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Wet brewers' grains or bean curd pomance as partial replacement of soybean meal for lactating cows
Animal Feed Science and Technology 74 (1998) 123±134
Wet brewers' grains or bean curd pomance as partial replacement of soybean meal for lactating cows Peter Wen-Shyg Chioua,*, Chao-Ren Chena, Kuen-Jaw Chenb, Bi Yua a
Department of Animal Science, National Chung-Hsing University, Taichung, Taiwan b Taiwan Livestock Research Institute, Hsin-Hua, Tainan, Taiwan Received 27 November 1997; accepted 2 April 1998
Abstract The purpose of this study was to evaluate the effects of supplementation of the by-product, brewers' grains and the bean curd pomance, on the performance of lactating cows and their ruminal characteristics. Through this, we wanted to increase resource utilization and to eliminate pollution from these by-products. Thirty-two Holstein lactating cows were allocated randomly into four dietary treatment groups. The experimental diets were formulated to be isoenergetic and isonitrogenous according to National Research Council (1989), and containing 35% corn silage, 20% alfalfa hay and 45% concentrates on DM basis. The dietary treatments consisted of the inclusion of different by-products sources. These included soybean bean (as the control), brewers' grains, bean curd pomance, and the mixed by-products (containing the same amount of brewers' grains and bean curd pomance). The experimental feeding lasted for eight weeks after one week of adaptation. In addition, four rumen cannulated Holstein cows were used in a 44 Latin square with 10-day period for collecting rumen samples. Results showed that cows that were fed the bean curd pomance diet produced significantly more milk than those that were fed the brewers' grains diet or the mixed by-product diet. The cows on the control diet produced significantly less milk than the other treatment groups (P<0.05). Both the control and brewers' grains groups consumed more feed than those in the bean curd pomance and mixed by-products diet groups (P<0.05). The cows that were fed the mixed by-products diet produced a significantly lower percentage of milk fat, total solids, milk protein and milk lactose than the others (P<0.05). The milk lactose percentage was significantly higher for cows that were fed the bean curd pomance than those fed the brewers' grains diet (P<0.05). Cows that were fed the bean curd pomance produced significantly more milk fat, total solids, milk protein and milk lactose than the others (P<0.05). Cows that were fed the mixed by-products diet produced significantly lower amount of milk fat, total solids and milk protein than the control and brewers' grains group (P<0.05). These diets did not significantly * Corresponding author. Tel.: +886 4 287 0613; fax : +886 4 286 0265 0377-8401/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved PII S 0 3 7 7 - 8 4 0 1 ( 9 8 ) 0 0 1 7 0 - 9
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influence the body weight of the cows. It, however, significantly influenced the ruminal characteristics (P<0.05). # 1998 Elsevier Science B.V. Keywords: Wet brewers' grains; Bean curd pomance; By-products; Lactating dairy cows
1. Introduction Brewers' grains are the by-products from brewer industry. It is an extracted residue of barley malt, alone or in mixture with other cereal grains or grain products resulting from production of wort or beer. These products are rich in crude protein (CP), crude fiber (CF), ether extract (EE), vitamins and minerals. The nutrient contents of these products except for starch are proportionally richer than most of the barleys. It contains high protein and crude fiber. Therefore, it is mostly used as a protein supplement for cattle. Bean curd pomance, on the other hand, is a by-product of the manufacturing process of bean curd. Bean curd, also known as soybean cake or Chinese cheese, and is one of the major protein sources in Asia. It contains high CP, EE and CF with minimum vitamins. Fresh bean curd pomance contains only 9±12% dry matter. The average CP, EE, CF, ash and NFE content of bean curd pomance is 20.3%, 6.0%, 15.8%, 2.6% and 50.9% of DM, respectively. It contains high undegradable protein CP of 61.75 (Chiou et al., 1995). Therefore, the bean curd pomance is also a good source of protein for dairy cattle. Since both wet brewer grains and bean curd pomance contain high undegradable protein, these will be a good supplement source of ruminal by-pass protein for lactating cows. This study, therefore, aims to evaluate the feeding value of wet brewer grains and bean curd pomance as undegradable protein supplement for lactating cows. 2. Materials and methods 2.1. Experimental diets Experimental diets were formulated according to the nutrient requirement of National Research Council (1989), and based on the assumption of lactating cows with 550 kg body weight, and producing 25 kg of 3.5% FCM daily. The dietary treatments were the control diet, wet brewers' grains diet (WBG), fresh bean curd pomance diet (BCP), and a mixed by-products diet (MBP), respectively. The control diet used soybean meal (SBM) as the protein supplement. The WBG diet and BCP diet supplemented 10% (DM basis) of WBG or BCP as the protein supplement, respectively. The MBP diet contains 5% (DM basis) of WBG and BCP. Table 1 presented the experimental diets that were formulated as isoenergetic, isonitrogenous, and isoundegradable nitrogen. They contain 35% corn silage, 20% alfalfa hay and 45% concentrate on DM basis. Experimental diets were fed as total mixed rations (TMR). The concentrates were premixed and were pelleted through a 3-mm die at 708C once every week, and daily
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Table 1 Ingredients and nutrient composition of the experimental total mixed rations on dry matter basis Experimental rations Ingredients, g/kg Alfalfa hay Corn silage Full fat soybean Soybean meal, 44% Corn Wet brewers' grain Bean curd pomance Lard Dicalcium phosphate Limestone Salt Premixa Total Calculated nutrient value Crude protein, CP NEL, MJ/kg Undegradable protein, %CP Analysed nutrient value Dry matter Crude protein ADF NDF
Control
WBG
BCP
MBP
200.0 350.0 19.8 90.5 313.5 Ð Ð 14.7 5.6 1.8 3.0 1.0 1000.0
200.0 350.0 10.0 81.5 242.1 100.0 Ð 5.0 6.9 0.5 3.0 1.0 1000.0
200.0 350.0 23.9 62.5 227.2 Ð 100.0 24.6 7.9 0.2 3.0 1.0 1000.0
200.0 350.0 15.7 63.3 232.6 50.0 50.0 26.8 7.6 0.1 3.0 1.0 1000.0
160.0 7.027 38.0
160.0 7.027 38.0
160.0 7.027 38.0
160.0 7.027 38.0
505.0 157.1 229.7 397.3
436.4 166.4 225.6 432.9
388.2 158.0 240.3 395.4
396.2 158.9 231.6 404.3
a
Each kilogram of premix contains: Vit. A, 10 000 000 IU; Vit. E, 70 000 IU; Vit D3, 1 600 000 IU;Fe, 50 g; Zn, 40 g; Mn, 40 g; Co, 0.1 g; Cu, 10 g; Se, 0.1 g.
mixed with corn silage, alfalfa hay and by-products. The moisture content of the roughage was measured weekly for the adjustment of the as-fed ration composition. 2.2. Animal and management in feeding trial Thirty-two early lactating cows that produced more than 20 kg milk daily were selected and were allocated to the four treatment groups according to their milk yield and number of lactation. Cows were confined in individual pens most of the time during the experimental period. They were released for exercise twice daily from 0400 to 1000 hours and 1300 to 1700 hours. The experimental cattle were dewormed once every two weeks during the experimental period. After one week of adaptation, the cows started the eight weeks feeding trial. These cows were individually fed ad libitum with 2±3 kg orts in two meals per day (0630 and 1700 hours). Water was provided individually with an automatic bowl type drinker. The animals were milked twice a day at 0430 and 1600 hours. During the feeding period, the dry matter intake and the milk yield were daily recorded. Milk samples were taken once every other week. The live-weights of the cows were calculated by two consecutive days' measurements every four weeks from the start of the trial. Feed samples were taken weekly and dried in a 608C ventilated oven for 48 h.
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2.3. Ruminal studies Four ruminal fistulated dry cows were randomly assigned to the four dietary treatments in a Latin square design with four observations per treatment. Each of four periods used the four cows and consisted of 17 days with a 7-day adaptation and a 10-day experimental diet feeding. On the last two days of the feeding period, rumen samples of 200 ml were collected from the ruminal fistula before and 1, 2, 3, 4, 6 and 8 h after the meal, and the pH of the ruminal samples were measured immediately after withdrawal. After filtering through four layers of cheese cotton, the ruminal samples were then diluted (5:1) with 25% metaphosphoric acid. Samples were sealed and preserved at ÿ188C for analysis of ammonia nitrogen and volatile fatty acid concentration. 2.4. Chemical analysis Analysis of the feed samples was done according to the methods of the Association of Official Analytical Chemists (AOAC, 1984). The neutral detergent fibre (NDF) and acid detergent fibre (ADF) were analyzed according to the methods of Van Soest et al. (1991) using an automatic fibre analyzer (Fibertec System M, Tecator AB). The milk composition of fat, protein, lactose and total solids was analyzed by a milk scanner (Foss Electric Co., Milko Scan 255 A/B types) using the infra-red method of AOAC (1984). The pH value of rumen fluid was measured by a pH meter (Suntex TS-1). Concentration of ruminal ammonia nitrogen was analyzed by an automatic Kjeldahl analyzer according to Chaney and Marbach (1962). Ruminal concentrations of volatile fatty acids were determined by gas chromatography (Hitachi G-3000) according to Parker and McMillan (1976). 2.5. Statistical analysis A completely randomized design for the feeding trial and a Latin square design for the ruminal studies was applied to find dietary effects. Analysis of the variance was calculated with the general linear model procedure (GLM) of the Statistical Analysis System Institute Inc. (1985). Least square means were used to compare the difference of the treatment means. 3. Results and discussion 3.1. The effect on dry matter Table 2 presented the dietary effect on the performance and efficiency of nutrient utilization in lactating cows. The effect of dietary treatment on the DM intake of lactating cows was significant (P<0.05). The cows in the control and the WBG groups consumed significantly more feed DM than cows in the BCP or MBP groups (P<0.05). This implied that on inclusion 10% of bulky and high water content WBG in the lactating diet did not
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Table 2 Effects of dietary treatment on the performance of lactating cows Ingredients Performance, kg/day Dry matter intake Milk yield 4% FCM Milk composition, g/kg Total solids Milk fat Milk protein Milk lactose Yield of milk composition, kg/day Total solids Milk fat Milk protein Milk lactose Efficiency, kg/kg DM intake/milk yield DM intake/FCM yield NEL intake/FCM yield, Mj/kg CP intake/FCM yield CP intake/milk protein yield Live-weight Initial weight, kg Changes, % 1st 4-week 2nd 4-week All period a,b,c,d
Control 19.05a 25.99c 24.91c
WBG 18.84a 26.67b 25.60b
BCP 18.27b 27.99a 27.00a
MBP 18.10b 26.62b 24.20d
SEM 0.33 0.41 0.32
117.1a 37.1a 27.7a 45.5ab
117.2a 37.3a 27.5a 44.7b
118.2a 37.6a 27.7a 46.0a
100.9b 33.9b 26.2b 43.6c
2.1 1.4 0.6 1.1
30.5b 9.7b 7.2b 11.8b
31.2b 9.9b 7.3b 11.9b
33.1a 10.5a 7.7a 12.9a
29.5c 9.0c 7.0c 11.7b
0.7 0.4 0.2 0.3
0.74a 0.78a 5.35a 0.12a 4.28a
0.74a 0.77a 5.31a 0.12a 4.29a
0.67c 0.71b 4.85b 0.11b 3.88b
0.69b 0.76a 5.23a 0.12a 4.24a
541
542
568
536
102 101 103
103 101 104
101 102 102
102 101 103
0.015 0.025 0.176 0.004 0.145
1.4 1.2 1.6
Means in the same row with different letters are significantly different (P<0.05).
depress the feed DM intake. An inclusion of 10% WBG was still far below the 30% WBG maximum suggested by Murdock et al. (1981). A similar result was also obtained by West et al. (1994) that an inclusion of 15% or 30% WBG (35.5% DM) into the lactating diet did not significantly influence the dry matter intake. Although cows in both the BCP and the MBP group consumed more feed than the control group on the as-fed basis, the dry matter intakes were still significantly less than in the control group (P<0.05). This was attributed to the high water content of the BCP diet (61%) and the MBP diet (60%) as compared to the control diet (49%). Lahr et al. (1983) also derived the same results that dry matter intake decreases with the increase of dietary water content. 3.2. The effect on the milk yield Dietary treatment significantly influenced the milk yield of the lactating cows (P<0.05), cows in the control diet yielded significantly less milk than those in the other three treatment groups (P<0.05). Conversely, cows in the BCP group produced significantly more milk than those in the WBG or the MBP group (P<0.05). Cows in
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the BCP diet also yielded a significantly more 4% FCM than those in the other groups, where cows in the WBG produced significantly more FCM than the control or the MBP diet (P<0.05). However, cows in the MBP diet produced significantly less of 4% FCM than that in the control group (P<0.05). The live-weight changes of the cows in the WBG did not significantly differ from those in the control group during the experimental feeding period. They, in fact, gained weight during this period. This implied a high feed efficiency of cows that were fed the WBG diet or an underestimation of the NRC NEL value. Murdock et al. (1981) re-evaluated the nutritive value of WBG for lactating dairy cows and found the NEL value of 7.36 MJ/kg instead of 6.27 MJ/kg of National Research Council (1989). Hoffman and Armentano (1988) substituted 23.1% WBG for SBM in early lactating dairy diet. They found that cows in both groups consumed a similar amount of feed dry matter. They also obtained a trend of higher milk yields in the WBG group as compared to the SBM groups (P>0.05). Polan et al. (1985) compared different levels of the WBG inclusion (13.0%, 20.6% and 29.0% of DM) with different levels of protein (14.5%, 16.0% and 17.5% of DM) in the diet for the mid-lactating cows. They showed a significant improvement of the milk yield (P<0.05) by the WBG inclusion. From the result of better milk yield and protein utilization efficiency of the WBG as compared to the equal amount of the soybean meal intake, they concluded that the protein quality of WBG is superior to the SBM. 3.3. The effect on milk composition Dietary treatment significantly influenced the composition of milk (P<0.05). The concentrations of total solids, milk fat, milk protein and lactose were significantly lower in milk of cows that were in the MBP group than those in the other treatment groups (P<0.05). The lactose percentage was significantly higher in the milk that produced from the BCP group than that from the WBG or the MBP group (P<0.05). Cows that were fed the BCP diet produced significantly more total solids, milk fat, milk protein and lactose daily than those in the other three dietary groups (P<0.05), where those in the control and in the WBG group yielded significantly more of the total solids, milk fat and milk protein than those in the MBP group (P<0.05). The composition of milk produced from the WBG group was not significantly different from that of the control group. Concentration of milk protein was not significantly different in milk that was produced from the control, the WBG or the BCP group. Since the dietary protein and energy intake are highly correlated to the concentration of milk protein it produced, and since diets were formulated on iso-nitrogenous and equal energy basis, the milk protein content from the BCP group cows should be lower than that from the other groups because of the low DM intake. The BCP diets, however, contained highly soluble protein that provided more ruminal available protein (RAP)(Chiou et al., 1995). A high RAP may contribute to the high propionate concentration in the rumen. The increase in ruminal propionate concentration will eventually provide more glucose to the mammary gland. This will increase insulin secretion and amino acids absorption, and will eventually enhance milk protein production by the mammary gland (Aldrich et al., 1993). Although our data showed a slightly higher propionic acid concentration in the BCP group in this trial, both the BCP and the control group produced milk with a similar protein concentration. These
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may contribute to the same amount of ruminal available protein in both treatment groups. Cows on the BCP diet yielded more milk than those in the control or the WBG group. Therefore, cows of the BCP group produced significantly more lactose daily than those of the other groups (P<0.05). The concentration and the daily yield of the total solids and milk fat also showed a trend similar to the milk protein. This result agreed with Johnson et al. (1987) that a substitute of 25.6% of WBG for 14.3% SBM did not influence the concentration and yield of milk fat, milk protein, lactose and total solids. With 19% dried brewers' grains substituted for soybean meal, Seymour and Polan (1986) also showed an insignificant difference in milk yield, and percentage of milk fat and milk protein. 3.4. The effect on efficiency of lactation The effects of dietary treatment on the efficiency of DM, energy and protein utilization were significantly different (P<0.05). The amount of feed DM required to produce a unit of milk was significantly less in the BCP diet compared to the other diets (P<0.05). Cows on the MBP diet also required significantly less feed DM to produce a unit of milk as compared to the control and the WBG diet (P<0.05). Cows in the BCP group used DM, NEL, CP significantly more efficient in producing 4% FCM than those in the other treatment groups (P<0.05). The BCP group also obtained higher protein efficiency in the production of milk protein than the other treatment groups (P<0.05). During the experimental period, cows on the BCP diet compared to the other treatment groups did not significantly change their live-weight. This implied that the better performance of cows on the BCP diet is because of the better use of protein and energy, and not because of a transfer from the body reserve. Regarding the utilization of the wet brewers' grain, cows used DM, energy and protein with similar efficiency on the WBG diet as well as on the control diet. Using 15% or 30% of the WBG substitute for soybean meal in the lactating diets during the summer months, West et al. (1994) derived similar results of the dry matter efficiency in milk production. 3.5. The effects on the rumen fermentation Table 3 presented the effects of different by-products supplement on ruminal characteristics. Fig. 1 showed the effects on the post-feeding ruminal pH. From the figure, it is seen that the ruminal pH values in all treatment groups were above 6.6 before feeding and dropped to around 6.2 shortly after the meal, and returned to the normal range 8 h postprandial. It also shows a slightly high ruminal pH value in the WBG and the MBP from 3 to 8 h postprandially. The averaged daily ruminal pH of the cows that were fed MBP was significantly higher than that of cows that were fed the control diet (P<0.05), where it showed a trend of higher ruminal pH values in the cows that were fed either the BCP or the WBG diet compared to the control diet (P>0.05)(Table 3). Davis et al. (1983) also showed similar results in cows that were fed the pressed brewers' grains diet (either 20%, 30% or 40%) the ruminal pH value increased as compared to the control group. The ruminal pH dropped steeper and reached 6.02 after 6 h of feeding, and then remained low even after 8 h of feeding in the cows that were on the control diet as
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Table 3 Effects of different by-products supplementation on the ruminal pH, ammonia nitrogen and volatile fatty acids Items
Control
pH value NH3-N, mg/dl Total VFA, mM Acetate, mol % Propionate, mol % Acetate/propionate Isobutyrate, mol % Butyrate, mol % Isovalerate, mol % Valerate, mol % a,b,c,d
b
6.18 22.57b 89.04a 66.05a 16.89d 3.95a 1.16c 12.58a 1.92b 1.40bc
WBG ab
6.26 21.58b 78.49b 65.77a 17.61c 3.79b 1.25b 12.10bc 1.88b 1.39c
BCP
MBP ab
6.25 25.43a 79.76b 63.41c 19.67a 3.31d 1.35a 11.91c 2.14a 1.53a
SEM a
6.29 22.85ab 78.55b 64.21b 18.70b 3.47c 1.32a 12.23b 2.06a 1.48ab
0.05 1.40 1.79 0.33 0.28 0.07 0.03 0.16 0.05 0.04
Means in the same row with different letters are significantly different (P<0.05).
Fig. 1. Effects of different by-products supplementation on the ruminal pH value.
compared to the treatment groups. This was probable due to the high available carbohydrate and adequate amount of RAP in the control diet, enhancing ruminal fermentation with an increase of VFA, hence a decreasing pH value. Conversely, cows that were fed the by-product diets have a high pH value in the rumen. This may be due to their content of high dietary fiber or their low content of dietary available carbohydrate.
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Fig. 2. Effects of different by-products supplementation on the ruminal ammonia nitrogen concentration. a,b,c represents means in the same postgrandial hours followed by different letters are significantly different (P<0.05).
Fig. 2 showed the effects of dietary treatment on the ruminal ammonia concentration. The concentration of the ruminal ammonia increased after feeding, and reached a plateau at 2 h postprandial, and then declined afterwards. The effect of dietary treatment on the ruminal ammonia concentration was significant about 2±3 h postprandial. The ruminal ammonia concentration of the cows that were fed the BCP diet was significantly higher than in all the other treatment groups (P<0.05) and remained on the plateau (Fig. 2). Therefore, the mean ruminal ammonia concentration was significantly higher in the BCP than the control and WBG group (P<0.05)(Table 3). This may be attributed to the high soluble protein in the BCP (24.9%)(Chiou et al., 1995) as compared to the SBM (20.4%) and the WBG (10.5%)(Polan et al., 1985). This implied that adding some soluble carbohydrate may further improve the ruminal fermentation in the BCP diet. Murdock et al. (1981) added 15 or 30% of the WBG to substitute SBM, and showed a lower concentration of ruminal ammonia in the WBG groups. Our data only showed the trend of a lower ruminal ammonia in the WBG than in the other groups (P>0.05); This may attribute to the lower inclusion rate of the WBG in this trial. Fig. 3 presents the effects of dietary treatment on the ruminal total VFA concentration. The concentration of the ruminal VFA increased after feeding, reached a plateau 1 h postprandial, and remained highly concentrated (90 mM) until 8 h postprandial. The effect of dietary treatment on the ruminal VFA concentration was significantly different (P<0.05). The ruminal total VFA concentration increased significantly faster (P<0.05)
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Fig. 3. Effects of different by-products supplementation on the ruminal total volatile fatty acids concentration. a,b,c represents means in the same postgrandial hours followed by different letters are significantly different(P<0.05).
and remained highly concentrated 8 h after feeding in the cows that were fed the control diet compared to those in the other dietary treatment groups. This high VFA concentration coincided with a low ruminal pH in the control group. The pH value was the lowest all the time and remained significantly lower than in the other treatment groups 7 and 8 h postprandial (P<0.05). The high concentration of the mean ruminal total VFA as shown in Table 3 suggested that the control diet provided more soluble carbohydrate for microbial fermentation in the rumen than the other treatment diets. Soybean meal contains higher soluble carbohydrate after oil is extracted from the soybean. Batajoo and Shaver (1994) showed a decrease of total VFA concentration with a decrease of dietary non-fiber carbohydrate. Davis et al. (1983) also derived a similar result that an inclusion of 20%, 30% or 40% of the pressed brewers' grains in the diet depressed the concentration of the ruminal total VFA. It appears that a partial substitute of soybean meal by the WBG or the BCP caused lower ruminal VFA production. Dietary treatment significantly influenced the concentration of individual VFA (P<0.05). The molar percent of acetate was significantly higher in the control and the WBG compared to the BCP and the MBP (P<0.05). This may be attributed to the
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significantly lower feed DM intake (P<0.05) and probably higher fat inclusion in both the BCP and the MBP diet. The partial substitution of WBG did not significantly influence the ruminal acetate concentration in this trial (P>0.05). Cozzi and Polan (1994) substituted SBM with 16% dried brewers' grains with equal amount of the ADF in the diet and obtained a similar concentration of ruminal acetate. The inclusion of different by-products significantly influenced the concentration (molar percent) of the ruminal propionate (P<0.05); The concentrations of the ruminal propionate from high to low was in the order of BCP, MBP, WBG and the control group. The high concentrations of propionate may attribute to the high RAP content in the BCP. This agreed with the result of Aldrich et al. (1993) that a high RAP increases the ruminal propionate due to an increase of microbial synthesis of protein in the rumen. The high ruminal propionate also correlated to the high milk lactose. This is also reflected in the BCP diet in this trial. Dietary treatment significantly influenced the ratio of acetate to propionate (P<0.05). The ratio was significantly higher in the control group than in all the other treatment groups (P<0.05), where the WBG was significantly higher than the BCP and the MBP (P<0.05). The ruminal C2/C3 ratio generally reflected the percentage of milk fat. This high ruminal C2/C3 ratio reflecting high milk fat percentage were also shown in this trial except in the BCP group. The result of a low C2/C3 ratio with high milk fat content in the BCP group may attribute to the high dietary fat inclusion in the BCP diet. It appears that a low level of wet brewers' grain inclusion to substitute for soybean meal in a lactating dairy diet will result in an equal or better lactating performance. Partially substitute soybean meal by bean curd pomance give a better lactation performance. The feed dry matter intake of a cow will not be limited by the low level of inclusion of brewers' grain in the lactating diet. However, it will be limited by the bean curd pomance inclusion due to its high moisture content. References Aldrich, J.M., Muller, L.D., Varga, G.A., Griel, L.G., Jr., 1993. Nonstructural carbohydrate and protein effects on rumen fermentation, nutrient flow, and performance of dary cows. J. Dairy Sci. 76, 1091±1105. AOAC. 1984. Official Methods of Analysis. 13th ed., Association of Official Analytical Chemists, Washington, DC. Batajoo, K.K., Shaver, R.D., 1994. Impact of nonfiber carbohydrate on intake, digestion, and milk production by dairy cows. J. Dairy Sci. 77, 1580±1588. Chaney, A.L., Marbach, E.P., 1962. Modified reagents for determination of urea and ammonia. Clin. Chem. 8, 130±132. Chiou, P.W.S., Chen, K.J., Kuo, K.S., Hsu, J.C., Yu, B., 1995. Studies on the protein degradabilities of feedstuffs in Taiwan. Anim. Feed Sci. Technol. 55, 215±226. Cozzi, G., Polan, C.E., 1994. Corn gluten meal or dried brewers grains as partial replacement for soybean meal in the diet of Holstein cows. J. Dairy Sci. 77, 825±834. Davis, C.L., Grenawalt, D.A., McCoy, G.C., 1983. Feeding value of pressed brewers' grains for lactating dairy cows. J. Dairy Sci. 66, 73±79. Hoffman, P.C., Armentano, L.E., 1988. Comparison of brewers wet and dried grains and soybean meal as supplements for dairy cattle. Nutr. Rep. Int. 38, 655±663. Johnson, C.O.L.E., Huber, J.T., King, K.J., 1987. Storage and utilization of brewers wet grains in diets for lactating dairy cows. J. Dairy Sci. 70, 98±107.
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Lahr, D.A., Otterby, D.E., Johnson, D.G., Linn, J.G., Lundquist, R.G., 1983. Effects of moisture content of complete diets on feed intake and milk production by cows. J. Dairy Sci. 66, 1891±1900. Murdock, F.R., Hodgson, A.S., Riley, R.E., Jr., 1981. Nutritive value of wet brewers grains for lactating dairy cows. J. Dairy Sci. 64, 1826±1832. National Research Council, 1989. Nutrient Requirements of Diary Cattle. 7th rev. ed., National Academy Press, Washington, DC. 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. Polan, C.E., Herrington, T.A., Wark, W.A., Armentano, L.E., 1985. Milk production response to diets supplemented with dried brewers grains, wet brewers grains, or soybean meal. J. Dairy Sci. 68, 2016±2026. Statistical Analysis System Institute Inc., 1985. SAS User's Guide, version 5, SAS Institute Inc., Cary, NC. Seymour, W.M., Polan, C.E., 1986. Dietary energy regulation during gestation on susequent lactational response to soybean meal or dried brewers grains. J. Dairy Sci. 69, 2837±2845. Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods of dietary fiber, neutral detergent fiber, and nonstarch poly-saccharides in relation to animal nutrition. J. Dairy Sci. 71, 3583±3597. West, J.W., Ely, L.O., Martin, S.A., 1994. Wet brewers grains for lactating dairy cows during hot, humid weather. J. Dairy Sci. 77, 196±204.
Wet brewers' grains or bean curd pomance as partial replacement of soybean meal for lactating cows Peter Wen-Shyg Chioua,*, Chao-Ren Chena, Kuen-Jaw Chenb, Bi Yua a
Department of Animal Science, National Chung-Hsing University, Taichung, Taiwan b Taiwan Livestock Research Institute, Hsin-Hua, Tainan, Taiwan Received 27 November 1997; accepted 2 April 1998
Abstract The purpose of this study was to evaluate the effects of supplementation of the by-product, brewers' grains and the bean curd pomance, on the performance of lactating cows and their ruminal characteristics. Through this, we wanted to increase resource utilization and to eliminate pollution from these by-products. Thirty-two Holstein lactating cows were allocated randomly into four dietary treatment groups. The experimental diets were formulated to be isoenergetic and isonitrogenous according to National Research Council (1989), and containing 35% corn silage, 20% alfalfa hay and 45% concentrates on DM basis. The dietary treatments consisted of the inclusion of different by-products sources. These included soybean bean (as the control), brewers' grains, bean curd pomance, and the mixed by-products (containing the same amount of brewers' grains and bean curd pomance). The experimental feeding lasted for eight weeks after one week of adaptation. In addition, four rumen cannulated Holstein cows were used in a 44 Latin square with 10-day period for collecting rumen samples. Results showed that cows that were fed the bean curd pomance diet produced significantly more milk than those that were fed the brewers' grains diet or the mixed by-product diet. The cows on the control diet produced significantly less milk than the other treatment groups (P<0.05). Both the control and brewers' grains groups consumed more feed than those in the bean curd pomance and mixed by-products diet groups (P<0.05). The cows that were fed the mixed by-products diet produced a significantly lower percentage of milk fat, total solids, milk protein and milk lactose than the others (P<0.05). The milk lactose percentage was significantly higher for cows that were fed the bean curd pomance than those fed the brewers' grains diet (P<0.05). Cows that were fed the bean curd pomance produced significantly more milk fat, total solids, milk protein and milk lactose than the others (P<0.05). Cows that were fed the mixed by-products diet produced significantly lower amount of milk fat, total solids and milk protein than the control and brewers' grains group (P<0.05). These diets did not significantly * Corresponding author. Tel.: +886 4 287 0613; fax : +886 4 286 0265 0377-8401/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved PII S 0 3 7 7 - 8 4 0 1 ( 9 8 ) 0 0 1 7 0 - 9
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influence the body weight of the cows. It, however, significantly influenced the ruminal characteristics (P<0.05). # 1998 Elsevier Science B.V. Keywords: Wet brewers' grains; Bean curd pomance; By-products; Lactating dairy cows
1. Introduction Brewers' grains are the by-products from brewer industry. It is an extracted residue of barley malt, alone or in mixture with other cereal grains or grain products resulting from production of wort or beer. These products are rich in crude protein (CP), crude fiber (CF), ether extract (EE), vitamins and minerals. The nutrient contents of these products except for starch are proportionally richer than most of the barleys. It contains high protein and crude fiber. Therefore, it is mostly used as a protein supplement for cattle. Bean curd pomance, on the other hand, is a by-product of the manufacturing process of bean curd. Bean curd, also known as soybean cake or Chinese cheese, and is one of the major protein sources in Asia. It contains high CP, EE and CF with minimum vitamins. Fresh bean curd pomance contains only 9±12% dry matter. The average CP, EE, CF, ash and NFE content of bean curd pomance is 20.3%, 6.0%, 15.8%, 2.6% and 50.9% of DM, respectively. It contains high undegradable protein CP of 61.75 (Chiou et al., 1995). Therefore, the bean curd pomance is also a good source of protein for dairy cattle. Since both wet brewer grains and bean curd pomance contain high undegradable protein, these will be a good supplement source of ruminal by-pass protein for lactating cows. This study, therefore, aims to evaluate the feeding value of wet brewer grains and bean curd pomance as undegradable protein supplement for lactating cows. 2. Materials and methods 2.1. Experimental diets Experimental diets were formulated according to the nutrient requirement of National Research Council (1989), and based on the assumption of lactating cows with 550 kg body weight, and producing 25 kg of 3.5% FCM daily. The dietary treatments were the control diet, wet brewers' grains diet (WBG), fresh bean curd pomance diet (BCP), and a mixed by-products diet (MBP), respectively. The control diet used soybean meal (SBM) as the protein supplement. The WBG diet and BCP diet supplemented 10% (DM basis) of WBG or BCP as the protein supplement, respectively. The MBP diet contains 5% (DM basis) of WBG and BCP. Table 1 presented the experimental diets that were formulated as isoenergetic, isonitrogenous, and isoundegradable nitrogen. They contain 35% corn silage, 20% alfalfa hay and 45% concentrate on DM basis. Experimental diets were fed as total mixed rations (TMR). The concentrates were premixed and were pelleted through a 3-mm die at 708C once every week, and daily
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Table 1 Ingredients and nutrient composition of the experimental total mixed rations on dry matter basis Experimental rations Ingredients, g/kg Alfalfa hay Corn silage Full fat soybean Soybean meal, 44% Corn Wet brewers' grain Bean curd pomance Lard Dicalcium phosphate Limestone Salt Premixa Total Calculated nutrient value Crude protein, CP NEL, MJ/kg Undegradable protein, %CP Analysed nutrient value Dry matter Crude protein ADF NDF
Control
WBG
BCP
MBP
200.0 350.0 19.8 90.5 313.5 Ð Ð 14.7 5.6 1.8 3.0 1.0 1000.0
200.0 350.0 10.0 81.5 242.1 100.0 Ð 5.0 6.9 0.5 3.0 1.0 1000.0
200.0 350.0 23.9 62.5 227.2 Ð 100.0 24.6 7.9 0.2 3.0 1.0 1000.0
200.0 350.0 15.7 63.3 232.6 50.0 50.0 26.8 7.6 0.1 3.0 1.0 1000.0
160.0 7.027 38.0
160.0 7.027 38.0
160.0 7.027 38.0
160.0 7.027 38.0
505.0 157.1 229.7 397.3
436.4 166.4 225.6 432.9
388.2 158.0 240.3 395.4
396.2 158.9 231.6 404.3
a
Each kilogram of premix contains: Vit. A, 10 000 000 IU; Vit. E, 70 000 IU; Vit D3, 1 600 000 IU;Fe, 50 g; Zn, 40 g; Mn, 40 g; Co, 0.1 g; Cu, 10 g; Se, 0.1 g.
mixed with corn silage, alfalfa hay and by-products. The moisture content of the roughage was measured weekly for the adjustment of the as-fed ration composition. 2.2. Animal and management in feeding trial Thirty-two early lactating cows that produced more than 20 kg milk daily were selected and were allocated to the four treatment groups according to their milk yield and number of lactation. Cows were confined in individual pens most of the time during the experimental period. They were released for exercise twice daily from 0400 to 1000 hours and 1300 to 1700 hours. The experimental cattle were dewormed once every two weeks during the experimental period. After one week of adaptation, the cows started the eight weeks feeding trial. These cows were individually fed ad libitum with 2±3 kg orts in two meals per day (0630 and 1700 hours). Water was provided individually with an automatic bowl type drinker. The animals were milked twice a day at 0430 and 1600 hours. During the feeding period, the dry matter intake and the milk yield were daily recorded. Milk samples were taken once every other week. The live-weights of the cows were calculated by two consecutive days' measurements every four weeks from the start of the trial. Feed samples were taken weekly and dried in a 608C ventilated oven for 48 h.
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2.3. Ruminal studies Four ruminal fistulated dry cows were randomly assigned to the four dietary treatments in a Latin square design with four observations per treatment. Each of four periods used the four cows and consisted of 17 days with a 7-day adaptation and a 10-day experimental diet feeding. On the last two days of the feeding period, rumen samples of 200 ml were collected from the ruminal fistula before and 1, 2, 3, 4, 6 and 8 h after the meal, and the pH of the ruminal samples were measured immediately after withdrawal. After filtering through four layers of cheese cotton, the ruminal samples were then diluted (5:1) with 25% metaphosphoric acid. Samples were sealed and preserved at ÿ188C for analysis of ammonia nitrogen and volatile fatty acid concentration. 2.4. Chemical analysis Analysis of the feed samples was done according to the methods of the Association of Official Analytical Chemists (AOAC, 1984). The neutral detergent fibre (NDF) and acid detergent fibre (ADF) were analyzed according to the methods of Van Soest et al. (1991) using an automatic fibre analyzer (Fibertec System M, Tecator AB). The milk composition of fat, protein, lactose and total solids was analyzed by a milk scanner (Foss Electric Co., Milko Scan 255 A/B types) using the infra-red method of AOAC (1984). The pH value of rumen fluid was measured by a pH meter (Suntex TS-1). Concentration of ruminal ammonia nitrogen was analyzed by an automatic Kjeldahl analyzer according to Chaney and Marbach (1962). Ruminal concentrations of volatile fatty acids were determined by gas chromatography (Hitachi G-3000) according to Parker and McMillan (1976). 2.5. Statistical analysis A completely randomized design for the feeding trial and a Latin square design for the ruminal studies was applied to find dietary effects. Analysis of the variance was calculated with the general linear model procedure (GLM) of the Statistical Analysis System Institute Inc. (1985). Least square means were used to compare the difference of the treatment means. 3. Results and discussion 3.1. The effect on dry matter Table 2 presented the dietary effect on the performance and efficiency of nutrient utilization in lactating cows. The effect of dietary treatment on the DM intake of lactating cows was significant (P<0.05). The cows in the control and the WBG groups consumed significantly more feed DM than cows in the BCP or MBP groups (P<0.05). This implied that on inclusion 10% of bulky and high water content WBG in the lactating diet did not
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Table 2 Effects of dietary treatment on the performance of lactating cows Ingredients Performance, kg/day Dry matter intake Milk yield 4% FCM Milk composition, g/kg Total solids Milk fat Milk protein Milk lactose Yield of milk composition, kg/day Total solids Milk fat Milk protein Milk lactose Efficiency, kg/kg DM intake/milk yield DM intake/FCM yield NEL intake/FCM yield, Mj/kg CP intake/FCM yield CP intake/milk protein yield Live-weight Initial weight, kg Changes, % 1st 4-week 2nd 4-week All period a,b,c,d
Control 19.05a 25.99c 24.91c
WBG 18.84a 26.67b 25.60b
BCP 18.27b 27.99a 27.00a
MBP 18.10b 26.62b 24.20d
SEM 0.33 0.41 0.32
117.1a 37.1a 27.7a 45.5ab
117.2a 37.3a 27.5a 44.7b
118.2a 37.6a 27.7a 46.0a
100.9b 33.9b 26.2b 43.6c
2.1 1.4 0.6 1.1
30.5b 9.7b 7.2b 11.8b
31.2b 9.9b 7.3b 11.9b
33.1a 10.5a 7.7a 12.9a
29.5c 9.0c 7.0c 11.7b
0.7 0.4 0.2 0.3
0.74a 0.78a 5.35a 0.12a 4.28a
0.74a 0.77a 5.31a 0.12a 4.29a
0.67c 0.71b 4.85b 0.11b 3.88b
0.69b 0.76a 5.23a 0.12a 4.24a
541
542
568
536
102 101 103
103 101 104
101 102 102
102 101 103
0.015 0.025 0.176 0.004 0.145
1.4 1.2 1.6
Means in the same row with different letters are significantly different (P<0.05).
depress the feed DM intake. An inclusion of 10% WBG was still far below the 30% WBG maximum suggested by Murdock et al. (1981). A similar result was also obtained by West et al. (1994) that an inclusion of 15% or 30% WBG (35.5% DM) into the lactating diet did not significantly influence the dry matter intake. Although cows in both the BCP and the MBP group consumed more feed than the control group on the as-fed basis, the dry matter intakes were still significantly less than in the control group (P<0.05). This was attributed to the high water content of the BCP diet (61%) and the MBP diet (60%) as compared to the control diet (49%). Lahr et al. (1983) also derived the same results that dry matter intake decreases with the increase of dietary water content. 3.2. The effect on the milk yield Dietary treatment significantly influenced the milk yield of the lactating cows (P<0.05), cows in the control diet yielded significantly less milk than those in the other three treatment groups (P<0.05). Conversely, cows in the BCP group produced significantly more milk than those in the WBG or the MBP group (P<0.05). Cows in
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the BCP diet also yielded a significantly more 4% FCM than those in the other groups, where cows in the WBG produced significantly more FCM than the control or the MBP diet (P<0.05). However, cows in the MBP diet produced significantly less of 4% FCM than that in the control group (P<0.05). The live-weight changes of the cows in the WBG did not significantly differ from those in the control group during the experimental feeding period. They, in fact, gained weight during this period. This implied a high feed efficiency of cows that were fed the WBG diet or an underestimation of the NRC NEL value. Murdock et al. (1981) re-evaluated the nutritive value of WBG for lactating dairy cows and found the NEL value of 7.36 MJ/kg instead of 6.27 MJ/kg of National Research Council (1989). Hoffman and Armentano (1988) substituted 23.1% WBG for SBM in early lactating dairy diet. They found that cows in both groups consumed a similar amount of feed dry matter. They also obtained a trend of higher milk yields in the WBG group as compared to the SBM groups (P>0.05). Polan et al. (1985) compared different levels of the WBG inclusion (13.0%, 20.6% and 29.0% of DM) with different levels of protein (14.5%, 16.0% and 17.5% of DM) in the diet for the mid-lactating cows. They showed a significant improvement of the milk yield (P<0.05) by the WBG inclusion. From the result of better milk yield and protein utilization efficiency of the WBG as compared to the equal amount of the soybean meal intake, they concluded that the protein quality of WBG is superior to the SBM. 3.3. The effect on milk composition Dietary treatment significantly influenced the composition of milk (P<0.05). The concentrations of total solids, milk fat, milk protein and lactose were significantly lower in milk of cows that were in the MBP group than those in the other treatment groups (P<0.05). The lactose percentage was significantly higher in the milk that produced from the BCP group than that from the WBG or the MBP group (P<0.05). Cows that were fed the BCP diet produced significantly more total solids, milk fat, milk protein and lactose daily than those in the other three dietary groups (P<0.05), where those in the control and in the WBG group yielded significantly more of the total solids, milk fat and milk protein than those in the MBP group (P<0.05). The composition of milk produced from the WBG group was not significantly different from that of the control group. Concentration of milk protein was not significantly different in milk that was produced from the control, the WBG or the BCP group. Since the dietary protein and energy intake are highly correlated to the concentration of milk protein it produced, and since diets were formulated on iso-nitrogenous and equal energy basis, the milk protein content from the BCP group cows should be lower than that from the other groups because of the low DM intake. The BCP diets, however, contained highly soluble protein that provided more ruminal available protein (RAP)(Chiou et al., 1995). A high RAP may contribute to the high propionate concentration in the rumen. The increase in ruminal propionate concentration will eventually provide more glucose to the mammary gland. This will increase insulin secretion and amino acids absorption, and will eventually enhance milk protein production by the mammary gland (Aldrich et al., 1993). Although our data showed a slightly higher propionic acid concentration in the BCP group in this trial, both the BCP and the control group produced milk with a similar protein concentration. These
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may contribute to the same amount of ruminal available protein in both treatment groups. Cows on the BCP diet yielded more milk than those in the control or the WBG group. Therefore, cows of the BCP group produced significantly more lactose daily than those of the other groups (P<0.05). The concentration and the daily yield of the total solids and milk fat also showed a trend similar to the milk protein. This result agreed with Johnson et al. (1987) that a substitute of 25.6% of WBG for 14.3% SBM did not influence the concentration and yield of milk fat, milk protein, lactose and total solids. With 19% dried brewers' grains substituted for soybean meal, Seymour and Polan (1986) also showed an insignificant difference in milk yield, and percentage of milk fat and milk protein. 3.4. The effect on efficiency of lactation The effects of dietary treatment on the efficiency of DM, energy and protein utilization were significantly different (P<0.05). The amount of feed DM required to produce a unit of milk was significantly less in the BCP diet compared to the other diets (P<0.05). Cows on the MBP diet also required significantly less feed DM to produce a unit of milk as compared to the control and the WBG diet (P<0.05). Cows in the BCP group used DM, NEL, CP significantly more efficient in producing 4% FCM than those in the other treatment groups (P<0.05). The BCP group also obtained higher protein efficiency in the production of milk protein than the other treatment groups (P<0.05). During the experimental period, cows on the BCP diet compared to the other treatment groups did not significantly change their live-weight. This implied that the better performance of cows on the BCP diet is because of the better use of protein and energy, and not because of a transfer from the body reserve. Regarding the utilization of the wet brewers' grain, cows used DM, energy and protein with similar efficiency on the WBG diet as well as on the control diet. Using 15% or 30% of the WBG substitute for soybean meal in the lactating diets during the summer months, West et al. (1994) derived similar results of the dry matter efficiency in milk production. 3.5. The effects on the rumen fermentation Table 3 presented the effects of different by-products supplement on ruminal characteristics. Fig. 1 showed the effects on the post-feeding ruminal pH. From the figure, it is seen that the ruminal pH values in all treatment groups were above 6.6 before feeding and dropped to around 6.2 shortly after the meal, and returned to the normal range 8 h postprandial. It also shows a slightly high ruminal pH value in the WBG and the MBP from 3 to 8 h postprandially. The averaged daily ruminal pH of the cows that were fed MBP was significantly higher than that of cows that were fed the control diet (P<0.05), where it showed a trend of higher ruminal pH values in the cows that were fed either the BCP or the WBG diet compared to the control diet (P>0.05)(Table 3). Davis et al. (1983) also showed similar results in cows that were fed the pressed brewers' grains diet (either 20%, 30% or 40%) the ruminal pH value increased as compared to the control group. The ruminal pH dropped steeper and reached 6.02 after 6 h of feeding, and then remained low even after 8 h of feeding in the cows that were on the control diet as
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Table 3 Effects of different by-products supplementation on the ruminal pH, ammonia nitrogen and volatile fatty acids Items
Control
pH value NH3-N, mg/dl Total VFA, mM Acetate, mol % Propionate, mol % Acetate/propionate Isobutyrate, mol % Butyrate, mol % Isovalerate, mol % Valerate, mol % a,b,c,d
b
6.18 22.57b 89.04a 66.05a 16.89d 3.95a 1.16c 12.58a 1.92b 1.40bc
WBG ab
6.26 21.58b 78.49b 65.77a 17.61c 3.79b 1.25b 12.10bc 1.88b 1.39c
BCP
MBP ab
6.25 25.43a 79.76b 63.41c 19.67a 3.31d 1.35a 11.91c 2.14a 1.53a
SEM a
6.29 22.85ab 78.55b 64.21b 18.70b 3.47c 1.32a 12.23b 2.06a 1.48ab
0.05 1.40 1.79 0.33 0.28 0.07 0.03 0.16 0.05 0.04
Means in the same row with different letters are significantly different (P<0.05).
Fig. 1. Effects of different by-products supplementation on the ruminal pH value.
compared to the treatment groups. This was probable due to the high available carbohydrate and adequate amount of RAP in the control diet, enhancing ruminal fermentation with an increase of VFA, hence a decreasing pH value. Conversely, cows that were fed the by-product diets have a high pH value in the rumen. This may be due to their content of high dietary fiber or their low content of dietary available carbohydrate.
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Fig. 2. Effects of different by-products supplementation on the ruminal ammonia nitrogen concentration. a,b,c represents means in the same postgrandial hours followed by different letters are significantly different (P<0.05).
Fig. 2 showed the effects of dietary treatment on the ruminal ammonia concentration. The concentration of the ruminal ammonia increased after feeding, and reached a plateau at 2 h postprandial, and then declined afterwards. The effect of dietary treatment on the ruminal ammonia concentration was significant about 2±3 h postprandial. The ruminal ammonia concentration of the cows that were fed the BCP diet was significantly higher than in all the other treatment groups (P<0.05) and remained on the plateau (Fig. 2). Therefore, the mean ruminal ammonia concentration was significantly higher in the BCP than the control and WBG group (P<0.05)(Table 3). This may be attributed to the high soluble protein in the BCP (24.9%)(Chiou et al., 1995) as compared to the SBM (20.4%) and the WBG (10.5%)(Polan et al., 1985). This implied that adding some soluble carbohydrate may further improve the ruminal fermentation in the BCP diet. Murdock et al. (1981) added 15 or 30% of the WBG to substitute SBM, and showed a lower concentration of ruminal ammonia in the WBG groups. Our data only showed the trend of a lower ruminal ammonia in the WBG than in the other groups (P>0.05); This may attribute to the lower inclusion rate of the WBG in this trial. Fig. 3 presents the effects of dietary treatment on the ruminal total VFA concentration. The concentration of the ruminal VFA increased after feeding, reached a plateau 1 h postprandial, and remained highly concentrated (90 mM) until 8 h postprandial. The effect of dietary treatment on the ruminal VFA concentration was significantly different (P<0.05). The ruminal total VFA concentration increased significantly faster (P<0.05)
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Fig. 3. Effects of different by-products supplementation on the ruminal total volatile fatty acids concentration. a,b,c represents means in the same postgrandial hours followed by different letters are significantly different(P<0.05).
and remained highly concentrated 8 h after feeding in the cows that were fed the control diet compared to those in the other dietary treatment groups. This high VFA concentration coincided with a low ruminal pH in the control group. The pH value was the lowest all the time and remained significantly lower than in the other treatment groups 7 and 8 h postprandial (P<0.05). The high concentration of the mean ruminal total VFA as shown in Table 3 suggested that the control diet provided more soluble carbohydrate for microbial fermentation in the rumen than the other treatment diets. Soybean meal contains higher soluble carbohydrate after oil is extracted from the soybean. Batajoo and Shaver (1994) showed a decrease of total VFA concentration with a decrease of dietary non-fiber carbohydrate. Davis et al. (1983) also derived a similar result that an inclusion of 20%, 30% or 40% of the pressed brewers' grains in the diet depressed the concentration of the ruminal total VFA. It appears that a partial substitute of soybean meal by the WBG or the BCP caused lower ruminal VFA production. Dietary treatment significantly influenced the concentration of individual VFA (P<0.05). The molar percent of acetate was significantly higher in the control and the WBG compared to the BCP and the MBP (P<0.05). This may be attributed to the
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significantly lower feed DM intake (P<0.05) and probably higher fat inclusion in both the BCP and the MBP diet. The partial substitution of WBG did not significantly influence the ruminal acetate concentration in this trial (P>0.05). Cozzi and Polan (1994) substituted SBM with 16% dried brewers' grains with equal amount of the ADF in the diet and obtained a similar concentration of ruminal acetate. The inclusion of different by-products significantly influenced the concentration (molar percent) of the ruminal propionate (P<0.05); The concentrations of the ruminal propionate from high to low was in the order of BCP, MBP, WBG and the control group. The high concentrations of propionate may attribute to the high RAP content in the BCP. This agreed with the result of Aldrich et al. (1993) that a high RAP increases the ruminal propionate due to an increase of microbial synthesis of protein in the rumen. The high ruminal propionate also correlated to the high milk lactose. This is also reflected in the BCP diet in this trial. Dietary treatment significantly influenced the ratio of acetate to propionate (P<0.05). The ratio was significantly higher in the control group than in all the other treatment groups (P<0.05), where the WBG was significantly higher than the BCP and the MBP (P<0.05). The ruminal C2/C3 ratio generally reflected the percentage of milk fat. This high ruminal C2/C3 ratio reflecting high milk fat percentage were also shown in this trial except in the BCP group. The result of a low C2/C3 ratio with high milk fat content in the BCP group may attribute to the high dietary fat inclusion in the BCP diet. It appears that a low level of wet brewers' grain inclusion to substitute for soybean meal in a lactating dairy diet will result in an equal or better lactating performance. Partially substitute soybean meal by bean curd pomance give a better lactation performance. The feed dry matter intake of a cow will not be limited by the low level of inclusion of brewers' grain in the lactating diet. However, it will be limited by the bean curd pomance inclusion due to its high moisture content. References Aldrich, J.M., Muller, L.D., Varga, G.A., Griel, L.G., Jr., 1993. Nonstructural carbohydrate and protein effects on rumen fermentation, nutrient flow, and performance of dary cows. J. Dairy Sci. 76, 1091±1105. AOAC. 1984. Official Methods of Analysis. 13th ed., Association of Official Analytical Chemists, Washington, DC. Batajoo, K.K., Shaver, R.D., 1994. Impact of nonfiber carbohydrate on intake, digestion, and milk production by dairy cows. J. Dairy Sci. 77, 1580±1588. Chaney, A.L., Marbach, E.P., 1962. Modified reagents for determination of urea and ammonia. Clin. Chem. 8, 130±132. Chiou, P.W.S., Chen, K.J., Kuo, K.S., Hsu, J.C., Yu, B., 1995. Studies on the protein degradabilities of feedstuffs in Taiwan. Anim. Feed Sci. Technol. 55, 215±226. Cozzi, G., Polan, C.E., 1994. Corn gluten meal or dried brewers grains as partial replacement for soybean meal in the diet of Holstein cows. J. Dairy Sci. 77, 825±834. Davis, C.L., Grenawalt, D.A., McCoy, G.C., 1983. Feeding value of pressed brewers' grains for lactating dairy cows. J. Dairy Sci. 66, 73±79. Hoffman, P.C., Armentano, L.E., 1988. Comparison of brewers wet and dried grains and soybean meal as supplements for dairy cattle. Nutr. Rep. Int. 38, 655±663. Johnson, C.O.L.E., Huber, J.T., King, K.J., 1987. Storage and utilization of brewers wet grains in diets for lactating dairy cows. J. Dairy Sci. 70, 98±107.
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