Plasma Concentration and Lipid Composition of Lipoproteins in Lactating Dairy Cows Fed Control and High Grain Diets

Six multiparous Holstein cows ranging from 7 to 19 wk postpartum were in a switchback design to determine effects of feeding high grain diets on lipoprotein concentration and composition in blood. Percents concentrate, alfalfa haylage, and corn silage of control and high grain diets were 50, 83; 25, 9; and 25, 8 dry matter. Milk yield (kg/day), milk fat percentage, and fat yield (g/day) averaged 27.7, 3.58, 997 and 30.2, 2.45, 729 for control and high grain treatments. Very low density, low density, and high density lipoproteins were isolated by gel filtration of total lipoproteins obtained by ultracentrifugation. Lipoprotein concentrations in blood plasma of cows fed the control or high grain diets were similar. Triglyceride, phospholipid, cholesterol, and cholesterol ester contents of each lipoprotein class were not altered by treatment. High grain feeding increased octadecadienoic fatty acid content of low density and high density lipoprotein cholesterol esters and decreased octadecenoic and octadecatrienoic acids. The trend was similar for the very low density lipoprotein fraction. Phospholipid octadecenoic acid decreased in all lipoprotein fractions but only significantly for high density lipoproteins. It is unlikely that differences in lipid composition of plasma lipoproteins caused alterations in lipoprotein metabolism leading to fat depression in this and other similar studies.     

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.     

Palatability of Methionine Hydroxy Analog or DL-Methionine for Lactating Dairy Cows

A decrease in grain intake occurred initially after feeding supplemental methionine hydroxy analog (top-dressed or mixed with concentrate) but top-dressing DL-methionine did not affect intakes. After initial adjustment (1 to 3 d), cows generally returned to normal grain intakes on diets supplemented with methionine hydroxy analog. Intake patterns were similar at all methionine hydroxy analog levels, which attained three to four times that recommended for supplementation. Increases in plasma free methionine at methionine hydroxy analog intakes above 40 g/d suggest bypass of additive for intestinal absorption.     

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.     

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

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

Organic Acid Treatment of High Dry Matter Corn Silage Fed Lactating Dairy Cows,

In four experiments, lactating Holstein cows were used to evaluate the nutritive value of corn silages treated with organic acids. Propionic, formic, and acetic acid treatment of silage with medium dry matter (34 to 39%) in two experiments slightly increased silage intake but had little effect on milk yields. However, addition of propionic acid to silages with high dry matter (42 to 47%) in three experiments increased silage intake 12%, total intake 6%, and milk yields 5%. Formic acid added to high dry matter silages was less effective than propionic in increasing intakes. Decreasing dry matter of silage from 43% to 36% with water added at ensiling did not improve intakes or milk yields. Propionic treatment decreased silage temperatures during fermentation and feeding and lowered fungal counts of silage exposed to air. Normal concentrations of lactic and acetic acids and pH values resulted from propionic treatment. Propionic treatment of high dry matter silage appeared profitable.     

脲酶抑制剂预混料饲喂泌乳奶牛效果试验

介绍了用16头健康泌乳奶牛进行饲喂脲抑制剂预混料的对比试验，结果表明，饲喂脲酶抑制剂预混料的试验组，泌乳奶牛平均日产标准乳18．18kg／头，未添加饲喂的对照组，泌乳奶牛平均日产标准16．84kg／头。前者比后提高产奶量7．96％，差异显著（P＜0．05）。试验期间，试验组比对照组增加盈利1．15元／d，增收效益明显。     

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.     

Cubed Complete Rations for Lactating Dairy Cows

Production by cows fed cubed complete rations as compared to the same ration components fed separately as long hay and concentrate was determined in two experiments. The cubed rations reduced milk fat percentages in both experiments and total fat production in one experiment. Solids-not-fat was increased slightly by cubed rations. Lower efficiency of feed utilization for the production of 4% fat-corrected milk was evident for cows fed cubed rations. Losses of body weight following parturition were reduced, and subsequent weight recoveries were more rapid in cows fed cubed rations. Also, molar ratios of acetic/propionic acids in the rumen were reduced. Effects of rations on milk composition, changes in body weight, and ratios of volatile fatty acids appear to be related to differences in coarseness or texture of the roughage components of cubed and baled hay rations. The results of these feeding experiments indicate complete rations prepared by cubing chopped alfalfa hay and concentrates in conventional hay cubing equipment have limitations as the sole rations for high producing dairy cows.     

Microbial Protein Synthesis in Rumens of Cows Fed Dried Whole Whey

Two rumen-fistulated Holstein cows, weighing approximately 550 kg, were in an experiment with switchback design to evaluate effects of consuming large amounts (38% of total ration dry matter) of dried whole whey on synthesis of microbial protein in the rumen. Cows were fed total mixed rations of (dry matter) 45% corn silage, 10% alfalfa hay, and 45% concentrate mix. The concentrate mix was primarily corn and soybean meal (control) or 85% dried whole whey. Dry matter intakes averaged 16.4 and 15.3 kg/day for control and whey diets. Diaminopimelic acid nitrogen as percent of bacterial nitrogen was similar for both diets (.61 and .63% for control and whey diets). Likewise, aminoethylphosphonic acid nitrogen as percent of protozoal nitrogen was similar for both diets (.17 and .19% for control and whey diets). For the control diet, total ruminal nitrogen was estimated to be 45% bacterial and 27% protozoal. Bacteria and protozoa accounted for 52 and 22% of the total ruminal nitrogen in the cows fed the whey diet. Ruminal fluid volume (33.8 and 39.2 liters for control and dried whey diets) and dilution rates (10.2 and 12.8% h) were higher for dried whey. Ruminal ammonia (5.0 and 3.4 mg/dl) was lower for dried whey. Butyrate (16.5 and 24.4 moles/100 moles total volatile fatty acids) was higher, whereas propionate was lower (32.4 and 23.2 moles/100 moles total volatile fatty acids) when cows were fed dried whey. Bacterial synthesis appeared to be increased when cows were fed a diet containing large amounts of dried whey.     

Sodium Cloxacillin for Treatment of Mastitis in Lactating Cows

Sodium cloxacillin was used to treat 107 cows affected with acute mastitis and 138 affected with subclinical mastitis. Based on the application of conservative bacteriologic criteria, the cure rate was 53% for acute staphylococci mastitis and 65% for subclinical staphylococci mastitis. The cure rate for Streptococcus agalactiae infections was 91% in acute conditions and 92% in subclinical conditions. The cure rate was 73% for the acute infections and 88% in cases of subclinical infections when Streptococcus spp. “non ag” was the cause. Daily milk production had no effect on response rate. No adverse reactions due to treatment were reported by any investigator.     

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.     

Mammary Extraction of Propionate in Lactating Cows

Four cows with exteriorized carotid arteries were in an intensive study of concentrations in plasma and mammary extraction of propionate. A restricted-roughage, high-grain diet produced higher arterial propionate concentrations and larger carotid-subcutaneous abdominal vein (arteriovenous) differences than the control diet. Concomitant changes in acetate, β-hydroxybutyrate, and glucose in plasma and in fat and protein in milk were measured. Mammary arteriovenous difference in propionate was correlated negatively with milk fat percentage. However, since arterial propionate and β-hydroxybutyrate also were correlated negatively, evidence of a direct inhibitory effect of propionate in mammary gland is equivocal.     

Faecal Composition and Nitrogen Excretion of Rats Fed on Diets Containing Sweet Lupin (Lupinus angustifoliusL) or its Fractions

Five N balance studies were conducted to determine the faecal composition and N excretion of feeding raw Lupinus angustifolius seed meal and its fractions for growing rats using a semi-synthetic lactalbumin-based diet as control. Diets were formulated to have equal amounts of energy. The protein was incorporated at the level of 10% bulk and contained unsupplemented lupin seed meal (LMU) and fully supplemented lupin seed meal (LMFS) at 360 g kg⁻¹ diet, aqueous extract non-dialysed (LPAND) at 196 g kg⁻¹ aqueous extract dialysed soluble at pH 7·0 (LPAD) at 148 g kg⁻¹ aqueous extract dialysed insoluble at pH 7·0 (LPADI) at 124 g kg⁻¹, buffer dialysed soluble at pH 7·0 (BUSOL) at 136 g kg⁻¹, buffer dialysed insoluble at pH 7·0 (BUDI) at 119 g kg⁻¹ and lupin meal residue after aqueous and buffer extraction (LMR) at 170 g kg⁻¹ diet. Rats were pair-fed for 10 days with all the above diets which had been supplemented with essential amino acids up to the target requirements for rats. Faecal wet and dry weight were increased in rats fed on LMU, LMPS and LMR diets compared to those obtained from the control diet based on lactalbumin (milk protein) LACT. The higher faecal weight was largely due to water content. The higher faecal N excretion observed in LMU, LMFS, LPAND, LPAD, BUSOL, BUDI and LMR compared to that of LACT diet was significantly lower and thus which was assumed not to be due to a decrease in the digestibility of the dietary protein, which was over 90% as compared to that in the control group. Analysis suggested that an increase in endogenous N excretion is involved in the rise of its excretion in the faeces, and indicates a long-term effect of this seed as a protein and or fibre source in monogastrics.     

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.     

Factors Associated with Variation in Milk Fat Depression Resulting from High Grain Diets Fed to Dairy Cows

Thirty lactating Holstein cows were used in a crossover design with 4-wk periods to establish the relationship between chewing activity, molar proportions of ruminal volatile fatty acids, and milk fat depression resulting from feeding high grain-low forage diets. Milk production and dry matter intake were not affected by treatment. When cows were fed the high grain-low forage diet, milk fat decreased from 3.39 to 2.87%, ruminal acetate plus butyrate:propionate ratio decreased from 2.7 to 2.0, and total chewing time decreased from 659 min/24 h to 472 min/24 h. Percentage change in milk fat test between treatments was correlated to percentage change in the ruminal molar proportion of acetate, propionate, acetate plus butyrate:propionate ratio, and percentage change in total chewing time per kilogram neutral detergent fiber intake (n = 30, r = .38, −.50, .53, and −.30, respectively). More correlation coefficients were significant and correlations were higher if only cows that proceeded from control to high grain-low forage treatment were considered. As milk fat depression was increased by high grain feeding, magnitude of depression in chewing activity was decreased. Within treatment, time spent chewing increased as milk fat percentage decreased.     

A Computer Ration Evaluation Program for Heifers,Dry Cows,and Lactating Cows

A computer program designed to calculate ration dry matter, crude protein, total digestible nutrients, acid detergent fiber, cost, macrominerals, and microminerals was developed. Feeds, designated by number, and amounts fed are entered by the program user. A library file contains feeds and their standard laboratory analytical concentrations for all nutrients to be evaluated. Modification of Standard nutrient concentrations is made via screen editing. Three screens are used to accommodate all nutrients. The first screen contains dry matter, crude protein, total digestible nutrients, acid detergent fiber, and cost. Screens 2 and 3 contain, respectively, the macrominerals (calcium, phosphorus, sodium, magnesium, sulfur, and potassium) and microminerals (iron, cobalt, copper, manganese, zinc, and selenium). National Research Council's nutrient requirements are calculated and printed on the screen, and the percent of the requirement met by the ration being fed is displayed. This program has been used extensively by extension personnel, faculty, and students for ration evaluation, problem solving, trial-and-error ration balancing, and instruction to demonstrate the principles of ration balancing.     

Evaluation of High Oil Corn and Corn Silage for Lactating Cows

Forty multiparous Holstein cows in early lactation were used to compare their responses to high oil corn and corn silage with responses to control corn and corn silage. Treatments were total mixed diets containing: 1) 50% control concentrate, 50% control corn silage; 2) 50% high oil concentrate; 50% control corn silage; 3) 50% control concentrate, 50% high oil corn silage; and 4) 50% high oil concentrate, 50% high oil corn silage on a DM basis. Cows fed high oil corn had greater DM intake (21.9 vs. 19.6 kg/d) and ruminal acetate:propionate ratio (2.3 vs. 2.0) than animals fed control corn. Fiber digestibility and yield and composition of milk were similar among grain and silage types. Apparent digestibility of DM was lower for animals on high oil corn than for those fed control corn (69.7 vs. 73.3%). Apparent digestibility of ether extract was lower for animals consuming high oil corn silage than for those fed control corn silage (82.2 vs. 85.9%). De novo synthesized fatty acids in milk fat were reduced, but preformed fatty acids of dietary origin were increased on all diets. Efficiency of milk production was lower for diets containing high oil corn or corn silage. Postpartum body weight recovery was greater for cows fed high oil corn than cows fed control corn, indicating a more favorable energy status for these animals. High oil corn and corn silage allowed both high milk production and the deposition of body tissue.