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Effect of dietary protein source on performances and rumen characteristics of dairy cows
ANIMAL FEED SCIENCE AND TECHNOLOGY
ELSEVIER
Animal Feed Science Technology
68 (1997) 339-351
Effect of dietary protein source on performances and rumen characteristics of dairy cows Peter Wen-Shyg Chiou a,*, Bi Yu a, Shyi-Shiun Wu a, Kwen-Jaw Chen b ’Department of Animal Science, National Chung-Hsing University, Taichung, Taiwan b Taiwan Lirestock Research Institute, Hsin-Hua. Tainan, Taiwan Accepted 4 October
1996
Abstract A feeding trial of 8 weeks was carried out following a complete randomized design with 27 dairy cows in their second month of lactation. The aim was to evaluate the effect of three sources of dietary protein, soybean meal, fish meal and cottonseed meal, on the performances and rumen characteristics of dairy cows. Three rumen-fistulated dairy cows were assigned for the study of rumen fermentation. The source of dietary protein did not significantly influence the dry matter intake, but significantly affected milk yield (P < 0.05). The fish meal group produced significantly less milk, but the concentration of total solids, lactose and protein was higher than in the control group with soybean meal. The ruminal pH declined to its lowest level 1 h after feeding and gradually increased afterwards. The ruminal pH of the fish meal group was lowest 1 h postprandial, but did not reach the statistical difference level. The source of dietary protein did not significantly affect the ruminal ammonia concentration, but had a significant effect on the volatile fatty acid (VFA) concentration in the rumen (P < 0.05). Total VFA concentration was significantly higher in the cottonseed meal group than in the other treatment groups before and within 2 h after feeding (P < 0.05). Protein source also significantly influenced the acetate and the propionate concentration and their ratio (P < 0.05). From 1 to 2 h postfeeding, the ratios were not statistically different. However, the ratio was significantly higher from 4 to 8 h postprandial in the cottonseed meal group as compared to the fish meal group (P < 0.05). Compared to soybean meal, the ratio was only significant higher before feeding and from 4 to 6 h, postprandial (P < 0.05). 0 1997 Elsevier Science B.V. Keywords:
Protein source; Dairy cows; Ruminal characteristics
* Corresponding author. Department of Animal Science, National Chug-Hsing Road, Taichung, Taiwan. Tel.: + 886-4-2870613; fax: + 886-4-2860265. 0377.8401/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved. PII SO377-8401(97)00031-X
University,
250 Kuo-Kuang
340
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1. Introduction Supplementation of a high amount of undegradable protein to meet the absorbable protein requirements increased the milk yield in iso-protein rations for high-producing cows (NRC, 1985). Fish meal is an excellent source of undegradable protein. Cottonseed meal also contains a large amount of both crude and undegradable protein. In a feeding trial using alfalfa hay and silage as basal diet for early lactating cows, Grings et al. (1991) observed an increased feed intake and milk yield when the protein content of the diet was increased from 13.8 to 17.5% by a cottonseed meal supplement; the protein and fat content of the milk remained constant. Van Horn et al. (1979) obtained similar results with an increase of dietary protein to 16.3% by replacing soybean meal by cottonseed meal. Partially substituting soybean meal by fish meal fed to high-producing cows in early lactation, Broderick (1992) obtained an increase in the milk yield. Atwal and Erfle (1992) also found an improvement in yield and protein content of the milk with a herd producing an average of 30 kg d- ’ in early lactation and fed a 16% (crude protein) CP ration with partial substitution by fish meal. Hussein and Jordan (1991) reported that with a fish meal-substituted ration in early lactation, cows can obtain a better body condition and conception rate besides the increase in milk yield and protein content. The results from a fish meal supplement for cows with a low to moderate milk yield or in midlactation were different from those of high-yielding cows. Oldham (1984) and Sloan et al. (1988) fed a fish meal supplement to a herd with a mean milk production of 27 kg d-l, and obtained no advantageous result. Broderick (1992) obtained a similar result with a fish meal supplement in a midlactating herd. In a trial with 80 primiparous cows, Mantysaari et al. (1989) fed a 17.3% CP ration with an increasing amount of undegradable protein, from 32 to 37.8%, by substituting fish meal, and found no beneficial result. It appears that several factors, i.e., the mean milk yield and lactation period, should be considered when applying the system of ruminal undegradable protein in ration formulation. In addition, the digestion and absorption, the energy content of the ration, the amino acid profile of the undegradable protein will influence the performances. The aim of this study is to evaluate the effect of three sources of dietary protein: soybean meal, fish meal and cottonseed meal, on the performances and rumen characteristics of dairy cows.
2. Materials and methods 2.1. Experimental
ration formulation
Experimental diets were formulated according to the nutrient requirements of the NRC (1989). Experimental cows averaged 500 kg in body weight and produced an average of 25 kg of 3.5% fat-corrected milk daily. Three isonitrogenous and isoenergetic diets, presented in Table 1, were formulated, differing in protein source: soybean meal (control) and soybean meal partially substituted by fish meal or cottonseed meal. Concentrate ingredients, pelleted through a 3-mm
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Table 1 Diet formulation” Ingredients
Soybean meal 410 150 172 95 95 _
Corn silage Alfalfa hay Corn Soybean meal, 44% Soybean, full fat Cottonseed meal Fish meal Wheat bran Molasses Dicalcium phosphate Calcium carbonate Salt Premix b Total
Fish meal 410 150 216 70 37 45 45 15 2 4
45 15 6 6 5
1000
loo0
Cottonseed 410 150 170 18 74 100 45 15 7
1000
Calculated nutrient values Crude protein Undegradable protein, % CP
165 37.5
165 37.5
165 37.5
Analyzed nutrient values’ Crude protein, CP Neutral detergent libre Acid detergent fibre Soluble protein, % CP NPN, % soluble CP NDFIP, % CP ADFIP, % CP
163 382 201 31.7 84.7 16.3 8.0
165 396 191 31.0 87.6 15.7 6.9
160 387 216 34.3 84.6 17.0 8.2
“The figure are g/kg bPremix components 1,600,OOO IU; Fe: 50 ‘NPN is non-protein
of dietary (each kg g; Zn: 40 nitrogen,
dry matter contains): g; Mn: 40 NDFIP is
meal
except otherwise stated. vitamin A: 10,000.000 IU; Vitamin E: 70,OOG IU; Vitamin D: g; Co: 0.1 g; Cu: 10 g, I: 0.5 g; Se: 0.1 g. neutral detergent insoluble protein, and ADFIP is acid detergent
insoluble protein.
die at 70°C once every week, were mixed daily with corn silage and alfalfa hay. Moisture contents of the concentrate and roughage were measured weekly for adjusting the ration composition. 2.2. Animal and management
in feeding
trial
The experiment was a complete randomized design with 27 dairy cows (21 multiparous and six heifers) in their second month of lactation (55 f 20 days). Cows producing more than 20 kg of milk were selected and were randomly allocated into the three treatment groups. Cows were confined into individual pens most of the time during the experimental period, and were released for exercise twice daily from 03:30 to 06:30 and 13:00 to 1790. Cows were dewormed twice monthly during the experimental period.
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After 2 weeks of adaptation, the feeding trial started for 8 weeks. The cows were individually fed ad libitum, allowing 2 to 3 kg orts, in two meals per day (06:30, 17:OO). Water was provided individually with an automatic bowl-type drinker. Animals were milked twice daily at 05:OOand 16:O0. During the feeding trial, both temperature and humidity inside the dairy barn were continually monitored by an automatic recorder (R-704, Sate). Dry matter intake and milk yields were recorded daily. Milk samples were taken once every other week. Cows were weighed at the beginning, in the fourth week and at the end of the trial. The body weights were calculated as the average of two consecutive daily measurements. Feed samples were taken weekly and dried at 60°C in a ventilated oven for 48 h. Blood samples were taken 3 to 4 h postprandial from four cows per treatment every other week during the experimental period. 2.3. Ruminal studies Three dairy Holstein cows with rumen fistulas were randomly assigned to the three dietary treatments according to a Latin square design. Each treatment period was 10 days with 7 days of transitional period. Cows were individually fed ad libitum in two meals daily. Ruminal fluid samples of 200 ml were taken on the 9th and 10th day in the morning before the meal and 1, 2, 3, 4, 6, 8 h postprandial. Ruminal pH was measured immediately after withdrawal. Samples were then filtered through four layers of cheese cotton and diluted with 20% metaphosphoric acid. After mixing, the samples were sealed and preserved at - 18°C for later analysis of ammonia nitrogen and volatile fatty acid concentration. Crude protein degradability of the total mixed rations was measured by the in situ method of Orskov and McDonald (1979) and modified by Chiou et al. (1995) with the same three rumen-cannulated dairy cows from the rumen study trial. Cows were fed a total mixed ration of 15 kg dry matter with an equal amount of concentrate and roughage (dry basis), and were fed equally, divided six times with an evenly divided amount of feed every day. The samples were ground through a 2-mm mesh screen and were placed into the polyester bag with pore size of 53 f 10 pm. Modification concerning size of the nylon bag, changed from 4.5 X 6.5 cm to 10 X 20 cm, and sample size increased from 1 g to 8 g of dry matter. Instead of placing bags into a perforated tube, they were attached to an iron ring of 450 g, and were then connected to the rumen fistula by a 70-cm nylon cord. The incubation period was extended from five periods of 2, 4, 8, 12 and 24 h to seven periods with an addition of 48 h. Immediately after removal from the rumen, samples were put in ice-water to stop the microbial fermentation and were then mechanically washed with water 1.5 min three times. Samples were then dried in the 60°C air-draw oven for 48 h. 2.4. Chemical analysis Chemical analysis of feed samples was according to the methods of AOAC (1984). Neutral detergent fiber (NDF), acid detergent fiber (ADF) and insoluble nitrogen in NDF and ADF, were analyzed according to the method of Van Soest et al. (1991) using
P.W.-S. Chiou et al./Aninml
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Science Technology 68 (1997) 339-351
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an automatic fiber analyzer (Fibertec System M, Tecator). Soluble protein was determined by the procedure of Krishnamoorthy et al. (1983). Milk composition of fat, protein, lactose and total solids were analyzed by a milk scanner (Milk0 Scan 255 A/B types, Foss Electric) according to the infrared method of AOAC (1984). Plasma urea nitrogen was determined by an automatic blood chemical analyzer (Gilford system 103) according to the method of Cross and Jenny (1976). The pH value of rumen fluid was measured with a pH meter (Suntex SP-32). Concentration of ruminal ammonia nitrogen was analyzed by an automatic Kjeldhal apparatus according to AOAC (1984). Ruminal concentration of volatile fatty acids was determined according to Parker and McMillan (1976). 2.5. Statistical
analysis
A completely for the ruminal calculated with System (1988). means according
3. Results
randomized block design for the feeding trial and a Latin square design studies was applied to find dietary effects. Analysis of variance was the general linear model (GLM) procedure of the Statistical Analysis Duncan’s new multiple range test was used to compare the treatment to Steel and Torrie (1960).
and discussion
3.1. Effect on dry matter intake The results of the feeding trial are presented in Table 2. The source of dietary protein did not significantly influence the dry matter intake. Bowers et al. (1965) found that a high amount of fish meal (9.8% of diet) decreased palatability of the diet and feed intake. Inclusion of a smaller amount of fish meal (3.5% vs. 5.1%) in the ration had no impact on the feed intake of lactating cows (Carroll et al., 1994; Blauwiekel et al., 1990). In this trial too, fish meal did not affect dry matter intake. This may be due to the small amount of fish meal (4.5%) in the experimental diet or to the corn silage that masked the flavor of fish meal. An increase of cottonseed meal in the diet from 8.6% to 24.2% did not influence the dry matter intake by lactating cows (Grings et al., 1991). Even up to 45% cottonseed meal in the diet did not significantly affect the feed intake of lactating cows (Lindsey et al., 1980). In this trial, only 10% cottonseed meal was added in the ration, resulting in a similar dry matter intake as the control group. 3.2. Effect on the milk yield The effect of the dietary protein source on milk yield was significant (P < 0.05). The milk yield in the fish meal group was on average 2.5 kg dd’ less than in the other groups. This result is different from that of Atwal and Erfle (1992) who obtained a higher milk yield by fish meal substitution in a 16% CP ration. Oldham (1984) and
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Table 2 Effect of dietary protein on the performance
Feed Science Technology 68 (1997) 339-351
and production
efficiency
of dairy cattle
Soybean meal
Fish meal
Cottonseed
DM intake d; milk yield, kg/day Dry matter intake Milk yield 4% FCM
22.7 26.5” 24.7
22.4 24.0b 23.6
22.4 26.5a 24.7
0.51 0.55 0.54
Milk composition, % Total solids Milk fat Milk protein Lactose
11.66b 3.59 2.70b 4.66b
12.63” 3.88 3.20a 4.85”
11.88”b 3.60 2.80b 4.69b
0.17 0.12 0.06 0.04
3.14 0.96 0.74 1.25
3.01 0.93 0.75 1.16
3.14 0.90 0.78 1.23
0.29 0.14 0.10 0.09
0.81b 0.86b
0.14 0.14
0.13b 3.70b
0.02 0.10
Milk Total Milk Milk Milk
components yield, kg/day solids fat protein lactose
Feed eficiency, kg/kg DM intake/milk yield DM intake/4% FCM yield
0.87b 0.91b
Protein eficiency, kg/kg CP intake/4% FCM yield CP intake/milk protein yield
0.15b 5.33&
“b’c’: Means in the same row with different subscript
0.19” 5.75” letters are significantly
meal
SEM
different (P < 0.05).
Sloan et al. (1988) found that a fish meal supplement did not improve milk yield with a mean yield less than 27 kg dd’. Blauwiekel et al. (1990) did not obtain a positive result for 4% fat-corrected milk by fish meal substitution in rations with equal crude (16.5%) and degradable protein (41.7%) concentration. Bruckeutal et al. (1989) also did not obtain an increase in milk yield by replacing 20% of soybean meal by fish meal. The lack of effect with fish meal may be explained by no positive response in the duodenal flow of dietary nitrogen or a decrease of microbial synthesis in rumen. In our trial, with rations containing the same level of crude (16.5%) and degradable protein (37.5%), the treatment did not significantly affect the 4% FCM (P > 0.05). 3.3. Effect on the milk composition The source of dietary protein significantly affected the total solids content of the milk (P < 0.05). Milk of the fish meal group contained more total solids, lactose and protein than the control group. There was a trend of a higher milk fat content. This trend is contradicting to most reports which showed a reduced milk fat percentage by fish meal supplementation (Sloan et al, 1988; Blauwiekel et al., 1990). They attributed this to the high levels of long-chain polyunsaturated fatty acids.
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34s
Broderick (1992) also obtained an increase in milk protein concentration by replacing soybean meal with fish meal in diets fed to high-yielding cows. They attributed this to the high available dietary amino acid content escaping degradation in rumen. Although milk composition was affected by the source of protein, the daily yields of milk components showed no significant differences among the treatment groups. This is due to the lower milk yield in the fish meal group. 3.4. Effect on the production
eficiency
Dietary sources of protein significantly influenced the efficiency of milk production (P < 0.05). Cows fed the fish meal ration produced milk less efficiently than the soybean or the cottonseed meal group (P < 0.05). There was no significant difference in the efficiency of milk production between the soybean and the cottonseed meal group. The efficiency of protein utilization, i.e., milk protein production per unit of the protein intake, showed the same trend. The fish meal group used protein least efficiently, whereas the cottonseed meal group obtained the most efficient protein production. The unsaturated fatty acid of the fish meal may inhibit ruminal bacterial fermentation (Hoover et al., 1989). Whether this adverse effect resulted in the poor performance in the fish meal group requires further investigation. 3.5. Effect on the serum nitrogen The effect of dietary protein source on the concentration of plasma urea nitrogen was not significant (Table 3). The plasma urea concentration was lowest in the cottonseed meal group, but did not reach the significance level. Grings et al. (1991) suggested that the urea level in the plasma increased with an increase of dietary protein. The plasma urea level was not influenced by the source of protein, whether it was from degradable or from undegradable protein (Roseler et al., 1993). This may imply that the ruminal ammonia level remains adequate for microbial synthesizing, without an excess amount of ruminal nitrogen flow into the blood stream (Fig. 2).
Table 3 Effect of dietary protein on the plasma urea nitrogen concentration Items Plasma urea Live-weight 4th week/O 8th week/4th 8th week/O
Soybean meal nitrogen (mg/dl) change (%) week week week
Fish meal
and liveweight
changes of the cows
Cottonseed
meal
SEM
15.6
15.3
14.6
2.6
99.8 103.6” 103.9”
100.6 104.9a 104.3a
99.7 101.9b 102.2b
2.6 2.4 1.7
a’b’c’:Means in the same row with different subscript
letters are significantly
different (P < 0.05).
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3.6. Effect on the body weight change The relative body weight change during the experimental period is presented in Table 3. Body weight changes were significantly different among the treatment groups in the second period of 4 weeks and in the whole 8-week feeding trial. This was due to the significantly lower body weight gain in the cottonseed meal group during the second period. Cows usually lose body weight with increasing milk yields during peak lactation. Most cows in this trial lost body weight in the first month and regained weight during the second 4-week period. This means that cows could not ingest enough feed for lactation and mobilized body reserves during the first 4 weeks. This weight loss was recovered during the second 4-week period. 3.7. Evaluation of degradable protein The degradation characteristics and the effective degradability of crude protein are presented in Table 4. Effective protein degradability at an outflow rate of 8% per hour was 75.9%, 70.6% and 79.7% for the soybean meal, the fish meal and the cottonseed meal ration, respectively. These values are much higher than the value of 62.5%, calculated from the ration formulation. Van Straalen and Tamminga (1990) showed that protein degradability values substantially differed among laboratories, and that the variation was even higher for forage proteins. Fish meal is generally considered as a highly undegradable protein source. However, Orskov (1982) reported a wide range of protein degradability in fish meal from 11 to 52%. Kaufmann and Lupping (1982) attributed this to factors in the manufacturing process: the storage period of raw fish before processing, types of drying, addition of preservatives, heating duration and proportion of fish solubles added back to the meal. The quality of fish meal greatly affects its nutrient and feeding value for lactating cows. In purchasing fish meal for ruminant diets, the detailed information and quality control are required.
Table 4 Degradation
characteristics
Total mixed ration
Soybean meal Fish meal Cottonseed meal
and effective Degradation
degradability
of crude protein of total mixed experimental
rations
Effective degradability outflow ratesb (% hr- ‘>
characteristic?
a
b
C
5
8
59.6 54.6 66.2
37.8 36.9 29.1
6.1 6.2 7.0
80.31 74.94 83.08
75.89 70.63 79.68
a a = The portion (percentage) of insoluble protein solubilized at initiation of incubation; b = the fraction (percentage) of crude protein potentially degradable in the rumen; and c = the constant rate (percentage per h) of disappearance of b. b Effective degradability of crude protein calculated for k = 5, or 8 (% h-’ ) solid outflow rates.
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Feed Science Technology 68 (lY971339-351
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3.8. Effect on the rumen fermentation Data obtained from the trial with the rumen-fistulated cows, pH value, ammonia nitrogen and volatile fatty acid (VFA) concentration are presented in Figs. 1-3, respectively. The ruminal pH declined to its lowest level 1 h after feeding and gradually increased afterwards. The pH 1 h postprandial was lowest for the fish meal group, but did not reach the statistical difference level. Bowers et al. (1965) used soybean meal, fish meal, peanut meal or cottonseed meal as protein supplement and found that the ruminal pH in the fish meal group was significantly lower than in the other protein groups (P < 0.01). The low potassium content in fish meal compared to plant protein (0.3% vs. 2%) resulting in a lower buffering capacity may be the reason. In this trial, the fish meal inclusion was much lower compared to the trial performed by Bowers et al. (1965) (4.5% vs. 9.8%), which may explain the nonsignificant influence on ruminal pH. The sources of dietary protein did not significantly influence the ruminal ammonia concentration. The ammonia level reached a peak 3 h after feeding, and declined afterwards. Christensen et al. (1993) indicated that the level of ruminal ammonia increased as the level of dietary protein or dietary degradable protein increased. Because in this experiment isonitrogenous rations were designed, the ruminal level did not differ statistically. The ammonia level remained above 10 pmol d-’ I- ‘, even 8 h after feeding which should be adequate for optimum microbial synthesis (5 pmol dd’ ll ‘1 in the rumen as suggested by Satter and Roffler (1975). The effect of the dietary source of protein was significant on the total VFA concentration in the rumen (P < 0.05). Total VFA concentration was significantly higher in the cottonseed meal group than in the other treatment groups before and within
0
1
2
3
4
Postprandial
5
6
7
8
time, h
Fig. 1. Effect of the source of dietary protein on the ruminal pH of cannulated group; ( W) fish meal group; ( A ) cottonseed meal group.
dairy cattle. (0)
soybean meal
P. W.-S. Chiou et al. /Animal Feed Science Technology 68 (1997) 339-351
348
I-----0
1
2
3
4
5
postprandial
6
7
a
time, h
Fig. 2. Effect of the source of dietary protein on the rumhal (symbols as in Fig. 1).
ammonia
nitrogen
of cannulated
dairy cattle
2 h after feeding (P < 0.05), which may reflect a better ruminal fermentation. The ruminal total VFA concentration in the cottonseed meal treatment was also significantly higher 3 to 4 h, postprandial, as compared to the fish meal group (P < 0.05). The total
f
I
0 0
1
1
3
4
postprandial
5
6
7
8
time. h
Fig. 3. Effect of the source of dietary protein on the ruminal total volatile fatty acid production dairy cattle (symbols as in Fig. 1).
of cannulated
P. W.-S. Chiou et al. /Animal Feed Science Technology 68 (19971339-351
f
0
1
*
3
4
Postprandial
Fig. 4. Effect of the source of dietary protein on the ruminal cattle (symbols as in Fig. 1).
5
time,
8
7
8
h
acetic acid concentration
of cannulated
dairy
VFA concentrations were not significantly different among the treatment groups during 4 to 8 h postprandial. This may be due to the more stabilized ruminal conditions in total mixed rations. The acetic and propionic acid concentration are presented in Figs. 4 and 5, respectively. The dietary source of protein significantly influenced the acetate and propionate concentration (P < 0.05). Except during the first hour after feeding, the concentration of ruminal acetic acid was significantly higher in the cottonseed meal group as compared to Propionate concentration was significantly higher in the the other groups (P < 0.05). fish meal group than in the soybean meal group (P < 0.05) most of the time except from 1 to 4 h, postprandial. With infusions of propionate in the rumen, Hurtaud et al. (1993) This may explain the lower milk displayed a trend of decline in milk yields (P = 0.119). yields in the fish meal group. The dietary source of protein significantly influenced the ratio of acetate to propionate concentration in the rumen (P < 0.05). From 1 to 3 h postfeeding, the ratios were not statistically different. However, the ratio was significantly higher from 4 to 8 h postprandial in the cottonseed meal group as compared to the fish meal group (P < 0.05). Compared to soybean meal, it was only significantly higher before and during 4-6 h after feeding (P < 0.05). In an in vitro continuous fermentation trial, Hoover et al. (1989) showed that the ratio of acetate to propionate and the yield of microbial protein were lower with fish meal than with soybean meal. They ascribed that to fish oil that inhibits microbial growth. From the rumen characteristics, it appears that cottonseed meal resulted in an adequate ruminal ammonia content for microbial synthesis and a ruminal pH above 6.2; Therefore it provides better fermentation conditions and higher total VFA concentration.
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1
0
t
2
3
4
Postprandial
5
*
7
8
time, h
Fig. 5. Effect of the source of dietary protein on the ruminal propionic cattle (symbols as in Fig. 1).
acid concentration
of cannulated
dairy
On the other hand, the ruminal pH declines below 6.2 1 h after feeding in the fish meal group. Low ruminal pH will inhibit cellulose digestion in the rumen as shown by Orskov (1987). Furthermore, the unsaturated fatty acids of fish meal may inhibit growth of the ruminal microbes (Hoover et al., 19891, resulting in poor ruminal fermentation.
Acknowledgements
The authors thank the Agricultural Council of Taiwan for financial support of this project. Project number is 83-Science and Technology-2.29-Muh-21(8).
References AOAC, 1984. Official methods of analysis, 13th edn. Association of Official Analytical Chemists. Washington, DC, pp. 152-162. Atwal, A.S., Ertle, J.D., 1992. Effect of feeding fish meal to cows on digestibility, milk production and milk composition. J. Dairy Sci. 75, 502-507. Blauwiekel, R., Hoover, W.H., Slider, S.D., Miller, T.K., 1990. Effect of fish meal protein supplementation on milk yield and composition and blood constituents of dairy cows. J. Dairy Sci. 73, 3217-3221. Bowers, H.B., Preston, T.R., McLeod, N.A., McDonald, I., Philip, E.B., 1965. Intensive beef production: 5. The effect of different sources of protein on nitrogen retention. Anim. Prod. 7, 303-309. Broderick, G.S., 1992. Relative value of fish meal versus soybean meal for lactating dairy cows fed alfalfa silage as sole forage. J. Dairy Sci. 75, 174-183. Bruckeutal, I., Drori, D., Kaim, M., Lehrer, H., Folman, Y., 1989. Effects of source and level of protein on milk yield and reproductive performance of high-producing primiparous and multiparous dairy cows. Anim. Prod. 48, 319-329.
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Carroll, D.J., Hossain, F.R., Keller, M.R., 1994. Effect of supplemental fish meal on the lactation and reproductive performance of dairy cows. J. Dairy Sci. 77, 3058-3072. Chiou, P.W.S., Chen, K.J., Kuo, KS., Hsu, J.C., Yu, B., 1995. Studies on the protein degradabilities of feedstuffs in Taiwan. Anim. Feed Sci. Technol. 55, 215-226. Christensen, R.A., Lynch, G.L., Clark, J.H., 1993. Influence of amount and degradability of protein on production of milk and milk components by Holstein cows. J. Dairy Sci. 76, 3490-3496. Cross, D.L., Jenny, B.F., 1976. Turkey litter silage in rations for dairy heifers. J. Dairy Sci. 59, 919-923. Grings, E.E., Roffler, R.E., Deitelhoff, D.P., 1991. Response of dairy cows in early lactation to additions of cottonseed meal in alfalfa-based diets. J. Dairy Sci. 74, 2580-2587. Hoover, W.H., Miller, T.K., Stokes, S.R., 1989. Effect of fish meal on bacterial fermentation in continuous culture. J. Dairy Sci. 72, 2991-2998. Hurtaud, C., Rulquin, H., Verite, R., 1993. Effect of infused volatile fatty acids and caseinate on milk composition and coagulation in dairy cows. J. Dairy Sci. 76, 301 l-3020. Hussein, H.S., Jordan, R.M., 1991. Fish meal as a protein supplement in ruminant diets: a review. J. Anim. Sci. 69, 2147-2156. Kaufmann, W., Lupping, W., 1982. Protected proteins and protected amino acids for ruminants. In: Miller, E.L., Pike, I.H., Van Es, A.J.H. (Eds.), Protein Contribution of Feedstuffs for Ruminants: Application to Feed Formulation. Butterworth, London, pp. 36-75. Krishnamoorthy, U.C., Sniffen, C.J., Stem, M.D., Van Soest, P.J., 1983. Evaluation of a mathematical model of digesta and in vitro simulation of mmen proteolysis to estimate the rumen undegraded nitrogen content of feedstuffs. Br. J. Nutr. 50, 555-568. Lindsey, T.O., Hawkins, G.E., Guthrie, L.D., 1980. Physiological responses of lactating cows to gossypol from cottonseed meal rations. J. Dairy Sci. 63, 562-573. Mantysaari, P.E., Sniffen, C.J., Muscato, T.V., 1989. Performance of cows in early lactation fed isonitrogenous diets containing soybean meal or animal by-product meals. J. Dairy Sci. 72, 2958-2967. National Research Council, 1985. Ruminant Nitrogen Usage. National Academy Press, Washington, DC, pp. 7-22. National Research Council, 1989. Nutrient Requirements of Dairy Cattle, 6th edn. National Academy Press. Washington, DC, pp. 78-88. Oldham, J.D., 1984. Protein-energy relationships in dairy cows. J. Dairy Sci. 67, 1090-l 114. Orskov, E.R., 1982. Protein Nutrition in Ruminants, Academic Press, London, pp. 54-63. Orskov, E.R., 1987. The Feeding of Ruminants: Principles and Practice. Rowett Institute, Aberdeen, pp. 24-25. Orskov, E.R., McDonald, I., 1979. The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage. J. Agric. Sci. Camb. 92, 499-503. Parker, D.S., McMillan, R.T., 1976. The determination of volatile fatty acids in the caecum of the conscious rabbit. Br. J. Nutr. 35, 365-371. Roseler, D.K., Ferguson, J.D., Sniffen, C.J., Herrema, J., 1993. Dietary degradability effect on plasma and milk urea nitrogen and milk nonprotein nitrogen in Holstein cows. J. Dairy Sci. 76, 525-536. Statistical Analysis System, 1988. SAS User’s Guide, Statistics: General Linear Model. SAS Institute, Raleigh, NC. pp. 549-640. Satter, L.D., Roffler, R.E., 1975. Nitrogen requirements and utilization in dairy cattle. J. Dairy Sci. 58. 1219-1237. Sloan, B.K., Rowlinson, P., Armstrong, D.G., 1988. The influence of a formulated excess of rumen degradable protein or undegradable protein on milk production in dairy cows in early lactation. Anim. Sci. 46, 13-22. Steel, R.G.D., Torrie, J.H., 1960. Principles and Procedures of Statistics. McGraw-Hill, New York, pp. 107-109. Van Horn, H.H., Rometa, C.A., Wilcox, C.J., Marshall, S.P., Harris, B. Jr., 1979. Complete rations for dairy cattle: 8. Effect of percent and source of protein on milk yield and ration digestibility. J. Dairy Sci. 62, 1086-1093. Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for dietary fiber, neutral detergent fiber and nonstarch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74, 3583-3597. Van Straalen, W.M., Tamminga, S., 1990. Protein degradation of ruminant diets. In: Wiseman, J., Cole, D.J.A. (Eds.), Feed Evaluation. Butterworth, London, p. 55.
ELSEVIER
Animal Feed Science Technology
68 (1997) 339-351
Effect of dietary protein source on performances and rumen characteristics of dairy cows Peter Wen-Shyg Chiou a,*, Bi Yu a, Shyi-Shiun Wu a, Kwen-Jaw Chen b ’Department of Animal Science, National Chung-Hsing University, Taichung, Taiwan b Taiwan Lirestock Research Institute, Hsin-Hua. Tainan, Taiwan Accepted 4 October
1996
Abstract A feeding trial of 8 weeks was carried out following a complete randomized design with 27 dairy cows in their second month of lactation. The aim was to evaluate the effect of three sources of dietary protein, soybean meal, fish meal and cottonseed meal, on the performances and rumen characteristics of dairy cows. Three rumen-fistulated dairy cows were assigned for the study of rumen fermentation. The source of dietary protein did not significantly influence the dry matter intake, but significantly affected milk yield (P < 0.05). The fish meal group produced significantly less milk, but the concentration of total solids, lactose and protein was higher than in the control group with soybean meal. The ruminal pH declined to its lowest level 1 h after feeding and gradually increased afterwards. The ruminal pH of the fish meal group was lowest 1 h postprandial, but did not reach the statistical difference level. The source of dietary protein did not significantly affect the ruminal ammonia concentration, but had a significant effect on the volatile fatty acid (VFA) concentration in the rumen (P < 0.05). Total VFA concentration was significantly higher in the cottonseed meal group than in the other treatment groups before and within 2 h after feeding (P < 0.05). Protein source also significantly influenced the acetate and the propionate concentration and their ratio (P < 0.05). From 1 to 2 h postfeeding, the ratios were not statistically different. However, the ratio was significantly higher from 4 to 8 h postprandial in the cottonseed meal group as compared to the fish meal group (P < 0.05). Compared to soybean meal, the ratio was only significant higher before feeding and from 4 to 6 h, postprandial (P < 0.05). 0 1997 Elsevier Science B.V. Keywords:
Protein source; Dairy cows; Ruminal characteristics
* Corresponding author. Department of Animal Science, National Chug-Hsing Road, Taichung, Taiwan. Tel.: + 886-4-2870613; fax: + 886-4-2860265. 0377.8401/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved. PII SO377-8401(97)00031-X
University,
250 Kuo-Kuang
340
P. W.-S. Chiou et al./Animal Feed Science Technology 68 (1997) 339-351
1. Introduction Supplementation of a high amount of undegradable protein to meet the absorbable protein requirements increased the milk yield in iso-protein rations for high-producing cows (NRC, 1985). Fish meal is an excellent source of undegradable protein. Cottonseed meal also contains a large amount of both crude and undegradable protein. In a feeding trial using alfalfa hay and silage as basal diet for early lactating cows, Grings et al. (1991) observed an increased feed intake and milk yield when the protein content of the diet was increased from 13.8 to 17.5% by a cottonseed meal supplement; the protein and fat content of the milk remained constant. Van Horn et al. (1979) obtained similar results with an increase of dietary protein to 16.3% by replacing soybean meal by cottonseed meal. Partially substituting soybean meal by fish meal fed to high-producing cows in early lactation, Broderick (1992) obtained an increase in the milk yield. Atwal and Erfle (1992) also found an improvement in yield and protein content of the milk with a herd producing an average of 30 kg d- ’ in early lactation and fed a 16% (crude protein) CP ration with partial substitution by fish meal. Hussein and Jordan (1991) reported that with a fish meal-substituted ration in early lactation, cows can obtain a better body condition and conception rate besides the increase in milk yield and protein content. The results from a fish meal supplement for cows with a low to moderate milk yield or in midlactation were different from those of high-yielding cows. Oldham (1984) and Sloan et al. (1988) fed a fish meal supplement to a herd with a mean milk production of 27 kg d-l, and obtained no advantageous result. Broderick (1992) obtained a similar result with a fish meal supplement in a midlactating herd. In a trial with 80 primiparous cows, Mantysaari et al. (1989) fed a 17.3% CP ration with an increasing amount of undegradable protein, from 32 to 37.8%, by substituting fish meal, and found no beneficial result. It appears that several factors, i.e., the mean milk yield and lactation period, should be considered when applying the system of ruminal undegradable protein in ration formulation. In addition, the digestion and absorption, the energy content of the ration, the amino acid profile of the undegradable protein will influence the performances. The aim of this study is to evaluate the effect of three sources of dietary protein: soybean meal, fish meal and cottonseed meal, on the performances and rumen characteristics of dairy cows.
2. Materials and methods 2.1. Experimental
ration formulation
Experimental diets were formulated according to the nutrient requirements of the NRC (1989). Experimental cows averaged 500 kg in body weight and produced an average of 25 kg of 3.5% fat-corrected milk daily. Three isonitrogenous and isoenergetic diets, presented in Table 1, were formulated, differing in protein source: soybean meal (control) and soybean meal partially substituted by fish meal or cottonseed meal. Concentrate ingredients, pelleted through a 3-mm
P. W.-S. Chiou et al. /Animal Feed Science Technology 68 (1997) 339-351
341
Table 1 Diet formulation” Ingredients
Soybean meal 410 150 172 95 95 _
Corn silage Alfalfa hay Corn Soybean meal, 44% Soybean, full fat Cottonseed meal Fish meal Wheat bran Molasses Dicalcium phosphate Calcium carbonate Salt Premix b Total
Fish meal 410 150 216 70 37 45 45 15 2 4
45 15 6 6 5
1000
loo0
Cottonseed 410 150 170 18 74 100 45 15 7
1000
Calculated nutrient values Crude protein Undegradable protein, % CP
165 37.5
165 37.5
165 37.5
Analyzed nutrient values’ Crude protein, CP Neutral detergent libre Acid detergent fibre Soluble protein, % CP NPN, % soluble CP NDFIP, % CP ADFIP, % CP
163 382 201 31.7 84.7 16.3 8.0
165 396 191 31.0 87.6 15.7 6.9
160 387 216 34.3 84.6 17.0 8.2
“The figure are g/kg bPremix components 1,600,OOO IU; Fe: 50 ‘NPN is non-protein
of dietary (each kg g; Zn: 40 nitrogen,
dry matter contains): g; Mn: 40 NDFIP is
meal
except otherwise stated. vitamin A: 10,000.000 IU; Vitamin E: 70,OOG IU; Vitamin D: g; Co: 0.1 g; Cu: 10 g, I: 0.5 g; Se: 0.1 g. neutral detergent insoluble protein, and ADFIP is acid detergent
insoluble protein.
die at 70°C once every week, were mixed daily with corn silage and alfalfa hay. Moisture contents of the concentrate and roughage were measured weekly for adjusting the ration composition. 2.2. Animal and management
in feeding
trial
The experiment was a complete randomized design with 27 dairy cows (21 multiparous and six heifers) in their second month of lactation (55 f 20 days). Cows producing more than 20 kg of milk were selected and were randomly allocated into the three treatment groups. Cows were confined into individual pens most of the time during the experimental period, and were released for exercise twice daily from 03:30 to 06:30 and 13:00 to 1790. Cows were dewormed twice monthly during the experimental period.
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After 2 weeks of adaptation, the feeding trial started for 8 weeks. The cows were individually fed ad libitum, allowing 2 to 3 kg orts, in two meals per day (06:30, 17:OO). Water was provided individually with an automatic bowl-type drinker. Animals were milked twice daily at 05:OOand 16:O0. During the feeding trial, both temperature and humidity inside the dairy barn were continually monitored by an automatic recorder (R-704, Sate). Dry matter intake and milk yields were recorded daily. Milk samples were taken once every other week. Cows were weighed at the beginning, in the fourth week and at the end of the trial. The body weights were calculated as the average of two consecutive daily measurements. Feed samples were taken weekly and dried at 60°C in a ventilated oven for 48 h. Blood samples were taken 3 to 4 h postprandial from four cows per treatment every other week during the experimental period. 2.3. Ruminal studies Three dairy Holstein cows with rumen fistulas were randomly assigned to the three dietary treatments according to a Latin square design. Each treatment period was 10 days with 7 days of transitional period. Cows were individually fed ad libitum in two meals daily. Ruminal fluid samples of 200 ml were taken on the 9th and 10th day in the morning before the meal and 1, 2, 3, 4, 6, 8 h postprandial. Ruminal pH was measured immediately after withdrawal. Samples were then filtered through four layers of cheese cotton and diluted with 20% metaphosphoric acid. After mixing, the samples were sealed and preserved at - 18°C for later analysis of ammonia nitrogen and volatile fatty acid concentration. Crude protein degradability of the total mixed rations was measured by the in situ method of Orskov and McDonald (1979) and modified by Chiou et al. (1995) with the same three rumen-cannulated dairy cows from the rumen study trial. Cows were fed a total mixed ration of 15 kg dry matter with an equal amount of concentrate and roughage (dry basis), and were fed equally, divided six times with an evenly divided amount of feed every day. The samples were ground through a 2-mm mesh screen and were placed into the polyester bag with pore size of 53 f 10 pm. Modification concerning size of the nylon bag, changed from 4.5 X 6.5 cm to 10 X 20 cm, and sample size increased from 1 g to 8 g of dry matter. Instead of placing bags into a perforated tube, they were attached to an iron ring of 450 g, and were then connected to the rumen fistula by a 70-cm nylon cord. The incubation period was extended from five periods of 2, 4, 8, 12 and 24 h to seven periods with an addition of 48 h. Immediately after removal from the rumen, samples were put in ice-water to stop the microbial fermentation and were then mechanically washed with water 1.5 min three times. Samples were then dried in the 60°C air-draw oven for 48 h. 2.4. Chemical analysis Chemical analysis of feed samples was according to the methods of AOAC (1984). Neutral detergent fiber (NDF), acid detergent fiber (ADF) and insoluble nitrogen in NDF and ADF, were analyzed according to the method of Van Soest et al. (1991) using
P.W.-S. Chiou et al./Aninml
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Science Technology 68 (1997) 339-351
343
an automatic fiber analyzer (Fibertec System M, Tecator). Soluble protein was determined by the procedure of Krishnamoorthy et al. (1983). Milk composition of fat, protein, lactose and total solids were analyzed by a milk scanner (Milk0 Scan 255 A/B types, Foss Electric) according to the infrared method of AOAC (1984). Plasma urea nitrogen was determined by an automatic blood chemical analyzer (Gilford system 103) according to the method of Cross and Jenny (1976). The pH value of rumen fluid was measured with a pH meter (Suntex SP-32). Concentration of ruminal ammonia nitrogen was analyzed by an automatic Kjeldhal apparatus according to AOAC (1984). Ruminal concentration of volatile fatty acids was determined according to Parker and McMillan (1976). 2.5. Statistical
analysis
A completely for the ruminal calculated with System (1988). means according
3. Results
randomized block design for the feeding trial and a Latin square design studies was applied to find dietary effects. Analysis of variance was the general linear model (GLM) procedure of the Statistical Analysis Duncan’s new multiple range test was used to compare the treatment to Steel and Torrie (1960).
and discussion
3.1. Effect on dry matter intake The results of the feeding trial are presented in Table 2. The source of dietary protein did not significantly influence the dry matter intake. Bowers et al. (1965) found that a high amount of fish meal (9.8% of diet) decreased palatability of the diet and feed intake. Inclusion of a smaller amount of fish meal (3.5% vs. 5.1%) in the ration had no impact on the feed intake of lactating cows (Carroll et al., 1994; Blauwiekel et al., 1990). In this trial too, fish meal did not affect dry matter intake. This may be due to the small amount of fish meal (4.5%) in the experimental diet or to the corn silage that masked the flavor of fish meal. An increase of cottonseed meal in the diet from 8.6% to 24.2% did not influence the dry matter intake by lactating cows (Grings et al., 1991). Even up to 45% cottonseed meal in the diet did not significantly affect the feed intake of lactating cows (Lindsey et al., 1980). In this trial, only 10% cottonseed meal was added in the ration, resulting in a similar dry matter intake as the control group. 3.2. Effect on the milk yield The effect of the dietary protein source on milk yield was significant (P < 0.05). The milk yield in the fish meal group was on average 2.5 kg dd’ less than in the other groups. This result is different from that of Atwal and Erfle (1992) who obtained a higher milk yield by fish meal substitution in a 16% CP ration. Oldham (1984) and
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P. W.-S. Chiou et al./Animal
Table 2 Effect of dietary protein on the performance
Feed Science Technology 68 (1997) 339-351
and production
efficiency
of dairy cattle
Soybean meal
Fish meal
Cottonseed
DM intake d; milk yield, kg/day Dry matter intake Milk yield 4% FCM
22.7 26.5” 24.7
22.4 24.0b 23.6
22.4 26.5a 24.7
0.51 0.55 0.54
Milk composition, % Total solids Milk fat Milk protein Lactose
11.66b 3.59 2.70b 4.66b
12.63” 3.88 3.20a 4.85”
11.88”b 3.60 2.80b 4.69b
0.17 0.12 0.06 0.04
3.14 0.96 0.74 1.25
3.01 0.93 0.75 1.16
3.14 0.90 0.78 1.23
0.29 0.14 0.10 0.09
0.81b 0.86b
0.14 0.14
0.13b 3.70b
0.02 0.10
Milk Total Milk Milk Milk
components yield, kg/day solids fat protein lactose
Feed eficiency, kg/kg DM intake/milk yield DM intake/4% FCM yield
0.87b 0.91b
Protein eficiency, kg/kg CP intake/4% FCM yield CP intake/milk protein yield
0.15b 5.33&
“b’c’: Means in the same row with different subscript
0.19” 5.75” letters are significantly
meal
SEM
different (P < 0.05).
Sloan et al. (1988) found that a fish meal supplement did not improve milk yield with a mean yield less than 27 kg dd’. Blauwiekel et al. (1990) did not obtain a positive result for 4% fat-corrected milk by fish meal substitution in rations with equal crude (16.5%) and degradable protein (41.7%) concentration. Bruckeutal et al. (1989) also did not obtain an increase in milk yield by replacing 20% of soybean meal by fish meal. The lack of effect with fish meal may be explained by no positive response in the duodenal flow of dietary nitrogen or a decrease of microbial synthesis in rumen. In our trial, with rations containing the same level of crude (16.5%) and degradable protein (37.5%), the treatment did not significantly affect the 4% FCM (P > 0.05). 3.3. Effect on the milk composition The source of dietary protein significantly affected the total solids content of the milk (P < 0.05). Milk of the fish meal group contained more total solids, lactose and protein than the control group. There was a trend of a higher milk fat content. This trend is contradicting to most reports which showed a reduced milk fat percentage by fish meal supplementation (Sloan et al, 1988; Blauwiekel et al., 1990). They attributed this to the high levels of long-chain polyunsaturated fatty acids.
P. W.-S. Chiou et al. /Animal Feed Science Technology 68 (1997) 339-351
34s
Broderick (1992) also obtained an increase in milk protein concentration by replacing soybean meal with fish meal in diets fed to high-yielding cows. They attributed this to the high available dietary amino acid content escaping degradation in rumen. Although milk composition was affected by the source of protein, the daily yields of milk components showed no significant differences among the treatment groups. This is due to the lower milk yield in the fish meal group. 3.4. Effect on the production
eficiency
Dietary sources of protein significantly influenced the efficiency of milk production (P < 0.05). Cows fed the fish meal ration produced milk less efficiently than the soybean or the cottonseed meal group (P < 0.05). There was no significant difference in the efficiency of milk production between the soybean and the cottonseed meal group. The efficiency of protein utilization, i.e., milk protein production per unit of the protein intake, showed the same trend. The fish meal group used protein least efficiently, whereas the cottonseed meal group obtained the most efficient protein production. The unsaturated fatty acid of the fish meal may inhibit ruminal bacterial fermentation (Hoover et al., 1989). Whether this adverse effect resulted in the poor performance in the fish meal group requires further investigation. 3.5. Effect on the serum nitrogen The effect of dietary protein source on the concentration of plasma urea nitrogen was not significant (Table 3). The plasma urea concentration was lowest in the cottonseed meal group, but did not reach the significance level. Grings et al. (1991) suggested that the urea level in the plasma increased with an increase of dietary protein. The plasma urea level was not influenced by the source of protein, whether it was from degradable or from undegradable protein (Roseler et al., 1993). This may imply that the ruminal ammonia level remains adequate for microbial synthesizing, without an excess amount of ruminal nitrogen flow into the blood stream (Fig. 2).
Table 3 Effect of dietary protein on the plasma urea nitrogen concentration Items Plasma urea Live-weight 4th week/O 8th week/4th 8th week/O
Soybean meal nitrogen (mg/dl) change (%) week week week
Fish meal
and liveweight
changes of the cows
Cottonseed
meal
SEM
15.6
15.3
14.6
2.6
99.8 103.6” 103.9”
100.6 104.9a 104.3a
99.7 101.9b 102.2b
2.6 2.4 1.7
a’b’c’:Means in the same row with different subscript
letters are significantly
different (P < 0.05).
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346
3.6. Effect on the body weight change The relative body weight change during the experimental period is presented in Table 3. Body weight changes were significantly different among the treatment groups in the second period of 4 weeks and in the whole 8-week feeding trial. This was due to the significantly lower body weight gain in the cottonseed meal group during the second period. Cows usually lose body weight with increasing milk yields during peak lactation. Most cows in this trial lost body weight in the first month and regained weight during the second 4-week period. This means that cows could not ingest enough feed for lactation and mobilized body reserves during the first 4 weeks. This weight loss was recovered during the second 4-week period. 3.7. Evaluation of degradable protein The degradation characteristics and the effective degradability of crude protein are presented in Table 4. Effective protein degradability at an outflow rate of 8% per hour was 75.9%, 70.6% and 79.7% for the soybean meal, the fish meal and the cottonseed meal ration, respectively. These values are much higher than the value of 62.5%, calculated from the ration formulation. Van Straalen and Tamminga (1990) showed that protein degradability values substantially differed among laboratories, and that the variation was even higher for forage proteins. Fish meal is generally considered as a highly undegradable protein source. However, Orskov (1982) reported a wide range of protein degradability in fish meal from 11 to 52%. Kaufmann and Lupping (1982) attributed this to factors in the manufacturing process: the storage period of raw fish before processing, types of drying, addition of preservatives, heating duration and proportion of fish solubles added back to the meal. The quality of fish meal greatly affects its nutrient and feeding value for lactating cows. In purchasing fish meal for ruminant diets, the detailed information and quality control are required.
Table 4 Degradation
characteristics
Total mixed ration
Soybean meal Fish meal Cottonseed meal
and effective Degradation
degradability
of crude protein of total mixed experimental
rations
Effective degradability outflow ratesb (% hr- ‘>
characteristic?
a
b
C
5
8
59.6 54.6 66.2
37.8 36.9 29.1
6.1 6.2 7.0
80.31 74.94 83.08
75.89 70.63 79.68
a a = The portion (percentage) of insoluble protein solubilized at initiation of incubation; b = the fraction (percentage) of crude protein potentially degradable in the rumen; and c = the constant rate (percentage per h) of disappearance of b. b Effective degradability of crude protein calculated for k = 5, or 8 (% h-’ ) solid outflow rates.
P. W.-S. Chiou et al. /Animal
Feed Science Technology 68 (lY971339-351
347
3.8. Effect on the rumen fermentation Data obtained from the trial with the rumen-fistulated cows, pH value, ammonia nitrogen and volatile fatty acid (VFA) concentration are presented in Figs. 1-3, respectively. The ruminal pH declined to its lowest level 1 h after feeding and gradually increased afterwards. The pH 1 h postprandial was lowest for the fish meal group, but did not reach the statistical difference level. Bowers et al. (1965) used soybean meal, fish meal, peanut meal or cottonseed meal as protein supplement and found that the ruminal pH in the fish meal group was significantly lower than in the other protein groups (P < 0.01). The low potassium content in fish meal compared to plant protein (0.3% vs. 2%) resulting in a lower buffering capacity may be the reason. In this trial, the fish meal inclusion was much lower compared to the trial performed by Bowers et al. (1965) (4.5% vs. 9.8%), which may explain the nonsignificant influence on ruminal pH. The sources of dietary protein did not significantly influence the ruminal ammonia concentration. The ammonia level reached a peak 3 h after feeding, and declined afterwards. Christensen et al. (1993) indicated that the level of ruminal ammonia increased as the level of dietary protein or dietary degradable protein increased. Because in this experiment isonitrogenous rations were designed, the ruminal level did not differ statistically. The ammonia level remained above 10 pmol d-’ I- ‘, even 8 h after feeding which should be adequate for optimum microbial synthesis (5 pmol dd’ ll ‘1 in the rumen as suggested by Satter and Roffler (1975). The effect of the dietary source of protein was significant on the total VFA concentration in the rumen (P < 0.05). Total VFA concentration was significantly higher in the cottonseed meal group than in the other treatment groups before and within
0
1
2
3
4
Postprandial
5
6
7
8
time, h
Fig. 1. Effect of the source of dietary protein on the ruminal pH of cannulated group; ( W) fish meal group; ( A ) cottonseed meal group.
dairy cattle. (0)
soybean meal
P. W.-S. Chiou et al. /Animal Feed Science Technology 68 (1997) 339-351
348
I-----0
1
2
3
4
5
postprandial
6
7
a
time, h
Fig. 2. Effect of the source of dietary protein on the rumhal (symbols as in Fig. 1).
ammonia
nitrogen
of cannulated
dairy cattle
2 h after feeding (P < 0.05), which may reflect a better ruminal fermentation. The ruminal total VFA concentration in the cottonseed meal treatment was also significantly higher 3 to 4 h, postprandial, as compared to the fish meal group (P < 0.05). The total
f
I
0 0
1
1
3
4
postprandial
5
6
7
8
time. h
Fig. 3. Effect of the source of dietary protein on the ruminal total volatile fatty acid production dairy cattle (symbols as in Fig. 1).
of cannulated
P. W.-S. Chiou et al. /Animal Feed Science Technology 68 (19971339-351
f
0
1
*
3
4
Postprandial
Fig. 4. Effect of the source of dietary protein on the ruminal cattle (symbols as in Fig. 1).
5
time,
8
7
8
h
acetic acid concentration
of cannulated
dairy
VFA concentrations were not significantly different among the treatment groups during 4 to 8 h postprandial. This may be due to the more stabilized ruminal conditions in total mixed rations. The acetic and propionic acid concentration are presented in Figs. 4 and 5, respectively. The dietary source of protein significantly influenced the acetate and propionate concentration (P < 0.05). Except during the first hour after feeding, the concentration of ruminal acetic acid was significantly higher in the cottonseed meal group as compared to Propionate concentration was significantly higher in the the other groups (P < 0.05). fish meal group than in the soybean meal group (P < 0.05) most of the time except from 1 to 4 h, postprandial. With infusions of propionate in the rumen, Hurtaud et al. (1993) This may explain the lower milk displayed a trend of decline in milk yields (P = 0.119). yields in the fish meal group. The dietary source of protein significantly influenced the ratio of acetate to propionate concentration in the rumen (P < 0.05). From 1 to 3 h postfeeding, the ratios were not statistically different. However, the ratio was significantly higher from 4 to 8 h postprandial in the cottonseed meal group as compared to the fish meal group (P < 0.05). Compared to soybean meal, it was only significantly higher before and during 4-6 h after feeding (P < 0.05). In an in vitro continuous fermentation trial, Hoover et al. (1989) showed that the ratio of acetate to propionate and the yield of microbial protein were lower with fish meal than with soybean meal. They ascribed that to fish oil that inhibits microbial growth. From the rumen characteristics, it appears that cottonseed meal resulted in an adequate ruminal ammonia content for microbial synthesis and a ruminal pH above 6.2; Therefore it provides better fermentation conditions and higher total VFA concentration.
P. W.-S. Chiou et al. /Animal Feed Science Technology 68 (1997) 339-351
1
0
t
2
3
4
Postprandial
5
*
7
8
time, h
Fig. 5. Effect of the source of dietary protein on the ruminal propionic cattle (symbols as in Fig. 1).
acid concentration
of cannulated
dairy
On the other hand, the ruminal pH declines below 6.2 1 h after feeding in the fish meal group. Low ruminal pH will inhibit cellulose digestion in the rumen as shown by Orskov (1987). Furthermore, the unsaturated fatty acids of fish meal may inhibit growth of the ruminal microbes (Hoover et al., 19891, resulting in poor ruminal fermentation.
Acknowledgements
The authors thank the Agricultural Council of Taiwan for financial support of this project. Project number is 83-Science and Technology-2.29-Muh-21(8).
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