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.     

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.     

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.     

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.     

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.     

Alkali-Treated Forage for Early Lactation Dairy Cows: Effect on Lactation Performance and Nutrient Digestibility

Our objective was to determine the effect of sodium hydroxide treatment (4 g NaOH/100 g forage DM) of an alfalfa-orchardgrass forage and its subsequent utilization by early lactation dairy cows. Forage was harvested as hay. Complete mixed diets consisted of 55% control or treated hay and 45% concentrate (DM basis) and were fed to eight early lactation Holstein cows in a crossover design. Chemical composition of hays and complete diets were similar. Intake of dry matter was greater when cows were fed treated hay (23.4 vs. 22.2 kg/d), as was milk yield (32.3 vs. 30.9 kg/d). Yield of 4% FCM, however, did not differ between diets (27.8 vs. 27.4 kg/d). Cows fed the treated hay diet had increased concentrations of total rumen volatile fatty acids and ruminal acetate, decreased ruminal isobutyrate concentration and pH, and increased apparent digestibility of NDF, ADF, hemicellulose, and lignin. Sodium hydroxide treatment also increased the proportion of potentially digestible DM and NDF compared with that of untreated forage. Alkali treatment improved the utilization of medium quality forage in the early lactation dairy cow.     

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.     

Extruded Soybeans and Corn Gluten Meal as Supplemental Protein Sources for Lactating Dairy Cattle

Holstein cows in early lactation were used to compare three combinations of extruded whole soybeans and corn gluten meal to soybean meal. Treatments were (as a percentage of supplemental crude protein) 100% soybean meal; 75% whole soybeans extruded at 149°C, 25% corn gluten meal; 50% extruded soybeans, 50% corn gluten meal; and 25% extruded soybeans, 75% corn gluten meal. Diets were formulated to be 37.5% corn silage, 12.5% alfalfa cubes, and 50% concentrate (dry matter). Dietary crude protein was 15.7% of dry matter, and supplemental protein sources supplied 27% of total dietary protein. Diets were fed as total mixed rations and data were collected from 4 to 116 d postpartum.Milk and fat-corrected milk yields ranged from 31.0 to 34.3 and from 29.3 to 33.3 kg/d, respectively, and were greater for cows fed soybean meal than those cows fed 75 or 50% of their supplemental protein as extruded soybeans. Milk yield of cows consuming 75% of their supplemental protein from corn gluten meal was similar to all other treatments. Ruminal ammonia concentrations were lower in cows fed extruded soybeans and corn gluten meal compared with those fed soybean meal and ranged from 9.1 to 12.4mg/100 ml. Total volatile fatty acid concentration and pH did not differ among treatments. Combinations of extruded soybeans and corn gluten meal were not advantageous compared with soybean meal as a supplemental protein source for lactating cows in this experiment.     

Digestible energy values of diets with different fat supplements when fed to lactating dairy cows

A total collection digestion trial using high producing lactating cows (average milk yield = 40.7 kg/d) was conducted to measure the effect of different fat supplements on dietary digestible energy (DE) concentrations and to calculate the DE value of the supplements. A diet with no supplemental fat, 2 diets with 1.75 or 3.5% (dry basis) Ca salts of palm fatty acids (Ca-PFA), and 2 diets with 1.6 or 3.2% hydrogenated triacylglycerides from palm oil (HPO) were fed in a 5 x 5 Latin square experiment with 28-d periods. Concentrations of supplemental long-chain fatty acids in the diets were 1.7 and 3.4% for the 2 supplementation rates. Dry matter intake was reduced when cows were fed the high concentration of Ca-PFA, but cows fed Ca-PFA produced more milk than cows fed the control diet or diets with HPO. The type or amount of fat supplementation did not affect measures of rumen fermentation or in situ fiber digestibility. Digestibility of energy, dry matter, and organic matter were higher for diets with Ca-PFA than for diets with HPO, mainly because of increased fatty acid digestibility. The dietary concentration of DE was similar between the control diet and diets with HPO (2.97 Mcal/kg), but it increased as the concentration of Ca-PFA increased (3.04 and 3.16 Mcal/kg for low and high supplementation rates). The calculated DE concentrations of the supplements averaged 7.3 and 3.1 Mcal/kg for Ca-PFA and HPO. The 2001 National Research Council dairy model accurately estimated DE concentrations in all diets (<1% difference).     

Protected methionine supplementation with extruded blend of soybeans and soybean meal for dairy cows

Methionine may be the first amino acid limiting milk production in early lactation cows. To evaluate this further, 23 high producing Holstein cows (9 multiparous and 14 primiparous) were fed an extruded blend of soybeans and soybean meal (40:60) without or with 15 g of added DL-methionine as 50 g of ruminally protected methionine product during wk 4 to 16 postpartum. Cows were fed a 15.8% crude protein total mixed ration consisting of 30% (dry basis) corn silage, 15% alfalfa hay, and 55% concentrate mix. Covariant-adjusted yields of milk (35.3 and 33.9 kg/d) and solids-corrected milk (29.3 and 28.2 kg/d) were lower for cows fed ruminally protected methionine, whereas yields of 4% fat-corrected milk (28.2 and 27.4 kg/d) were similar. Percentages of fat (2.68 and 2.69) and solids-not-fat (8.82 and 8.83) were similar, and percentages of protein (2.86 and 2.90) were higher from cows fed supplemental methionine. Dry matter intakes (20.5 and 21.6 kg/d) were higher for cows fed ruminally protected methionine. Methionine concentrations in arterial and venous serum were elevated slightly by feeding supplemental methionine. Although methionine was still the first-limiting amino acid as calculated by two different methods, supplementation of this diet with ruminally protected methionine did not increase production of early lactation cows.     

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).     

Effect of Zinc Chloride or Zinc Sulfate Treatment of Protein Supplement on Milk Production

Production response to protein supplements treated with Zn salts to increase rumen escape was evaluated with 27 lactating Holstein cows in a switchback design trial with three treatments. Pelleted supplements fed with corn silage as total mixed rations were: 1) 18% protein, untreated, 2) 15% protein, treated with .5% zinc chloride, and 3) 15% protein, treated with .65% zinc sulfate. Corresponding total mixed rations (TMR) fed ad libitum contained 15, 12.6, and 13% crude protein. Each cow was offered 2.3 kg of alfalfa-orchardgrass hay daily. Dry matter intake (DMI) 17.2, 16.8, 17.0 kg/d), DMI as percent of body weight (2.74, 2.68, 2.73%), and milk total solids (10.8, 10.7, 10.6%) were similar, although low for TMR 1 to 3, respectively. Daily milk production and fat percentage were 26.4, 26.5, and 26.2 kg and 3.16, 3.21, and 3.26%, respectively. Plasma and milk Zn concentrations (1.15, 1.35, 1.33: 3.68, 4.37, 4.17 ppm) were relatively normal despite dietary concentrations of 135, 1386, and 1264 ppm. Body weight change, total milk yield, fat percent, FCM, milk protein yield, and SNF produced were similar among treatments. Dietary crude protein intake was highest for total mixed ration 1 but was lower than recommended on all diets as a result of low DMI.     

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.     

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 corn processing and supplemental hay on rumen environment and lactation performance of dairy cows grazing grass-legume pasture

The effect of corn processing (9 kg of dry matter/d of ground dry shelled or 9 kg of dry matter/d of steam rolled) and supplemental hay (0 or 3.2 kg of dry matter/d of alfalfa hay) on milk yield and composition, rumen environment, and starch utilization by lactating cows grazing grass-legume pasture was studied. Twelve rumen cannulated, multiparous Holstein cows in early lactation (95 d in milk), were assigned to a 4 x 4 Latin square design replicated three times. Treatments were ground shelled corn-based concentrate, ground shelled corn-based concentrate plus alfalfa hay, steam-rolled, corn-based concentrate, or steam-rolled, corn-based concentrate plus alfalfa hay. Supplements were fed in equal proportions twice daily. Cows fed steam-rolled corn tended to have higher percentage of milk protein and lower milk urea nitrogen concentrations than cows fed shelled corn. Milk yield was not affected by corn processing or hay supplementation. Intake of pasture forage but not total dry matter intake was reduced by hay supplementation. Starch plus free glucose digestibility in the total tract was not affected by grain processing; however, starch plus free glucose digestibility tended to increase with hay supplementation. Supplemental hay increased starch plus free glucose digestibility through changes in rumen digestion kinetics. Hay supplementation reduced the liquid rate of passage, and tended to reduce particulate turnover. Rumen degradability of pasture forage organic matter tended to be higher for cows fed supplemental hay. Supplemental hay in these diets had a greater impact on starch utilization than corn processing.     

Effects of feeding supplemental organic iron to late gestation and early lactation dairy cows

The objectives of this experiment were to determine the Fe status of cows in late gestation and early lactation and determine whether measures of Fe status and milk production were affected by feeding supplemental organic Fe. Starting 60 d before anticipated calving, cows and heifers were fed diets with 0 or 30 mg/kg of supplemental Fe (Availa-Fe, Zinpro Corp., Eden Prairie, MN). All animals changed to prefresh diets at 14 d before anticipated calving and then to lactation diets following calving; the Fe supplementation rates (0 or 30 mg/kg) remained constant. The experiment ended at 63 d in milk. Hematocrit, hemoglobin, serum Fe, unsaturated Fe binding capacity, and percentage Fe binding saturation were measured at the start of the experiment, 7 d before calving, 7 d after calving, and at 60 d in milk. Treatment did not affect any measure of Fe status and values did not change greatly over time. Milk production (averaged 41 kg/d), milk composition, and dry matter intake during early lactation (averaged 20.4 kg/d) were not affected by treatment. The somatic cell count of milk was reduced when cows were fed supplemental Fe (114,000 vs. 94,000 cells/mL). The limited response to supplemental Fe may have been because basal diets were adequate in Fe (ranged from 282 to 336 mg of Fe/kg of DM) even though most of the basal dietary Fe was provided by forages, which are generally considered poor sources of available Fe.     

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

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

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.     

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.