples were taken for each period. Digestibility trials. During the last 3 wk of each period, two groups of three cows were kept consecutively in metabolic cages, each for 10 days. During 8 of these 10 days, feces, urine, and refused feed of each cow were collected and samples of the food were taken. Chemical analyses were carried out on two pooled samples of 4 days each according to the methods of the AOAC (3). The energy content of the samples was determined with an adiabatic bomb calorimeter; the energy of methane was estimated according to the formula of Blaxter (4); and the metabolizable energy was calculated. The determination of the energy content of milk was based on daily measured milk yield and composition and calculated by the solidscorrected milk (SCM) equation of Tyrrell and Reid (15). Results
The general health and condition of the cows during the experiment was satisfactory. During the preliminary period on change from the farm to the experimental ration, milk yield dropped sharply (averaging 6 kg milk/T~mLE 2. Average daffy feed consumption, milk yield and composition, and weight gain per cow. Treatment Factor
A
B
C
SE.
Dry matter intake (kg) Total 13.38 12.35 11.11 In concentrates 7.67 8.53 9.19 +--.027 As straw 5.71 3.82 1 . 9 2 ---.112 Milk yield (kg) 47o FCM
13.26 13.65 13.46 ±.24 11.64 11.87 11.41 ±.36
Milk components ( ~ ) Fat 3.19 3.10 2.99 4-.103 SNF 8.22 8.24 8.26 ±.093 TS ll.1O 11.31 11.20 ±.072 Weight gain (g)
391
132
97
±200
Standard error of treatment difference. FCM = fat-corrected milk, SNF = solids-notfat, TS -- total solids. 3Boehringer Mmmheim, GmbH. JOURNAL OF DAIRY SCIENCE VOL. 56, No. I I
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H A L E V I ET AL
TABLE 3. pH and composition of volatile fatty acids of the rumen juice of cows.
TABLE 5, Digestibility and related measurements of diets fed to cows. Treatment
Treatment A pH
7.00
Acetic acid Propionie acid Butyric acid Valerie acid Iso-valerie acid C~.:C3
B
C
7.11
6.92
--(mol %)-68.9~ 67.3d 63.4 ¢ 18.0 18.4 20.9 1O.0 10.7 11.3 1.53b 1.75b 2.30~ 1.26° 1.48" 1.61 ~ 3.8P 3 . 7 5 " 3.18~
SE +_ .097 +_ .79 +_1.29 +_ .68 +- .118 +- .059 +_ .11
~,b Differences significant at P < .05. c,a Differences significant at P < .01. SE ---- standard error of treatment difference, cow per day). During the experimental periods, the decline in milk yield was normal. I n Table 2, data on food intake, milk yield and composition, and body weight changes in the various treatments are presented. The cows in treatment A left on the average 13% of the offered straw during the last 3 wks of the experiment. The calculation of the various data was based on amounts actually consumed by each individual cow. (Refusals ranged from .14 to 1.46 kg straw.) In other treatments there was no food rejection. Although the three treatments did not produce a significant difference in performance, there was a trend toward increasing fat content of milk and live weight gain with increasing percentage of straw in the ration. Data on the pH of and VFA in rumen liquor are in Table 3. The pH did not differ among the treatments. The composition of VFA (% mol) of treatments A and B did not differ significantly, b u t the acetic, valeric, and iso-
Glucose ( rag/ 100 ml) Free fatty acids (FFA) (mg/ 100 ml)
FFA C 16 C 18 C 18:1 C 18:2 C 18:3
C
54.9
55.2
56.6
percentage 27.9 26.1 30.5 10.9 3.6
27.9 24.9 31.4 12.7 3.4
61.9 65.2 67.3 _+2.2 56.2 53.4 42.9 +_6.8 68.6 67.8 68.5 +_1.1 62.8 67.8 68.5 +_2.7 go of gross energy 7.9 8.3 8.3 2.92 2.73 2,79+_ ,29 52.0 56.8 57.4 +_2.9 2.19 2.41 2.42 - .12 82.7 83.7 83.7
_+ .69
TABLE 6. Tile efficiency of use of metabolizable energy (ME) for milk production of cows.
+_1.52 +_1.94 +_3.18 +2.51 +_2.30
Different from b at P < .05. SE = standard error of treatment difference. JOURNAL OF DAIRY SCIENCE VOL. 56, NO. 11
SE~
a Standard error of treatment difference.
3.411b 4.527 ~ 3.023 b +_ .34 27.2 24.7 33.5 11.2 2.4
C
SE
Treatment B
Apparent digestibility Dry matter (DM) Crude fiber Nitrogen Energy Loss of energy as CH4 computed Urine Metabolizable energy goof gross energy Keal/g DM intake %digested energy
B
valerie acid concentrations (% mol) of treatment C were significantly different from those of the other treatments. The acetate-propionate ratio was above 3:1 in all treatments; the differences in the ratio of treatment C to ratios in treatments A and B were significant. The concentration of plasma glucose and the composition of plasma F F A were not significantly different whereas plasma FFA in treatment B differed significantly from the two other treatments (Table 4). There were no significant differences in digestion coefficients between pooled samples of the first or last 4 days. Therefore, the average value of these two samples is given for 8 days in Table 5. Increasing the percentage of straw in the ration brought about decreased apparent digestibility of the dry matter and energy. Digestion coefficients of the crude fiber showed a reverse tendency. In all three treatments the digestibility of crude protein was similar. Metabolizable energy per unit of dry matter in rations of treatments B and C was virtually equal and lower in the ration of treatment A, as can be seen from Table 5. Table 6 presents the data for efficiency of
TABLE 4. Plasma glucose, plasma free fatty acids, and their composition, of cows.
A
A
Treatment A B C
Intake (Meal ME/ cow/day ) 29.64 30.24 26.77
Gross efficiency of Energy value use of ME of milk (SCM) for milk ( Meal/ produecow/day ) tion ( go) 9.34 9.48 9.33
SCM ---- solids-corrected milk.
31.5 31.3 34.9
STRAW THE
SOLE ROUGHAGE
use of metabolizable energy for milk production which were not significantly different. These data were obtained from cows put on metabolic cages. Discussion
That all cows fed the ration of treatment A left over some of the supplied straw, makes the feeding practice in this treatment virtually ad lib. In this treatment the average consumption of straw was 5.7 kg DM, which is only slightly less than that consumed by cows fed ad lib. with similar rations in pelleted form (2, 12, 14). The fat percentage of the milk was similar in all three treatments but slightly higher than in the preceding period when the cows were fed a regular farm ration. We emphasize that, according to the literature, a ratio of the ruminal VFA Co:Ca as in these three treatments should be connected with a higher milk fat percentage than that in our experiment. Although weight gain was measured after the cows had become accustomed to the ration, it is, nevertheless, possible that part of the change in the body weight was due to changes in the fill of the digestive tract. Rumen acetic aeicl was high in all three treatments (Table 3), but the difference between treal~nent C and the two other treatments was significant. The high acetic acid may be the result of a specific fermentation pattern of straw suggested also by Montgomery and Baumgardt (10). The conspicuously lower digestion coefficient for crude fiber in treatment C (Table 5) could be explained as resulting from the high concentrate content of the ration. Greater amounts of concentrates in the rumen depress the digestibility of cellulose (10). This again explains the relatively low digestion coefficient of DM of ration C which was calculated as 70% from the tables of Bondi and Neumark (5). (The calculated digestion coefflcients of DM of rations A and B were 62.3 and 65.5.) The bulk of nitrogen supply was derived in all three treatments from the concentrate, which resulted in small differences between the digestion coefficients, as could be expected. The metabolizable energy content per gram DM intake was lower in all three treatments than that calculated (Table 1). Metabolizable energy content in the ration of treatment A was in excellent agreement with the value obtained for sheep with a complete diet by Wainman et al. (16). The ME value for the ration
1427
of treatment C was much lower than the calculated one. This may be due to the relatively low digestion coefficients of this ration. Intake of ME was calculated for a higher milk production than that which was really obtained, but the ME intake calculated by analysis of the experimental data (Table 6) was lower than the theoretical calculated intake of ME at the beginning of the experiment. The higher gross efficiency in treatment C may result from the fact that cows consuming ration C received even less ME than those consuming rations A and B. The results of this trial show that cows in mid-lactation can be fed successfully on a ration of concentrate with wheat straw as the sole roughage. This is of importance for countries where production of ronghages is expensive or limited by water shortage. Furthermore, under conditions where the price ratio between concentrates and straw is wide, feeding of rations similar to treatment A becomes more profitable. Cows of treatments B and C were fed restricted rations, and it may be assumed that ad lib. feeding of these rations could maintain higher milk production. For a more extensive use of straw and materials containing large amounts of crude fiber for high-producing cows, processing of these materials would be necessary to increase their intake. Acknowledgments
We would like to acknowledge the technical assistance of Mr. A. Harel and Mr. Z. Edelman. References
(1) Agricultural Research Council. 1965. The nutrient requirements of farm livestock. No. 2. Ruminants. Technical Reviews and Summaries, H.M.S., London. (2) Amir, S., J. Kali, H. Neumark, M. Bleiberg, and A. Halevi. 1971. Straw as the sole roughage in the ration of dairy cows. Swedish-Israeli Symposium, Uppsala, Sweden. (3) Association of Official Agricultural Chemists. 1960. Official methods of analysis, 9th ed. Washington, D.C. (4) Blaxter, K. L. 1961. The utilization of the energy of food. Proe. 2nd Conf. Energy Metabolism, Wageningen. EAAP Pub. 10, p. 211. (5) Bondi, A., and H. Neumark. 1960. Table o~ composition of feeds for cattle and sheep. Agricultural Calendar (in Hebrew). Hassadeh Publishers, Tel Aviv. JOURNAL OF DAIRY SCIENCE VOL. 56, NO. 11
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HALEVI ET AL
(6) Cottyu, B. G., and C. V. Boucque. 1968. Rapid method for the gas-chromatographic determination of volatile fatty acids in rumen fluid. J. Agr. Food Chem. 16:105. (7) Levi, D., S. Amir, Z. Holzer, and H. Nenmark, 1972. Ground and pelleted straw and hay for fattening Israeli-Friesian male calves. Anim. Prod. 15:157. (8) Lucas, H. L. 1956. Switchback trials for more than two treatments. J. Dairy Sci. 39:146. (9) Luddy, F. E., R. A. Barford and R. W. Riemensehneider. 1960. Direct conversion of lipid components to their fatty acid methyl esters. J. Amer. Oil Chem. Soc. 37: 447. (10) Montgomery, M. J., and B. R. Baumgardt. 1965. Regulation of food intake in ruminants. 2. Ration varying in energy concentration and physical form. ]. Dairy Sci. 48:1623. (11) National Research Council. 1966. Nutrient
JOURNAL OF
DAIRYSCIENCEVOL. 56, No. I1
(12)
(13) (14)
(15) (16)
requirements of dairy cattle. Pub. Nat. Acad. Nat. Res. Council, Washington, D.C. 1349. Owen, J. B., E. L. Miller, and P. S. Bridge. 1969. Complete diets given ad libitum to dairy cows - the effect o.f the level of inclusion of milled straw. J. Agr. Sci. 72:351. Storry, J. E., and B. Tuckly. 1967. Thinlayer chromatography of plasma lipids by single development. Lipids 2:501. Thomson, I. 1970. Possibilities for complete pelleted diets for ruminants. 21st Annu. Manufacturing Europe. Ass. Anita. Producers, Budapest. August, 1970. (Miraco) Tyrrell, H. F., and J. T. Reid. 1965. Prediction of the energy value of cow's milk. J. Dairy Sci. 48:1215. Wainman, F. W., K. L. Blaxter, and J. D. Pullar. 1970. The nutritive value for ruminants of a complete processed diet based on barley straw. J. Agr. Sci. 74:311.
os
Sole Roughage in Diets for
A. HALEVI, H. NEUMARK, and S. AMIR Agricultural Research Organization, The Volcani Center Department of Animal Science, P.O.B. 6, Bet Dagan, Israel Abstract
cows which were to be fed large amounts of concentrates. Rations with straw as the sole roughage depressed milk fat percentage and were of low efficiency when the percentage of straw was low (2, 12). A high intake of straw was achieved in trials where whole pelleted rations were fed (2, 12, 14). This procedure seems to be the only way of feeding an appropriate ratio of straw-concentrate for highproducing cows whereas a sufficient intake of straw could be achieved for cows in mid-lactation by chopping the straw. This trial was designed to examine the effect of different percentages of chopped straw in the diet fed to cows in mid-lactation on the yield and composition of milk, feed value, and relative proportions of volatile fatty acid (VFA) formed in the rumen.
A complete switch-back trial was designed for 12 cows in mid-lactation; they received three different rations of chopped wheat straw (Triticum aestivmn) and concentrates - 45:55 (A), 30:70 (B), and 15:85% (C). Milk yield and composition in all three treatments were similar; milk fat was relatively low although the molar percentage of ruminal acetic acid was high in all groups. Concentration of plasma glucose was similar in all three groups whereas plasma free fatty acids of group B were higher than for the two others. Differences in the composition of plasma free fatty acids were not significant. Digestibility of dry matter decreased slighly with increasing percentage of straw in the ration; metabolizable energy per gram dry matter was equal in rations B and C and lower in ration A. Cows in group C showed a higher gross efllciency in using metabo]izable energy for milk production.
Methods
Introduction
Straw as a by-product of grain production is of low nutritional value and low protein content and rich in crude fiber. It is used mainly for bedding and fed only occasionally to cattle of low production. The use of straw as a major supplier of crude fiber for rations of dairy carte could enable the farmer to obtain higher profits from part of his land by changing from growing fodder crops to growing a cash crop. Straw can be fed successfully to high-producing dairy and beef cattle instead of conventional roughage (2, 7, 12, 14). Amir et al. (2) assumed that it would be difficult to achieve a high intake of long straw for high-lactating Received February 16, 1973. a Contribution from the Agricultural Research Organization, The Volcanl Center, Bet Dagan, Israel. 1973 Series, No. 117-E. =Supported by a grant of the USDA (P.L. 480).
Twelve adult Israeli-Friesian cows in midlactation with a milk yield of 17 to 21 kg milk/day were in this experiment. The animals were allotted to three treatments (A, B, C) in a complete switch-back design (8) with three periods of 38 days. Statistical analysis was on the last 3 wk of each period. The ration contained chopped wheat straw (length of straw 6 cm) and concentrates. In treatments A, B, and C the ratio of straw to concentrates was 45:55, 30:70, and 15:85%. Concentrates of different amounts of protein were prepared to ensure equal protein per unit of dry matter (DM). Milking was three times daily and feeding was four times daily. Food was weighed before each feeding, and refused feed was weighed once a day. Every l0 days the cows were weighed on 2 consecutive days. Three weeks prior to the beginning of the experiment, all cows were fed the ration of treatment B. During this pre-experimental period they were fed 20% above requirement to provide a gradual change from higher farm feeding to the lower feeding of the experiment. Energy requirement for each cow was calculated according to milk yield and body weight at the end of the preliminary period; for the
1424
STRAW T H E SOLE
TABLE 1. Average feed requirement, chemical composition, and calorie value of the rations fed in three treatments. Factor
Treatment A
Feed requirement - - ( Straw 6.32 Concentrates 7.74 Metabolizable energy a - Per kg DM 2.38 In the ration 33.5 Component - Crude protein 12.5 Crude fiber 20.2 N-free extract 57.9 Fat 2.0 Minerals 7.4
B
C
kg DM ) ~ 3.66 1.69 8.59 9.29 (Meal) - 2.62 2.86 32.1 31.4 ( % DM ) 12.3 12.9 14.7 9.5 64.3 69.4 2.3 2.6 6.4 5.6
~Nutritional values according to NRC standards ( i l ) . DM = dry matter. various diets the cows were to receive, this feeding was kept unchanged during the whole experimental period without taking into account changes in milk yield or body weight. All calculations for energy requirements, except for maintenance, were based on metabolizable energy as recommended by the ARC (1), For maintenance, 100 kcal/kgW .r~ were allowed instead of the 85 kcal/kgW -~3 recommended by the ARC. Table 1 presents the composition of the rations fed to the animals in the three treatments. Gl,ucose and free fatty acids (FFA) in plasma. On the 26th and 36th days of each period, 1 h after the first meal of the day, blood samples were drawn from the Vena iugularis by vacutainer tubes. The quantitative and qualitative determination of the FFA blood plasma was done by first separating the FFA by thin-layer chromatography according to the method of Storry and Cfuckly (13). Then, the FFA were eluted from the gel by chloroform and prepared for gas chromatography by methylation with diazo-methane according to Luddy et al. (9). For gas-liquid chromatography a Perkin-Elmer F l l apparatus was used. A glass column of about 1.63 m length and an internal diameter of 4 mm was filled with Gas chrom P as support, coated with 10% ethyl-glycol-succinate. Temperature of oven was 175 C and of injector, 210 C. The plasma glucose content was measured colorimetrically by Biochemia Test Combination s based on specific oxidation of glucose by glucose oxidase. Rumen volatile fatty acids (VFA ). Samples of rumen liquor were taken immediately after
1425
ROUGHAGE
drawing of the blood samples, and the VFA content of the rumen liquor was determined by gas-liquid chromatography according to the method of Cottyn and Boucque (6). The pH of the tureen liquor also was measured. Milk fat and total solids were determined in samples of two consecutive days. Six milk samples were taken for each period. Digestibility trials. During the last 3 wk of each period, two groups of three cows were kept consecutively in metabolic cages, each for 10 days. During 8 of these 10 days, feces, urine, and refused feed of each cow were collected and samples of the food were taken. Chemical analyses were carried out on two pooled samples of 4 days each according to the methods of the AOAC (3). The energy content of the samples was determined with an adiabatic bomb calorimeter; the energy of methane was estimated according to the formula of Blaxter (4); and the metabolizable energy was calculated. The determination of the energy content of milk was based on daily measured milk yield and composition and calculated by the solidscorrected milk (SCM) equation of Tyrrell and Reid (15). Results
The general health and condition of the cows during the experiment was satisfactory. During the preliminary period on change from the farm to the experimental ration, milk yield dropped sharply (averaging 6 kg milk/T~mLE 2. Average daffy feed consumption, milk yield and composition, and weight gain per cow. Treatment Factor
A
B
C
SE.
Dry matter intake (kg) Total 13.38 12.35 11.11 In concentrates 7.67 8.53 9.19 +--.027 As straw 5.71 3.82 1 . 9 2 ---.112 Milk yield (kg) 47o FCM
13.26 13.65 13.46 ±.24 11.64 11.87 11.41 ±.36
Milk components ( ~ ) Fat 3.19 3.10 2.99 4-.103 SNF 8.22 8.24 8.26 ±.093 TS ll.1O 11.31 11.20 ±.072 Weight gain (g)
391
132
97
±200
Standard error of treatment difference. FCM = fat-corrected milk, SNF = solids-notfat, TS -- total solids. 3Boehringer Mmmheim, GmbH. JOURNAL OF DAIRY SCIENCE VOL. 56, No. I I
1426
H A L E V I ET AL
TABLE 3. pH and composition of volatile fatty acids of the rumen juice of cows.
TABLE 5, Digestibility and related measurements of diets fed to cows. Treatment
Treatment A pH
7.00
Acetic acid Propionie acid Butyric acid Valerie acid Iso-valerie acid C~.:C3
B
C
7.11
6.92
--(mol %)-68.9~ 67.3d 63.4 ¢ 18.0 18.4 20.9 1O.0 10.7 11.3 1.53b 1.75b 2.30~ 1.26° 1.48" 1.61 ~ 3.8P 3 . 7 5 " 3.18~
SE +_ .097 +_ .79 +_1.29 +_ .68 +- .118 +- .059 +_ .11
~,b Differences significant at P < .05. c,a Differences significant at P < .01. SE ---- standard error of treatment difference, cow per day). During the experimental periods, the decline in milk yield was normal. I n Table 2, data on food intake, milk yield and composition, and body weight changes in the various treatments are presented. The cows in treatment A left on the average 13% of the offered straw during the last 3 wks of the experiment. The calculation of the various data was based on amounts actually consumed by each individual cow. (Refusals ranged from .14 to 1.46 kg straw.) In other treatments there was no food rejection. Although the three treatments did not produce a significant difference in performance, there was a trend toward increasing fat content of milk and live weight gain with increasing percentage of straw in the ration. Data on the pH of and VFA in rumen liquor are in Table 3. The pH did not differ among the treatments. The composition of VFA (% mol) of treatments A and B did not differ significantly, b u t the acetic, valeric, and iso-
Glucose ( rag/ 100 ml) Free fatty acids (FFA) (mg/ 100 ml)
FFA C 16 C 18 C 18:1 C 18:2 C 18:3
C
54.9
55.2
56.6
percentage 27.9 26.1 30.5 10.9 3.6
27.9 24.9 31.4 12.7 3.4
61.9 65.2 67.3 _+2.2 56.2 53.4 42.9 +_6.8 68.6 67.8 68.5 +_1.1 62.8 67.8 68.5 +_2.7 go of gross energy 7.9 8.3 8.3 2.92 2.73 2,79+_ ,29 52.0 56.8 57.4 +_2.9 2.19 2.41 2.42 - .12 82.7 83.7 83.7
_+ .69
TABLE 6. Tile efficiency of use of metabolizable energy (ME) for milk production of cows.
+_1.52 +_1.94 +_3.18 +2.51 +_2.30
Different from b at P < .05. SE = standard error of treatment difference. JOURNAL OF DAIRY SCIENCE VOL. 56, NO. 11
SE~
a Standard error of treatment difference.
3.411b 4.527 ~ 3.023 b +_ .34 27.2 24.7 33.5 11.2 2.4
C
SE
Treatment B
Apparent digestibility Dry matter (DM) Crude fiber Nitrogen Energy Loss of energy as CH4 computed Urine Metabolizable energy goof gross energy Keal/g DM intake %digested energy
B
valerie acid concentrations (% mol) of treatment C were significantly different from those of the other treatments. The acetate-propionate ratio was above 3:1 in all treatments; the differences in the ratio of treatment C to ratios in treatments A and B were significant. The concentration of plasma glucose and the composition of plasma F F A were not significantly different whereas plasma FFA in treatment B differed significantly from the two other treatments (Table 4). There were no significant differences in digestion coefficients between pooled samples of the first or last 4 days. Therefore, the average value of these two samples is given for 8 days in Table 5. Increasing the percentage of straw in the ration brought about decreased apparent digestibility of the dry matter and energy. Digestion coefficients of the crude fiber showed a reverse tendency. In all three treatments the digestibility of crude protein was similar. Metabolizable energy per unit of dry matter in rations of treatments B and C was virtually equal and lower in the ration of treatment A, as can be seen from Table 5. Table 6 presents the data for efficiency of
TABLE 4. Plasma glucose, plasma free fatty acids, and their composition, of cows.
A
A
Treatment A B C
Intake (Meal ME/ cow/day ) 29.64 30.24 26.77
Gross efficiency of Energy value use of ME of milk (SCM) for milk ( Meal/ produecow/day ) tion ( go) 9.34 9.48 9.33
SCM ---- solids-corrected milk.
31.5 31.3 34.9
STRAW THE
SOLE ROUGHAGE
use of metabolizable energy for milk production which were not significantly different. These data were obtained from cows put on metabolic cages. Discussion
That all cows fed the ration of treatment A left over some of the supplied straw, makes the feeding practice in this treatment virtually ad lib. In this treatment the average consumption of straw was 5.7 kg DM, which is only slightly less than that consumed by cows fed ad lib. with similar rations in pelleted form (2, 12, 14). The fat percentage of the milk was similar in all three treatments but slightly higher than in the preceding period when the cows were fed a regular farm ration. We emphasize that, according to the literature, a ratio of the ruminal VFA Co:Ca as in these three treatments should be connected with a higher milk fat percentage than that in our experiment. Although weight gain was measured after the cows had become accustomed to the ration, it is, nevertheless, possible that part of the change in the body weight was due to changes in the fill of the digestive tract. Rumen acetic aeicl was high in all three treatments (Table 3), but the difference between treal~nent C and the two other treatments was significant. The high acetic acid may be the result of a specific fermentation pattern of straw suggested also by Montgomery and Baumgardt (10). The conspicuously lower digestion coefficient for crude fiber in treatment C (Table 5) could be explained as resulting from the high concentrate content of the ration. Greater amounts of concentrates in the rumen depress the digestibility of cellulose (10). This again explains the relatively low digestion coefficient of DM of ration C which was calculated as 70% from the tables of Bondi and Neumark (5). (The calculated digestion coefflcients of DM of rations A and B were 62.3 and 65.5.) The bulk of nitrogen supply was derived in all three treatments from the concentrate, which resulted in small differences between the digestion coefficients, as could be expected. The metabolizable energy content per gram DM intake was lower in all three treatments than that calculated (Table 1). Metabolizable energy content in the ration of treatment A was in excellent agreement with the value obtained for sheep with a complete diet by Wainman et al. (16). The ME value for the ration
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of treatment C was much lower than the calculated one. This may be due to the relatively low digestion coefficients of this ration. Intake of ME was calculated for a higher milk production than that which was really obtained, but the ME intake calculated by analysis of the experimental data (Table 6) was lower than the theoretical calculated intake of ME at the beginning of the experiment. The higher gross efficiency in treatment C may result from the fact that cows consuming ration C received even less ME than those consuming rations A and B. The results of this trial show that cows in mid-lactation can be fed successfully on a ration of concentrate with wheat straw as the sole roughage. This is of importance for countries where production of ronghages is expensive or limited by water shortage. Furthermore, under conditions where the price ratio between concentrates and straw is wide, feeding of rations similar to treatment A becomes more profitable. Cows of treatments B and C were fed restricted rations, and it may be assumed that ad lib. feeding of these rations could maintain higher milk production. For a more extensive use of straw and materials containing large amounts of crude fiber for high-producing cows, processing of these materials would be necessary to increase their intake. Acknowledgments
We would like to acknowledge the technical assistance of Mr. A. Harel and Mr. Z. Edelman. References
(1) Agricultural Research Council. 1965. The nutrient requirements of farm livestock. No. 2. Ruminants. Technical Reviews and Summaries, H.M.S., London. (2) Amir, S., J. Kali, H. Neumark, M. Bleiberg, and A. Halevi. 1971. Straw as the sole roughage in the ration of dairy cows. Swedish-Israeli Symposium, Uppsala, Sweden. (3) Association of Official Agricultural Chemists. 1960. Official methods of analysis, 9th ed. Washington, D.C. (4) Blaxter, K. L. 1961. The utilization of the energy of food. Proe. 2nd Conf. Energy Metabolism, Wageningen. EAAP Pub. 10, p. 211. (5) Bondi, A., and H. Neumark. 1960. Table o~ composition of feeds for cattle and sheep. Agricultural Calendar (in Hebrew). Hassadeh Publishers, Tel Aviv. JOURNAL OF DAIRY SCIENCE VOL. 56, NO. 11
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(6) Cottyu, B. G., and C. V. Boucque. 1968. Rapid method for the gas-chromatographic determination of volatile fatty acids in rumen fluid. J. Agr. Food Chem. 16:105. (7) Levi, D., S. Amir, Z. Holzer, and H. Nenmark, 1972. Ground and pelleted straw and hay for fattening Israeli-Friesian male calves. Anim. Prod. 15:157. (8) Lucas, H. L. 1956. Switchback trials for more than two treatments. J. Dairy Sci. 39:146. (9) Luddy, F. E., R. A. Barford and R. W. Riemensehneider. 1960. Direct conversion of lipid components to their fatty acid methyl esters. J. Amer. Oil Chem. Soc. 37: 447. (10) Montgomery, M. J., and B. R. Baumgardt. 1965. Regulation of food intake in ruminants. 2. Ration varying in energy concentration and physical form. ]. Dairy Sci. 48:1623. (11) National Research Council. 1966. Nutrient
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DAIRYSCIENCEVOL. 56, No. I1
(12)
(13) (14)
(15) (16)
requirements of dairy cattle. Pub. Nat. Acad. Nat. Res. Council, Washington, D.C. 1349. Owen, J. B., E. L. Miller, and P. S. Bridge. 1969. Complete diets given ad libitum to dairy cows - the effect o.f the level of inclusion of milled straw. J. Agr. Sci. 72:351. Storry, J. E., and B. Tuckly. 1967. Thinlayer chromatography of plasma lipids by single development. Lipids 2:501. Thomson, I. 1970. Possibilities for complete pelleted diets for ruminants. 21st Annu. Manufacturing Europe. Ass. Anita. Producers, Budapest. August, 1970. (Miraco) Tyrrell, H. F., and J. T. Reid. 1965. Prediction of the energy value of cow's milk. J. Dairy Sci. 48:1215. Wainman, F. W., K. L. Blaxter, and J. D. Pullar. 1970. The nutritive value for ruminants of a complete processed diet based on barley straw. J. Agr. Sci. 74:311.