Forage Growth and Performance of Grazing Dairy Cows Supplemented with Concentrate and Chopped or Long Hay

Holstein and Brown Swiss cows were in three groups of eight in a 3 × 3 Latin square design with 4-wk periods. Cows averaged 88 d in lactation at start of trial. All cows simultaneously grazed grass and clover pastures on a rotational basis. Supplement treatments were concentrate (A), concentrate with 10% added chopped hay (B), and concentrate plus 1 kg long hay/cow daily (C). Concentrate was offered at 1 kg/3 kg 4% fat-corrected milk to cows on A and C, and 1 kg/2.7 kg to those on B. Forage growth, amounts available for grazing, and average dry matter intake were measured by clipping subsamples prior to and after each grazing and by use of cages placed in the field.Milk yields and milk fat percentages were 27.1, 3.34; 27.9, 3.32; and 28.3, 3.20 for treatments A, B, and C, respectively. Differences between A and C were significant. Milk fat percentage decreased moderately when cows first went to pasture.There were no treatment differences in fat yield, milk protein percentage, yield of fat-corrected milk, rumen fluid composition, or body weight gain.Available forage per cow exceeded 22 kg dry matter/cow daily except during one 10-d period toward the end of the trial when it amounted to 16.6 kg. Intake of dry matter from pasturage, measured by the sward cutting technique, averaged 14.5 kg./cow daily over the 12 wk.     

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.     

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.     

Lactational and Systemic Responses to the Supplementation of Protected Methionine in Soybean Meal Diets

Twenty-seven Holstein cows (14 primiparous and 13 multiparous) were randomly assigned to diets containing soybean meal without or with 15 g of added DL-methionine daily, provided as 50 g of ruminally protected methionine product, during wk 4 through 16 postpartum. Cows were fed a 15.3% crude protein total mixed diet of (dry matter basis) 30% corn silage, 15% alfalfa hay, and 55% concentrate mix. Yields of milk (32.9 and 35.2 kg/d), 4% fat-corrected milk (27.8 and 29.5 kg/d), and solids-corrected milk (28.5 and 30.1 kg/d) were higher for cows fed supplemental methionine. Milk protein percentage (2.99 and 3.06) was increased with supplemental methionine, while the percentage of fat (2.96 and 3.00), solids-not-fat (8.69 and 8.73), and total solids (11.67 and 11.71) were similar among diets. Dry matter intake (19.3 and 21.3 kg/d) was higher with methionine supplementation. Ruminal pH, volatile fatty acids, ammonia, and serum urea were generally unaffected by methionine supplementation. Concentrations of methionine in arterial and venous serum were elevated slightly by methionine supplementation, but the first-limiting amino acid for milk production, as calculated by several methods, was not changed.     

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.     

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.     

Protected Methionine and Heat-Treated Soybean Meal for High Producing Dairy Cows

Twenty-four high producing Holstein cows (14 primiparous and 10 multiparous) were fed concentrate mix containing heat-treated soybean meal without or with 15 g of added DL-methionine daily provided as 50 g of ruminally protected methionine product during wk 4 through 16 postpartum. The 15% crude protein mixed diets contained 30% (dry matter basis) corn silage, 15% alfalfa hay, and 55% concentrate mix. Covariant adjusted yields of milk (34.6 and 33.1 kg/d), 4% fat-corrected milk (28.4 and 27.6 kg/d), and solids-corrected milk (29.0 and 28.5 kg/d) were not increased by feeding supplemental methionine. Percentages of fat (2.81 and 2.92) and protein (2.88 and 2.92) were similar, whereas total solids (11.49 and 12.69) and solids-not-fat (8.68 and 8.77) were higher with supplemental methionine. Dry matter intakes (20.2 and 21.0 kg/d) were higher when cows were fed supplemental methionine. Ruminal pH, volatile fatty acids, and ammonia as well as blood serum urea and glucose were generally unaffected by methionine supplementation. Concentrations of methionine in arterial and venous plasma were elevated slightly when additional methionine was fed. The first-limiting amino acid for milk production, methionine, was calculated by several methods and was not changed by feeding supplemental ruminally protected methionine.     

Response by Dairy Cows to Hay Supplement with Early Spring Grazing or to Delay in Turning to Pasture

Effects of moving cows from winter feeding to pasture at two stages of plant maturity and of supplementing long hay were observed. Holsteins were assigned to groups of seven as: A, moved to early pasture on May 2; B, same as A except supplemented with 2.7 kg long hay dry matter per cow daily; and C, retained on barn feeding until moved to mature pasture on May 23. Groups A and B were observed on pasture for 6 wk and group C for 3 wk. Concentrate was fed according to production. Dry matter intake as pasture was 16.6 and 15.8 kg per cow daily by groups A and B, respectively. Milk yield and milk protein percentage increased and milk fat percentage decreased when groups A and B went to pasture. Group C declined in milk yield and milk protein percentage compared with group A. Plasma stearic and linoleic acids were higher and oleic acid was lower in group B than in A. Plasma linolenic acid was lower in group C than in group A. There were no differences in rumen fluid composition or pH. The decline in milk fat content when cows were moved from indoor feeding to immature pasture appeared unrelated to inadequate dietary fiber or low ratio of acetate to propionate in rumen fluid.     

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.     

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.     

Influence of Pecan Shells and Hulls as a Roughage Source on Milk Production,Rumen Fermentation,and Digestion in Ruminants,

In Experiment 1, 20 lambs (36 kg) were fed five diets containing 0, 5, or 10% pecan shells or hulls to evaluate digestion and nitrogen balance. Digestion was not depressed by diets containing 5% shells. Protein digestibility was not reduced and nitrogen balance was higher for lambs fed 5% hulls than for lambs in other groups. In Experiment 2, 8 Holstein cows (29.3 kg milk/d) were assigned to two diets: basal and basal with 5% shells in the grain mix. Cows fed diets containing shells produced the same amount of milk and milk fat as control cows. In Experiment 3, 12 Holstein cows (27.3 kg milk/d) were assigned to the same two diets used in Experiment 2 and a third treatment received 5% pecan hulls in the grain mix. Cows fed shells or hull diets reduced concentrate intake and milk production. In Experiment 4, 12 Hereford × Angus steers (474.5 kg) were fed diets used in Experiment 3 to examine rumen fermentation, digestion, and passage rates. Steers fed hulls had lower rumen ammonia N and higher rumen pH compared with steers fed the basal diet. Total rumen volatile fatty acid concentration was not different among treatments. Generally, rumen fluid from steers fed hulls had higher proportions of acetate and lower porportions of butyrate. Rumen fluid and particulate passage rates and digestion measurements were not affected by addition of shells or hulls.     

Comparison of Low Alkaloid Tall Fescues and Orchardgrass for Lactating Jersey Cows

Johnstone (prevarietal release) and Kenhy, new varieties of tall fescue (Festuca arundinacea Schreb), were compared with Boone orchardgrass (Dactylis glomerata) in 2 yr. Cultivars were maintained in a vegetative stage by removal of excess growth. Johnstone seed and the resulting cultivar were 6.7% infected with endophyte fungus (Acremonium coenophialum). Forage from each cultivar was chopped daily and fed individually to five lactating Jersey cows for 12 wk in 1983 and to eight cows for 9 wk in 1984. Cows were fed 6.8 and 4.5 kg daily of a 16% crude protein concentrate in 1983 and in 1984, respectively. No evidence of fescue toxicosis was observed in 1983, but a trend toward depressed prolactin occurred in 1984 for Johnstone tall fescue. Daily dry matter intake, intake as percent body weight, and daily milk production were significantly higher on orchardgrass than on tall fescues. Intake as percent body weight, daily milk, milk protein, and fat-corrected milk were significantly higher on Johnstone than on Kenhy tall fescue. Although the experimental design did not allow direct comparison, performance appeared to be as good on Johnstone fescue as on orchardgrass. The inferior animal performance on fescue compared with orchardgrass seems to be due entirely to Kenhy.     

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).     

Formulating Dairy Rations with Neutral Detergent Fiber. 1. Effect of Silage Source

Alfalfa and corn silages were evaluated as sources of forage fiber in diets for early lactation cows formulated to contain equal amounts of neutral detergent fiber. Diets were designed to contain 32% neutral detergent fiber and 17% crude protein. Twenty-four cows were assigned on the basis of parity and calving date to one of three experimental diets fed as complete mixed rations. Silage contents of the three complete mixed rations on a dry basis were 54.8% alfalfa silage, 67.4% corn silage, and 60.1% of a 1:1 combination of these two silages. The remainder of the experimental rations was composed of corn, soybean meal, minerals, and vitamins. Experimental rations were fed for a 9-wk period, which was preceded and followed by 3-wk periods when all cows were fed a standard diet. Using the average of pre- and postexperimental period means as a covariate, no significant differences were found among the experimental means for actual milk and fat-corrected milk yield or milk composition. Daily dry matter intake as a percent of body weight was lower for cows fed the corn silage-based diet. There were no differences in milk production between alfalfa silage and corn silage when diets contained similar concentrations of neutral detergent fiber. Rations containing 32% neutral detergent fiber were adequate for cows in early lactation producing approximately 30 kg of 4% fat-corrected milk/d.     

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.     

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.     

Effects of potassium buffers on feed intake in lactating dairy cows and on rumen fermentation in vivo and in vitro

Twenty-four Holstein cows were used to compare acceptance of concentrates and complete rations containing 1) no buffer, 2) 1.8% potassium bicarbonate, 3) 1.2% potassium carbonate, or 4) 1.5% sodium bicarbonate in the concentrate. When concentrate and a forage blend were offered separately (comparison period 1), concentrate intake did not differ among treatments, but forage blend consumption and complete ration intake was greater with the potassium carbonate ration (comparison period 2). Rumen pH did not differ, but urine pH was higher in cows fed complete rations containing buffers. Cows fed potassium carbonate had higher milk fat percentages than cows fed sodium bicarbonate during the first comparison period and higher than controls during the second comparison period and produced more 3.5% fat-corrected milk and solids-corrected milk than cows fed sodium bicarbonate in both comparison periods. Milk protein percentage was lower in cows fed potassium carbonate diets as compared with those fed sodium bicarbonate diets, but total protein production was similar. In three continuous culture in vitro trials, potassium carbonate maintained fermenter pH comparably to sodium bicarbonate, and total volatile fatty acid and acetate production were similar.     

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.     

Temporary alterations to postpartum milking frequency affect whole-lactation milk production and the energy status of pasture-grazed dairy cows

This study investigated the immediate and long-term effects of temporary alterations to postpartum milking frequency (MF) on milk production, body condition score (BCS), and indicators of energy status in pasture-grazed cows supplemented with concentrates. Multiparous Holstein-Friesian cows (n = 150) were randomly assigned to 1 of 5 groups at calving: milked twice daily (2×) throughout lactation (control), or milked either once daily (1×) or 3 times daily (3×) for 3 or 6 wk immediately postpartum, and then 2× for the remainder of lactation. During wk 1 to 3 postpartum, cows milked 1× produced 15% less milk and 17% less energy-corrected milk (ECM) than cows milked 2×. This immediate production loss increased to 20% less milk and 22% less ECM during wk 4 to 6 postpartum for cows that remained on 1× milking; these animals also produced less than 1× cows switched to 2× milking after 3 wk. During wk 8 to 32, when all cows were milked 2×, those previously milked 1× had sustained reductions in milk (−6%) and ECM (−8%) yields, which were not affected by the duration of reduced postpartum MF. In contrast, cows milked 3× postpartum had 7% greater milk yields during wk 1 to 6 compared with 2× controls, irrespective of the duration of increased MF. Milk yields also remained numerically greater (+5%) during wk 8 to 32 in cows previously milked 3×. Nevertheless, yields of ECM were not increased by 3× milking, because of lower milk fat and protein contents that persisted for the rest of lactation. In addition, indicators of cow energy status reflected an increasing state of negative energy balance with increasing MF. Cows milked 1× postpartum had greater plasma glucose and lower plasma nonesterified fatty acid concentrations during the reduced MF, and plasma glucose remained lower for 2 wk after cows had switched to 2× milking. Moreover, BCS was improved relative to 2× controls from wk 5 to 6. In contrast, cows milked 3× had lower plasma glucose concentrations, greater plasma nonesterified fatty acid concentrations, and greater BCS loss during wk 1 to 3; however, greater body fat mobilization was not sustained, indicating that additional energy supplements may be required to achieve better milk production responses. In conclusion, temporary 1× milking had lactation-long negative effects on milk and milk component yields but improved cow energy status and BCS, whereas temporary 3× milking immediately increased milk yield but did not improve milk fat and protein yields in pasture-grazed cows.