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.     

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.     

Influence of Pelleting Whole Cottonseed on Ration Digestibility and Milk Production and Composition

Two trials were conducted to determine the effect of pelleting whole cottonseed on milk production and composition and ration digestibility. In trial 1, four multiparous Holstein cows were paired by production and used in a 2 × 2 reversal design with 37-d experimental periods. Cow receiving pelleted cottonseed produced 35.12 kg/d milk and 31.74 kg/d of 4% fat corrected milk as compared with 33.41 and 29.83 for cows receiving whole cottonseed. There were no significant differences in dry matter intake or milk composition between treatments. Yield of total solids and lactose was greater for cows receiving pelleted cottonseed as compared with whole cottonseed. Apparent digestibility coefficients for dry matter, gross energy, and crude protein were not different due to pelleting.In trial 2, four ruminal and abomasally cannulated Holstein steers were paired in a 2 × 2 reversal design and fed either pelleted on whole cottonseed for 10 d followed by a 7-d collection. Steers receiving the pelleted cottonseed had higher intakes of gross energy and crude protein. There were greater amounts of total crude protein and crude protein in the particulate phase of abomasal digesta from steers receiving pelleted cottonseed as compared with whole cottonseed. Apparent digestibility for crude protein for the whole tract was not different due to treatment.     

The effect of supplemental concentrate fed during the dry period on morphological and functional aspects of rumen adaptation in dairy cattle during the dry period and early lactation

Ten rumen-cannulated Holstein-Friesian cows were used to examine the effect of feeding supplemental concentrate during the dry period on rumen papillae morphology and fractional absorption rate (k_a) of volatile fatty acids (VFA) during the dry period and subsequent lactation. Treatment consisted of supplemental concentrate [3.0 kg of dry matter (DM)/d] from 28 d antepartum (ap) until the day of calving, whereas control did not receive supplemental concentrate. Cows were fed for ad libitum intake and had free access to the dry period ration (27% grass silage, 28% corn silage, 35% wheat straw, and 11% soybean meal on a DM basis) and, from calving onward, to a basal lactation ration (42% grass silage, 42% corn silage, and 16% soybean meal on a DM basis). From 1 to 3 d postpartum (pp), all cows were fed 0.9 kg DM/d of concentrate, which increased linearly thereafter to 8.9 kg of DM/d on d 11 pp. At 28, 18, and 8 d ap, and 3, 17, 31, and 45 d pp, rumen papillae were collected and k_aVFA was measured in all cows. On average, 13.8 (standard deviation: 3.8) papillae were collected each from the ventral, caudodorsal, and caudoventral rumen sacs per cow per day. The k_aVFA was measured by incubating a standardized buffer fluid (45 L), containing 120 mM VFA (60% acetic, 25% propionic, and 15% butyric acid) and Co-EDTA as fluid passage marker, in the evacuated and washed rumen. Treatment did not affect ap or pp DM and energy intakes or milk yield and composition. Treatment increased papillae surface area, which was 19 and 29% larger at 18 and 8 d ap compared with 28 d ap, respectively. Surface area increased, mainly due to an increase in papillae width. However, treatment did not increase k_aVFA at 18 and 8 d ap compared with 28 d ap. In the control group, no changes in papillae surface area or k_aVFA were observed during the dry period. In the treatment group, papillae surface area decreased between 8 d ap and 3 d pp, whereas no decrease was observed for control. From 3 to 45 d pp, papillae surface area and k_aVFA increased for all cows by approximately 50%, but the ap concentrate treatment did not affect k_aVFA pp. In conclusion, the efficacy of supplemental concentrate during the dry period to increase papillae surface area and k_aVFA in preparation for subsequent lactation is not supported by the present study. Current observations underline the importance of functional measurements in lieu of morphological measurements to assess changes in the adapting rumen wall.     

Brown Midrib Corn Silage in Dairy Cattle Rations,

Two groups of 12 Holstein cows past peak lactation were fed complete mixed diets containing either brown midrib corn silage or its normal genetic counterpart. All cows were fed a standardization ration containing another corn silage prior to and after the experimental period. Performance during the experimental period was expressed as deviation from standardization. Cows fed brown midrib silage produced .66 kg more milk per day that tested .28 percentage units less fat during the 4-wk experimental period than during standardization. Control cows produced .10 kg more milk per day in the experimental period as compared to standardization without difference in fat test. On a fat-corrected basis (4%) there was no difference in milk yield between treatments.     

Feeding Value of Dry Corn,Ensiled High Moisture Corn,and Propionic Acid Treated High Moisture Corn Fed with Hay or Haylage for Lactating Dairy Cows

Trial 1. Fifty lactating Holstein and Brown Swiss cows were assigned to six groups in a 3 × 2 factorial design and fed one of six diets for 16 wk: (1) dry corn + hay, (2) dry corn + haylage, (3) ensiled high moisture corn + hay, (4) ensiled high moisture corn + haylage, (5) propionic acid treated corn + hay, and (6) propionic acid treated corn + haylage. Quantities equal in dry matter of dry corn, ensiled corn, and acid treated corn were offered in the ratio of 1 kg concentrate (corn and supplement) for each 2.75 kg milk produced. Forage was fed free choice. Means adjusted by covariance for cows fed diets 1 to 6 averaged: dry matter intake (kg/day), 16.7, 20.0, 17.4, 20.6, 17.1, 20.0; 4% fat-corrected milk (kg/day), 21.8, 21.1, 22.6, 23.5, 22.4, 23.4; milk fat percent, 3.54, 3.45, 3.63, 3.53, 3.62, 3.80; and acetate to propionate ratio 3.53, 3.85, 3.73, 3.66, 3.13, 3.32. Cows fed ensiled corn and acid treated corn produced more 4% fat-corrected milk than did cows fed dry corn. The molar percent acetate to propionate ratio in rumen fluid of cows fed acid treated corn was lower than for cows fed dry corn or ensiled corn.Trial 2. Dry corn or propionic acid treated corn was fed to 12 cows in combination with a supplement, 4.54 kg of hay, and ad libitum haylage. Means adjusted by covariance for cows fed dry corn and acid treated corn averaged: dry matter intake (kg/day), 18.2 and 17.7; 4% fat-corrected milk (kg/day), 20.6 and 20.1; and total digestible nutrients (%) 63.7 and 58.7.Any of these methods are acceptable for storing corn, and feeding this corn in properly supplemented diets will yield acceptable lactation performance.     

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.     

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.     

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.     

Urea on Flaked Soybean Hulls as a Protein Replacement for Dairy Cows

In Experiment I a Latin square design was used to study the utilization of urea nitrogen adsorbed on flaked soybean hulls in normal rations of high producing dairy cows. Concentrates containing urea, urea with supplemental minerals, or soybean meal as the protein supplement were fed with corn silage and alfalfa in a total ration of approximately 17% crude protein. Both urea concentrates contained 2.7% urea. Animals fed urea and soybean had similar milk yields (28.7 and 27.9 kg/day), milk protein, and digestible dry matter intakes. Urea with mineral produced lower milk yield (25.3 kg/day), milk protein, and dry matter intakes, probably because of excessive mineral content. Urea nitrogen of plasma was similar for all three diets. Essential amino acids of plasma were lower for urea than for soybean while for urea mineral the essential amino acids were midway between the other two. In Experiment 2 a switchback design was used to compare the urea-soybean hull concentrate diet of Experiment 1 (17% crude protein) to a negative control diet consisting of its basal components without urea adjusted to 12% protein with wheat bran. Milk yield was 1.2 kg/day higher when the urea diet was fed. Perhaps due to improved urea distribution in the rumen, flaked soybean hulls with urea were effective in maintaining the feed intake necessary for high milk production.     

Alfalfa Silage or Hay Versus Corn Silage as the Sole Forage for Lactating Dairy Cows

In Trial 1, three rations were fed to 21 cows in a 3 × 3 Latin square: 60% alfalfa silage, 60% corn silage, and 79% corn silage (dry matter basis) with the balance from corn and soybean meal. Acid detergent fiber measures indicated alfalfa and corn silage were of excellent quality. Milk production was similar on 60% forage rations but lower on 79% corn silage. Milk fat was reduced on 60% corn silage. In Trial 2, four rations were fed to 16 cows in a 4 × 4 Latin square: 63% alfalfa silage, 60% alfalfa hay, 60% corn silage, and 76% corn silage. Alfalfa forages were higher in acid detergent fiber but corn silage was similar to Trial 1. Dry matter digestibility was highest on 60% corn silage, intermediate on 63% alfalfa silage and 76% corn silage, and lowest on 60% alfalfa hay. Milk production was similar on the diets containing 60 and 63% forage and lower on 76% corn silage. Milk protein concentration was reduced on the alfalfa diets. Highest protein secretion and feed conversion was supported by 60% corn silage. In both trials, potentially digestible neutral detergent fiber from alfalfa was more digestible than that from corn silage, and concentrations of urea in milk and blood were highly correlated. Results indicate high quality alfalfa silage is comparable to corn silage for milk production.     

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.     

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).     

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.     

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.     

Short communication: Temporal effect of feeding potassium carbonate sesquihydrate on milk fat in lactating dairy cows fed a fat-depressing diet

A lactation study with 10 multiparous dairy cows in early lactation, with an average of 64 days in milk (standard deviation = 37), were used to evaluate how quickly milk fat concentration would change when potassium carbonate sesquihydrate was abruptly added to the diet. The experiment had 3 periods. In period 1 (d 0 to 7) all cows were fed the same basal (control) diet with 1.8% soy oil, dry basis; in period 2 (d 8 to 28) 5 cows received the control diet, whereas the other 5 cows received the control diet plus 0.59% of added K with K carbonate sesquihydrate; and in period 3 (d 29 to 42) all 10 cows received the control diet. The control diet was formulated for a dietary cation-anion difference (DCAD), calculated as Na + K ? Cl ? S, of 37.7 mEq/100 g of dry matter (DM), 1.74% of DM as K, and 5.7% long-chain fatty acids (DM%), which included 1.8% of DM as soybean oil. Period 1 was used as a covariate. In period 2, d 8 to 28, 5 cows remained on the control diet whereas 5 cows were fed with the control diet plus K carbonate sesquihydrate (DCAD+ diet; DCAD of 54.3 mEq/100 g DM and 2.33% of DM as K). After feeding the DCAD+ diet, we noted a difference in milk fat concentration from 3.9 to 4.3% within 72 h. Over the 21 d of period 2, the DCAD+ diet resulted in significantly greater milk fat percentage from 4.0 to 4.3%, lactose from 4.74 to 4.82%, and fat efficiency in the form of fat in milk divided by fat in DMI from 1.27 to 1.49, without affecting dry matter intake (DMI), milk protein concentration, solids-not fat concentration, 3.5% fat-corrected milk, and protein efficiency in the form of protein in milk divided by protein in DMI. In period 3 (d 29–42), all cows were again fed the control diet, resulting in a tendency for greater milk fat concentration, significantly greater lactose concentration, and fat efficiency in the form of fat in milk divided by fat in DMI for the cows having received the DCAD+ diet during period 2. In conclusion, the abrupt addition of K carbonate sesquihydrate resulted in a greater milk fat concentration and tended to maintain the greater concentration after cessation of K carbonate sesquihydrate feeding.     

Dry Matter Intake in Dairy Heifers. 1. Factors Affecting Intake of Heifers under Intensive Management

Effects of body weight, body weight gain, ration acid detergent fiber, neutral detergent fiber, bulk density, and ambient temperature on intake of dry matter and digestible energy were examined using 118 Holstein heifers weighing 100 to 400 kg. Animals grouped according to body weight (100, 200, 300 kg) were fed total mixed rations (corn silage, ground hay, high moisture corn, soybean meal) once daily for 28 d. Rations were balanced to mean body weight according to National Research Council recommendations for protein, vitamins, and minerals and to 85, 95, 105, and 115% of recommended total digestible nutrients. Second order polynomial regression of ration fiber content and density explained 20 and 21% of variation in dry matter intake and 46 and 45% of digestible energy intake. Dry matter intake increased linearly with increasing body weight and gain. Dry matter intake correlated −.42, −.42, and .39 with acid detergent fiber, neutral detergent fiber, and bulk density when neutral detergent fiber was greater than 42% of dry matter and .03, −.03, and −.02 when less than 42%. Predictions of dry matter intake should include body weight, gain, and polynomial terms of ration fiber or ration energy to account for changing metabolic systems controlling intake.     

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.     

Effect of acarbose on milk yield and composition in early-lactation dairy cattle fed a ration to induce subacute ruminal acidosis

Subacute ruminal acidosis reduces lactation performance in dairy cattle and most often occurs in animals fed a high concentrate:forage ration with large amounts of readily fermentable starch, which results in increased production of volatile fatty acids and lactic acid and a reduction in ruminal pH. Acarbose is commercially available (Glucobay, Bayer, Wuppertal, Germany) and indicated for the control of blood glucose in diabetic patients. In cattle, acarbose acts as an α-amylase and glucosidase inhibitor that slows the rate of degradation of starch to glucose, thereby reducing the rate of volatile fatty acid production and maintaining rumen pH at higher levels. The ability of acarbose to reverse the reduced feed intake and milk fat percentage and yield associated with a high concentrate:forage ration with a high risk of inducing subacute ruminal acidosis was evaluated in 2 experiments with lactating dairy cattle. In 2 preliminary experiments, the effects of a 70:30 concentrate:forage ration on ruminal pH and lactation were evaluated. Ruminal pH was monitored in 5 Holstein steers with ruminal cannulas every 10 min for 5 d. Ruminal pH was <5.5 for at least 4 h in 79% of the animal days. In dairy cows, the 70:30 concentrate:forage ration decreased feed intake 5%, milk fat percentage 7%, and milk fat yield 8% compared with a 50:50 concentrate:forage ration but did not affect milk yield. Early lactating dairy cattle were offered the 70:30 concentrate:forage ration with 0 or 0.75 g/d of acarbose added in a crossover design in 2 experiments. In the first experiment, acarbose increased dry matter feed intake (23.1 vs. 21.6 kg/d) and 3.5% fat-corrected milk yield (33.7 vs. 31.7 kg/d) because of an increase in percentage milk fat (3.33 vs. 3.04%) compared with control cows. In the second experiment, cows were fasted for 3 h before the morning feeding to induce consumption of a large meal to mimic conditions that might be associated with unplanned delayed feeding. In this experiment, acarbose also increased feed intake (22.5 vs. 21.8 kg/d) and 3.5% fat-corrected milk yield (36.9 vs. 33.9 kg/d) due to increased percentage milk fat (3.14 vs. 2.66%) compared with controls. Thus, acarbose reversed the decreased feed intake and low milk fat percentage and yield associated with feeding a high concentrate:forage ration shown to induce subacute ruminal acidosis in Holstein steers.