Changes in biomarkers of metabolic stress during late gestation of dairy cows associated with colostrum volume and immunoglobulin content.

The objective of this observational study was to compare the metabolic status of dairy cows during the last 6 wk of gestation based on colostrum volume and immunoglobulin content. For this, healthy Holstein cows were randomly selected from 3 commercial herds in Michigan. In each farm, 4 cohorts of 21 cows (1 per season), stratified by parity, were enrolled (n = 228). Cows were blood sampled weekly during the last 6 wk of gestation, and biomarkers related to nutrient utilization, oxidant status, and inflammation were quantified in serum. Cows were milked within 6 h of calving, and the volume of colostrum produced was recorded and an aliquot collected. Concentration of IgG, IgA, and IgM were measured by radial immunodiffusion. Cows were grouped into high or low colostrum producer, high or low IgG, high or low IgA, and high or low IgM. For volume category, we arbitrarily defined 6 L of colostrum (4 L for first and 2 L for second feeding of calves) as the cutoff point, whereas for IgG we used the industry standard of ≥50 g/L. To create groups of low and high IgM or IgA, we used the median of these immunoglobulin as the cutoff point. Colostrum volume was lowest in winter, but no differences were observed among parity groups. Conversely, colostrum IgG concentration was highest in fall and winter, but colostrum IgM was lowest at these seasons. However, colostrum immunoglobulin content only showed a negative weak correlation with volume (Spearman's correlation coefficient < -0.28). Compared with low colostrum producer, high colostrum producer cows had higher concentrations of antioxidant potential and ß-hydroxybutyrate, and lower cholesterol and oxidant status index. Cows with high IgG showed higher concentrations of glucose compared with low IgG. Cows with high IgA had higher concentrations of cholesterol, reactive oxygen and nitrogen species, oxidant status index, and total protein, whereas ß-hydroxybutyrate and glucose were lower compared with low IgA. Biomarkers of metabolic stress were not significantly different between high IgM and low IgM. Nevertheless, the differences observed did not result in differences in inflammatory status between animals in any of the colostrum variable categories analyzed, suggesting that physiological homeostasis was not disrupted during late gestation in association with the colostrum variables studied. Overall, the great variability observed in colostrum variables suggests that colostrogenesis is a complex and multifactorial process. However, our results suggest that greater availability of antioxidants during late gestation could support the production of higher volumes of colostrum, which needs to be explored in future trials.

Impact of 2 Versus 1 Colostrum Meals on Failure of Transfer of Passive Immunity, Pre-Weaning Morbidity and Mortality, and Performance of Dairy Calves in a Large Dairy Herd.

Failure of transfer of passive immunity (FTPI) due to inadequate ingestion of colostral immunoglobulins by calves is associated with increased mortality and morbidity risks. Feeding calves a sufficient amount of quality-tested colostrum within the first hours of life is essential for successfully transferring passive immunity. Many farms have implemented a second meal of colostrum to maximize the opportunities for passive immunity transfer. However, excellent passive immunity can be achieved with a single feeding of sufficient quality-tested colostrum. Moreover, there is currently no evidence demonstrating the impact of a second colostrum feeding within 24 h of life in calves receiving adequate volumes of quality-tested colostrum in an initial feeding. Hence, the objective of this retrospective cohort study was to compare the risks of FPTI, pre-weaning morbidity and mortality, and growth and performance between dairy calves that received one or two feedings of colostrum. For this, the health and production records of a large dairy herd were analyzed. At this farm, newborn calves receive 3 L of quality-tested colostrum soon after birth, followed by another 2 L 5-6 h later. However, at times of shortages of colostrum, calves only receive the initial 3 L meal. The records of 2064 male and 2272 female calves were analyzed, where 4156 and 180 calves received 2 and 1 colostrum meals, respectively. Data from both sexes were included in the analysis of the risks of FTPI, morbidity, and mortality; however, only data from heifer calves were utilized for growth and performance analysis. Survival analysis, and logistic and linear regression models were used to investigate the impact of receiving two feedings of colostrum on calf FTPI status, morbidity, mortality, reproductive indices, pre-weaning average daily gain (ADG), and first lactation 305-d Mature Equivalent milk production (305ME). Calves that received two feedings of colostrum had lower odds of FTPI, a lower probability of being treated for respiratory disease, diarrhea, or any disease, and a greater pre-weaning ADG. However, there was no association between the number of colostrum feedings and pre-weaning mortality, and the probabilities of first insemination and first calving, although heifers receiving two colostrum feedings tended to receive fewer inseminations and to have a greater first lactation 305ME. Collectively, our results suggest that feeding calves a second feeding of colostrum 5-6 h after the initial feeding soon after birth could be an effective strategy to decrease FTPI and morbidity and optimize ADG in dairy calves pre-weaning.

Effect of preweaning disease on the reproductive performance and first-lactation milk production of heifers in a large dairy herd.

Raising replacement heifers represents a substantial cost in dairy farms, with reproductive efficiency being one of the main factors driving the total rearing cost. Diseases during the preweaning period, such as diarrhea or bovine respiratory disease (BRD), are reported at high incidence risks worldwide. However, the long-term effects of disease before weaning on productive and reproductive performance remain controversial. This retrospective cohort study explored the extent to which diseases such as diarrhea or BRD during the preweaning period affected average daily gain (ADG), herd removal, reproductive indices, and 305-d mature equivalent milk production (305ME) of replacement heifers. The health, growth, and production records of 2,272 female calves from a large dairy herd were used; 487 and 926 of the calves had BRD and diarrhea, respectively, before weaning. The reproductive variables age at first service, age at successful service, age at calving, and pregnancies per artificial insemination were calculated. Associations of disease status with reproduction indices, removal from herd, ADG, and 305ME were evaluated by survival analysis and mixed models. Heifers with a history of BRD before weaning were less likely to be inseminated or achieve first calving than heifers without BRD. However, BRD status did not change the age at first insemination of calving among those being inseminated or reaching first calving, respectively. There were also no differences in ADG, 305ME, and pregnancies per artificial insemination between heifers with and without a history of BRD. A history of diarrhea preweaning was not associated with changes in the probability of being inseminated, having a confirmed pregnancy, or reaching first calving. However, heifers affected by diarrhea required more inseminations to become pregnant. Diarrhea status was also associated with a 325-kg reduction in 305ME in the first lactation and a 50 g/d reduction in ADG. Collectively, our results demonstrate some long-term effects of diseases before weaning on the reproductive efficiency of heifers and first-lactation 305ME production, but with limited effect on the time to achieve critical reproductive performance indicators.