Production of lactating dairy cows fed alfalfa or red clover silage at equal dry matter or crude protein contents in the diet

Two Latin square trials, using 21 or 24 multiparous lactating Holstein cows, compared the feeding value of red clover and alfalfa silages harvested over 2 yr. Red clover silages averaged 2 percentage units lower in crude protein (CP) and more than 2 percentage units lower in neutral detergent fiber and acid detergent fiber than did alfalfa silage. In trial 1, diets were formulated to 60% dry matter (DM) from alfalfa, red clover silage, or alfalfa plus red clover silage (grown together); CP was adjusted to about 16.5% by adding soybean meal, and the balance of dietary DM was from ground high moisture ear corn. Nonprotein N in red clover and alfalfa-red clover silages was 80% of that in alfalfa silage. Although DM intake was 2.5 and 1.3 kg/d lower on red clover and alfalfa plus red clover, yield of milk and milk components was not different among diets. In trial 2, four diets containing rolled high moisture shelled corn were formulated to 60% DM from alfalfa or red clover silage, or 48% DM from alfalfa or red clover silage plus 12% DM from corn silage. The first three diets contained 2.9% soybean meal, and the red clover-corn silage diet contained 5.6% soybean meal; the 60% alfalfa diet contained 18.4% CP, and the other three diets averaged 16.5% CP. Nonprotein N in red clover silage was 62% of that in alfalfa silage. Intake of DM was about 2 (no corn silage) and 1 kg/d (plus corn silage) lower on red clover. Yield of milk and milk components was not different among the first three diets; however, yields of milk, total protein, and true protein were higher on red clover-corn silage with added soybean meal. Replacing alfalfa with red clover improved feed and N efficiency and apparent digestibility of DM, organic matter, neutral detergent fiber, acid detergent fiber, and hemicellulose in both trials. Net energy of lactation computed from animal performance data was 18% greater in red clover than alfalfa. Data on milk and blood urea and N efficiency suggested better N utilization on red clover.     

Effect of low level monensin supplementation on the production of dairy cows fed alfalfa silage

Effectiveness of low level monensin supplementation on N utilization in lactating dairy cows fed alfalfa silage was assessed using 48 multiparous Holsteins. Cows were fed a covariate diet [% of dry matter (DM): 56% alfalfa silage, 39% ground high moisture corn, 3% soybean meal, 1% ground corn, 1% vitamin-mineral supplements] for 2 wk, then grouped by days in milk into blocks of 4. Cows were randomly assigned within blocks to 1 of 4 diets that were fed for 10 wk: 1) control (covariate diet), 2) control plus 3% fish meal (replacing DM from high moisture corn), 3) monensin (10 mg/kg DM), and 4) monensin plus 3% fish meal. Diets 1 and 3 averaged 16.7% crude protein (25% from free AA in alfalfa silage); diets 2 and 4 averaged 18.5% crude protein. Monensin intake averaged 16 mg/d on diets 1 and 2 (due to contamination) and 248 mg/d on diets 3 and 4. There was no effect of fish meal or monensin on DM intake. However, weight gain and yield of milk, protein, and SNF increased with fish meal feeding, indicating metabolizable protein limited production. Feeding monensin increased blood glucose but reduced yield of 3.5% fat-corrected milk, milk fat content and yield, and milk protein content and yield. Apparent N efficiency was greatest on monensin (diet 3) but lowest on monensin plus fish meal (diet 4). Fish meal reduced blood glucose concentration and apparent N efficiency, and increased concentrations of milk and blood urea. Monensin increased ruminal propionate concentration and decreased concentration of acetate and butyrate and acetate:propionate in ruminally cannulated cows fed the experimental diets. However, these changes were small, suggesting that too little monensin was fed. Fish meal reduced ruminal total amino acid (AA) but monensin did not alter ruminal NH(3) or total AA. Both fish meal and monensin increased NH(3) formation from casein AA using ruminal inoculum from the cannulated cows. There was no evidence from this trial that feeding 250 mg of monensin per day to lactating cows improved N utilization by reducing ruminal catabolism of the large amounts of free AA in alfalfa silage.     

Effects of different protein supplements on milk production and nutrient utilization in lactating dairy cows

Sixteen (8 ruminally cannulated) multiparous and 8 primiparous lactating Holstein cows were used in 6 replicated 4 × 4 Latin squares to test the effects of feeding supplemental protein as urea, solvent soybean meal (SSBM), cottonseed meal (CSM), or canola meal (CM) on milk production, nutrient utilization, and ruminal metabolism. All diets contained (% of DM) 21% alfalfa silage and 35% corn silage plus 1) 2% urea plus 41% high-moisture shelled corn (HMSC), 2) 12% SSBM plus 31% HMSC, 3) 14% CSM plus 29% HMSC, or 4) 16% CM plus 27% HMSC. Crude protein was equal across diets, averaging 16.6%. Intake and production were substantially reduced, and milk urea, blood urea, and ruminal ammonia were increased on urea vs. the diets supplemented with true protein. Although intake was lower in cows fed SSBM compared with CM, no differences were observed for milk yield among SSBM, CSM, and CM. Yields of fat and protein both were lower on CSM than on CM, whereas SSBM was intermediate. Milk urea and milk protein contents also decreased when CSM replaced SSBM or CM. Diet did not affect ruminal volatile fatty acids except that isobutyrate concentration was lowest on urea, intermediate on CSM, and greatest on SSBM and CM. Urinary excretion of urea N and total N was greatest on urea, intermediate on SSBM and CM, and lowest on CSM. Apparent N efficiency (milk N/N intake) was lower on the CSM diet than on the SSBM diet. Overall, production and N utilization were compromised when the diets of high-yielding dairy cows were supplemented with urea rather than true protein and the value of the true proteins, from most to least effective, was in the order CM > SSBM > CSM.     

Production and nitrogen utilization in lactating dairy cows fed ground field peas with or without ruminally protected lysine and methionine

Previous research has shown that cows fed ≥24% of the diet dry matter (DM) as field peas decreased milk yield as well as concentration and yield of milk protein, possibly due to reduced DM intake and limited supply of Lys and Met. Twelve multiparous and 4 primiparous lactating Holstein cows were randomly assigned to 1 of 4 diets in a replicated 4 × 4 Latin square design. The diets contained (DM basis) 34.8% corn silage, 15.2% grass-legume silage, 5.9% roasted soybean, 2.4% mineral-vitamin premix, 2.0% alfalfa pellets, and either (1) 36% ground corn, 2.4% soybean meal, and 1.3% urea (UR), (2) 29.7% ground corn, 9.8% soybean meal, 0.13% ruminally protected (RP) Lys, and 0.07% RP-Met (CSBAA), (3) 25% ground field peas, 12.3% ground corn, and 2.4% soybean meal (FP), or (4) FP supplemented with 0.15% RP-Lys and 0.05% RP-Met (FPAA). Our objective was to test the effects of FP versus UR, FPAA versus CSBAA, and FPAA versus FP on milk yield and composition, N utilization, nutrient digestibility, ruminal fermentation profile, and plasma concentration of AA. Milk yield did not differ across diets. Compared with cows fed UR, those fed FP had greater DM intake, concentration and yield of milk true protein, apparent total-tract digestibility of fiber, urinary excretion of purine derivatives, and concentrations of total volatile fatty acids in the rumen and Lys in plasma, and less milk urea N and ruminal NH₃-N. The concentration of milk urea N, as well as the concentration and yield of milk fat increased in cows fed FPAA versus CSBAA. Moreover, cows fed FPAA had greater ruminal concentration of total volatile fatty acids, increased proportions of acetate and isobutyrate, and decreased proportions of propionate and valerate than those fed CSBAA. The plasma concentrations of His, Leu, and Phe decreased, whereas plasma Met increased and plasma Lys tended to increase in cows fed FPAA versus CSBAA. Concentration of milk true protein, but not yield, was increased in cows fed FPAA versus FP. However, cows fed FPAA showed decreased concentrations of His and Leu in plasma compared with those fed FP. Overall, compared with the CSBAA diet, feeding FPAA did not negatively affect milk yield and milk protein synthesis. Furthermore, RP-Lys and RP-Met supplementation of the FP diet did not improve milk yield or milk protein synthesis, but decreased urinary urea N excretion.     

Effect of grain level and protein source on ruminal fermentation, degradability, and digestion in milking cows fed silage

Five primiparous Holstein cows (483 kg BW) of low productivity were used in a 4 x 5 incomplete Latin square design to study the effects of feeding two levels of grain containing soybean meal and one level of grain containing fish meal on feed intake, milk production, digestibility, and rumen fermentation. Animals all were fed alfalfa silage for ad libitum intake. Collection of data was between wk 11 and 24 of lactation. The four treatments were an all silage diet (control), silage and medium concentrate fed at 1.8% BW containing soybean meal, and silage and low concentrate fed at 1.3% BW containing either soybean meal or fish meal. Treatments other than control were designed to give similar CP intake from the concentrate, which was based on high moisture corn and cob meal. Milk production and composition were similar among treatments except for fat percentage, which was significantly lower for low grain soybean meal. Intake of DM was higher on medium grain soybean meal compared with the other treatments. Average BW and change in BW (.11 kg/d) were not affected by treatments. Digestibility of DM was higher for cows fed grain (68 to 73%) than for those fed the control diet (60%). Generally, feeding concentrate at 1.3 or 1.8% BW and supplementing with soybean meal or fish meal resulted in pH and concentrations of NH3 N and VFA similar to those observed on the all silage diet. Feeding concentrate at 1.3 or 1.8% BW and supplying fish meal or soybean meal did not change feed utilization enough to increase milk production in low producing cows compared with an all silage diet.     

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.     

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.     

Effects of varying dietary protein and energy levels on the production of lactating dairy cows

Forty-five multiparous and 18 primiparous Holstein cows were fed three levels of crude protein (CP), each at three levels of neutral detergent fiber (NDF), to identify optimal dietary CP and energy. Cows were blocked by parity and days in milk into seven groups of nine and randomly assigned to an incomplete 9 x 9 Latin square trial with four, 4-wk periods. Diets were formulated from alfalfa and corn silages, high-moisture corn, soybean meal, minerals, and vitamins. Forage was 60% alfalfa and 40% corn silage on all diets; NDF contents of 36, 32, and 28% were obtained by feeding 75, 63, and 50% forage, respectively. Dietary CP contents of 15.1, 16.7, and 18.4% were obtained by replacing high-moisture corn with soybean meal. Production data were from the last 2 wk of each period. Spot fecal and urine samples were collected from 36 cows to estimate N excretion using fecal indigestible acid detergent fiber (ADF) and urinary creatinine as markers. There were no interactions (P > or = 0.08) between dietary CP and NDF for any trait; thus, effects of CP were not confounded by NDF or vice versa. Intake of DM and fat yield were lower on 15.1% CP than at higher CP. There were linear increases in milk urea and urinary N excretion and linear decreases in N efficiency with increasing CP. Increasing CP from 15.1 to 18.4% reduced milk N from 31 to 25% of dietary N, increased urinary N from 23 to 35% of dietary N, and reduced fecal N from 45 to 41% of dietary N. Decreasing NDF gave linear increases in BW gain, yield of milk, protein, true protein, lactose, and SNF, and milk/DM intake and milk N/N intake, and linear decreases in milk urea. However, fat yield was lower on 28% than 32% NDF. Reducing NDF from 36 to 28% increased purine derivative excretion by 19%, suggesting increased microbial protein. Increasing CP by adding soybean meal to diets fed cows averaging 34 kg/d of milk increased intake and fat yield but depressed N efficiency. Increasing dietary energy by reducing forage improved milk yield and efficiency and decreased excretion of environmentally labile urinary N.     

Effect of dietary crude protein concentration on milk production and nitrogen utilization in lactating dairy cows

Forty lactating Holstein cows, including 10 with ruminal cannulas, were blocked by days in milk into 8 groups and then randomly assigned to 1 of 8 incomplete 5 × 5 Latin squares to assess the effects of 5 levels of dietary crude protein (CP) on milk production and N use. Diets contained 25% alfalfa silage, 25% corn silage, and 50% concentrate, on a dry matter (DM) basis. Rolled high-moisture shelled corn was replaced with solvent-extracted soybean meal to increase CP from 13.5 to 15.0, 16.5, 17.9, and 19.4% of DM. Each of the 4 experimental periods lasted 28 d, with 14 d for adaptation and 14 d for data collection. Spot sampling of ruminal digesta, blood, urine, and feces was conducted on d 21 of each period. Intake of DM was not affected by diet but milk fat content as well as ruminal acetate, NH₃, and branched-chain volatile fatty acids, urinary allantoin, and blood and milk urea all increased linearly with increasing CP. Milk and protein yield showed trends for quadratic responses to dietary CP and were, respectively, 38.3 and 1.18 kg/d at 16.5% CP. As a proportion of N intake, urinary N excretion increased from 23.8 to 36.2%, whereas N secreted in milk decreased from 36.5 to 25.4%, as dietary protein increased from 13.5 to 19.4%. Under the conditions of this study, yield of milk and protein were not increased by feeding more than 16.5% CP. The linear increase in urinary N excretion resulted from a sharp decline in N efficiency as dietary CP content increased.     

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.     

Performance of lactating dairy cows fed alfalfa or red clover silage as the sole forage

Three Latin square trials, with 20 (two trials) or 24 (one trial) multiparous lactating Holstein cows (four in each trial with ruminal cannulae), compared the feeding value of red clover and alfalfa silages harvested over 3 yr. Overall, the forages contained similar amounts of neutral detergent fiber and acid detergent fiber; however, red clover silage contained more hemicellulose, less ash and crude protein (CP), and only 67% as much nonprotein N, as a proportion of total N, as did alfalfa silage. Diets were formulated with equal dry matter (DM) from alfalfa or red clover silage and contained on average 65% forage, 33 or 30% ground high moisture ear corn, and 0 or 3% low soluble fishmeal (DM basis). Diets fed in the Latin squares contained (mean dietary CP): 1) alfalfa (17.8% CP); 2) red clover (15.1% CP); 3) alfalfa plus fishmeal (19.6% CP); and 4) red clover plus fishmeal (16.9% CP). Although performance varied somewhat among trials, overall statistical analysis showed that replacing alfalfa with red clover reduced yields of milk, fat-corrected milk, fat, protein, lactose, and SNF; these effects were related to the 1.2 kg/d lower DM intake for cows fed red clover. Replacing alfalfa with red clover improved body weight gain and reduced concentrations of milk and blood urea and ruminal NH3. Apparent digestibility of DM, organic matter, neutral detergent fiber, acid detergent fiber, and hemicellulose all were greater when red clover was fed. There were no significant forage x fishmeal interactions for DM intake and yield of milk and milk components, indicating that supplementation with rumen undegradable protein gave similar increases in production on both forages. Net energy of lactation (NE(L)), estimated from maintenance, mean milk yield, and body weight change, in alfalfa and red clover silage were, respectively, 1.25 and 1.38 Mcal NE(L)/kg of DM, indicating 10% greater NE(L) in red clover.     

Slow-release urea and highly fermentable sugars in diets fed to lactating dairy cows

This experiment was designed to test the inclusion of highly fermentable sugars (FS) in dairy rations and their interactions with a slow-release urea (SU) product. The FS are a blend of liquid coproducts from the corn milling and cheese industries, and the SU is calcium chloride urea. Eight multiparous and 4 primiparous Brown Swiss cows (117 ± 46 d in milk) were blocked by parity and utilized in a multiple Latin square design. Basal diets were formulated for 16.6% crude protein and 1.55 Mcal/kg of net energy for lactation and contained 35% of dietary dry matter as corn silage, 15% alfalfa hay, 34% of a concentrate mix containing varying proportions of ground shelled corn and soybean meal, and 16% of a constant concentrate premix. The premix consisted of equal proportions of corn distillers grains, soybean hulls, expeller soybean meal, vitamins, and minerals across all diets. Diets contained either no supplemental FS (NFS) or FS (8.64% RationMate) and either no SU (NSU) or SU (0.61% Ruma Pro) in a 2 × 2 factorial arrangement of treatments. Feeding FS tended to decrease milk production compared with feeding NFS. Milk fat percentage was increased for cows fed FS compared with NFS. Feeding SU decreased dry matter intake and increased feed efficiency compared with cows fed NSU. Dietary treatment had no effect on energy-corrected milk, milk fat yield, milk protein percentage, or milk urea N. Feeding FS increased the molar proportion of ruminal butyrate and decreased the molar proportion of propionate; however, no other effects were observed on ruminal fermentation. No interactions between FS and SU were observed. It was concluded that the replacement of corn and soybean meal with dietary FS increased milk fat percentage and that the replacement of soybean meal with SU significantly improved feed efficiency.     

Effect of high fiber energy supplements on nutrient digestibility and milk production of lactating dairy cows.

Sixteen multiparous Holstein cows past peak lactation were used in a 4 x 4 Latin square design replicated four times to determine the production response and digestibility of diets containing high fiber energy supplements. Corn gluten feed, soybean hulls, or wheat middlings were substituted for a portion of corn, soybean meal, and corn silage in the control diet to provide 22% of the total dietary DM. Intake of DM was decreased when cows consumed wheat middlings compared with control and soybean hulls. Actual milk and SCM yields and milk fat percentage were not different among treatments. Milk protein percentage was greater when cows consumed corn gluten feed compared with soybean hulls. Apparent digestibility of DM was greater when cows consumed soybean hulls compared with wheat middlings. Intake and apparent digestibility of ADF and NDF were greater when cows consumed soybean hulls. Cows consuming wheat middlings had intermediate intake and decreased apparent digestibility of NDF compared with controls. Intake and apparent digestibility of NDF were not different when cows received corn gluten feed compared with control or wheat middlings. High fiber energy supplements supported milk production equally; however, differences in DM and nutrient intake, milk composition, and nutrient apparent digestibility were significant.     

Effect of ammoniated barley silage on ruminal fermentation, nitrogen supply to the small intestine, ruminal and whole tract digestion, and milk production of Holstein cows

The effect of ammonia on barley silage fermentation characteristics, and the digestion and utilization of ammoniated barley silage by lactating Holstein cows fed three isonitrogenous diets (14.5% CP, DM basis) were examined. Whole plant barley was chopped and treated with anhydrous ammonia (1%, DM basis) at ensiling. Untreated barley silage was supplemented with either canola meal or urea. Cows were fed complete mixed diets (50% silage and 50% concentrate mixture, DM basis). Addition of ammonia increased total N, water-insoluble N, lactic acid, and pH in silage. Based on the application rate, 77.7% of the added ammonia N was recovered, and increased water-insoluble N was equal to 49.8% of added ammonia N. Addition of ammonia to barley silage increased ruminal concentrations of ammonia and propionate, and supplies of nonammonia N, microbial N, and total N to the small intestine. Ruminal effective degradabilities of DM and CP of barley silage and complete mixed diets, and whole tract digestibility of DM and CP of complete mixed diets were not affected by supplemental N source. Milk yield and milk composition of cows fed the ammoniated barley silage were similar to those of cows fed the diets supplemented with canola meal or urea.     

Feeding heat-treated full fat soybeans to cows in early lactation.

Forty-six multiparous Holstein cows were fed one of three total mixed diets from 15 to 119 d postpartum with alfalfa silage as the only forage. Each diet contained 50% forage and 50% concentrate on a DM basis. Diets were formulated to be isonitrogenous by replacing corn and solvent soybean meal with raw soybeans or heat-treated soybeans. The proportion of protein supplement in the diet on a DM basis was 10% soybean meal, 13% raw soybeans, or 13% heat-treated soybeans. The soybeans were heat-treated to maximize the amount of available lysine passing to the small intestine. The soybean meal diet was fed to all cows during wk 1 and 2 postpartum for covariate adjustment of DMI and milk production. Intake of DM was similar across treatments. Feeding heat-treated soybeans supported more milk (4.5 kg/d), 3.5% FCM (4.0 kg/d), and milk protein (.09 kg/d) than soybean meal or raw soybeans. Milk fat percentage was not altered by treatments. However, milk protein percentage was depressed in cows fed heat-treated soybeans compared with soybean meal (2.85 vs. 2.99%, respectively). Milk production response of cows fed properly heat-treated soybeans compared with soybean meal with alfalfa silage as the sole forage is thought to be related primarily to improved supply of undegraded intake 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 feeding formate-treated alfalfa silage or red clover silage on the production of lactating dairy cows

In trial 1, 15 Holsteins were fed 3 total mixed rations (TMR) with 33% neutral detergent fiber in 3 × 3 Latin squares (28-d periods). Two TMR contained (dry matter basis): 40% control alfalfa silage (CAS) or 40% ammonium tetraformate-treated alfalfa silage (TAS), 20% corn silage (CS), 33% high-moisture shelled corn (HMSC), 6% solvent soybean meal (SSBM), and 18% crude protein (CP); the third TMR contained 54% red clover silage (RCS), 6% dried molasses, 33% HMSC, 6% SSBM, and 16.3% CP. Silages differed in nonprotein N (NPN) and acid detergent insoluble N (ADIN; % of total N): 50 and 4% (CAS); 45 and 3% (TAS); 27 and 8% (RCS). Replacing CAS with TAS increased intake, yields of milk, fat-corrected milk, protein, and solids-not-fat, and apparent dry matter and N efficiency. Replacing CAS with RCS increased intake and N efficiency but not milk yield. Replacing CAS or TAS with RCS lowered milk urea N, increased apparent nutrient digestibility, and diverted N excretion from urine to feces. In trial 2, 24 Holsteins (8 ruminally cannulated) were fed 4 TMR in 4 × 4 Latin squares (28-d periods). Diets included the CAS, TAS, and RCS (RCS1) fed in trial 1 plus an immature RCS (RCS2; 29% NPN, 4% ADIN). The CAS, TAS, and RCS2 diets contained 36% HMSC and 3% SSBM and the RCS1 diet contained 31% HMSC and 9% SSBM. All TMR had 50% legume silage, 10% CS, 27% neutral detergent fiber, and 17 to 18% CP. Little difference was observed between cows fed CAS and TAS. Intakes of DM and yields of milk, fat-corrected milk, fat, protein, lactose, and solids-not-fat, and milk fat and protein content were greater on alfalfa silage vs. RCS. Blood urea N, milk urea N, ruminal ammonia, and total urinary N excretion were reduced on RCS, suggesting better N utilization on the lower NPN silage. Apparent N efficiency tended to be higher for cows fed RCS but there was no difference when N efficiency was expressed as kilograms of milk yield per kilogram of total N excreted.     

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.     

Effect of source of rumen-degraded protein on production and ruminal metabolism in lactating dairy cows

Twenty-eight (8 with ruminal cannulas) lactating Holstein cows were assigned to seven 4 × 4 Latin squares in a 16-wk trial to study the effects on production and ruminal metabolism of feeding differing proportions of rumen-degraded protein (RDP) from soybean meal and urea. Diets contained [dry matter (DM) basis] 40% corn silage, 15% alfalfa silage, 28 to 30% high-moisture corn, plus varying levels of ground dry shelled corn, solvent- and lignosulfonate-treated soybean meal, and urea. Proportions of the soybean meals, urea, and dry corn were adjusted such that all diets contained 16.1% crude protein and 10.5% RDP, with urea providing 0, 1.2, 2.4, and 3.7% RDP (DM basis). As urea supplied greater proportions of RDP, there were linear decreases in DM intake, yield of milk, 3.5% fat-corrected milk, fat, protein, and solids-not-fat, and of weight gain. Milk contents of fat, protein, and solids-not-fat were not affected by source of RDP. Replacing soybean meal RDP with urea RDP resulted in several linear responses: increased excretion of urinary urea-N and concentration of milk urea-N, blood urea-N, and ruminal ammonia-N and decreased excretion of fecal N; there was also a trend for increased excretion of total urinary N. A linear increase in neutral detergent fiber (NDF) digestibility, probably due to digestion of NDF-N from lignosulfonate-treated soybean meal, was observed with greater urea intake. Omasal sampling revealed small but significant effects of N source on measured RDP supply, which averaged 11.0% (DM basis) across diets. Increasing the proportion of RDP from urea resulted in linear decrease in omasal flow of dietary nonammonia N (NAN) and microbial NAN and in microbial growth efficiency (microbial NAN/unit of organic matter truly digested in the rumen). These changes were paralleled by large linear reductions in omasal flows of essential, nonessential, and total amino acids. Overall, these results indicated that replacing soybean meal RDP with that from urea reduced yield of milk and milk components, largely because of depressed microbial protein formation in the rumen and that RDP from nonprotein-N sources was not as effective as RDP provided by true protein.     

Effect of fish meal and expeller-processed soybean meal fed to dairy cows receiving bovine somatotropin (sometribove).

Forty-eight multiparous cows were blocked by calving date and milk production and assigned randomly to a TMR formulated to contain 68 or 55% of dietary CP as ruminally degradable CP. Diets contained corn silage, alfalfa haylage, and ground corn. Supplemental CP was soybean meal for the control diet or a combination of soybean meal, expeller-processed soybean meal, and fish meal for the low degradable protein diet. Two 10-wk phases began on d 31 +/- 3 (phase 1) and 110 +/- 7 postpartum [phase 2, all cows received subcutaneous implantations of pelleted (400 mg) bST (sometribove) every 14 d]. Dietary energy, CP, ruminally degradable CP, NDF, and ADF were similar between dietary treatments. Production of FCM increased in response to bST but was not affected by dietary treatment. Cows fed the expeller-processed soybean meal and fish meal TMR produced milk that contained less milk fat in phase 1 and less milk protein content in both phases. The DMI, BW, and body condition scores were not affected by diet. Hematocrit, plasma urea N, albumin, total protein, creatinine, glucose, and serum insulin were similar between dietary treatments. Replacing soybean meal with expeller processed soybean meal and fish meal did not affect ruminal degradation of protein or milk production but decreased milk fat and protein contents.