Protein supply from undegraded dietary protein

Fecal consistency as related to dietary composition in lactating Holstein cows

A trial was designed to study the relationships of dietary fiber and protein percentage and source to fecal consistency in lactating cattle. Thirty Holstein cows were assigned randomly to one of six TMR through four 21-d periods. The TMR were formulated to contain 17 or 25% ADF and CP of 15 or 22% with soybean meal supplementation or 22% with a combination of corn gluten and soybean meals. Two forage combinations were corn silage with or without alfalfa. Fecal consistency was evaluated using a four-point visual observation scale. Lower dietary fiber reduced fecal pH, score, NDF, and ADF but increased fecal DM and starch. A higher percentage of soybean meal lowered fecal DM and fecal score. Forage source affected fecal DM, NDF, ADF, and starch, but not pH or score. Prediction of fecal score from dietary components and cow parameters resulted in dietary DM percentage and 4% FCM as the most related variables. Accurate prediction of fecal consistency score from dietary and cow parameters was not possible.

In vivo degradation of protein in diets formulated for two degradabilities

In vivo protein degradability of two basal diets and bacterial protein synthesis were determined in four lactating dairy cows equipped with ruminal and duodenal cannulas. The diets contained corn silage, high moisture corn, and either soybean meal or a 60:40 mixture of soybean meal and corn gluten meal. Diets had calculated ruminal protein degradabilities of 69.3 and 62.3%, respectively. Both diets contained approximately 14% CP and 21% ADF. Duodenal flows of total N, total protein N, microbial N, and duodenal recovery of ingested N tended to be higher for the soybean meal and corn gluten meal diet; ruminally degraded CP was significantly lower than for the soybean meal diet. Ruminal ammonia and plasma urea concentrations tended to be higher for the soybean meal diet, as were molar percentages of butyrate and valerate. Ruminal and total tract apparent digestibilities of CP and OM were not significantly different between diets. Ruminal degradation of protein in the two diets differed by the amount predicted by the NRC system for lactating cows, although absolute values were lower than most previous estimates for similar diets.

Microbial protein synthesis and flows of nitrogen fractions to the duodenum of dairy cows

Attempts have been made to increase nutrient availability for milk production by increasing feed intake, optimizing ruminal fermentation, and supplementing nutrients to the diet that will escape ruminal degradation. Energy and N are the nutritional factors that most often limit microbial growth and milk production. Ruminal fermentation and flow of microbial and dietary protein to the small intestine are affected by feed intake and by the amount and source of energy and protein in the diet. Feeding protein and carbohydrate that are not degraded in the rumen increases the quantity of dietary protein that passes to the small intestine but may decrease the quantity of microbial protein that is synthesized in the rumen. This often results in only small differences in the total NAN that passes to the small intestine. Because microbial protein supplies a large quantity of total AA that passes to the small intestine, differences in passage of individual AA often are only slight. Additional research with cows consuming large amounts of feed are needed to identify combinations of feed ingredients that synchronize availabilities of energy and N for optimizing ruminal digestion, microbial protein synthesis, nutrient flow to the small intestine, and milk production and composition.

Determining optimal heat treatment of soybeans by measuring available lysine chemically and biologically with rats to maximize protein utilization by ruminants

Soybeans were heated in a forced air oven at 120 and 130 degrees C for 60 and 180 min, and at 140, 150 and 160 degrees C for 10, 30, 60, 90 and 120 min. Two types of measurements were used to determine optimal heat treatment of soybeans to maximize protein utilization by ruminants. One was to estimate the rate and extent of protein degradation in the rumen using an in vitro ruminal system. The second was to determine the nutritional availability of lysine. Methods used to determine available lysine were an indirect fluorodinitro-benzene chemical method and a rat growth assay. The product of undegraded intake protein and available lysine content was used to estimate the amount of lysine that would escape ruminal degradation and be available for intestinal absorption. As heat input increased, ruminal undegraded intake protein increased, and protein degradation rates and total and available lysine decreased. As temperature increased, the time required to maximize post-ruminal available lysine decreased. The optimal heat treatment for soybeans heated in a forced air oven was: 140 degrees C for 120 min or greater, 150 degrees C for 60 min or 160 degrees C for 30 min. A loss of 15-22% of chemically determined available lysine was necessary to achieve the heat treatment that resulted in maximal post-ruminal available lysine.

Feeding supplemental fat and undegraded intake protein to early lactation dairy cows

Forty-eight Holstein cows (16 primiparous) were fed alfalfa silage-based TMR containing 18% CP with 33 or 36% of the CP as undegraded intake protein and with 0 or 2.8% supplemental fat (DM basis). Expeller soybean meal replaced solvent soybean meal to vary undegraded intake protein, and sodium alginate-treated tallow was used as the fat source. A standard diet containing solvent soybean meal without fat was fed during the first 21 d postpartum for covariate adjustment of milk production. A continuous lactation design with 2 x 2 factorial arrangement of treatments was used with supplemental fat and undegraded intake protein as main effects. Feeding supplemental fat increased actual milk (32.9 vs. 31.7 kg/d) but decreased milk protein concentration. Cows fed supplemental fat also had higher BW, and weight gain was significant with time. Increasing undegraded intake protein did not affect milk yield, composition, or component yield. There were no significant interactions between supplemental fat and undegraded intake protein on milk yield or composition. Milk fatty acid composition was not altered by addition of undegraded intake protein, but C6 to C14 fatty acids were reduced by adding supplemental fat. Results do not support the strategy of increasing levels of undegraded intake protein when supplemental fat is fed. Variation in undegraded intake protein content of feed-stuffs appears to be of more importance in ration formulation than interactions between supplemental fat and protein.

Lactational performance of high producing dairy cows fed diets containing salmon meal and urea

Thirty Holstein cows were used in a 12-wk trial to study the effects of salmon meal and urea on lactational performance. Two experimental diets, one containing 5.6% salmon meal and the other 5.2% salmon meal plus .42% urea, were compared with a soybean meal control diet. Salmon meal and urea replaced a portion of the soybean meal. Dietary undegraded intake protein levels (expressed as percentage of CP) were 28.8, 35.6, and 32.4% for soybean meal, salmon meal, and salmon meal plus urea. Total mixed diets (average 17.3% CP, 17.6% ADF) consisting of 60% concentrate mixture and 40% bromegrass silage (DM basis) were fed twice daily. Total DMI was lower with salmon meal compared with soybean meal (20.2 versus 22.2 kg/d); salmon meal plus urea (21.2 kg/d) was intermediate. Actual milk production was similar for all diets (average 41.1 kg/d). Percentage milk fat and 4% FCM yield were lower with salmon meal (2.56%, 31.6 kg/d) and salmon meal plus urea (2.50%, 31.4 kg/d) than with soybean meal (3.03%, 35.9 kg/d). Gross efficiency (weight FCM/weight DMI) was higher for soybean meal than for salmon meal and salmon meal plus urea. Acetate: propionate tended to be higher with the soybean meal diet. The use of a high oil fish meal to provide a source of rumen undegraded intake protein, alone or in combination with urea, resulted in a decrease in milk fat percentage and yield without any beneficial effects on milk production or lactational efficiency.

Lactation response and body composition of cows receiving somatotropin and three ratios of forage to concentrate

Ninety multiparous Holstein cows were used to determine the effect of ration energy density and bST on lactation performance and whole body chemical composition. Seventy-eight cows, averaging 43.6 d postpartum, were assigned for 168 d to TMR with forage: concentrate ratios of 40:60, 50:50, and 60:40 (DM basis). Half of the cows on each ration received subcutaneously either 0 or 640 mg bST/28 d. Whole body chemical composition was determined by comparative slaughter in 12 cows (means = 35.9 d postpartum) prior to initiation of treatment and in 35 cows after either 84 or 168 d of treatment. Net energy intake was greater for 40:60 and 50:50 than for 60:40. Milk fat percentage was reduced in cows fed 40:60. Ration did not affect milk, 3.5% FCM, and DMI. There were no differences among rations for total body fat, protein, water, and calories. The bST increased milk and 3.5% FCM but had no effect on DM and net energy intakes. Yield of 3.5% FCM by cows receiving bST and fed 40:60 was 1.9 kg/d more and for 50:50 it was 2.7 kg/d more than for those fed 60:40. Administration of bST reduced total body fat and calories but did not affect protein and water. Partitioning of calories to milk at the expense of fat deposition is the primary mechanism for the galactopoietic action of bST.

Responses of dairy cows to supplemental rumen-protected forms of methionine and lysine

Multiparous Holstein cows at six universities were utilized to examine effects of ruminally protected methionine and lysine on lactational performance. Three hundred and four cows began the study; 259 cows were included in the production analysis. Following a 21-d standardization period, cows received a basal diet of corn silage and ground corn supplemented with one of five dietary treatments, which were supplements of soybean meal or corn gluten meal, the latter with zero and three combinations of protected methionine and lysine (methionine; methionine and lysine; methionine and double (2x) lysine). Treatment effects were evaluated during early, mid, late, and total lactation (22 to 112, 113 to 224, 225 to 280, and 22 to 280 d postpartum, respectively). On a DM basis, ratios of forage to concentrate (50:50, 60:40, and 70:30) increased, and dietary CP (16.0, 14.5, and 13.0%) decreased during the three periods of lactation. Amount of amino acid supplementation also decreased (15, 12, and 9 g/d methionine; 20, 16, and 12 g/d lysine; and 40, 32, and 24 g/d 2x lysine) with period of lactation. Actual and least squares means for milk, FCM, and milk protein yields were greater for soybean than for corn gluten meal during early, mid, and total lactation. In addition, these variables responded linearly to lysine in early lactation. Response to lysine was quadratic during mid and total lactation for these variables. Differences in nutrient intake explained production responses to protein sources but not to lysine. Serum amino acid responses primarily reflected differences in dietary protein source and rumen-protected amino acid.

Effects of calcium salts of fatty acids and protein source on ruminal fermentation and nutrient flow to duodenum of cows

Four Holstein cows fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square to investigate the effects of calcium salts of long-chain fatty acids (fat) and source of protein (fish meal or soybean meal) on ruminal fermentation, flow of nutrients to the small intestine, and animal performance. Cows were fed for ad libitum intake a diet of 30% alfalfa haylage, 20% corn silage, and 50% concentrate on a DM basis. Treatments, arranged in a 2 x 2 (fat x protein) factorial, were 1) soybean meal, no fat; 2) soybean meal, fat; 3) fish meal, no fat; and 4) fish meal, fat. Intake of DM was not affected by fat or protein source, but feeding fat decreased the amount of OM truly digested in the rumen. Starch intake was decreased, but flow of starch to the duodenum was not altered by feeding fat. Nonammonia N and microbial N flows to the duodenum were not affected by treatment comparisons. However, efficiency of microbial growth was increased by feeding fat, but not by source of protein. Passage of amino acids to the duodenum was not affected by source of protein, probably because fish meal contributed only 17% of the total dietary CP, and microbial N constituted about 50% of the NAN passing to the duodenum; this had an equalizing effect on the pattern and quantity of amino acids that passed to the duodenum. Feeding fat or different sources of protein did not alter milk production. Milk fat percentage was increased, and protein percentage was decreased when fat was fed, but yields of milk fat and protein were not different.

Effects of source and amount of protein on ruminal fermentation and passage of nutrients to the small intestine of lactating cows

Four Holstein cows fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square to investigate the effects of source (corn gluten meal or soybean meal) and amount (14.5 or 11.0%) of CP on ruminal fermentation, passage of nutrients to the small intestine, and animal performance. Cows wee fed for ad libitum intake a diet of 60% corn silage and 40% concentrate on a DM basis. The treatments, arranged in a 2 x 2 (source x amount of CP) factorial, were 1) 14.5% CP, soybean meal; 2) 11.0% CP, soybean meal; 3) 14.5% CP, corn gluten meal; and 4) 11.0% CP, corn gluten meal. Digestion in the rumen of OM, starch, ADF, and NDF was not affected by source or amount of CP in the diet. Total VFA and NH3 concentrations in ruminal fluid were increased by feeding diets that contained 14.5% CP or soybean meal. FLows of non-NH3 N and amino acids to the duodenum were greater in cows fed the 14.5% CP diets because of a greater flow of non-NH3 nonmicrobial N to the duodenum. Larger amounts of lysine passed to the duodenum when cows were fed soybean meal compared with corn gluten meal. Microbial N flow to the duodenum and efficiency of microbial growth were not affected by treatments, suggesting that ruminal NH3 concentration was not limiting for maximal microbial protein synthesis. Feeding 14.5% CP diets increased the production of milk (29.5 vs. 26.8 kg/d) and milk protein compared with 11.0% CP diets, possibly because of greater passage of amino acids to the small intestine. Feeding soybean meal to cows increased production of milk protein compared with feeding corn gluten meal, possibly because more lysine passed to the small intestine.

Sites of digestion in beef steers fed bermudagrass hay and supplemented with high-nitrogen feeds alone or mixed with tallow

Five crossbred beef steers (329 kg) were used in a 5 x 5 Latin square experiment with 14-d periods to determine the effects of supplementation with high-nitrogen (N) feeds alone or mixed with tallow on sites of digestion with a basal diet of bermudagrass hay. Hay was 1.93% nitrogen, 75% neutral detergent fibre and fed at 1.83% of body weight (dry matter; DM). Supplements were basal (B; 105 g DM): 81.8% dried molasses product (DMP) and 18.2% calcium carbonate (CC); soybean meal (S; 942 g DM): 88.0% soybean meal, 9.8% DMP and 2.2% CC; S mixed with 9.8% tallow (SF; 1041 g DM); corn gluten and blood meals (CB; 662 g DM): 62.5% corn gluten meal, 20.8% blood meal, 13.6% DMP and 3.0% CC; CB mixed with 13.2% tallow (CBF; 757 g DM). Total N intake was 117, 185, 187, 174 and 172 g/d, and duodenal N flow was 121, 148, 143, 162 and 169 g/d for B, S, SF, CB and CBF, respectively, being lower for B than for other treatments and higher for supplements with the corn gluten and blood meal mix than for soybean meal (P less than 0.05). Duodenal microbial N flow was 39, 51, 49, 38 and 45 g/d for B, S, SF, CB and CBF, respectively, being greater (P less than 0.05) for supplements with soybean meal than with corn gluten and blood meals. Duodenal flow of feed N was greater (P less than 0.05) with than without high-N feeds and for supplemental corn gluten and blood meals than for soybean meal (78, 90, 86, 117 and 116 g/d for B, S, SF, CB and CBF, respectively). In conclusion, mixing of tallow and high-N feeds did not affect the extent of ruminal N disappearance, and soybean meal supplementation increased duodenal N flow less than did supplementation with corn gluten and blood meals. Increased duodenal N flow with soybean meal was associated with about equal elevations of ruminal outflow of microbial and feed N, whereas the corn gluten-blood meal mix affected the intestinal protein supply by increasing ruminal escape of feed protein.

Response of early lactation dairy cows fed diets varying in source of nonstructural carbohydrate and crude protein

Seventy-six high producing Holstein cows were randomly assigned in a 2 x 2 factorial to evaluate two sources of nonstructural carbohydrates (corn and barley), which supposedly differed in degradability of starch with two sources of CP degradability (soybean meal and urea) in the concentrate mix during wk 4 through 14 postpartum. Total mixed diets, formulated to be isonitrogenous at 16% CP, contained (DM) 40% corn silage, 10% alfalfa hay, and 50% of the respective concentrate mix. Nonstructural carbohydrate degradability was similar for concentrate mixes containing corn or barley. Production of milk (32.2 and 31.8 kg/d) was similar, but production of 4% FCM (29.1 and 27.4 kg/d) and SCM (29.1 and 27.5 kg/d) was decreased for cows fed barley due to lower percentages of fat (3.39 and 3.22) and SNF (8.65 and 8.59). Percentages of protein (3.09 and 3.08) were similar for cows fed corn and barley diets. Degradability of CP did not affect production of milk (31.9 and 32.0 kg/d), 4% FCM (28.5 and 28.0 kg/d), and SCM (28.4 and 28.2 kg/d) for cows fed soybean meal and urea. Dry matter intake was lower for cows fed barley (20.7 and 19.2 kg/d), but intakes (20.1 and 19.8 kg/d) were similar for cows fed soybean meal and urea. Providing an alternative nonstructural carbohydrate source (barley versus corn) did not increase utilization of a more readily degradable CP source (urea versus soybean meal).

Effects of dietary protein degradability and casein or amino acid infusions on production and plasma amino acids in dairy cows

Responses to daily abomasal infusions of 400 g sodium caseinate, 400 g hydrolyzed casein, or 11.3 g L-methionine plus 30.1 g L-lysine were compared in eight Holstein cows fed diets with estimated ruminal protein degradabilities of 70 and 60.%. Basal diets contained corn silage and corn with either soybean meal or 66.7:33.3 soybean meal:corn gluten meal added. Infusion with Methionine plus lysine increased milk protein content when cows fed either diet but increased milk fat content and yield only when the soybean meal diet was fed. Sodium caseinate increased milk and milk protein production and decreased milk fat percentage. Concentration of total essential amino acids, branched chain amino acids, and urea cycle amino acids were increased by the infusion of both casein sources. Methionine-lysine infusion increased plasma lysine and taurine, a metabolite of methionine, suggesting that absorbed methionine was extensively metabolized. Results demonstrate an impact of both ruminal degradability of dietary protein and form of infused protein on amino acid nutrition of lactating daily cows.

Prediction of duodenal nitrogen supply from degradation or organic and nitrogenous matter in situ

The contribution of different feedstuffs to nitrogen reaching the duodenum was evaluated in situ. Dacron bags containing barley grain, corn grain, wheat silage, corn silage, alfalfa hay, rye grass, whole cottonseeds, or soybean meal were suspended in the rumens of three dairy cows fed roughage and concentrate diets. The effective degradability of the nitrogenous and organic matter of feedstuffs was calculated from their residues after incubation in the rumen for 3, 6, 9, 12, 24, 36, or 48 h. The duodenal nitrogen content at ruminal outflows of 2, 5, or 8%/h was calculated as the sum of undegradable dietary nitrogen and potential microbial nitrogen (assuming 32 g N/kg ruminally degradable organic matter). Comparison of the in situ estimates with previously reported in vivo measurements of duodenal nitrogen in cattle fed diets with similar ingredients to the tested feedstuffs yielded a linear relationship (r2 = .887). The dacron bag technique appears to hold promise for the prediction of nitrogen flow to the duodenum.

Influence of varying protein and starch degradabilities on performance of lactating cows

A milk production and digestibility trial with 32 cows (2 X 2 factorial with 8 cows per treatment) was conducted to test animal response to varying rumen degradation of dietary starch and protein. Four rations (barley-cottonseed, barley-brewers dried grains, milo-cottonseed, and milobrewers dried grains) were compared in early lactation cows fed 65% concentrate and 35% forage for 60 d. Digestibilities of starch were higher for barley than milo diets; whereas, those for organic matter were higher for cottonseed meal than brewers dried grains. Milk production was highest on barley-cottonseed with mean adjusted values of (kg/d): 37.4, 34.9, 34.2, and 34.6 for respective treatments. Dry matter intakes were not different among rations. Milk fat was higher on milo than barley with respective diets averaging (%): 3.1, 2.9, 3.4, and 3.6, and resulting in lowest FCM for the barley-brewers dried grains diet. Milk protein was not altered by treatment. These data suggest that responses to varying protein degradability can be altered by rate of starch breakdown in the rumen.

In situ evaluation of the ruminal and intestinal digestibility of heat-treated whole cottonseeds

The effect of heating whole cottonseeds on the degradability of DM and CP in the rumen and the small intestine of lactating cows was determined in situ. Whole cottonseeds were heated for 1 or 2 h at 140, 160, or 180 degrees C prior to digestion. The degradation of DM and CP was determined in dacron bags suspended in the rumen for 3, 6, 9, 24, and 48 h. Bags incubated in the rumen for 24 h were introduced into the small intestine through a duodenal cannula and subsequently recovered in feces. The effective ruminal degradabilities of DM and of CP were evaluated, assuming a ruminal outflow rate of .08/h. Heating of whole cottonseeds decreased the degradability of DM and CP in the rumen with a corresponding increase in the amounts digested in the small intestine. The calculated temperature at which this effect was first observed was 130 degrees C. Following optimal heating amount of digestible CP reaching the small intestine more than doubled. The agreement between these findings and the results of previous in vivo experiments suggest that the dacron bag technique may reliably be used for determination of nutrient availability in the intestine.

Utilization of wheat in complete rations for lactating cows

Effects of different amounts of wheat, protected amino acids, and increased rumen escape protein in high wheat rations were evaluated in two trials with dairy cows. In trial 1, concentrate mixtures with 0, 40, or 60% hard red winter wheat were included in a complete ration with 45% sorghum silage (dry basis). Intake of DM and CP was not affected by treatment. Milk yield declined (28.8, 28.0, 27.3 kg/d) as amount of wheat in the ration increased. In a second trial, concentrate mixtures with 60% wheat were compared with a control corn-base mixture. One wheat mixture was supplemented with protected lysine and methionine and another had protected lysine and methionine plus estimated rumen escape protein equal to the control. Intake of DM and CP was not affected. Milk yield of cows fed rations containing wheat, with or without protected amino acids, was lower than that of cows fed the control ration or the wheat ration in which rumen escape protein was equal to the control (29.1 and 29.0 vs. 30.8 and 30.2 kg/d). Responses of cows fed concentrate mixtures containing wheat appeared to be related to utilization of protein.

Lactational response of dairy cows to diets varying in ruminal solubilities of carbohydrate and crude protein

Sixty high producing Holstein cows were randomly assigned in a 3 x 2 factorial to evaluate three sources of carbohydrates that differed in solubility and degradability (corn, barley, and dried whey) with two sources of CP solubility (soybean meal and urea) during wk 4 through 14 postpartum. Total mixed diets, formulated to be isonitrogenous at 16% CP, contained (DM basis) 40% corn silage, 10% chopped alfalfa hay, and 50% of the respective concentrate mix. Milk production (32.8, 31.5, and 31.3 kg/d) was highest for cows fed corn, whereas 4% FCM (30.0, 27.9, and 29.5 kg/d) was similar for cows fed corn and dried whey and lower for cows fed barley. Percentages of fat (3.37, 3.36, and 3.51) and protein (3.05, 3.00, and 2.98) were similar for cows fed all carbohydrate sources. Solubility of protein (soybean meal versus urea) did not affect production of milk (32.2 and 31.5 kg/d) and 4% FCM (29.4, and 28.9 kg/d). Intake of DM was lowest for cows fed barley (20.4, 18.8, and 20.5 kg/d), and intakes were similar (19.9 and 19.9 kg/d) for cows fed soybean meal and urea. Providing sources of carbohydrates in the diet that are more soluble and degradable (i.e., barley or dried whey) did not give the expected increase in utilization of a highly soluble CP source (urea) for milk production.

Supplementation of cows grazing tropical grass swards with concentrates varying in protein level and degradability

Twelve Holstein and Brown Swiss cows participated in a replicated and balanced 3 x 3 Latin square experiment with 4-wk periods to test three commercial concentrate feeds as supplements to grazing at 4 cows/ha on mixed grass herbage of 6.94% mean CP. Available herbage DM was estimated at 27.5, 21.7, and 15.1 kg/cow per d in successive periods. Excessive rainfall had adverse effects in periods 2 and 3. Treatments were concentrates with 18, 15, or 15% CP with Protek (protein treated by a propietary process) as fed. Mean overall results were daily concentrate intake, 7.44 +/- 1.37 kg; daily milk yield, 17.3 +/- 4.8 kg: percentages of milk fat, SNF, and protein, 3.18 +/- .80, 8.58 +/- .28, and 2.94 +/- .27; FCM per concentrate DM, 2.33 +/- .41; and daily BW loss, .28 +/- .53 kg. Differences among treatments were small and unimportant. Concentrate allowances were intended to satisfy NE1 needs, but the anticipated contribution from pasture was overestimated. Energy rather than protein was deemed first limiting to animal performance, and neither CP higher than 15% in the concentrate nor protein protection was useful under these conditions.

Relative value of solvent and expeller soybean meal for lactating dairy cows

Nitrogen solubility and enzymatic and rumen in vitro degradabilities indicated protein from expeller soybean meal was more resistant to ruminal degradation than that from solvent soybean meal. This was confirmed in Trial 1 by reduced rumen ammonia and branched-chain volatile fatty acids, and by 64% more supplemental protein escaping the rumen when cows were fed expeller soybean meal. In Trial 2, rations supplemented with either solvent or expeller soybean meal, averaging 16.4% protein, were fed to 12 cows in a crossover study. Production averaged 35.3 kg/d but was not influenced by diet. A small but significant improvement in milk to feed ratio occurred with expeller soybean meal. In Trial 3, four sources of protein were fed to 20 cows in a 4 X 4 Latin square: 6.3% solvent, 4.1% expeller (plus .3% urea), 10.0% solvent, or 6.6% expeller soybean meal. Production of milk and milk components was similar on the diets containing 6.3 and 6.6% soybean meal, intermediate on 10.0% solvent, and least on the expeller-urea diet. Milk to feed was equal and greatest on diets containing 6.6% expeller and 10.0% solvent soybean meal, indicating comparable utilization of the expeller diet containing only 60% as much supplemental protein.