Effect of Nitrogen Solubility on Nitrogen Lactating Dairy Cattle,

Three nitrogen-balance trials were used to measure nitrogen utilization in lactating dairy cows. In each trial, the basic diet was a complete feed containing 55% corn silage and 45% grain mixture (dry-matter basis). The crude protein contents of the complete diets in trials 1, 2, and 3 were 12, 13, and 15%, respectively. Four high-producing Holstein cows similar in age and producing ability and within 30 to 45 days postpartum were used in each 12-wk trial in a Latin-square experimental design. Urea was the treatment variable supplying approximately 0, 8, 16, or 24% of the total dietary nitrogen. The measured solubility of the nitrogen in the diets ranged from 31.5 to 48.7%. The data were fitted to a multiple linear-regression model to determine coefficients of nitrogen utilization. The utilization coefficients for soluble nitrogen and insoluble nitrogen were relatively constant across the three trials, but in each trial the utilization coefficient for insoluble nitrogen was greater than for soluble nitrogen.     

Supplemental Niacin for Lactating Cows Fed Diets of Natural Protein or Nonprotein Nitrogen

Thirty-two Holstein cows, 16 in early and 16 in midlactation, were assigned to four treatments: 1) soybean meal protein plus niacin; 2) soybean meal without niacin; 3) nonprotein nitrogen plus niacin; and 4) nonprotein nitrogen without niacin. Niacin dose was 6 g per day, and nonprotein nitrogen supplied 20% of total nitrogen for those treatments. Differences between treatments in milk yields were not significant, but milk persistencies tended to be highest for cows in early lactation fed niacin during wk 9 and 10 of treatment. Intakes of dry matter did not differ significantly, but cows fed nonprotein nitrogen without niacin had lowest intakes per 100 kg bodyweight. Differences between treatments in feed utilization, milk composition, bodyweight changes, plasma ammonia, rumen pH, rumen volatile fatty acids, dry matter digestibilities, nitrogen digestibilities, and retained nitrogen were not significant.     

Influence of Intake of Rumen Undegradable Protein on Milk Production of Late Lactation Holstein Cows

Twenty Holstein cows, in late lactation, were assigned to five equal groups in an orthogonal design to determine effects of a rapidly rumen degraded protein source (canola meal) low in estimated rumen undegradable protein substituted for a slowly rumen degraded protein source (corn gluten meal) high in rumen undegradable protein on feed intake, milk production, and milk composition. Cows were fed total mixed rations based upon barley silage, haycrop silage, barley grain, and supplemental protein in three 4-wk periods, subsequent to a 4-wk covariate period. In situ rumen incubation of extreme diets and estimation of intermediate diets indicated that all diets exceeded Agricultural Research Council (United Kingdom) recommendations for rumen degradable and undegradable protein as well as NRC recommendations for rumen degradable protein. However, two to four diets, dependent upon assumed ruminal turnover rates, did not meet NRC recommendations for undegradable protein. Dry matter intake and milk yield were not influenced by substitution of canola meal with corn gluten meal to increase dietary undegradable protein content. Daily yield and milk percent of lactose, fat, and protein were not influenced by substitution. Results do not support NRC recommendations to supplement diets based upon these ensiled forages and barley grain for late lactation cows with protein sources resistent to rumen degradation. Results broadly support lower amounts of rumen undegraded protein recommended by the Agricultural Research Council.     

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.     

Heritability Estimates for First Lactation Milk Yield of Registered and Nonregistered Holstein Cows

Heritabilities of milk yield and fat test were estimated from first lactation records of 196,672 Holstein daughter-dam pairs separately for registered and nonregistered cows for four milk yield groups and by years of freshening of the daughter. The model included herd-season and sire of the daughter. Heritability estimates were similar for registered and nonregistered cows averaging about .33 for milk yield and .62 for fat test. Estimates of heritability increased slightly over time for both milk yield and fat test. Heritability of fat test was similar for all groups. Heritability estimates for milk yield, however, averaged about .25 in low, about .35 in middle, and about .40 in high groups.     

Effects of a Hot Climate on the Performance of First Lactation Holstein Cows Grouped by Coat Color,

Dairy Herd Improvement data from 432 Holstein cows were analyzed to determine if coat color was a significant source of variation in the performance of first lactation cows in a hot climate. One of three coat color scores was subjectively assigned to first lactation Holstein cows. White coat color was less than 40% black (15% of the cows), mixed coat color was 40 to 60% black (42% of the cows), and black coat color was greater than 60% black (43% of the cows). Coat color by season of freshening interaction was not an important source of variation for any of the production traits Studied; but cows were cooled during the first 130 d of lactation, perhaps removing any advantage white cows may have had during the summer months. The interaction between coat color and season of freshening was significant for days open and services per conception. White cows freshening in February and March required fewer services per conception and had fewer open days than the mixed and black cows. The heritability estimate of coat color was .22 using a paternal half-sib analysis. Additional studies, with more white cows represented, would be useful to elucidate the effects of coat color on production in a hot climate.     

Effect of Ration Protein Content and Solubility on Milk Production of Primiparous Holstein Heifers

Twenty-eight primiparous heifers were blocked at calving and assigned to four dietary treatments in a 2 × 2 factorial arrangement of two crude protein concentrations (15.4 and 20.7%) and two protein solubilities (22.8 and 53% of protein). Heat-treated soybeans replaced raw soybeans in low solubility rations. Rations were offered for the first 10 wk of lactation divided into two 5-wk periods. Feed was offered ad libitum in period 1 and restricted in period 2. Digestibility and N balance were measured at completion of the lactation study. Body weight change, DM intake, milk yield, milk protein percentage, rumen pH, and total VFA were not affected by treatments. Milk fat percentage was increased by higher CP content during period 1, resulting in a 16.2% increase in 4% FCM. Plasma urea N and rumen NH₃ were elevated by higher CP content. Reducing protein solubility depressed rumen NH₃. A protein × solubility interaction for the acetate to propionate ratio suggests that protein and solubility combinations that optimized plasma urea N and rumen NH₃ provided a more favorable rumen environment and supported highest milk production. Nitrogen digestibility was influenced most by ration CP; however, lower solubility improved DM and N digestibilities. Both dietary CP content and solubility must be considered to maintain optimum rumen environment.     

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.     

Insoluble Nitrogen for Milk Production in Holstein Cows via Increases in Voluntary Intake and Nitrogen Utilization

Influences of insoluble and soluble N on milk production and N use were studied in 24 Holstein cows. The basal diet (grain: corn silage plus urea, 1:1 dry matter) contained 12% crude protein (60% insoluble N). Urea or soybean meal was added to the basal diet, increasing the crude protein to 15% with 43 and 67% insoluble N, respectively. Balance studies were performed during wk 4, 10, and 22 of lactation. Multiple regression analyses were performed on balance data adjusted for metabolic size to determine coefficients of soluble and insoluble N use. Intake of N, partitioned into insoluble and soluble N, accounted for 76, 30, 61, and 10% of the variation in dry matter intake, milk yield, milk N, and body weight^.75, respectively. Utilization coefficients for insoluble N were higher for dry matter intake, milk N, and weight^.75 but lower for milk yield. Urea supplementation increased dry matter intake; however, much of the milk yield by cows fed urea was attributed to a greater weight^.75 loss. In contrast, cows fed soybean meal as a source of insoluble N maintained both weight^.75 and higher milk production because of higher dry matter intake and more efficient use of N.     

Genetic and Phenotypic Relationships Between Lactation Cell Counts and Milk Yield and Composition of Holstein Cows

Monthly somatic cell count data were collected between February 1977 and February 1982 for Holstein cows in 928 herds enrolled on the Quebec Dairy Herd Analysis Service. The geometric mean of the log monthly cell counts was calculated for each lactation. Official lactation records for 305-day milk, fat, and protein yields, and fat and protein percents were obtained for same cows. There were 18,189 cows in first lactation representing 257 sires, 13,225 in second lactation representing 206 sires, and 8,683 in third lactation representing 151 sires. Heritabilities of yield traits and protein percent increased across three lactations. Heritability of fat percent was similar in first and third lactations but decreased slightly in second lactations. Heritability of lactation cell count was small, being least in second lactations. Genetic correlations between lactation cell count and yield traits were positive in first lactations, small and negative in second lactations, and small and positive in third lactations. Genetic correlations between lactation cell count and fat and protein contents were small in the three lactations. Phenotypic correlations between lactation cell count and production traits were small in each of the three lactations. Genetic correlations between yield traits in early lactation and lactation cell count in a subsequent lactation were positive. The genetic correlation between protein percent in an early lactation and cell count in a later lactation was large between first and second lactations, decreased between second and third lactation, and small between first and third lactations. Genetic correlations were small and negative for fat percent.     

Forage Quality and Concentrate for Cows in Early Lactation

The objective was to evaluate effects of alfalfa quality and concentrate proportion in diets during early lactation on milk production, milk composition, feed intake, and body weight. Sixty-eight Holstein cows (24 first lactation and 44 older cows) were assigned to one of four diets during the first 14 wk of lactation. Diets contained either early cut or normal cut alfalfa hay mixed with 30 or 50% concentrate. Forage quality and concentrate did not affect milk yield or dry matter intake for either older or first lactation cows. Milk fat percent was reduced by higher concentrate (3.7 versus 3.3%) but was not affected by forage quality for older cows. Milk protein was higher for early cut (3.2%) compared with normal cut (3.1%) hay. For first lactation cows, milk fat percent increased with declining forage quality (3.5 versus 3.9%) and increased with declining concentrate (3.6 versus 3.9%). Yields of milk components were not different for forage quality or concentrate except for higher yield of milk protein for early cut hay diets fed to older cows.     

Effects of Body Condition and Protein on Milk Fat Depression in Early Lactation Dairy Cows

Twenty multiparous and 16 primiparous Holstein cows were fed either a high energy or low energy diet during the dry period to achieve different degrees of body condition. Three weeks postpartum, cows were randomly assigned to either a high protein (23% CP) or a low protein (14.5% CP) diet. The diet contained 21% ADF during wk 3 through 6 postpartum and lowered to 9% ADF during wk 7 through 14 postpartum to depress fat test. Cows fed the low energy prepartum diet had less fat depression when fed the high protein postpartum diet compared with the low protein diet. Milk fat depression was more severe for all cows fed the high energy prepartum diet. Depression in milk fat percentage for multiparous cows was 30.8, 10.2, 34.5, and 26.0% for high energy-high protein, low energy-high protein, high energy-low protein, and low energy-low protein groups, respectively. For primiparous cows, milk fat depression was 37.3, 24.1, 37.0, and 34.6%. After the fiber change, depression in acetate to propionate ratio was less for multiparous cows fed high protein than for those fed low protein. Prepartum energy did not influence acetate to propionate ratio depression that resulted from the fiber change.     

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.     

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

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.     

Effects of Early and Late Breeding of Heifers on Multiple Lactation Performance of Dairy Cows

Dairy heifers were randomly divided into two treatment groups. One group of 253 heifers was bred at first estrus after 350 d of age and the second group of 249 heifers after reaching 462 d of age. Feeding and management practices were identical; groups differed only in age at first breeding. This report compares production of second and third lactations, reproductive traits observed during first and second lactations, and lifetime performance. Comparisons of heifer reproduction and first lactation production were reported earlier. Although the 462-d breeding age group of heifers had slightly better first lactation performances than the 350-d breeding age group, these advantages were not carried over to second and third lactations. No significant differences existed in three-parity performance between the two breeding groups. The 350-d breeding group had longer 61-mo productive life (730 vs. 623 d), produced greater 61-mo total milk (10,693 vs. 9218 kg), and yielded more milk per day of 61-mo herdlife (6.8 vs. 5.9 kg). A reduction of 1 mo in age at first calving would increase three-parity and 61-mo total milk by 427 and 554 kg, respectively. Results from this study suggest that early breeding is a viable and practical approach to improve profitability for the dairy industry.     

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.     

Effect of Temperature and Moisture Content on the Kinetics of Trypsin Inhibitor Activity, Protein in vitro Digestibility and Nitrogen Solubility of Cowpea Flour

Samples of finely ground cowpea flour containing 7.5%, 19.4% and 25.5% moisture were heated in sealed tubes at 100° 125° and 150°C for periods of 0.5 to 120 min. First order rate constants for losses of trypsin inhibitor activity and nitrogen solubility ranged from 1 × 10^?2 to 18 min^?1 and from 4 × 10^?2 to 8 min^?1 respectively. In vitro protein digestibility (IVD) increased, then decreased with heating as described by sequential first order kinetics. Rate constants for increase of IVD varied from 0.13 to 12 min^?1, while for decrease in IVD the range was 5 × 10^?5 to 3 × 10^?2 min^?1. Activation energies and relationships between In k and water activity were computed.     

Aerobic Storage and Utilization of Ammonia-Treated Distillers Wet Grains for Lactating Dairy Cows

Two experiments were conducted to determine the influence of NH₃ treatment on the aerobic stability of distillers wet grains and value of the NH₃-treated grains as protein supplements for lactating cows. In Experiment 1, fresh distillers wet grains were treated with NH₃ at 0, 1.57, 3.14, or 4.71% of DM, compacted in polyethylene bags, and kept in aerobic storage at 16, 27, or 38°C for 14 d. Intermediate and high NH₃ reduced temperature increases, mold growth, and spoilage and improved DM recoveries. Low ammonia grains were less stable and deteriorated faster than untreated grains.In Experiment 2, lactating Holstein cows were supplemented with NH₃-treated distillers wet grains (13.8% of total DM) or soybean meal (10.1% of total DM) for 70 d. Intakes of DM tended to be lower on ammoniated grains (19.4 and 17.6 kg/d). Milk yields (27.1 vs. 27.9 kg/d) and composition were not significantly different among treatments, but efficiency of converting feed to milk and income over feed costs were greater for ammoniated grains than soybean meal.