The effect of a diet containing excess quickly degradable nitrogen (QDN) on reproductive and metabolic hormonal profiles of lactating dairy cows

Correlations between periparturient serum concentrations of non-esterified fatty acids, beta-hydroxybutyric acid, bilirubin, and urea and the occurrence of clinical and subclinical postpartum bovine endometritis

BACKGROUND

Postpartum endometritis in cattle is a multifactorial disease with high economic impact. Both, clinical endometritis (CE) and subclinical endometritis (SCE) result in decreased reproductive performance. Results from in vitro studies led to the implication that non-esterified fatty acids (NEFA), beta-hydroxybutyric acid (BHBA), bilirubin, and urea could be used as predictors for endometritis in veterinary practice. In this field study, we set out to establish optimal predictor cut points of these metabolic parameters for the detection of CE and SCE. Serum samples were collected one week prior to parturition (wk -1), in the first week postpartum (wk +1) and between 28 and 35 days postpartum (wk +5) from 209 Holstein-Friesian cows. At wk +5, all cows were examined for signs of CE and SCE.

RESULTS

Higher concentrations of urea at wk +1 were associated with increased odds of CE (OR = 1.7, P = 0.04) in primiparous (PP) cows. A predictor cut point of 3.9 mmol/L (sensitivity: 61%, specificity: 70%) was determined. In multiparous (MP) cows, the logistic regression model revealed that higher concentrations of NEFA at wk -1 were associated with increased odds of CE and SCE (healthy vs. CE: OR = 9.1, P = 0.05; healthy vs. SCE: OR = 12.1, P = 0.04). A predictor cut point of 0.3 mmol/L (sensitivity: 38%, specificity: 87% and sensitivity: 35%, specificity: 89%, respectively) was determined. Increasing concentrations of urea at wk +5 were associated with decreased odds of CE (healthy vs. CE: OR = 0.6, P = 0.01; SCE vs. CE: OR = 0.5, P = 0.03). A predictor cut point of 3.8 mmol/L (sensitivity: 52%, specificity: 81%) was determined. For BHBA and bilirubin relationships with CE or SCE were not detected.

CONCLUSIONS

The corresponding combinations of sensitivity and specificity of the determined predictor cut points were not satisfactory for practical use. Thus, the analysed parameters, i.e. NEFA, BHBA, bilirubin, and urea, at the chosen time points, i.e. at wk -1, at wk +1, and at wk +5 relative to calving, are unsatisfactory for disease prediction. Further research is required to clarify the questions raised by the current study.

A review of the nutritional value of lupins for dairy cows

Australia is the world’s leading source of lupin grain, producing ~1 million tonnes annually, of which 30% is used by the domestic livestock industry and the rest is exported for use in animal diets, including dairy cows. The domestic dairy industry uses ~70 000 tonnes annually, mainly as a supplementary feed source in pasture-based systems. Although much published information exists on the nutritive value of lupins for dairy cows, it tends to be fragmented and, in some important instances, exists only in the form of reports or publications outside the mainstream scientific journals. This paper aims to present a critical assessment of the current knowledge regarding the nutritional value of lupins as a feed for dairy cows, and offers recommendations for future research. For cows grazing pasture or fed diets based on conserved pasture or cereal hay, the mean fractional response to lupin feeding was 0.53 kg milk/kg DM lupins, with a range of 0–0.97 kg/kg. The mean fractional forage substitution rate was 0.54 kg DM/kg lupins, and this appeared to be independent of the type of basal forage. In experiments using cows fed iso-nitrogenous and iso-energetic total mixed rations, substituting oilseed protein such as soybean meal with cracked lupin grain had no significant effects on yield of milk, fat, and protein, but it reduced milk protein concentration and had mixed effects on fat concentration. There were no significant differences in milk yield or in fat or protein concentration when lupins were substituted for other pulse grains such as faba beans or peas. Treatment of lupin grain with heat or formaldehyde reduced lupin protein degradability in the rumen, but was not shown to have consistent benefits over untreated lupins in terms of increased milk yield. Substitution of cereal grains with an equivalent weight of lupins in dairy concentrate rations generally resulted in increased yield of milk, fat, and protein, and a higher fat concentration. The higher yield responses in most cases could be explained on the basis of the higher metabolisable energy content of lupins compared with cereal grains, although the contribution from a potentially lower incidence of rumen lactic acidosis could not be discounted. Feeding Lupinus albus lupins to cows significantly increased the concentration of C18 : 1 in milk and reduced that of C12 : 0–C16 : 0, thus shifting the fatty acid profile of milk towards national dietary guidelines for improved cardiovascular health in human populations. Although the review lists some recommendations for improving the nutritive value of lupins, current commercially available cultivars possess characteristics that make them attractive as a feedstuff for dairy cows.

The effect of feeding diets high in quickly degradable nitrogen on follicular development and embryo growth in lactating Holstein dairy cows

This study investigated the effect on follicular and embryo development of increasing quickly degradable nitrogen (QDN) intake in lactating Holstein dairy cows. Forty mature post-partum cows were fed one of two diets for a minimum of 10 weeks, starting 10 days before first insemination. The Control diet was a high production dairy ration. The High QDN diet comprised the Control ration plus 250 g urea/head/day. Both diets were formulated to ensure that the energy requirements of the cows were satisfied. The High QDN treatment resulted in a significant increase in milk urea, plasma urea and plasma ammonia concentrations. The highest plasma urea (8.2 mmol/l) and ammonia concentrations (120 micromol/l) were recorded within 7 days of the urea supplement being added to the diet. There was no effect of diet on plasma progesterone or glucose concentration. There was also no significant effect of treatment on follicular development or embryo growth. The results from this study suggest that the lactating cow can adapt to increased intakes of QDN if the increase starts at least 10 days before insemination.