A farming systems study of abortion in dairy cattle on the Atherton Tableland. 3. Metabolic factors

An association with a rank correlation of 0.55 (p = 0.06) was obtained between monthly rainfall and monthly abortions for a group of 24 farms in tropical Australia where cows grazed predominantly summer rain-dependent pasture. A similar association was found among cows grazing nitrogen-fertilised, irrigated pasture in winter in the same area. On farms with irrigated pasture the first service conception and abortion rates in herds which grazed intensively during the night (abortion 8.9%; first service conception 42.9%) differed significantly from those which grazed during the day (abortion 6.4%; first service conception 52.9%), and this suggested that increased abortion rates and decreased first conception rates may be part of the one syndrome. An hypothesis was developed that the feeding of immature nitrogen-fertilised pasture, rich in protein and stimulated by rain or irrigation, is associated with an increased abortion rate and a depressed conception rate. Other evidence included an increased susceptibility of first lactation cows to abortion, a lower abortion rate in late pregnant dry cows fed more mature pasture, a 20% repeat abortion rate in the population sampled and the lack of conclusive evidence for infectious and selected non-infectious agents. There were no other observed clinical signs in most aborting cows.

Impact of protein nutrition on reproduction in dairy cows

In most but not all published studies, feeding diets with high concentrations of crude protein decreased reproductive efficiency. We were able to resolve some of the inconsistencies among published reports by considering the fate of consumed protein in the rumen and then using logistic regression analysis to identify factors affecting pregnancy. Our models showed that type and amount of protein fed explained much of the variation in conception rate. Age and dietary concentration of energy were identified as modifiers of the impact of protein on reproduction. Protein nutrition can affect reproduction through toxic effects of ammonia and its metabolites on gametes and early embryos, through deficiencies of amino acids, and by exacerbations of negative balances of energy. Alterations in the hypothalamic-hypophyseal-ovarian axis may be responsible for many of the effects of protein on reproduction.

Influence of protein intake and feeding strategy on reproductive performance of dairy cows

A study was conducted to determine the impact of dietary CP concentration (13 vs. 20%) and feeding strategy (total mixed ration vs. separate feeding of the forage and concentrate) on reproductive performance of 57 early lactation dairy cows. Cows were assigned to one of four treatments in a 2 x 2 factorial arrangement. Rations composed of 40% forage (50% grass-legume silage:50% corn silage) and 60% concentrate (DM basis) were fed from d 5 to 100 postpartum. Cows fed a total mixed ration had lower ruminal ammonia and plasma urea N concentrations compared with cows fed separately. Feeding strategy groups showed no differences in reproductive performance. Cows fed a 20% CP ration had higher CP intake, higher ruminal ammonia, and higher urea N concentration in plasma and vaginal mucus. There were no differences between low and high CP groups in days to first observed estrus (24 vs. 27), days to first service (55 vs. 59), days open (72 vs 82) or services per conception (1.5 vs. 1.8). Days to first estimated ovulation were longer (22 vs. 17) in the high vs. low CP groups, and there was an interaction between protein intake and lactation number. Cows managed with an intensive program for detection of estrus and for reproductive health did not show differences in reproductive efficiency when fed 13 or 20% CP rations.

Evaluation of calcium lignosulfonate-treated soybean meal as a source of rumen protected protein for dairy cattle

Four Holstein cows fitted with ruminal, duodenal, and ileal cannulae were used in a 4 x 4 Latin square design to measure ruminal protein degradation and small intestinal digestion of diets containing untreated soybean meal or soybean meal treated with heat and either water, xylose, or calcium lignosulfonate. Diets consisting of 40% corn silage, 10% alfalfa cubes, and 50% grain mix, and averaging 16.8% crude protein (DM basis) were fed four times daily. Approximately 50% of the total dietary protein was supplied by the respective soybean meal source. Ruminal protein degradation was 70.6, 69.6, 55.8, and 53.7% for diets containing untreated soybean meal, water-soybean meal, xylose-soybean meal, and calcium lignosulfonate-soybean meal, respectively. Duodenal non-NH3 N flow (g/d) and absorption of non-NH3 N (g/d) in the small intestine were generally not affected by treatment. Duodenal bacterial N flow (g/d) was lower with xylose-soybean meal and lignosulfonate-soybean meal than with untreated soybean meal. Treatment of soybean meal with xylose or calcium lignosulfonate was successful in decreasing ruminal protein degradation. However, it may be necessary to include a source of readily fermentable N in diets that contain protected proteins in order to supply adequate NH3 N for microbial protein synthesis.

Influence of dietary protein on reproductive performance of dairy cows

From 10 +/- 3.5 d after parturition to 149 +/- 3.5 d of lactation, 146 cows (109 Holstein and 37 Ayrshires) were fed either a 15 or 20% crude protein diet of 45% sorghum silage and 55% concentrate. Milk production was enhanced by the 20% protein diet, but percentage of milk fat and protein were unchanged. Average daily intake of DM was unaffected by diet. Actual decreases in body weight and condition were small, although cows on 15% protein lost more condition. Concentration of plasma urea nitrogen increased rapidly during the first 4 wk of the experiment with cows on the 20% protein diet maintaining a 10 mg/dl advantage after the 4th wk on experiment. Diet did not affect the postpartum interval to first normal corpus luteum and standing estrus. Cows were inseminated artificially between 55 and 145 d post-calving with one freeze batch of semen from one bull of each appropriate breed mainly by one inseminator. Overall, days open, services per conception, and percentage cows pregnant on experiment were 80, 1.40, and 85, respectively. Concentration of protein in the diet did not affect these reproductive traits. There was no conflict between the amount of dietary protein provided for lactation and reproduction in this experiment.

Ruminal protein degradation and protein value of feeds

The relationship between dry matter (DM) degradation and crude protein (CP) degradation in the dairy cow's rumen was determined with a view to defining the protein value of feeds for ruminants. The nylon bag technique was applied for these studies. For all the feeds investigate (green fodder and preserves from cocks-foot, ryegrass, alfalfa/grass and meadow grass, as well as alfalfa, extracted soybean meal) a significantly positive relationship was found to exist between the levels of DM and CP degradation (r = 0.73 to 1.0). The regression coefficient b1 (CP degradation as regressor) was found to average 0.87. The positive relationship between DM degradation and CP degradation implies that microbial protein amount and unfermented feed protein at the duodenum are negatively correlated. Model calculations show that, on account of the compensation between microbial protein and feed protein at the duodenum, in feeds with a CP concentration below 200 g/kg DM, the extent of ruminal protein degradation does not exert a marked influence on duodenal protein passage. The partial calculation of the duodenal protein supply on the basis of undegraded feed protein and microbial protein, as practiced in the new models of protein evaluation, leads to systematic errors unless the relationship between DM degradation and CP degradation is considered.

Effects of diet nitrogen and forage nitrogen insolubility on performance of cows in early lactation

Thirty-six Holsteins were allotted at parturition to six treatments to measure effects of diet nitrogen and increased insolubility of silage nitrogen on performance and ruminal, plasma, and milk constituents during the first 100 d of lactation. Diets contained 40% concentrate and 60% silage in dry matter. The six silage treatments were untreated corn silage (low nitrogen); untreated corn silage and untreated alfalfa silage (1:1); untreated corn silage and formaldehyde and formic acid-treated alfalfa silage (1:1); ammonia-treated corn silage (low nitrogen); treated corn silage and untreated alfalfa silage (1:1); or treated corn silage and treated alfalfa silage (1:1). Diets containing ammonia-treated corn silage had higher hot water-insoluble nitrogen and diets containing formaldehyde and formic acid-treated alfalfa had higher autoclaved rumen fluid-insoluble and hot water-insoluble nitrogen that their respective untreated silage diets. Dry matter intake, daily yields of milk and its constituents, ruminal NH3 nitrogen, and plasma urea nitrogen were lower for cows consuming low nitrogen diets containing only corn silage compared with cows consuming high nitrogen diets containing alfalfa. Dry matter intake and milk protein yields were greater for cows consuming treated alfalfa compared with untreated alfalfa in the diet. Daily 4% fat-corrected milk yields tended to be higher for diets containing treated alfalfa than untreated alfalfa. Cows fed diets containing NH3-treated corn silage had similar milk, fat, and protein yields compared with diets containing untreated corn silage and urea in the concentrate.

Relative value of solvent and expeller soybean meal for lactating dairy cows

Nitrogen solubility and enzymatic and rumen in vitro degradabilities indicated protein from expeller soybean meal was more resistant to ruminal degradation than that from solvent soybean meal. This was confirmed in Trial 1 by reduced rumen ammonia and branched-chain volatile fatty acids, and by 64% more supplemental protein escaping the rumen when cows were fed expeller soybean meal. In Trial 2, rations supplemented with either solvent or expeller soybean meal, averaging 16.4% protein, were fed to 12 cows in a crossover study. Production averaged 35.3 kg/d but was not influenced by diet. A small but significant improvement in milk to feed ratio occurred with expeller soybean meal. In Trial 3, four sources of protein were fed to 20 cows in a 4 X 4 Latin square: 6.3% solvent, 4.1% expeller (plus .3% urea), 10.0% solvent, or 6.6% expeller soybean meal. Production of milk and milk components was similar on the diets containing 6.3 and 6.6% soybean meal, intermediate on 10.0% solvent, and least on the expeller-urea diet. Milk to feed was equal and greatest on diets containing 6.6% expeller and 10.0% solvent soybean meal, indicating comparable utilization of the expeller diet containing only 60% as much supplemental protein.

Influence of formaldehyde-treated soybean meal on milk production

Forty-eight Holstein cows were fed one of four diets containing 12.5% crude protein (negative control); 15.5% crude protein with untreated soybean meal; 15.5% crude protein with formaldehyde (.3%)-treated soybean meal; or 18% crude protein (positive control). Diets were 60% concentrate, 22% corn silage, 14% alfalfa hay, and 4% beet pulp (dry matter). Data were collected during the first 200 d of lactation. Dry matter intake, milk, and milk component yields did not differ among cows fed the untreated soybean meal, treated soybean meal, and positive control diets. Cows fed negative control diet consumed less dry matter and produced less milk than cows fed the other diets. Milk protein yield was lower for cows fed the negative control diet compared with the other diets. Nonprotein nitrogen content of milk increased as dietary protein increased.

Production responses in early lactation to additions of soybean meal to diets containing predominantly corn silage

Responses in yield of milk and intake of dry matter to increased concentrations of dietary crude protein by cows in early lactation were modeled from published data. The data base was 625 Holstein cows in second or later lactation fed diets primarily composed of corn grain and a combination of corn silage and alfalfa. Dietary crude protein as a percent of dry matter ranged from 9.5 to 20.2% and was varied with soybean meal. Exponential models were developed to predict changes in milk yield and dry matter intake per unit change in dietary crude protein. The consequence of changes in concentration of dietary crude protein on performance can be predicted with the models. The dose-response relationships can be used with relevant price information to estimate the concentration of crude protein that maximizes returns over feed costs. Profitability is improved by adjusting concentration of dietary crude protein for changes in the price of soybean meal. Present feeding standards could be enhanced by incorporation of information on dose-response and economics.

Effect of high crude protein on pituitary and ovarian function in Holstein cows

Intact and ovariectomized cows were used to determine the effect of high amounts of dietary crude protein on pituitary regulation of luteinizing hormone. Estrus was synchronized with prostaglandin F2 alpha in 10 intact dry cows fed 15 or 25% crude protein, and serum luteinizing hormone profiles were evaluated during both follicular and luteal phases of the estrous cycle. Serum progesterone, pituitary luteinizing hormone content, and luteinizing hormone-releasing hormone receptors were also measured. Basal concentrations of serum luteinizing hormone tended to be lower during the follicular phase and were significantly higher during the luteal phase in cows fed 25% crude protein. Serum progesterone was not affected by dietary treatment. In 10 ovariectomized cows fed 24% crude protein, amplitude of luteinizing hormone response to luteinizing hormone-releasing hormone challenge tended to be smaller than that of 8 cows fed 16% crude protein, although total luteinizing hormone released in response to luteinizing hormone releasing hormone challenge was not different between dietary treatments. In both intact and ovariectomized cows, pulsatile luteinizing hormone patterns, pituitary luteinizing hormone content, and luteinizing hormone-releasing hormone receptors were not influenced by treatment. High dietary crude protein did not have a primary effect on luteinizing hormone or progesterone in nonlactating cows.

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.

Varying protein content and nitrogen solubility for pluriparous, lactating Holstein cows: digestive performance during early lactation

Thirty-four pluriparous Holstein cows were used to examine effects of crude protein (15.3 vs. 13.6%, dry matter basis) and nitrogen solubility (39.7 vs. 47.9%) on digestibility, energy and protein balances, and related traits during early lactation. Cows were assigned randomly at parturition to treatments in a 2 X 2 factorial arrangement; measurements were during wk 6, 10, and 14 postpartum. Diets were protein supplements (varying in protein content and nitrogen solubility), low-protein concentrate, corn silage treated with urea at ensiling, and wilted grass silage fed individually for ad libitum intake. Reducing nitrogen solubility of diet improved energy intake and productive energy factors but resulted in no significant increase of milk yield or body tissue balances, although body fat balance tended to be higher for low-solubility diets. There was no effect on overall partition of nitrogen in the body. Digestibility of carbohydrates and protein was higher for 15.3 than for 13.6% crude protein diets, resulting in higher total digestible nutrients and digestible and metabolizable energy of dry matter. Raising crude protein in the ration decreased milk yield of cows in early lactation but generally increased body tissue balances. Concentrations of rumen ammonia and blood urea nitrogen were not influenced by nitrogen solubility; increasing dietary protein increased concentrations of both, although not enough to increase consumption of free water. Best digestive efficiency was for animals fed the ration of medium crude protein and low nitrogen solubility.

Interaction of protein percent with caloric density and protein source for lactating cows

Experiment 1 was to test effect of three ratios of energy to protein in complete mixed diets for 36 lactating cows in three, 28-d periods. Energy was varied with cottonseed hulls, pelleted ground corrugated boxes, and a mixture of the two. Crude protein was varied with soybean meal to give energy:crude protein of 5.7, 5.0, and 4.6 for each energy amount. Cottonseed meal was compared with soybean meal in corrugated box diets. Feed intake was much higher with cottonseed hulls, and appreciable feedlot bloat resulted from pelleted ground corrugated box diets. Data adjusted to equal feed intake showed significant effect of energy to crude protein ratio on milk yield and improved digestion of organic matter with soybean meal vs. cottonseed meal. Experiment 2 tested the hypothesis that lactating cows consuming high-protein alfalfa may benefit from supplemental protein. Diets were 50% forage. Six diets were 14 or 18% crude protein in three ratios of alfalfa hay to corn silage (0:100, 50:50, 100:0). Additional corn silage diets were to compare: 14 versus 18% protein from distiller's dried grains with solubles only and with .5 or .9% urea (four diets); two 14% protein diets compared .6% added potassium chloride with or without .5% urea. Thirty-six Holstein cows in early lactation received one of the 12 diets in each of three 28-d periods. Distiller's grains with solubles markedly depressed milk yield (2.2 kg/d) and milk protein (.22%); heat damage of distiller's grains was evident. Protein interacted with alfalfa so gain in milk from 18 versus 14% increased from .55 to 1.36 to 2.66 kg/d as alfalfa changed from 0 to 50 to 100%. Thus, crude protein of alfalfa was not as effective as that from soybean meal in supporting milk yield.

Effects of particle size and formaldehyde treatment of soybean meal on milk production and composition for dairy cows

Twenty-four lactating dairy cattle were used to study the effects of formaldehyde treatment and reduction of particle size of soybean meal on milk production and composition. Cows were fed diets containing one of the following soybean meals: 1) untreated, coarse; 2) untreated, fine; 3) formaldehyde-treated, fine. Formaldehyde reduced the solubility of soybean meal protein from 22.7 to 2.9%. Grinding soybean meal reduced particle size from 842 to 249 micron. Formaldehyde treatment did not affect intake or milk production but resulted in higher efficiency of milk production (1.43 versus 1.46 kg fat-corrected milk/kg dry matter intake). Milk protein (3.08 versus 2.85%) and solids-not-fat (8.51 versus 8.35%) contents were reduced by formaldehyde. Cows fed fine soybean meal had higher dry matter intakes (22.0 versus 20.8 kg dry matter/day) and gained more body weight; however, milk production was not affected by particle size. Grinding soybean meal reduced production efficiency (1.47 versus 1.42 kg milk/kg dry matter intake) and milk fat (3.70 versus 3.33%). Lack of production response and reduced milk protein from formaldehyde treatment suggests possible overprotection of protein. Fine grinding of soybean meal appeared to favor body weight gain rather than milk production.

Ammonia: its effects on biological systems, metabolic hormones, and reproduction

The physical, chemical properties of ammonia, its sources and detoxification, its effects in biological systems, its influence upon insulin action and glucose metabolism, and its possible effects on reproduction are discussed. Present chemical methods do not distinguish nonionic from ionic forms. At physiological pH, nonionic ammonia concentrations remain low but are primarily responsible for toxic effects. Thus, biologically significant changes of ammonia concentrations may not be revealed by determinations of ammonia in blood plasma. For these and other reasons the subacute toxicity of ammonia often is unrecognized, and its effects on intermediary metabolism and the hormonal milieu in normal and disease states remain poorly understood. Effects of ammonia may be stimulatory at low concentrations and inhibitory as concentrations rise or exposure is extended. Extensive experiments in eight ureotelic species, including man, show that urinary excretion of orotic acid becomes significantly elevated when the quantity of ammonia presented to the liver exceeds the capacity for normal detoxification. Present evidence with arginine and other intermediates of the urea cycle suggest that these substances influence glucose metabolism and insulin action. Recent studies of dairy cattle provide speculative evidence that high protein feeding or forms of protein that lead to elevated ammonia concentrations in tissue decrease conception rates and increase the calving to conception interval of dairy cows. Limited data concerning luteinizing hormone concentrations and steroid hormone metabolism are insufficient to establish whether differences in reproductive performance are due to changes of hormonal physiology, intrauterine environment, or metabolism.

Early lactational response to supplemental protein by dairy cows fed grass-legume forage

A total of 24 primiparous and 46 multiparous Holstein cows were in two trials to determine the influence of concentration of dietary protein on performance during early lactation. Treatments were 13.5 or 16.5% dietary crude protein for the first 12 wk of lactation. Complete mixed diets of grass-legume forage and concentrates were fed for ad libitum consumption. Treatment patterns repeated across trials. Yields of milk and 3.5% fat-corrected milk, intake of dry matter, and returns over feed costs were improved by feeding the diet with 16.5% crude protein. Percent milk fat, body weight change, and reproductive performance were unaffected by treatment. The results demonstrate benefit, during early lactation, from supplementing protein to grass-legume based diets containing 13.5% crude protein. Performance responses to increased concentrations of dietary crude protein during early lactation appear greater for multiparous than primiparous cows.

Effect of rumen protein degradability on milk yield of dairy cows in early lactation

Twenty-four mature Holstein cows were fed diets of 40% corn silage and 60% concentrate (dry matter) beginning at parturition through wk 16 of lactation. A control concentrate (corn, soybean meal, and barley) was fed through wk 4 followed by assignment of cows to either a concentrate of low or high rumen protein degradability. In situ trials with two fistulated cows fed similar diets yielded rumen protein degradabilities of 78.5, 70.3, 69.9, 67.3, 49.1, and 36.5% for barley, corn, corn gluten feed, soybean meal, brewer's grains, and cottonseed meal. The low degradability concentrate (corn, cottonseed meal, brewer's grains, and corn gluten feed) had an estimated rumen protein degradation of 52.9% and a total ration crude protein of 14.3%. The high degradability concentrate containing corn, barley, and soybean meal was 72.8% rumen degradable, and total ration protein for this treatment was 14.5%. Dry matter intakes were 21.0 and 22.0 kg/day for the low and high degradability diets. Milk yield, fat percent, and fat-corrected milk were not affected by treatment. Milk protein percent and protein yield decreased from 3.00 to 2.84% and 1.07 to .99 kg/day in the high and low degradability diets. Efficacy of use of degradability as a criterion for feed formulation is questioned until understanding of both feed protein breakdown and microbial synthesis is greater.

Relationship of dietary crude protein to composition of uterine secretions and blood in high-producing postpartum dairy cows

Effects of dietary crude proteins on constituents of plasma and uterine secretions were examined at various stages of the estrous cycle of high producing Holstein cows. Eighteen cows were assigned randomly to isocaloric diets (74% total digestible nutrients) containing either 12 or 23% crude protein (dry matter) on day 40 postpartum. Uterine secretion and coccygeal blood samples were collected at estrus, days 5 and 15 of the first estrous cycle after day 50 postpartum, and at the subsequent estrus. The 23% crude protein diet resulted in higher concentrations of ammonia in blood, urea in blood plasma and uterine secretion, and phosphorus and potassium in plasma. Zinc increased during the estrous cycle in plasma of cows fed 23% crude protein and decreased in cows fed 12% crude protein. Magnesium concentrations in uterine secretions were lower in cows on 23% crude protein. Potassium and phosphorus also were lower in uterine secretions of cows fed 23% crude protein but only during the luteal phase of the estrous cycle. Zinc concentrations in uterine secretions decreased faster during the estrous cycle in cows fed 12% crude protein than in cows fed 23% crude protein. Thus, the crude protein content of the diet altered concentrations in blood of ammonia and concentrations in plasma of urea, phosphorus, potassium, and zinc. Crude protein content of the diet altered concentrations in uterine secretion of urea, magnesium, potassium, phosphorus, and zinc.

The effect of dietary and climatic factors on fertility, and on plasma progesterone and oestradiol-17 beta levels in dairy cows

The effects of high dietary protein concentrations, high ambient temperatures and low dietary beta-carotene levels on fertility and on plasma progesterone and oestradiol-17 beta levels in high-yielding dairy cows, are described. High-yielding dairy cows were fed diets containing 15 or 20% crude protein. Cows fed the higher level of protein were less fertile and had a lower plasma progesterone concentration during the oestrous cycle preceding the first insemination. This phenomenon was especially pronounced in cows fed a diet containing 85% concentrates and 15% hay, where plasma progesterone levels during days 9-17 of the oestrous cycle were 2.5-3.7 ng/ml in cows fed the high level of protein and 4.0-5.5 ng/ml in cows fed the low level of protein (P less than or equal to 0.05). In cows fed 50% more energy before parturition, plasma progesterone levels did not differ between animals fed the low and high protein diets. Heat stress, which caused a rise in body temperature, decreased fertility and plasma progesterone levels during the luteal phase of the oestrous cycle but increased plasma oestradiol-17 beta levels during the 36 h preceding the onset of oestrus from 5 to 7 pg/ml (P less than or equal to 0.005). The effect on fertility of supplementing the diet of dairy heifers and cows with beta-carotene is reviewed. In some of the experiments where the basal plasma beta-carotene levels were lower than 50 micrograms/100 ml, beta-carotene supplementation significantly increased fertility. However, in no case was fertility affected when plasma beta-carotene levels exceeded 150 micrograms/100 ml. The possible relationships among body weight changes, energy balance, plasma progesterone levels and fertility of dairy cows are discussed.

Effects of formaldehyde treated soybean meal on milk yield, milk composition, and nutrient digestibility in the dairy cow

The nutritional value of soybean meal that had been treated with formaldehyde (.3 g/100 g) to inhibit microbial degradation of soybean meal protein in the rumen was investigated. Four experimental diets were fed ad libitum during wk 4 to 43 of lactation to Holstein cows randomly assigned to diets in a 2 x 2 factorial arrangement of dietary crude protein (12 and 14%) and formaldehyde treatment (untreated and treated soybean meal). Concentrate, corn silage, and alfalfa-grass hay provided 53.0, 35.4, and 11.6% of the daily intake of dry matter. Analysis of covariance revealed that digestibility of dietary crude protein by cows fed formaldehyde treated soybean meal was lower than by cows fed untreated soybean meal (62.4 versus 65.4%). Similar quantities of milk, 4% fat-corrected milk, milk fat, and milk solids-not-fat (overall means of 7998, 7402, 281, and 660 kg/301 days of lactation) were produced by cows fed different diets. This was true whether the data were summarized during peak production (day 22 to 63), during days 22 to 119 when crude protein intake did not meet requirements, or during the complete experiment (days 22 to 301 of lactation). Milk protein (total nitrogen x 6.38) produced by cows fed soybean meal treated with formaldehyde was less than by cows fed untreated soybean meal during days 22 to 63 and during days 22 to 119 (47 versus 44 kg/cow and 103 versus 97 kg/cow). Changes in body weight of cows during lactation were similar among treatments. Treating soybean meal with .3 g formaldehyde/100 g may decrease availability of soybean meal protein for use by lactating dairy cows.

Performance of high producing cows in early lactation fed protein of varying amounts, sources, and degradability

Eighty-four multiparous Holstein cows were fed a standard ration from 0 to 21 days postpartum and treatment rations from 22 to 91 days. Treatments varied in amount and source of protein, and only cows averaging at least 26 kg milk daily from 8 to 21 days postpartum were used. Experimental variables included protein percent (11.3, 14.5, 17.5), ammoniated versus untreated corn silage, and heated (2.5 h at 140 degrees C in forced draft oven) versus normal soybean meal. Treatments by protein percent and supplement types were: 1) 11%, untreated silage, normal soy; 2) 14%, ammonia silage, heated soy; 3) 14%, untreated silage, heated soy; 4) 14%, untreated silage, normal soy; 5) 17%, ammonia silage, heated soy; 6) 17%, untreated silage, heated soy; and 7) 17%, untreated silage, normal soy. Milk production and dry matter intakes increased with increased protein. Differences were greater between 11 and 14% than between 14 and 17%. At 14 and 17% protein, cows fed normal soy produced less than those fed heated soy, but silage treatments were not different. The 17% ration containing ammonia silage and heated soy resulted in greatest milk production and highest income over feed costs. A combination of heated soybean meal to limit rumen degradability and ammonia in corn silage to furnish nonprotein nitrogen was the most productive and profitable of several rations compared for cows early in lactation.

Discussion: Implications of the stress syndrome to animal performance and health

Similarities of blood metabolic and immunologic reactions that occur in cattle exposed to heat stress, other chronic stress-inducing environmental factors, and administration of pituitary, adrenal, and thyroid hormones have been described. Chronic stress can predispose cattle to both metabolic and infectious diseases. Improved characterization of endocrine, metabolic, and immunologic relationships offers promising means for studying effects of various treatment regimens on animal health, production, and reproduction.