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.

Rates of utilization of glucose, acetate, and lactate and activities of selected enzymes were determined in vitro to evaluate the effects of age and diet on lipogenesis in perirenal adipose tissue of calves. Three-day-old Holstein bull calves were fed up to 12 wk of age on one of three dietary treatments: a high carbohydrate milk replacer; a high fat milk replacer; and weaning at 6 wk of age from high fat replacer to calf starter. Adipose tissue biopsies were obtained from calves at 2, 5, 8, and 12 wk of age. Rates of fatty acid synthesis and activities of enzymes of the pentose phosphate and citrate cleavage pathways were increased in calves fed high carbohydrate milk replacer. These parameters were decreased in calves fed high fat replacer and were further depressed after weaning. Substrate preference for fatty acid synthesis in all calves was acetate, then lactate, then glucose. With increase in age from 2 to 12 wk, adipose tissue of calves fed milk replacer partitioned more acetate and lactate toward fatty acid synthesis and less toward oxidation. The pentose phosphate cycle was characterized by high rate of recycling and contributed at least 50% of reducing equivalents required for fatty acid synthesis. It appeared that several features of lipogenesis characteristic of functional ruminants are also shared by preruminant calves.

Mammary gland tissue slices from three lactating Holstein cows were incubated in Krebs-Ringer bicarbonate-based media with varying concentrations of lactate and other substrates. Conversions of 1- and 2-carbon-14 of lactate to carbon dioxide, fatty acids, citrate, glyceride glycerol, and lactose were determined.\r\n\r\nEffects of acetate, glucose, beta-hydroxybutyrate, stearate, and pyruvate on lactate metabolism were evaluated. Oxidation of lactate increased asymptotically with lactate concentration. Low acetate concentration stimulated oxidation of carbon 2 of lactate slightly while higher acetate availability inhibited lactate oxidation. Conversion of lactate to fatty acids increased linearly with lactate concentration. This conversion of lactate was inhibited strongly by acetate. Significant conversion of carbon 2 of lactate to glyceride-glycerol but not lactose was detected.\r\n\r\nBovine mammary glands have the capacity of utilize sizeable quantities of lactate for oxidation and lipogenesis. Both phenomena are highly dependent on availability of acetate. Pyruvate dehydrogenase and citrate lyase could represent important regulatory sites in vivo for determination of tissue preference for acetate over lactate. Results indicate factors other than an inactive malate transhydrogenation cycle likely limit glucose conversion to fatty acids.

Thirty-eight older (second and greater lactation) and 15 Holstein cows in first lactation were in a full lactation (44 wk) study to evaluate the effect of either twice or three times daily milking on yield of milk and milk components, milk composition, feed intake, and body weight change. All cows were managed alike and were fed diets of high, medium, and low energy concentration as lactation progressed from calving to 44 wk. First lactation cows were switched from diets of high energy to lower energy at the same milk production as lactation advanced. Dietary changes for older cows milked twice and three times (A) were at similar production, whereas three times (B) cows were switched to lower energy at higher milk production. Older cows milked three times daily (A and B) produced 17 and 13% more milk over the entire lactation than cows milked twice daily. Dry matter and energy intakes were not affected by three times milking, but gain of body weight was reduced. Cows milked three times daily during their first lactation produced 6% more milk than their twice counterparts, although this increase was not significant. Dry matter and energy intakes were not affected by three times daily milking, but three times milking of first lactation cows reduced weight gain over the lactation. Reproductive performance of cows milked three times daily was not significantly different from cows milked twice daily. Herds milking three times will require high management of nutrition and reproduction.

Mammary gland tissues from three lactating Holstein cows were sampled and slices incubated with various concentrations of glucose and in combinations with other substrates in Krebs-Ringer bicarbonate-based media. Conversions of 1-and 2-carbon-14 glucose to carbon dioxide, lactose, glyceride-glycerol, citrate, and fatty acids were determined. Glucose utilization increased asymptotically with glucose availability. Carbon dioxide, lactose, and glyceride glycerol production accounted for nearly 90% of glucose recovered. Only trace quantities of glucose were recovered as fatty acids. Estimates of apparent affinities for glucose use were in a physiological concentration range of glucose. Oxidation of glucose was positively correlated with availability of acetate. Acetate availability increased the ratio of 1-carbon-14 glucose to 2-carbon-14 glucose oxidation and decreased glucose conversion to fatty acids. Glucose conversion to glyceride-glycerol was not affected by acetate availability. Primary uses of glucose are in lactose and glyceride glycerol synthesis and formation of reduced nicotinamide adenine dinucleotide phosphate for lipogenesis. Extensive use of glucose for these purposes may limit amounts available for fatty acid synthesis.

The influence of age, carbohydrate-fat ratios of milk replacers, and development of ruminal function on growth, health, and blood glucose concentrations were evaluated in calves. Colostrum-fed, 3-day-old Holstein bull calves were fed to 12 wk on one of three dietary treatments: 1) a high carbohydrate, low fat (60.5% glucose, 9.5% lactose, and 3% lard) milk replacer; 2) a low carbohydrate, high fat (23% glucose, 12.5% lactose, and 30% lard) milk replacer; and 3) weaning at 6 wk of age from high-fat replacer to a standard calf starter. The high fat milk replacer was superior to low fat milk replacer for total weight gains and efficiency of feed conversion. Rates of weight gain of starter calves were similar to those of calves fed low fat. Calves fed the diet with low fat had a high incidence of diarrhea, an occasional outbreak of a yeast-related ethanol intoxication syndrome, and high concentrations of glucose in urine. Irrespective of milk replacer composition or development of ruminal function, plasma and whole blood glucose concentrations declined rapidly in the first 6 wk. Corpuscular glucose declined steadily with age in all calves. This age-related decrease of blood glucose concentration of calves seems to be a constitutive phenomenon.

In Experiment 1, 14 lactation goats of various breeds were used to measure changes of milk fat content during the milking process. Milking was divided into quarterly intervals with equal amounts of milk. There was an increase of fat percent of quarterly fractions through milking.

Commercial, Nonpareil, and Neplus almond hulls containing 31.5 and 13.2, 27.5 and 11.7, and 27.6 and 9.8% acid detergent fiber and lignin were fed in two digestion studies. Digestibilities of control, 20 and 40% commercial almond hull, 20 and 40% Nonpareil, and 20 and 40% Neplus diets for dry matter were: 70.4; 67.3, 65.4; 68.7, 66.3; 69.9, and 66.4%; and for energy were 70.1; 65.8, 63.9; 68.6, 64.7; 69.6, and 63.5%. Percent digestibilities of dry matter and energy calculated by regression were 56.7 and 51.0 for commercial, 62.4 and 58.7 for nonpareil, and 63.1 and 57.5 for Neplus almond hulls. Digestibilities of hulls were correlated with acid detergent fiber content.

In a calf nutrition-metabolism study in which a high glucose (60% glucose and 3% lard) versus a high fat (23% glucose and 30% lard) milk replacer were compared, a syndrome characterized by anorexia, an unstable gait, depression, a distended abdomen and an odor of alcohol on the breath was observed in some calves. These signs were associated with intoxicating levels of plasma ethanol and the predominance of the yeast species Torulopsis glabrata in gastrointestinal contents of afflicted calves. Nystatin, a yeast inhibitor, was extremely useful in preventing the problem.

Slices from mammary glands from six lactating Holstein cows were incubated in Krebs-Ringer bicarbonate-based media in the presence of varying concentrations of acetate, glucose, and lactate. Conversions of acetate to carbon dioxide, fatty acids, citrate, glyceride-glycerol, and lactose were determined. Specific effects of beta-hydroxybutyrate and stearate availability also were evaluated. Utilization of acetate for all functions usually followed Michaelis-Menten kinetics with apparent affinities in the physiological concentration range of acetate. Availability of glucose had a large "permissive" effect on acetate to conversion to fatty acids. However, acetate metabolism was independent of the availability of lactate. Conversion of acetate to glyceride-glycerol was significant. This indicates the possibility of bidirectional glycolytic flux, which could limit glucose conversion to fatty acids. Addition of stearate caused general increases of acetate metabolism. Conversion of acetate to fatty acids, carbon dioxide, and citrate was elevated in the absence of beta-hydroxybutyrate. The latter observation indicates beta-hydroxybutyrate may not be a required initiator of fatty acid synthesis in mammary tissue.

Three trials were to evaluate effects of sodium bicarbonate in alfalfa hay-based diets. In Experiment 1, four Jersey cows were fed diets of 40:60 chopped alfalfa hay:grain with either 0, .25, .5, and .75% sodium bicarbonate in a 4 X 4 Latin square digestion trial. Dry matter and fiber digestion were unaffected. Volatile fatty acids of ruminal fluid and milk fatty acids were not different. In Experiment 2, two rumen fistulated cattle were fed diets of Experiment 1 for changes of ruminal fluid characteristics at -1, 2, 4, and 8 h postfeeding. Volatile fatty acids of ruminal fluid and hydrogen ion concentration were not different across time with sodium bicarbonate. In Experiment 3, four Holstein cows with rumen cannulae were fed diets of 30:70 chopped alfalfa hay:grain with 0, .4, .8, and 1.2% sodium bicarbonate in a 4 X 4 Latin square. Dry matter and fiber digestion were unaffected. Ruminal fluid samples were collected at -1, 3, 6, and 9 h postfeeding. Volatile fatty acids were different only at 6 h with 0 and 1.2% sodium bicarbonate diets displaying lower concentrations. Rate of increase of hydrogen ion concentration was greater for diets containing 0 and .4% compared with .8 and 1.2% sodium bicarbonate between -1 and 6 h. Milk fatty acid composition, ruminal liquid dilution rate, and dry matter disappearance from nylon bags suspended in the rumen were not affected by sodium bicarbonate.

Three lactating, rumen fistulated cows (two Jerseys and one Holstein) were fed mixed diets containing (dry matter) 40% corn silage, 45% concentrate, and 15% coarse ground alfalfa hay. The corn silage was treated prior to ensiling with 1.4% ammonia (dry matter) to which 15nitrogen was added. Total fecal and urine collections and rumen sampling at 0, 2, and 4h after feeding were conducted for all three cows during the 3rd wk on the diet and again during the 6th wk on the diet for one of the cows. Average daily intake of dry matter and milk yield ranged from 7.4 to 7.2kg for the smallest Jersey to 18.3 and 33.0kg for the Holstein. Apparent digestibilities of total dietary dry matter, energy, and nitrogen were 65.6, 65.1, and 66.9%. Percent 15nitrogen excess in rumen ammonia was slightly greater than that in rumen bacteria prior to feeding. Concentrations of 15nitrogen in ammonia and bacteria increased during the first 2h after feeding, with the increase greatest for ammonia, and then plateaued to 4h after feeding. Ratios of 15nitrogen excess indicated that up to 70% of bacterial nitrogen was derived from rumen ammonia. All cows were at equilibrium or in positive nitrogen and 15nitrogen balance during collection periods. Proportion of 15nitrogen retained was much greater than that for nitrogen at 3 wk but was similar during the 6th wk on the diet, indicating that body 15nitrogen was essentially in equilibrium with diet or absorbed 15nitrogen at that time. Ratios of total nitrogen to 15nitrogen excretion in milk suggest that the [15nitrogen] ammonia added to corn prior to ensiling was utilized about 80% as efficiently for milk nitrogen as was total feed nitrogen and that the soluble and insoluble nitrogen compounds from the added ammonia were utilized with the same efficiencies as other nitrogen compounds in the diet with similar solubilities.

To determine whether dairy rations influence the accuracy of component analyses, fat, protein, lactose, and total solids were measured in milk produced by Holstein cows fed a basal ration or a ration containing either 7% extruded soybeans, 15% whole cottonseed, or 30% whole cottonseed for the first 15 wk postpartum. Samples from individual milkings were collected in the 14th and 15th wk from 12 or 13 cows in each group. Reference methods were Mojonnier for fat, Udy dye-binding for protein, polarimetry for lactose, and forced-air oven for total solids. The methods compared to reference methods were Milkotester and Babcock for fat and Infrared Milk Analyzer for fat, protein, lactose, and solids-not-fat. Fatty acid composition was determined by gas chromatography. For cows fed 30% whole cottonseed, Infrared Milk Analyzer fat measurements averaged .14% lower than by Mojonnier. For cows fed extruded soybeans or whole cottonseed, Milkotester fat measurements were higher than by Mojonnier, and Infrared Milk Analyzer protein measurements were higher than by Udy dye-binding. For cows fed whole cottonseed, Infrared Milk Analyzer solids-not-fat measurements were higher than by forced air oven. For cows fed extruded soybeans or whole cottonseed, differences between Babcock and Mojonnier fat measurements and between Infrared Milk Analyzer and polarimetric lactose measurements were not affected. For cows fed whole cottonseed, the mean molecular weight of the fatty aicds of milk fat was increased.

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Four lactating Holstein cows producing about 21 kg milk/day were fed complete rations containing 0, 5, 15, and 25% whole cottonseed in a 4 X 4 Latin square design. Diets were fed ad libitum. Periods were 21 days in length with total collections of feces and urine during the last 7 days of each period. Digestibilities o nitrogen, lipid, and energy increased with increasing cottonseed in the diet. There were no significant effects of cottonseed on digestibility or availability of fiber components, calcium, phosphorous, and magnesium. Cottonseed feeding did not affect dry matter intake or milk yield but did increase yields of milk fat and fat-corrected milk and decrease milk protein and solids-not-fat percentages. Synthesis of fatty acid in the mammary gland was depressed by about 50% on the 25% cottonseed diet, but transfer of dietary fat resulted in twofold increases in yields of stearic and oleic acids. Hydrogenation of cottonseed fatty acid in the rumen resulted in a fourfold increase in yield of trans oleic acid in milk fat. Samples from bulk milk tank and data collected from 55 commercial dairies showed similar changes in fatty acid composition of milk from cows fed whole cottonseed. There was no apparent effect of feeding up to 2.9 kg cottonseed dry matter per cow per day on calving interval or on incidence of displaced abomasum, ketosis, milk, fever, or retained placenta.

Chopped whole corn plant was treated before ensiling with 1.4% ammonia (of dry matter) to which .36% atom excess of 15N had been added. About 50 kg of material (14 kg dry matter) were placed in .5-mm polyethylene bags (of double thickness) which were evacuated and served as experimental silos. Silage samples were taken on days 0, 3, 7, 14, 21 and 50 and analyzed for N fractions. The 15N content of these fractions was analyzed by a mass spectrophotometer. N fractions of untreated silage were also determined. Between days 0 and 7 of fermentation, ammonia N decreased from 50 to 39% of the total silage N, with a corresponding increase in nonammonia N, from 50 to 60%. Thereafter, little change was noted in these fractions. Approximately 40% of the increase in non-ammonia N was in the soluble portion and 60% was in the insoluble portion. Insoluble N of treated silage was 50% higher than that of control silage. Initially, 89% of the N from added ammonia was recovered as ammonia, but this proportion decreased to 68% by day 7 and changed little thereafter. There was immediate incorporation of 43% of the ammonia into the insoluble N fraction. Most of the initial binding was as intact ammonia, with a subsequent release during fermentation. Because direct ammonia incorporation accounted for a higher percentage of the insoluble N increase on day 0 than on subsequent days, these data support earlier studies which showed that ammonia decreased breakdown of protein of the ensiled corn plant.

1.1. Serum concentrations of cholesterol, triglyceride and alpha lipoprotein cholesterol were determined in nine Holstein cows during different stages of their gestation and lactation cycles.2.2. Serum cholesterol concentrations and daily milk yields were significantly correlated during early and late lactation. The correlations were not significant over the entire lactation.3.3. Maximum values for serum cholesterol were observed at mid lactation and minimum at or near parturition. Serum triglyceride concentrations ranged from 4 to 33 mg/dl. Although prepartum levels for triglyceride tended to be higher than postpartum concentrations, no correlation with milk yield was noted.4.4. These data are compared with lipid changes which take place in other mammals during lactation.