Influence of Dietary Protein Concentration and Degradability on Milk Production,Composition, and Ruminal Protein Metabolism

Four groups of cows in early lactation, each group containing one mature cow and three cows in first lactation, were in a 4 × 4 Latin-square arrangement of treatments for us to study influences of altering quantity of undegraded dietary crude protein and quantity of crude protein on milk production and composition. Diets supplemented with protein sources were 1) soybean meal positive control (22.7% crude protein), 2) whole cottonseed-corn gluten meal (14.7% crude protein), 3) extruded whole soybean (14.5% crude protein), or 4) soybean meal supplemented (15.7% crude protein). Concentrate and sorghum silage were fed in a ratio of 62:38 dry matter. Dry matter intake was not influenced by dietary crude protein concentration or source. Cows consuming diet 2 produced less milk, milk protein, total solids, and solids-not-fat than cows receiving diets 1 and 4. Efficiency of conversion of dietary crude protein to milk protein was highest for cows receiving diet 3 and lowest for diet 1.Trial 2, a 4 × 4 Latin-square trial for collection of abomasal digesta, had four ruminal and abomasal cannulated steers and the four diets from the lactation trial; the trial was to determine the influence of source and concentrations of protein on quantity of protein reaching the abomasum daily. Crude protein intake by steers fed diet 1 was greater than for the other three diets. Percentages recovery of dietary crude protein were 122 and 130 for treatments 2 and 3, intermediate for treatment 4 (107%), and lowest for diet 1 (88.0%); crude protein digestibility in the total tract was highest for steers receiving diet 1.     

By-Product Feeds for Lactating Dairy Cows: Effects of Cottonseed Hulls,Sunflower Hulls,Corrugated Paper,Peanut Hulls,Sugarcane Bagasse,and Whole Cottonseed with Additives of Fat,Sodium Bicarbonate,and Aspergillus oryzae Product on Milk Production

In Experiment 1, Holstein cows (32) fed diets in three 28-day periods were used to evaluate a 3 × 2 × 2 factorial arrangement of fiber sources (sunflower hulls, pelleted cottonseed hulls, and pelleted undelinted cottonseed hulls at 35% of dry matter), fat (0 or 2.5%). and sodium bicarbonate (0 or 1.0%). Sixteen cows also received Aspergillus oryzae product (56.7 g/day) continuously. Sunflower hulls decreased daily intake (19.4 versus 25.1 kg), milk (23.3 versus 26.5 kg), milk protein (2.85 versus 2.95%), and body weight change (?.08 versus .90 kg), but milk fat percent was higher (3.54 versus 3.32%). Sunflower hulls depressed digestibility of dry matter, organic matter, and acid detergent fiber. Added fat reduced milk fat and protein percents. Experiment 2 evaluated fiber sources (20% ground corrugated cardboard boxes, combination of 10% cardboard and 10% peanut hulls, or 30% cottonseed hulls), animal fat (0 or 2.5%), sodium bicarbonate (0 or .75%), and condensed molasses solubles by-product from rum distilling (0 or 10%). Corrugated boxes effected lowest intake (18.0 kg/day), cottonseed hulls highest intake (23.5 kg/day), and combination intermediate (20.2 kg/day). Added fat depressed fat percent. Condensed molasses solubles lowered milk yield but increased milk fat percent (3.76 versus 3.30), molar percent of acetic acid, and ratio of acetic to propionic. In two other experiments whole cottonseed (12.5 or 15% of dry matter) with corn silage, pelleted steam pressure treated sugarcane bagasse, or cottonseed hulls increased milk yield but decreased milk fat percent, especially with pelleted bagasse.     

Effect of Masonex and Forms of Cottonseed Hulls on Dairy Cows

Thirty-six lactating Holstein cows were in a 5 × 3 factorial partially balanced incomplete block design with three missing categories to study effects of different forms of cottonseed hulls and liquid supplements on milk production and composition. Roughages were regular cottonseed hulls, pelleted cottonseed hulls, pelleted cottonseed hulls with 9% fat, pelleted undelinted cottonseed hulls, and pelleted undelinted cottonseed hulls with 9% fat. Liquid supplements were 8% Masonex² (hemicellulose extract) and 8% cane molasses. Control had no supplement. All rations were adjusted to contain 30% cottonseed hulls. Roughages with added fat gave total rations of 2.5% added fat (air dry).Least square means for daily intake of dry matter, milk yield, and fat percent were regular cottonseed hulls 21.6 kg, 20.3 kg, 3.37%; pelleted cottonseed hulls 20.3 kg, 21.4 kg, 3.06%; pelleted cottonseed hulls plus fat 20.1 kg, 21.2 kg, 2.51%; pelleted undelinted cottonseed plus fat 19.4 kg, 20.9 kg, 2.73%. Pelleted cottonseed hulls increased milk yield, decreased dry matter intake and milk fat percent, but did not affect milk fat yields. Rations with pelleted undelinted cottonseed hulls resulted in higher milk fat percent and body weight than pelleted cottonseed hulls. Added fat decreased milk fat percent and yield because of high degree of unsaturation. Liquid treatments produced no detectable effects on dry matter intake, milk yield, or fat percent.     

Exogenous β-mannanase improves feed conversion efficiency and reduces somatic cell count in dairy cattle

Exogenous fibrolytic enzymes have been shown to be a promising way to improve feed conversion efficiency (FCE). β-Mannanase is an important enzyme digesting the polysaccharide β-mannan in hemicellulose. Supplementation of diets with β-mannanase to improve FCE has been more extensively studied in nonruminants than in ruminants. The objective of this study was to investigate the effects of β-mannanase supplementation on nutrient digestibility, FCE, and nitrogen utilization in lactating Holstein dairy cows. Twelve post-peak-lactation multiparous Holstein cows producing 45.5 ± 6.6 kg/d of milk at 116 ± 19.0 d in milk were randomly allotted to 1 of 3 treatments in a 3 × 3 Latin square design with 3 periods of 18 d (15 d for adaptation plus 3 d for sample collection). All cows were fed the same basal diet and the 3 treatments differed only by the β-mannanase dose: 0% dry matter (DM; control), 0.1% of DM (low supplement, LS), and 0.2% of DM (high supplement, HS) supplemented to the basal diet. Supplementation of β-mannanase enzyme at the LS dose reduced dry matter intake (DMI) but did not affect milk yield or milk composition. Cows receiving LS produced 90 g more milk per kg of DMI compared with control cows. Somatic cell count (SCC) in milk was lower for cows fed the LS diet compared with cows fed control diets. Cows fed LS diet had lower DM, organic matter and crude protein digestibility compared with cows fed control diets. Starch, neutral detergent fiber, and acid detergent fiber digestibility were not affected by LS. Milk yield, DMI, SCC, and nutrient digestibility did not change for HS. Despite the reduced crude protein digestibility, reduced N intake led to similar fecal N excretions in LS cows and control cows (234 vs. 235 g/cow per day). Urinary N excretions remained similar between enzyme-fed and control cows (~190 g/cow per day), although the percentage of N intake partitioned to urinary N tended to be greater in LS than in control cows (31 vs. 27%). Cows fed LS significantly improved the percentage of apparently absorbed N partitioned to milk protein N (42 vs. 38%). When supplemented at 0.1% of dietary DM, β-mannanase can improve FCE and lower the SCC of dairy cows without affecting milk yield, milk composition, or total manure N excretions of dairy cows.     

Formaldehyde Treated Whey Protein Concentrate for Lactating Dairy Cattle

Four lactating Holstein cows were fed isonitrogenous rations of urea-corn silage and a 15% crude protein pelleted grain ration containing whey protein concentrate (34% protein) either untreated or treated with 1% formaldehyde on a protein basis. The trial design was three periods double reversal with 12 days per period during which milk and digestibility were measured the last 4 days of each period. Apparent nitrogen digestibility (%), productive nitrogen retained (milk plus retained, g/day), and dry matter digestibility were 60.0 and 53.9, 89.0 and 103.8, and 67.4 and 63.2 for cows fed untreated and treated rations. Productive nitrogen as a percent of absorbed was greater for cows fed the formaldehyde treated ration, suggesting more efficient utilization of absorbed nitrogen. Milk production, milk fat percent and yield, and 4% fat-corrected milk were greater for cows fed the treated ration. Milk fatty acid content was similar. Total daily milk nitrogen, true protein nitrogen, and casein nitrogen yields were not significantly higher for the treated ration. No differences in serum urea and rumen ammonia were major. Rumen volatile fatty acids were higher in cows fed the untreated rations at 4 and 6 h postfeeding. Differences in serum concentrations of most individual essential amino acids between tail and mammary blood were greater for cows fed the treated ration.     

Relationship between residual feed intake and digestibility for lactating Holstein cows fed high and low starch diets

We determined if differences in digestibility among cows explained variation in residual feed intake (RFI) in 4 crossover design experiments. Lactating Holstein cows (n = 109; 120 ± 30 d in milk; mean ± SD) were fed diets high (HS) or low (LS) in starch. The HS diets were 30% (±1.8%) starch and 27% (±1.2%) neutral detergent fiber (NDF); LS diets were 14% (±2.2%) starch and 40% (±5.3%) NDF. Each experiment consisted of two 28-d treatment periods, with apparent total-tract digestibility measured using indigestible NDF as an internal marker during the last 5 d of each period. Individual cow dry matter (DM) intake and milk yield were recorded daily, body weight was measured 3 to 5 times per week, and milk components were analyzed 2 d/wk. Individual DM intake was regressed on milk energy output, metabolic body weight, body energy gain, and fixed effects of parity, experiment, cohort (a group of cows that received treatments in the same sequence) nested within experiment, and diet nested within cohort and experiment, with the residual being RFI. High RFI cows ate more than expected and were deemed less efficient. Residual feed intake correlated negatively with digestibility of starch for both HS (r = ?0.31) and LS (r = ?0.23) diets, and with digestibilities of DM (r = ?0.30) and NDF (r = ?0.23) for LS diets but was not correlated with DM or NDF digestibility for HS diets. For each cohort within an experiment, cows were classified as high RFI (HRFI; >0.5 SD), medium RFI (MRFI; ±0.5 SD), and low RFI (LRFI; <?0.5 SD). Digestibility of DM was similar (~66%) among HRFI and LRFI for HS diets but greater for LRFI when fed LS diets (64 vs. 62%). For LS diets, digestibility of DM could account for up to 31% of the differences among HRFI and LRFI for apparent diet energy density, as determined from individual cow performance, indicating that digestibility explains some of the between-animal differences for the ability to convert gross energy into net energy. Some of the differences in digestibility between HRFI and LRFI were expected because cows with high RFI eat at a greater multiple of maintenance, and greater intake is associated with increased passage rate and digestibility depression. Based on these data, we conclude that a cow’s digestive ability explains none of the variation in RFI for cows eating high starch diets but 9 to 31% of the variation in RFI when cows are fed low starch diets. Perhaps differences in other metabolic processes, such as tissue turnover, heat production, or others related to maintenance, can account for more variation in RFI than digestibility.     

Varying Protein Content and Nitrogen Solubility for Pluriparous,Lactating Holstein Cows: Lactation Performance and Profitability

Effects on total lactation performance of varying ration crude protein (15.3 vs. 13.6% of dry matter) and nitrogen solubility (35 vs. 45% of total nitrogen) in early lactation was studied using 57 pluriparous Holstein cows. Grain was fed according to production so as to minimize change in body weight throughout lactation. Forages high in nitrogen solubility, corn and grass silages, were fed free-choice. Percent concentrate in ration dry matter was highest (64%) 5 to 8 wk postpartum and lowest (3%) 33 to 44 wk postpartum. Protein and nitrogen solubility were varied by formulating four protein supplements fed as 10% of the grain allocation, so differences in treatments applied narrowed as lactation progressed. Cows fed the medium-protein diets produced 196 kg more milk than those receiving low-protein diets, but their peak daily milk yield was only .6 kg higher. Cows receiving rations with reduced nitrogen solubility produced 347 kg more milk than those fed the higher solubility diets, but their peak daily milk yield was 1.0 kg lower. Income above fed cost for the lactation was highest and postpartum loss in body weight was least for cows receiving medium-protein and low-solubility rations in early lactation, but no differences were significant. Both milk yield (38.3 to 40.6 kg) and total dry matter intake (3.74 to 3.91% body weight) means were maximum 6 to 7 wk postpartum, but lactation performance was not proportional to peak milk yield. When cows are fed to minimize body fat mobilization, response to increased protein in the diet is small. Reducing nitrogen solubility of silage-based diets increased milk produced per unit grain fed. There were no adverse effects of treatments on breeding efficiency or herd health.     

Short communication: Effects of prill size of a palmitic acid–enriched fat supplement on the yield of milk and milk components,and nutrient digestibility of dairy cows

The objective of our experiment was to evaluate the effects of prill size of a palmitic acid–enriched fatty acid supplement (PA; 85% C16:0) on feed intake, nutrient digestibility, and production responses of dairy cows. Twenty-four primiparous and multiparous Holstein cows were assigned based on parity and production level to replicated 4 × 4 Latin squares balanced for carryover effects with 21-d periods. Treatments were a control diet (no added PA), or 2.0% PA added as a small prill size (PA-SM; 284 ± 12.4 µm), a medium prill size (PA-MD; 325 ± 14.7 µm), or a large prill size (PA-LG; 600 ± 17.4 µm) supplement. Overall, PA treatments increased milk fat content (4.25 vs. 3.99%), milk fat yield (1.48 vs. 1.39 kg/d), 3.5% fat-corrected milk (39.2 vs. 37.7 kg/d), and improved feed efficiency (fat-corrected milk:dry matter intake; 1.51 vs. 1.42) compared with control. Compared with control, PA treatments did not affect dry matter intake, body weight, body condition score, or yields of milk, protein, and lactose. The PA treatments increased neutral detergent fiber digestibility (44.8 vs. 42.4%) and reduced the digestibility of 16-carbon fatty acids (72.3 vs. 79.1%) and total fatty acids (76.6 vs. 80.3%). Compared with control, PA treatments reduced the contents of de novo synthesized milk fatty acids (23.0 vs. 25.8 g/100 g of fatty acids) and preformed milk fatty acids (36.3 vs. 39.1 g/100 g of fatty acids), but did not affect their yields. In contrast, PA treatments increased the content (40.8 vs. 35.1 g/100 g of fatty acids) and yield (570 vs. 436 g/d) of 16-carbon milk fatty acids compared with control. The PA prill size had no effect on dry matter intake, yield of milk and milk components, or feed efficiency. However, PA-LG tended to increase milk fat content compared with PA-SM (4.28 vs. 4.22%), and it increased 16-carbon fatty acid digestibility compared with PA-MD (74.2 vs. 71.0%) and PA-SM (74.2 vs. 71.7%). Additionally, PA-LG increased total fatty acid digestibility compared with PA-MD (78.1 vs. 75.6%) and PA-SM (78.1 vs. 76.0%). Results demonstrate that PA increased milk fat content and yield, and feed efficiency. Reducing prill size decreased fatty acid digestibility, but it had no effect on animal performance under the dietary conditions and prill sizes evaluated.     

No Associative Effects Between Corn and Haycrop Silages Fed to Lactating Dairy Cows

Four first-lactation Holstein cows were used 65 to 177 days postpartum in a 4 × 4 Latin square trial to evaluate possible associative feeding effects between corn and haycrop silages. Nutrient digestibility and nitrogen and energy balances were studied. Diets were concentrate mixture, urea-treated corn silage, and early-cut, wilted haycrop silage in dry matter ratios of 55:45:0, 55:30:15, 55:15:30, and 55:0:45. Rations were offered just below energy balance in each 28-day period. Ration components were fed separately, concurrently, and twice daily. Crude protein in concentrate, corn silage, and hay crop silage dry matter was 16.9, 11.1, and 12.5%. Milk yield (18 to 19 kg) and ration dry matter intake (2.61% body weight) were not significantly different among diets. Apparent digestibility of gross energy, dry matter, protein, and fiber was not different among diets, but fat was more digestible in corn silage. Partition of ingested energy and nitrogen was not affected by treatments except that urine nitrogen was higher in corn silage. No associative feeding effects were significant. The two silages were equivalent in supporting milk production when fed in equal dry matter amounts.     

Forage Growth and Performance of Grazing Dairy Cows Fed Concentrates with or Without Sodium Bicarbonate

Groups of 12 and 13 Holstein cows grazed rotarionally on mixtures of grasses and red clover. Cows were 28 to 150 days into lactation at start of the experiment. They were fed concentrate at 1 kg/3 kg of 4% fat-corrected milk with or without 1.9% sodium bicarbonate in a switchover trial of two 8-wk periods. Forage growth and composition, amounts available for grazing, and average intake were measured by subsamples clipped prior to and after each grazing and by use of cages placed in the field. Milk yields averaged 29.9 kg daily by cows on each treatment. Milk fat percentage decreased moderately when cows first went to pasture but were not different during the trial at 3.24 and 3.27% on control and buffer treatments. Milk protein percentages, proportions of ruminal volatile fatty acids, and body weight gains did not differ with treatment. Available forage exceeded 17 kg dry matter per cow daily. It was of good quality, as indicated by crude protein contents of 19 and 22%, acid detergent fiber less than 35%, and 67 to 70% in vitro digestibility. Average intake of forage dry matter, measured by the sward cutting technique, was 12.6 kg per cow daily over the 16 wk.     

Effects of Feeding Synthetic Zeolite A and Sodium Bicarbonate on Milk Production Nutrient Digestion,and Rate of Digesta Passage in Dairy Cows

Four rumen-cannulated Holstein cows were fed synthetic zeolite A and NaHCO₃ to evaluate their affect on milk production, nutrient digestibility, rumen fermentation, and rate of digesta passage. Treatments were allocated in a 2 × 2 factorial arrangement within a 4 × 4 Latin-square design. Treatments consisted of control; 1.0% NaHCO₃; 2.0% zeolite; and 1.0% NaHCO₃ plus 2.0% zeolite. A total mixed ration with 50:50 concentrate to forage (80% corn silage, 20% haylage) DM was fed.Intake of DM was lower for cows receiving zeolite (18.7 vs. 20.7 kg/d). Decreases were noted in daily milk (26.3 vs. 28.9 kg/d). 4% FCM (23.6 vs. 25.6 kg/d); milk fat yield (.86 vs. .93 kg/d); milk protein yield (.85 vs. .95 kg/d); and milk protein percent (3.21 vs. 3.34) with zeolite. Digestibilities of DM, organic matter, and crude protein were also decreased by zeolite but ADF digestion was unaffected. Rumen pH was increased, ruminal propionate decreased, and acetate:propionate ratio increased by zeolite. All other VFA plus rumen NH₃ were not affected by treatment. Decreases due to zeolite were observed in liquid fractional rate of passage and liquid flow rate when measured by Cr-EDTA in the feces. No treatment differences were found in fractional rate of passage of feed particles. Addition of NaHCO₃ had no significant effects.     

The effects of feeding rations that differ in fiber and fermentable starch within a day on milk production and the daily rhythm of feed intake and plasma hormones and metabolites in dairy cows

A daily pattern of feed intake, milk synthesis, and plasma metabolites and hormones occurs in dairy cows fed a total mixed ration once or twice a day. The objective of this study was to determine if feeding multiple rations within a day, complementing these rhythms, would improve milk production. Twelve Holstein cows were used in a replicated 3 × 3 Latin square design with 21-d periods. Cows were housed in tie stalls with feed tubs, and feed weight was recorded every 10 s for observation of feeding behavior. Rations were a low fiber and high fermentable starch ration [LFHS; 27.4% neutral detergent fiber (NDF) and 31.7% starch based on 55.7% corn silage and 14.1% steam-flaked corn], a high fiber and low fermentable starch ration (HFLS; 31.7% NDF and 22.3% starch based on 44% corn silage, 26.3% alfalfa haylage, and no steam-flaked corn), and a total mixed ration that was a 1:3 ratio of LFHS and HFLS (30.7% NDF, 24.5% starch). The control treatment (CON) cows were fed the total mixed ration at 0700 h, the high/low treatment (HL) fed HFLS ration at 0700 h and LFHS ration at 2200 h, and the low/high (LH) treatment fed LFHS ration at 0700 h and HFLS ration at 1100 h (LFHS and HFLS rations fed at a 1:3 ratio). No effect was found of treatment on daily milk, but LH decreased milk fat concentration and yield compared with HL (0.2 percentage units and 0.24 kg, respectively). Daily dry matter and NDF intake and total-tract digestibility did not differ between treatments. The HL treatment reduced intake at the morning-conditioned meal after feeding and reduced intake before the evening feeding. A treatment by time of day interaction was found for fecal NDF and indigestible NDF concentration, blood urea nitrogen (BUN), plasma insulin, and fatty acid concentration, and body temperature. The CON and LH treatments increased the daily amplitude of fecal NDF by 1.0 and 1.1 percentage units compared with HL. Plasma insulin was higher in HL than CON at 0100 and 0400 h, but lower at 1300 and 1900 h. Plasma fatty acids were higher for CON than HL at 0700 h and HL was lower than LH at 0400 and 1900 h. Plasma BUN was higher for HL than control at 0100 h, but lower at 1000 h. Body temperature in CON and HL treatments followed a similar diurnal pattern, whereas body temperature for LH was lower than that of HL treatment at 1300 and 2300 h. No daily rhythm was found of fecal indigestible NDF concentration, plasma glucose, or fatty acids detected in the HL treatment, and the amplitude of plasma insulin and BUN was lower for HL compared with CON (70 and 60% decrease, respectively). In conclusion, feeding 2 rations that differ in fiber and fermentable starch modifies diurnal rhythms in dairy cows. Furthermore, feeding a high fiber and low fermentable starch ration during the high intake period of the day may stabilize nutrient absorption across the day.     

Eating Rate of Lactating Cows Fed Four Physical Forms of the Same Grain Ration

Eleven cows in midlactation were fed grain rations in pelleted (.4 cm diameter), coarse (premix pellet with cracked corn), Ett® (crumbled pellet), or meal forms. Eating rate was measured during morning feedings for 5 consecutive days following a 2-day adjustment. Eating rate was computed by 4-min intervals during the 28-min eating period. Fat-corrected milk production, intake of corn silage, and of alfalfa hay averaged 19.3, 15.1, and 3.4 kg per day for all cows. Differences of ration intake were greatest during the first 8 min. Rate of eating was most rapid for the pelleted ration followed by coarse, Ett®, and meal forms. Total 28-min intake paralleled intake during initial 8 to 12 min. Physical form influenced ration intake initially when eating time was limited. Subsequent intake reduction probably is related to physiological feedback which also may be affected by physical form of the ration.     

Phenobarbital metabolism in the lactating dairy cow

Two Holstein cows were used to study the metabolism and excretion of phenobarbital in the lactating cow. Each cow received 6 g of sodium phenobarbital, intrarumenally, daily for 10 days. On the 10th day carbon 14 phenobarbital was mixed with the unlabeled material prior to dosing. Total milk, urine, and feces were collected for 6 days, and about 93% of the recovered radioactivity was in urine, 5% in milk, and 2% in feces. The biological half-lives of phenobarbital for milk, urine, and feces were 40.5, 29.5, and 46.5 h. From these values we calculated that 7 days after the last 6-g dose of phenobarbital the milk produced would contain less than .5 ppm of this compound.A second study determined how long after withdrawal from phenobarbital feeding the drug could be detected in milk. Three Holstein cows received 6 g of sodium phenobarbital, intrarumenally, daily for 10 days. Starting on the 11th day milk samples were collected at each milking and analyzed for phenobarbital by gas liquid chromatography and spectrophotometrically. After 7 days withdrawal, phenobarbital could not be detected in milk by either method.     

Role of Exogenous Oxytocin in Eliciting Milk Ejection in Dairy Cows

The efficacy of small doses of exogenous oxytocin in eliciting milk ejection was measured in eight lactating Holstein cows. Treatments comprised intravenous administration of .02, .05, .10, and .30 IU of oxytocin. The smallest dose of oxytocin that induced milk ejection in all cows was .10 IU. Administration of .10 and .30 IU produced greater peak rates of milk flow and shorter milking times. Ranges for these two variables were 2.9 to 3.9 kg/min and 4.8 to 5.6 min. Variations in milk yield (8.2 to 9.1 kg/milking) were not significant, but more fat was harvested after administration of the two higher doses. Differences in peak concentrations of serum oxytocin were 17.7 to 21.2 μU/ml. Differences in latent time before peak concentration was reached were 1.3 to 4.0 min.     

Effect of Feeding Frequency on Diurnal Dry Matter and Water Consumption,Liquid Dilution Rate,and Milk Yield in First Lactation

Four ruminally cannulated cows in first lactation (50 days postpartum) were assigned randomly to a 4 × 4 Latin square with the following feeding frequencies of the same total mixed ration: one, two, four, and eight times a day. Dry matter intake, water consumption, and ruminal pH were recorded hourly during 4-d collection (10-d adaptation between periods, Experiment 1). In Experiment 2, 30 animals were blocked by milk production on wk 4 postpartum and assigned to feeding one or four times a day through wk 19 postpartum. Individual feed consumption and milk production were recorded daily.Hourly consumption patterns of dry matter and water were variable over 24 h; once daily feeding tended to be more variable than other frequencies. Cows fed four times a day had higher ruminal liquid dilution rates than those fed eight times; feeding once and twice a day was not different from either. In Experiment 2, frequency of feeding total mixed ration had no significant influence on dry matter intake or milk yield; however, cows fed four times a day exhibited a consistent weekly tendency to be lower in dry matter intake and higher in milk yield than those fed once daily. Efficiency of fat-corrected milk production was slightly higher for cows fed four times than for those fed once daily.     

Supplemental Niacin for Lactating Cows Fed Diets of Natural Protein or Nonprotein Nitrogen

Thirty-two Holstein cows, 16 in early and 16 in midlactation, were assigned to four treatments: 1) soybean meal protein plus niacin; 2) soybean meal without niacin; 3) nonprotein nitrogen plus niacin; and 4) nonprotein nitrogen without niacin. Niacin dose was 6 g per day, and nonprotein nitrogen supplied 20% of total nitrogen for those treatments. Differences between treatments in milk yields were not significant, but milk persistencies tended to be highest for cows in early lactation fed niacin during wk 9 and 10 of treatment. Intakes of dry matter did not differ significantly, but cows fed nonprotein nitrogen without niacin had lowest intakes per 100 kg bodyweight. Differences between treatments in feed utilization, milk composition, bodyweight changes, plasma ammonia, rumen pH, rumen volatile fatty acids, dry matter digestibilities, nitrogen digestibilities, and retained nitrogen were not significant.     

Interaction of protein percent with caloric density and protein source for lactating cows

Experiment 1 was to test effect of three ratios of energy to protein in complete mixed diets for 36 lactating cows in three, 28-d periods. Energy was varied with cottonseed hulls, pelleted ground corrugated boxes, and a mixture of the two. Crude protein was varied with soybean meal to give energy:crude protein of 5.7, 5.0, and 4.6 for each energy amount. Cottonseed meal was compared with soybean meal in corrugated box diets. Feed intake was much higher with cottonseed hulls, and appreciable feedlot bloat resulted from pelleted ground corrugated box diets. Data adjusted to equal feed intake showed significant effect of energy to crude protein ratio on milk yield and improved digestion of organic matter with soybean meal vs. cottonseed meal. Experiment 2 tested the hypothesis that lactating cows consuming high-protein alfalfa may benefit from supplemental protein. Diets were 50% forage. Six diets were 14 or 18% crude protein in three ratios of alfalfa hay to corn silage (0:100, 50:50, 100:0). Additional corn silage diets were to compare: 14 versus 18% protein from distiller's dried grains with solubles only and with .5 or .9% urea (four diets); two 14% protein diets compared .6% added potassium chloride with or without .5% urea. Thirty-six Holstein cows in early lactation received one of the 12 diets in each of three 28-d periods. Distiller's grains with solubles markedly depressed milk yield (2.2 kg/d) and milk protein (.22%); heat damage of distiller's grains was evident. Protein interacted with alfalfa so gain in milk from 18 versus 14% increased from .55 to 1.36 to 2.66 kg/d as alfalfa changed from 0 to 50 to 100%. Thus, crude protein of alfalfa was not as effective as that from soybean meal in supporting milk yield.     

Effect of dry period length on milk yield over multiple lactations

Shortening or omitting the dry period (DP) can improve the energy balance of dairy cows in early lactation through a decrease in milk yield after calving. Little is known about the effect of a short or no DP on milk yield over multiple lactations. Our objectives were (1) to assess the effect of DP length over multiple lactations on milk yield, and (2) to assess if the prediction of milk yield in response to DP length could be improved by including individual cow characteristics before calving. Lactation data (2007 to 2015) of 16 Dutch dairy farms that apply no or short DP were used to compute cumulative milk yield in the 60 d before calving (additional yield) and in the 305 d after calving (305-d yield), and the mean daily yield over the interval from 60 d before calving to 60 d before next calving (effective lactation yield). The DP categories were no (0 to 2 wk), short (3 to 5 wk), standard (6 to 8 wk), and long (9 to 12 wk). The effect of current DP and previous DP on yields was analyzed with mixed models (n = 1,420 lactations). The highest effective lactation yield of fat- and protein-corrected milk (FPCM) was observed for cows with a standard current DP (27.6 kg per day); a daily decrease was observed of 0.6 kg for a long DP, 1.0 kg for a short DP, and 2.0 kg for no DP. Previous DP did not significantly affect the effective lactation yield. Thus, cows can be managed with short or no DP over consecutive lactations without a change in quantity of milk losses. Cows that received no DP for consecutive lactations had a lower additional yield before calving (?172 kg of FPCM), but a higher 305-d yield (+560 kg of FPCM), compared with cows that received no DP for the first time. This could lessen the improvement of the energy balance in early lactation when no DP is applied a second time compared with the first time. For the second objective, a basic model was explored to predict effective lactation yield based on parity, DP length, and first-parity 305-d yield (n = 2,866 lactations). The basic model was subsequently extended with data about recent yield, days open, and somatic cell count. Extending the model reduced the error of individual predictions by only 6%. Therefore, the basic model seems sufficient to predict the effect of DP length on effective lactation yield. Other individual cow characteristics can still be relevant, however, to make a practical and tailored decision about DP length.     

Response of High Producing Dairy Cows in Early Lactation to the Feeding of Heat-Treated Whole Soybeans

Fifty-eight multiparous cows were assigned randomly to one of two rations. Control cows received a concentrate mixture that contained 20% soybean meal as the protein supplement, and the experimental cows were fed a concentrate that contained 25% heat-treated whole soybeans. The experimental period started 10 d after calving and continued for 15 wk.Experimental cows peaked later in milk production (5 vs. 3 wk) but at a higher level (39.8 vs. 39.4 kg/d) than control cows. Although milk production was less during the first 4 wk, experimental cows surpassed the controls in wk 5 and increased the advantage to 2.0 kg/cow/d by wk 15. For the total 15-wk period, average milk production was 37.0 kg/d for the experimental cows compared with 36.2 kg/d for the controls.Total dry matter intake, lactation efficiency, body weight, and reproductive performance were similar for both treatments. Cows fed heated soybeans consumed more metabolizable energy, 61.6 vs. 60.4 Mcal/d for controls. Cows on experimental diet also had higher free fatty acids in plasma (5.6 vs. 4.8 mg/100 ml) and triglycerides (25.0 vs. 20.9 mg/100 ml). The acetate-to-propionate ratio of rumen acids was significantly lower in the experimental group (3.36 vs. 3.61).