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.     

Dehydrated Alfalfa in Dairy Cow Diets

The objective of Experiment 1 was to determine protein degradation in the rumen and amino acid supply to and absorption of amino acids from the intestine of lactating dairy cows receiving supplements of soybean meal or a combination of dehydrated alfalfa and corn gluten meal. Four lactating Holstein cows, fitted with ruminal, duodenal, and ileal cannulae, were used in a switchback experiment. Two diets consisting of 50% corn silage and 50% concentrate were fed. One diet contained soybean meal and the other contained a mixture of dehydrated alfalfa and corn gluten meal. It was estimated that 76% of the dietary protein was degraded in the rumen with the soybean meal diet compared with 62% with the dehydrated alfalfa:gluten meal diet. Flow of total amino acids to the duodenum was 13% higher for the dehydrated alfalfa:gluten meal than for the soybean meal diet.Experiment 2 consisted of two trials. The objective of Trial 1 was to measure rumen fermentation products in lactating dairy cows fed diets where dehydrated alfalfa, with or without urea, replaced 40% of the concentrate. The objective of Trial 2 was to measure milk production, milk composition, and plasma amino acids of dairy cows in early lactation fed the same diets as in Trial 1. Milk production was 34.7, 33.4, and 32.8 kg/d and milk fat was 3.48, 3.58, and 3.63% for the three diets, control, dehydrated alfalfa, and dehydrated alfalfa with urea.     

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 feeding diets composed of corn silage and a corn milling product with and without supplemental lysine and methionine to dairy cows

Formulating diets with high inclusion rates of a feed that provides necessary nutrients at lower-than-market prices for those nutrients should increase income over feed costs if the feed is not detrimental to yields of milk and milk components. The objective of this study was to determine whether cows fed a diet composed of approximately 53% corn silage, 44% corn milling product (68% dry matter, 21% crude protein, 37% neutral detergent fiber, and 9% starch) and 3% minerals (CMP) would have similar productivity as cows fed a control diet of predominantly corn silage, alfalfa silage, corn grain, and soybean meal. Based on the National Research Council (2001) dairy model, the CMP diet was inadequate in metabolizable methionine and extremely low in metabolizable lysine. A third treatment (CMP+AA) was the same as the CMP diet but was supplemented with rumen-protected lysine and methionine. Twenty-one Holstein cows were used in a replicated Latin square (28-d periods) design to evaluate production responses to the 3 diets. Diets were formulated to contain the same concentration of net energy for lactation and metabolizable protein (MP) based on the National Research Council model, but diets with CMP contained more neutral detergent fiber (38.3 vs. 31.4%) and less starch (21.6 vs. 30.5%) than the control diet. Lysine as a percent of MP was 6.5, 6.0, and 6.8 for the control, CMP, and CMP+AA diets, respectively, and methionine was 1.8, 1.8, and 2.3% of MP, respectively. Dry matter intake was not affected by diet (24.3 kg/d), but milk yield was lower for cows fed either CMP diet than for those fed control (36.0 vs 38.1 kg/d). Milk fat concentrations were normal and not affected by diet (3.7%). Milk protein concentration was greater for cows fed CMP+AA than for cows fed the other 2 treatments (3.19 vs. 3.11%); however, milk protein yield was greatest for cows fed the conventional diet. The concentration of methionine in plasma was significantly greater for cows fed CMP+AA than for cows fed the other diets. Plasma lysine concentrations were greater for cows fed the conventional diet than for those fed the other 2 diets. Plasma concentrations of several essential AA were lower for cows fed either CMP diet. Based on calculated energy balance, diets contained similar concentrations of net energy for lactation, but cows fed CMP diets partitioned more energy toward body energy reserves than did control cows, perhaps because supply of specific AA limited milk synthesis.     

Corn gluten meal and blood meal mixture for dairy cows in midlactation

Twelve midlactation Holstein cows were assigned to a switchback design with 4-wk periods to compare a corn gluten meal and blood meal mixture with soybean meal as supplemental protein sources. All experimental diets contained 60% ammoniated corn silage, on a dry basis, and a corn and oats (2:1) basal concentrate mixture. Diets were: urea control (12.5% CP); soybean meal (16.1% CP); low protein (14.3% CP) corn gluten and blood meal mixture; and high protein (16.8% CP) corn gluten and blood meal mixture. Cows fed the control diet consumed less DM, and produced less milk containing a lower percentage of protein than cows fed other diets. Protein efficiency and milk fat percentage were higher for cows fed the control diet than for cows fed the natural protein diets. Fat-corrected milk and fat yields did not differ among diets. The high protein diets (16.1 and 16.8% CP) decreased protein efficiency and increased SNF percentage. Milk yield per unit of DM intake was higher when cows fed the lower degradable protein source (corn gluten-blood meal) than when they were fed soybean meal. The low degradable protein mixture produced a similar lactation response to soybean meal at both the high and low concentrations of total dietary protein. This study indicates that the dietary protein and undegradable protein concentration needed by midlactation Holstein fed complete mixed diets may be lower than generally recommended.     

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.     

Feeding Lactating Dairy Cows Proteins Resistant to Ruminal Degradation

Sixty multiprious Holstein cows were fed treatment diets from 11 to 40 d postpartum with corn silage as the forage. Treatment diets each contained a different supplemental protein: 1) solvent soybean meal; 2) extruded soy product; 3) combination of corn gluten meal and distillers dried grains with solubles; and 4) a combination of protein sources from diets 2 and 3. Covariate adjusted means for milk (kg/d) and milk fat (%) for treatments 1 through 4 were 37.5, 3.14; 38.5, 3.19; 31.8, 3.45; and 35.2, 3.08. Milk protein content and DM intake were greatest for cows fed diet 1.In a second trial, 105 multiparous Holstein cows 13 d postpartum were placed on 7 treatment diets for 60 d. Treatments 1 to 5 contained equal amounts of corn silage and alfalfa silage as forage sources and contained either: 1) solvent soybean meal; 2) roasted soybean meal; 3) roasted soybeans; 4) roasted soybeans and urea; or 5) a mixture of corn distillers dried grains and corn gluten meal. Treatments 6 and 7 had alfalfa silage as the forage source and either 6) solvent soybean meal or 7) roasted soybeans as the supplemental protein. Feeding roasted soybeans with the alfalfa silage-based diets increased milk 2.0 kg/d, 4% FCM 4.6 kg/d, and fat .23 kg/d when compared with solvent soybean meal. Milk protein production was depressed by feeding a combination of distillers dried grains and corn gluten meal when compared with feeding diets containing soybean sources with the corn silage-alfalfa silage diets. Resistant protein sources may have greater value with diets containing alfalfa silage than with diets containing corn silage.     

Crude protein and rumen undergradable protein effects on reproduction and lactation performance of Holstein cows

We conducted a study to determine the effects of excess dietary crude protein (CP) and rumen undegradable protein (RUP) on reproduction and lactation performance of Holstein cows. During each of three yearly replicates, cows were blocked by previous mature equivalent milk production and randomly assigned at calving (n = 47; partum group) or at 42 +/- 21 d postpartum (n = 134; postpartum group) to the following dietary treatments: 1) ryegrass pasture supplemented with a corn and soybean meal grain mix (high CP, moderate RUP); 2) ryegrass pasture mornings and corn silage evenings, supplemented with grain as in diet 1 (moderate CP, moderate RUP control diet), and 3) ryegrass pasture mornings and corn silage evenings, supplemented with a grain mix containing corn, soybean meal, corn gluten meal, and blood meal (moderate CP, high RUP). Dietary CP and RUP concentrations were approximately 23.1, 5.8; 17.7, 5.0; and 17.2, 6.8% of dry matter for diets 1 to 3, respectively. Plasma urea N concentrations were highest in cows fed diet 1 (25.0 mg/dl), intermediate in cows on diet 2 (20.1 mg/dl), and lowest in cows on diet 3 (18.5 mg/dl). Cows fed excess dietary protein (diet 1) exhibited lower first breeding pregnancy rates (24.1 vs. 41.0%) and lower overall pregnancy rates (53.4 vs. 75.4%) than did cows fed diet 2, increasing time nonpregnant by an average of 15.1 d per cow. Reproductive performance was similar between cows fed diets 2 and 3. Mean fat-corrected milk (FCM) yield was not affected by protein concentration (diet 1 vs. 2); however, partum group cows that received supplemental RUP (diet 3) produced more 3.5% FCM than controls in early lactation. Feeding grain diets that contained excess dietary protein impaired the reproductive performance of dairy cows grazing ryegrass.     

Plasma amino acids and milk protein production by cows fed rumen-protected methionine and lysine

Eighteen Holstein cows in midlactation were used to study the effectiveness of encapsulated rumen-protected methionine and rumen-protected lysine to deliver methionine and lysine postruminally. The experimental design was a 2 X 2 factorial, a center point, and a control treatment run in a partially balanced, incomplete block design. Treatments were administered over three periods of 3 wk. Cows were fed a blended diet consisting of corn silage, corn, and soybean meal supplemented with five different amounts of rumen-protected methionine and lysine. The amounts of DL-methionine and L-lysine (g/d), respectively, supplied from the encapsulated rumen-protected preparations for the six treatments were 1) 0, 0; 2) 10.40, 18.00; 3) 4.52, 7.82; 4) 16.28, 7.82; 5) 16.28, 28.18; and 6) 4.52, 28.18. In vitro results indicate that amino acids in both of the encapsulated preparations were 94% stable at a pH (5.4), which simulated the rumen, and 94% released at a pH (2.9), which simulated the abomasal environment. A linear increase of plasma methionine and lysine was observed as the amount of methionine and lysine supplied postruminally increased. The concentrations (microgram/ml) of methionine and lysine in plasma for the six treatments were 1) 2.47, 9.05; 2) 3.73, 11.59; 3) 3.60, 11.86; 4) 6.09, 10.45; 5) 5.28, 13.43; and 6) 3.33, 13.27. Rumen-protected lysine increased feed intake, milk yield, and 4% fat-corrected milk production within the surface treatments but had no effect when compared with the unsupplemented control treatment. Rumen-protected methionine and lysine increased production of milk protein. Lysine appeared to improve the utilization of methionine.     

Supplementation of dairy cow diets with ammonium salts of volatile fatty acids

The objective was to determine the efficacy of a blend of ammonium salts of the volatile fatty acids, isobutyric, 2-methylbutyric, isovaleric, and valeric as a supplement to diets for dairy cows. Treatments of 0 (control) or 120 (supplemented) g/cow of the blend were fed daily from approximately 3 wk prepartum through a complete lactation. Five trials were conducted concurrently with a total of 116 multiparous Holstein cows. Dietary ingredients or combinations of ingredients differed in each of the trials. Diets contained either 1) corn gluten meal and urea, 2) soybean meal, or 3) cottonseed meal as the primary grain source of crude protein. The forage portion of the diets contained corn silage in combination with one or more of the following: alfalfa hay, alfalfa haylage, or wheat silage. Cows fed the supplement produced more milk and fat-corrected milk than the control cows for the 305-d lactation on four of the five diets, resulting in an average increase of 1.7 kg/d or 7%. Feed intake of cows on the supplemented diet was generally similar or lower than intake of the control cows throughout lactation, indicating that increased milk yield was associated with improved feed utilization. Percent milk fat was similar for cows on the supplemented diet, but fat yield was higher. Percent milk protein was lower for supplemented cows, but protein yield was about the same for both treatments because of higher milk yield. Health and reproduction were similar for all cows.     

Influence of rumen undegradable protein levels on feed intake and milk production of dairy cows

Twenty-seven dairy cows in midlactation were utilized in two experiments using 15 and 12 cows to determine effects of varying the delivery of ruminally undegraded protein on feed intake, milk production, and some rumen and plasma characteristics. In Experiment 1, cows consumed alfalfa silage ad libitum and one of three barley-based concentrates with either soybean meal (a rapidly rumen degraded protein source), corn gluten meal (a slowly degraded protein source), or an equal mixture of the two, fed at the rate of .36 kg/kg of milk produced. In Experiment 2, cows were fed total mixed diets based upon alfalfa silage, barley, and either soybean meal, corn gluten meal, or a mixture of soybean meal and whey powder (a protein source very rapidly degraded in the rumen). In sacco incubation procedures were used to estimate degradability of protein in all diets. All diets exceeded Agricultural Research Council recommendations for rumen degraded and undegraded protein as well as NRC recommendations for degraded protein. However, one to three of the six total diets, depending upon assumed ruminal turnover rates, did not meet NRC recommendations for undegraded protein. Production parameters, include DMI as well as milk yield and composition, were not influenced by diet in either experiment. Results do not support NRC recommendations for ruminally undegraded protein for midlactation dairy cows producing about 30 kg/d of milk and broadly support the lower recommendations of the Agricultural Research Council. Results also appear to question use of dietary energy intake to predict net rumen microbial protein yield.     

Protected methionine supplementation to a barley-based diet for cows during early lactation

Formulation of diets using barley and soybean meal should result in a diet that supplies less methionine than conventional corn and soybean meal diets. To evaluate this further, 28 high producing Holstein cows (10 primiparous and 18 multiparous) were fed a barley soybean meal diet without or with 15 g of added DL-methionine as 50 g of ruminally protected methionine product during wk 4 to 16 postpartum. Cows were fed a 15% CP total mixed diet consisting of (dry matter basis) 50% concentrate mix, 45% corn silage, and 5% chopped alfalfa hay. Yields of milk (30.3 and 29.8 kg/d), 4% fat-corrected milk (26.0 and 25.6 kg/d), and solids-corrected milk (26.3 and 25.9 kg/d) were similar for cows fed diets without or with added methionine. Percent of milk fat (3.08 and 3.16%) and solids-not-fat (8.66 and 8.71%) were similar, but percent protein (2.75 and 2.87%) was higher, from cows fed ruminally protected methionine. Methionine concentrations in arterial and venous serum were not significantly elevated by feeding ruminally protected methionine. Supplemental ruminally protected methionine did not increase milk production but did increase milk protein percentages in cows fed barley-based diets.     

Lactational response to soybean meal, heated soybean meal, and extruded soybeans with ruminally protected methionine

Seventy-three high producing Holstein cows were arranged in a 3 X 2 factorial to evaluate three protein supplements (soybean meal, heat-treated soybean meal, and extruded blend of soybeans and soybean meal) without or with 15 g/head/d of ruminally protected DL-methionine during wk 4 through 16 postpartum. Total mixed diets contained (DM basis) 30% corn silage, 15% alfalfa hay, and 55% of the respective concentrate mix. Milk production was higher when cows were fed either heated soybean product instead of soybean meal. Methionine supplementation increased production when fed with soybean meal (32.2 and 33.8 kg/d) but not when fed with heat-treated soybean meal (34.5 and 33.0 kg/d) or extruded soybeans (36.2 and 34.4 kg/d). Milk fat percentages were lower with extruded soybeans (3.01, 2.93, and 2.66) and were similar without (2.83) or with (2.90) supplemental methionine. Milk protein percentages were highest when fed soybean meal, lowest with extruded soybeans (3.02, 2.92, and 2.87), and higher with supplemental methionine (2.91 and 2.96). Dry matter intake was higher when fed supplemental methionine (20.0 and 21.3 kg/d). Production of milk in early lactation high producing dairy cows was increased by supplementing a soybean meal diet with ruminally protected methionine or by replacing the soybean meal with heat-treated soybean meal, soybeans, or a mixture of the two.     

Feeding reduced-fat dried distillers grains with solubles to lactating Holstein dairy cows does not alter milk composition or cause late blowing in cheese

Feeding dried distillers grains with solubles (DDGS) to lactating dairy cows has been implicated as a cause of late blowing defects in the production of Swiss-style cheeses. Our objectives were (1) to test the effect of feeding reduced-fat DDGS (RF-DDGS; ～6% fat) to lactating dairy cows on the composition of milk and on the suitability of the milk for production of baby Swiss cheese and (2) to evaluate the effect of diet on cow lactation performance. Lactating Holstein dairy cows were fed both dietary treatments in a 2 × 2 crossover design. Cows were housed in a 48-cow freestall pen equipped with individual feeding gates to record feed intake. The control diet was a corn, corn silage, and alfalfa hay diet supplemented with mechanically expelled soybean meal. The experimental diet was the same base ration, but 20% (dry matter basis) RF-DDGS were included in place of the expelled soybean meal. The RF-DDGS diet was additionally supplemented with rumen-protected lysine; diets were formulated to be isoenergetic and isonitrogenous. Cows were allowed ad libitum access to feed and water, fed twice daily, and milked 3 times daily. For cheese production, milk was collected and pooled 6 times for each dietary treatment. There was no treatment effect on milk yield (35.66 and 35.39 kg/d), milk fat production (1.27 and 1.25 kg/d), milk fat percentage (3.65 and 3.61%), milk protein production (1.05 and 1.08 kg/d), lactose percentage (4.62 and 4.64%), milk total solids (12.19 and 12.28%), and somatic cell count (232.57 and 287.22 × 10³ cells/mL) for control and RF-DDGS, respectively. However, dry matter intake was increased by treatment, which implied a reduction in feed efficiency. Milk protein percentage also increased (3.01 and 3.11%), whereas milk urea nitrogen decreased (14.18 and 12.99 mg/dL), indicating that protein utilization may be more efficient when cows are fed RF-DDGS. No differences in cheese were observed by a trained panel except cheese appearance; control cheese eyes were significantly, but not practically, larger than the RF-DDGS cheese. These results indicate that RF-DDGS can be effectively used in the rations of lactating Holstein cows with no deleterious effects on milk production and composition and metrics of the physiology of the cow (i.e., blood glucose and nonesterified fatty acids); however, feeding RF-DDGS increased dry matter intake, which decreased feed efficiency. Finally, feeding RF-DDGS did not negatively influence quality and suitability of milk for production of baby Swiss cheese.     

Corn distillers grains versus a blend of protein supplements with or without ruminally protected amino acids for lactating cows

In a replicated 4 x 4 Latin square design with 4-wk periods, we used 12 multiparous Holstein cows averaging 83 d postpartum to compare corn distillers grains (CDG) versus a blend (BLEND) of other protein sources with CDG (fish meal and soybean meal), and to determine the effectiveness of ruminally protected lysine and methionine (RPLM) in improving the utilization of CDG as a protein supplement for lactating cows. The 2 x 2 factorial arrangement of treatments was as follows: CDG diet, CDG diet plus RPLM, BLEND diet, and BLEND diet plus RPLM. All diets contained 30% corn silage, 20% alfalfa hay, and 50% the respective corn-based concentrate mixture. The array of amino acids available for absorption when cows were fed the BLEND diet was more desirable than for the CDG diet according to Milk Protein Score and Cornell Net Carbohydrate and Protein System. Dry matter intakes were similar among all diets. Milk yields (32.6, 31.7, 32.8, and 32.8 kg/d, respectively) were similar for cows fed all diets. Milk fat yields and percentages (3.72, 3.76, 3.67, and 3.63%) were unaffected by diet, but milk protein percentages (3.23, 3.26, 3.25, and 3.26%) tended to be higher when fed RPLM. Concentrations of most protein fractions in milk were similar for all diets, although beta-lactoglobulin was increased slightly when cows were fed BLEND diets. Lysine, Met, and Phe were indicated as the most limiting amino acids for all diets according to extraction efficiency and transfer efficiency of amino acid from blood by the mammary gland. Methionine status was apparently improved by RPLM supplementation; Lys status was improved by the BLEND diets. Milk yield and composition when cows were fed CDG were not further improved by feeding blends of protein sources or RPLM; however, such dietary changes improved Lys and Met status of the cows.     

Effect of rumen-protected lysine supplementation of diets based on corn protein fed to lactating dairy cows

This trial tested whether rumen-protected Lys (RPL) supplementation would improve the nutritive value of rumen-undegradable protein (RUP) from corn protein. Thirty-two lactating Holstein cows were blocked by days in milk and parity into 8 squares of 4 cows each in replicated 4 × 4 Latin squares. Treatments provided all supplemental crude protein from: (1) soy protein (67% expeller soybean meal plus 33% solvent soybean meal); (2) a blend of soy and corn protein (33% expeller soybean meal, 17% solvent soybean meal, 25% corn gluten meal plus 25% distillers dried grains with solubles); (3) corn protein (50% corn gluten meal plus 50% distillers dried grains with solubles); or (4) corn protein plus RPL [diet 3 top-dressed with RPL (125 g/d of AjiPro-L Generation 1, supplying an estimated 20 g of absorbable Lys/d)]. Diets contained (dry matter basis) 22% alfalfa silage, 43% corn silage, 18% ground high-moisture and dry corn, 2.4% mineral-vitamin premix, 1.5 to 3.9% soy hulls, 15% crude protein, 30 to 32% neutral detergent fiber and predicted to contain equal rumen-degradable protein, RUP, and metabolizable protein. Cows within squares were randomly assigned to treatment sequences and fed diets for 4-wk periods before switching; production data and blood samples were collected during last 2 wk of each period. Data were analyzed using the mixed procedures of SAS. Intake was highest on diet 1, intermediate on diets 2 and 3, and lowest on diet 4; body weight gain was highest on diet 3, intermediate on diets 1 and 2 and lowest on diet 4. Intakes and body weight changes were reflected by differences in milk/dry matter intake, which was highest on diets 2 and 4 and lowest on diet 3. Milk yield was lower on diet 3 (44.3 kg/d) than on diets 1, 2, and 4 (average 45.8 kg/d) and protein yield was highest on diets 1 and 2 (average 1.35 kg/d), intermediate on diet 4 (1.30 kg/d), and lowest on diet 3 (1.25 kg/d). No effects of diet were detected on ruminal metabolites. Free nonessential amino acids and total protein AA were elevated in blood plasma on diet 3, reflecting reduced utilization for milk protein synthesis. These results indicated that 50% dilution of soybean meal RUP with that from corn protein did not reduce yield and that supplementing RPL to the corn protein-based diet increased yield 1.1 kg of milk/d and 50 g of true protein/d.     

Influence of formaldehyde-treated soybean meal on milk production

Forty-eight Holstein cows were fed one of four diets containing 12.5% crude protein (negative control); 15.5% crude protein with untreated soybean meal; 15.5% crude protein with formaldehyde (.3%)-treated soybean meal; or 18% crude protein (positive control). Diets were 60% concentrate, 22% corn silage, 14% alfalfa hay, and 4% beet pulp (dry matter). Data were collected during the first 200 d of lactation. Dry matter intake, milk, and milk component yields did not differ among cows fed the untreated soybean meal, treated soybean meal, and positive control diets. Cows fed negative control diet consumed less dry matter and produced less milk than cows fed the other diets. Milk protein yield was lower for cows fed the negative control diet compared with the other diets. Nonprotein nitrogen content of milk increased as dietary protein increased.     

Evaluation of urea and dried whey in diets of cows during early lactation

Thirty-three Holstein cows were fed one of three concentrate mixtures supplemented with all protein (soybean meal), 1% urea, or 1% urea and 30% dried whey from wk 3 through 16 postpartum. Total mixed rations contained 40% (dry matter basis) corn silage, 10% alfalfa hay, and 50% concentrate mixture. Diets were formulated to be isonitrogenous at 16% crude protein, but soluble nitrogen was formulated to be approximately 23, 30, and 42% of total nitrogen. Milk yield was similar (33.8, 33.4, and 33.2 kg/d) for cows fed the three diets, whereas production of 4% fat-corrected milk (29.9, 28.0, and 29.2 kg/d) and solids-corrected milk (30.3, 28.6, and 29.6 kg/d) was higher for cows fed soybean meal and urea-dried whey. Milk fat percentages (3.23, 2.94, and 3.23%) were lower when cows were fed urea, but milk protein (3.10, 3.04, and 3.04%) and solids-not-fat (8.74, 8.79, and 8.81%) were not affected by diet. Dry matter intakes (22.0, 20.2, and 23.1 kg/d) were highest for cows fed urea-dried whey and lowest for cows fed urea. Molar percentages of ruminal acetate (56.6, 50.3, and 50.2%) were highest for cows fed soybean meal, propionate (24.8, 28.6, and 25.0%) was highest for cows fed urea, and butyrate (13.6, 14.4, and 18.4%) was highest for cows fed urea-dried whey. Concentrations of ruminal ammonia (11.8, 20.3, and 13.5 mg/dl) and serum urea (19.5, 22.9, and 16.5 mg/dl) were highest for cows fed urea. Utilization of urea nitrogen for milk production was improved by adding dried whey to diets of early lactation cows.     

Effect of total and rumen undegradable protein on the performance of cows fed low fiber diets.

Twelve multiparous and 18 primiparous Holstein cows were fed a 17.3% CP, 21.0% ADF diet during wk 2 through 6 postpartum. Cows then were assigned from wk 7 through 14 to one of three low fiber (10.7% ADF) dietary treatments containing either 14.4 or 18.7% CP, the latter with or without a soybean meal enhanced with rumen undegradable protein. Treatments had no effect on milk yield or composition in multiparous cows, although milk fat percentage was not depressed in multiparous cows receiving the low fiber diets. The soybean meal diet enhanced with rumen undegradable protein increased yields of milk, 4% FCM, fat, protein, and DMI compared with the 14.4% CP diet in primiparous cows; it also increased yields of 4% FCM and fat versus the 18.7% CP, untreated diet in primiparous cows. Blood urea N concentrations were greater for high CP diets than for the low CP diet in both parity groups. Rumen acetate: propionate ratios were higher for both high CP diets than for the low CP diet in multiparous cows. Soybean meal enhanced with rumen undegradable protein improved yields of milk and its components in primiparous cows fed low fiber diets, even when high protein diets were fed.     

Response of lactating cows to pelleted and unpelleted soybean meal after partial protein depletion

Twenty-four first-lactation cows, averaging 82 d postpartum, were protein depleted for 20 d by consuming a 9.4% crude protein diet. The cows were then assigned randomly and equally to a 2 X 3 factorial arrangement of dietary treatments in which either pelleted or unpelleted soybean meal containing 1% sodium bentonite was supplemented to corn or corn silage-based diets to yield 12.2, 15.4, or 18.1% crude protein, dry basis. Between 9 and 15 d of the depletion period, milk, milk protein production, and dry matter consumption decreased 20 to 25%. Blood hematocrit increased. On refeeding three amounts of protein, dry matter intake was greatest during week 4 of repletion. Milk production rapidly increased to a plateau averaging approximately 88% of preexperimental production with a somewhat greater response to the higher soybean rations. Neither intake, milk, milk protein production, plasma urea, serum albumin, or blood hematocrit provided any evidence that pelleted or unpelleted soybean meal differed nutritionally.