Holstein Cows In Early Lactation Research Articles

Effect of Rumen-Protected Methionine on Plasma Free Amino Acids and Production by Dairy Cows

The effectiveness of an encapsulated rumen-protected methionine compound (RPMet) for delivering methionine postruminally and its effect on plasma amino acid concentrations, milk production and milk composition were evaluated. Thirty multiparous Holstein cows in early lactation were randomly assigned to five levels of RPMet. RPMet was supplied at 0, 550, 1100, 1650 or 3300 mg/kg of concentrate resulting in an intake of 0, 6.9, 12.9, 19.6 or 40.2 g of supplemental DL-methionine/day for each cow. The basal diet was alfalfa-bromegrass hay and a 15.8% crude protein corn- and soybean meal-based concentrate mixture. The experiment was divided into pretreatment and treatment periods, each consisting of 21 days. Feed intake and milk production were measured daily, milk composition weekly and plasma amino acid concentrations twice daily on days 17 and 20 of the pretreatment period and on days 4, 10 and 21 of the treatment period. RPMet was effective in delivering methionine postruminally, which increased concentrations of methionine in plasma. Dry matter intake, milk production, milk composition and body weight were not significantly affected by RPMet.

Amino Acids in Plasma and Duodenal Digesta and Plasma Growth Hormone in Cows Fed Varying Amounts of Protein of Differing Degradability

Eighty-four Holstein cows in early lactation fed diets varying in protein percent (11, 14, and 17% crude protein) and degradability in the rumen (normal and heated soybean meal) were sampled for effects on amino acids and growth hormone in blood plasma, and amino acid profiles in the duodenal digesta. Essential and branched chain amino acids in plasma increased as protein and amount of protected protein in the diet increased. These changes were accompanied by decreased concentrations of nonessential amino acids. Plasma growth hormone was highest at low protein (11.3%) probably because of decreased intakes on this diet. Molar percentages of amino acids in duodenal contents were not affected by diet suggesting that our heat-treated soybean meal influenced quantity more than quality of amino acids available for absorption in the small intestines.

Nutritional Chloride Deficiency in Early Lactation Holstein Cows

Beginning 1 wk postpartum, weekly changes of feed and water intake, body weight, milk production, and electrolyte concentrations in serum, saliva, urine, milk, and feces were observed for 8 to 11 wk. Three dietary treatments differing in sodium chloride and sodium bicarbonate supplementation but containing equal sodium concentrations were used. Dietary chloride percents were low .10%, medium .27%, and high .45%. Consistently changes were significant for feed and water intake, body weight, milk production, and electrolyte concentrations in serum, urine, milk, and feces of cows fed the low chloride diet. By wk 8, body weight had declined from 575.0±56.7 to 476.7±54.3kg, and daily milk production decreased from a peak of 27.7±2.4 to 19.2±3.9kg for cows fed the low chloride diet. Serum chloride decreased from 106.0±2.8 to 75.5±6.7 meq/liter during the same time. Cows on the low chloride diet developed clinical signs of a deficiency characterized by depraved appetite, lethargy, hypophagia, emaciation, hypogalactiae, constipation, and cardiovascular depression. Metabolic alterations could be summarized as a severe primary hypochloremic, secondary hypokalemic, metabolic alkalosis.

Restricted Dietary Chloride with Sodium Bicarbonate Supplementation for Holstein Cows in Early Lactation

Over 2 wk, beginning 3 wk postpartum, daily changes of feed and water intake and milk production and composition were monitored in 25 cows allotted randomly among four dietary treatment groups differing in sodium chloride, sodium bicarbonate, and ad libitum supplementation by salt block. The basic complete diet was 54% corn silage, 27% shelled corn, and 16% soybean meal, dry basis. The four dietary treatments were control, .42% chloride; low, .10% chloride; low plus salt block, complete ration same as low with ad libitum salt block consumption; and control plus .7% sodium bicarbonate. Differences were consistently significant only for electrolyte concentrations in blood serum, urine, and feces of cows fed the low diet. In blood serum, chloride declined from 96.4±3.5 to 83.4±4.5 meq/liter, and serum total carbon dioxide rose from 28.4±1.9 to 36.9±2.6 meq/liter. Anion gap increased from 19.0±2.9 to a high of 23.4±3.5 meq/liter in blood serum at day 11. Metabolic derangements of cows fed the low diet may be summarized as subclinical primary hypochloremic, secondary hypokalemic metabolic alkalosis.

Effectiveness of Rumen-Protected Methionine for Delivering Methionine Postruminally in Dairy Cows

A methionine preparation encapsulated for protection from degradation in the rumen was studied in vitro and in vivo to determine: a) its effectiveness in delivering methionine postruminally; and b) its effect on the concentration of blood-plasma methionine and other amino acids and on production by dairy cows. Rumen-protected methionine was 94% stable in pH 5.4 buffer, which simulated ruminal pH, and it released 94% of methionine in pH 2.9 buffer, which simulated abomasal pH. Twenty-five Holstein cows in early lactation were used to evaluate this preparation in vivo. Cows were assigned randomly to receive one of the following five concentrations of rumen-protected methionine: 0, 157, 315, 472, and 630 mg/kg feed as fed. This trial consisted of a 3-wk base period (no rumen-protected methionine fed) followed by a 3-wk dose period (treatment diets fed). Methionine concentrations in blood plasma for the five dietary rumen-protected methionine concentrations were (µg/ml): 3.4, 4.0, 4.8, 5.1, and 5.3. Corresponding concentrations for the base period were (µg/ml): 3.2, 3.4, 3.5, 3.4, and 3.4. The linear increase of methionine in plasma indicates this preparation delivered methionine postruminally. There was no effect on concentration of other plasma amino acids. The cows receiving rumen-protected methionine consumed more feed and gained more weight than did the control cows. Other production measures were unaffected.

Effect of Exogenous Growth Hormone in Early and Late Lactation on Lactational Performance of Dairy Cows

Bovine growth hormone (51.5 IU/day) and placebo injections were administered for 10 days to four Holstein cows in early lactation (wk 12) and again in late lactation (wk 35). Milk productions in the last 5 days of each period were compared. In early lactation, growth hormone increased milk yield by 15%, fat yield by 17%, protein yield by 14%, and lactose yield by 21%. In late lactation the respective increases were 31, 42, 18, and 35%. For responses of early and late lactation to growth hormone on a quantitative basis, increases for milk yield (4.3 versus 3.9 kg/day) and milk energy secretion (3.3 versus 3.4 Mcal/day) were similar. Concurrent with these increased milk yields, ad libitum intakes of a complete mixed diet declined during the period of growth hormone treatment by 3% in early lactation and 16% in late lactation. During the 6h immediately following injections of growth hormone, blood plasma concentrations of growth hormone were elevated about 400% in early lactation and 700% in late lactation. Concentrations in plasma of free fatty acids were also higher during growth hormone treatment in late lactation but not in early lactation. Treatments did not affect plasma concentrations of glucose, insulin, glucagon, prolactin, tri-iodothyronine, thyroxine, or Cortisol in either early or late lactation. Daily administration of growth hormone in early or late lactation resulted in similar and substantial increases of milk yield and efficiency of milk production.

Factors Affecting Water Consumption by Holstein Cows in Early Lactation

Our objective was to examine relationships between water intake by dairy cows in early lactation and dry matter intake, milk production, sodium intake, and ambient temperature. After parturition, 19 multiparous Holstein cows were assigned randomly to one of four diets for 16 wk. Water consumption, dry matter intake, milk production, and maximum and minimum temperature were recorded daily and averaged weekly. There was no significant dietary effect on water intake, dry matter intake, or milk production; therefore, data were analyzed by stepwise multiple linear regression across diets. The final equation was: water intake (kg/day) = 15.99 + 1.58 (standard error .271)×dry matter intake (kg/day) + .90 (.157)×milk production (kg/day) + .05 (.023)×sodium intake (g/day) + 1.20 (.106)×minimum temperature (°C). Coefficient of multiple determination was .59. All temperature measures (mean, minimum, maximum) were closely correlated which justified the use of only one. Dry matter intake and milk production also were correlated but out of phase. Regression coefficients for milk production and sodium intake agreed with literature estimates. Major factors determining water consumption in early lactation have been identified and quantitated.

Evaluation of Magnetic Grain Feeder for Lactating Dairy Cows

A grain feeder activated by magnet to provide supplemental grain to high producing cows without physical separation of cows was tested with Holstein cows in early lactation. In trial 1 (30 wk), 20 cows were assigned alternately at calving to either a control group of 10 cows which received grain in the parlor at 1kg per 3kg milk or a magnet group of 10 cows which was offered 4.5kg of grain in the parlor plus access to the magnetic feeder 1h per cow per day until milk production dropped below 18kg daily. Corn silage was fed free choice and hay fed at approximately 3.0kg per head daily to both groups. Cows with magnets consumed more grain (9.1kg from the feeder) and more total dry matter daily and produced 3.5kg more milk per day with a lower fat test than control cows. When previous lactations were considered, milk yield was 1.5kg greater by the magnet group. In trial 2 (25 wk), 20 Holstein cows were assigned randomly to a total mixed ration of corn silage and grain (60:40 ratio) plus 2.2kg hay per cow or to a magnet group fed corn silage free choice, 2.2kg hay per cow daily, and the entire grain ration from the magnet activated feeder. Cows with magnets consumed more grain and less total dry matter daily and produced a similar amount of milk with a lower fat test than control cows. Number of meals per cow daily was large with short eating time per meal. The relationship between milk yield and eating time was low during both trials.

Protein Supplementation of an Alfalfa Hay-Sorghum Grain Ration for Cows in Early Lactation

We evaluated supplementing an alfalfa hay-sorghum grain ration with soybean oil meal in an alternating-treatment, single-reversal trial involving 37 comparisons and 23 Holstein cows in early lactation during 1974 to 1976. Data were collected for a week after a 1-wk preliminary period for each treatment. Intakes of dry matter and protein and production of milk for control and soybean meal treatments were 18.8 and 18.7 kg/day, 2.87 and 3.47 kg/day, and 29.9 and 31.0 kg/day. Percentages of milk fat, protein, ash, and total solids were not influenced by the treatments. Net efficiency of protein (feed protein minus maintenance requirement) averaged 80g per kg milk and 2,98g per g milk protein for the control treatment.

UREA AS A SUPPLEMENTAL NITROGEN SOURCE FOR LACTATING COWS

Fifteen Holstein cows in early lactation were allocated to three groups for a 17-wk period. During a 4-wk preliminary period, all cows received a soybean meal concentrate to give a total average ration crude protein of 15%. In the next 4 wk, cows were gradually adapted to zero (ZU), low (LU), and high (HU) urea-containing rations. Based on total intake, cows consumed rations with 9, 11 and 12% crude protein. Depressed concentrate intake in the HU group due to decreased palatability limited total crude protein intake of that group to 12%. Milk yield was not stimulated by increasing dietary crude protein from 9 to 11 or 12% with urea. The percent milk persistency was not maintained by urea feeding when compared to persistency in the previous lactation at which time all cows received a 13% crude protein diet. Nitrogen balance for cows in ZU, LU and HU groups was −11.9, 13.3 and −3.6 g/day, respectively. The inclusion of urea in the ration increased ruminal NH3-N (mg/100 ml) from 1.32 for the ZU group to 3.94 and 5.78 for the LU and HU groups. Rumen microbial numbers (measured by DNA concentration) were decreased in all three groups when intact protein was removed from the ration. The sum of the plasma concentrations of histidine, isoleucine, leucine, lysine, threonine and valine were significantly decreased in cows fed the high urea-containing ration.

Intake and Digestibility of Brown-Midrib Corn Silage by Lactating Dairy Cows1,2

Two short trials in 2 yr evaluated brown midrib-3 (bm3) mutant (low lignin) corn silage for Holstein cows in early lactation. In trial 1, five Holstein cows per group (bm3 or normal genetic counterpart) were fed individually a ration of corn silage and grain (60:40, dry matter) from wk 2 through wk 8 postcalving. Cows fed the bm3 ration consumed 19% more digestible dry matter and energy as a percent of body weight than cows fed the normal ration. Digestibilities of most components were 2 to 4 percentage units higher for the bm3 ration. Milk yield was not different between rations, but cows fed bm3 lost less body weight. In trial 2, five Holstein cows per group were fed individually a ration of either bm3 or normal silage supplemented with a concentrate mix at 85:15 silage to concentrate. The concentrate mix was formulated to meet needs for protein, minerals, and vitamins. Cows were on trial from wk 6 through wk 13 postcalving. All measures of daily intake of dry matter were greater for the bm3 ration while digestibilities of some components were reduced slightly. Digestible energy intake was 27% greater for the bm3 ration. Milk and milk component yields did not differ, but cows fed the bm3 ration gained more body weight. Total and individual ruminal volatile fatty acids were higher and pH lower with time after feeding for the bm3 ration.

A COMPARISON OF TWO METHODS OF COMBINING ALFALFA CUBES WITH CORN SILAGE FED TO LACTATING COWS

Sixteen Holstein cows in early lactation were assigned to a switch-back experiment consisting of two experimental periods 35 days in length separated by a 7-day changeover period. Treatments consisted of two feeding systems, alfalfa cubes ensiled with corn silage or alfalfa cubes fed with the corn silage. When cows were fed corn–alfalfa cube silage they consumed more forage, 2.26 vs. 2.16% of body weight per cow per day than when they were fed the alfalfa cubes with the silage. Fat-corrected milk yield was somewhat higher, 25.4 vs. 24.0 kg/day; fat percent and fat yield were greater, 3.13 vs. 2.70% and 918 vs. 814 g/day for corn–alfalfa cube silage as compared to cubes added at feeding time. However, milk yield was greater, 29.9 vs. 29.1 kg/day, and milk lactose percent was greater, 5.26 vs. 5.18% for cows fed cubes at feeding time compared to cows fed corn–alfalfa cube silage. There was no difference between feeding systems in blood minerals or metabolites with the exception of plasma urea nitrogen which was higher, 20.2 vs. 17.2 mg %, for the alfalfa cubes fed with the corn silage. Apparent dry matter and protein digestibility for the total ration were 68.1 and 71.6% when corn alfalfa cube silage was fed compared to 65.4 and 68.5% when the cubes were fed with the corn silage (P < 0.05). It was concluded from this study that alfalfa cubes ensiled with corn silage was an effective method of increasing the dry matter and protein content of corn silage and in improving the digestibility of the total ration.

Effect of Milking Intervals on the Rate of Milk and Fat Secretion

Summary Fifteen high-producing Holstein and Brown Swiss cows in early lactation were milked at 4,- 8-, 12-, 16-, and 20-hr. intervals. Ten I.U. of oxytocin were injected at the beginning and end of each interval to obtain residual milk. Each interval was repeated three times and each series of intervals was separated by a 12-hr. interval. The rates of milk, fat, and solids-not-fat secretion were linear for intervals up to and including 12 hr. Significant reductions in rates of secretion of these components were found at 16- and 20-hr. intervals between milkings as compared to the 4-, 8-, and 12-hr. intervals. The butterfat percentages for the different intervals were nearly the same, except for the 4-hr. interval, where an unexplainable increase took place. The solids-not-fat content was the same for all intervals. Preceding long intervals caused a depression of milk secretion during the 12-hr. intervals, but caused a marked increase in butterfat percentages.

THE EFFECT OF RELATIVE PROTEIN AND ENERGY CONTENT OF DAIRY RATIONS ON PRODUCTION AND COMPOSITION OF MILK

Two trials, each with 12 Holstein cows in early lactation, were conducted to study the effect on yield and composition of milk when the relative protein and energy contents of dairy rations were altered. A change-over design of experiments was used and digestibility of representative rations was determined with steers. A significant increase in fat-corrected milk production was obtained when energy (T.D.N.) intake was raised 5 to 12 per cent above recommended feeding standards. The protein content of the milk was increased (P < 0.05) when digestible crude protein was 20 to 30 per cent in excess of recommended allowances, but increases in milk production, in percentages of butterfat and solids-not-fat were not significant (P > 0.05). When molasses comprised up to 18 per cent of dry matter of a ration, digestion co-efficients for protein and fibre were reduced.

PASTURE MANAGEMENT STUDIES.: I. DAILY STRIP GRAZING VERSUS FREE RANGE GRAZING OF DAIRY CATTLE ON CULTIVATED PASTURE

Daily strip grazing was compared with free range grazing for dairy cows during three pasture seasons on replicated areas in a 5-year crop rotation. Seventy-two Holstein and Ayrshire cows in early lactation and twelve yearling heifers were used for the complete experiment.Pasture productivity was estimated by crediting the respective pasture plots with the T.D.N. required for the milk produced, for maintenance and gain, and for the estimated T.D.N. harvested as silage or hay. The T.D.N. fed in supplementary feed (silage, hay, and concentrate) and the T.D.N. equivalent of any body weight losses were deducted from the pasture production.Strip-grazing yields were 16.5 to 26.9 per cent higher than those from free range grazing. Surplus grass cut and supplement adjustment accounted for the major portion of these differences. While strip grazing appeared to maintain more persistent milk yields, total milk production did not differ significantly between the two systems. Milk composition (butterfat and solids-not-fat) did not differ significantly between the two systems of grazing and was not affected by the varying stages of pasture growth during strip-grazing cycles.