|Cobb, Clayton -|
|Ballou, Mike -|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 2, 2011
Publication Date: April 29, 2011
Citation: Hulbert, L.E., Cobb, C., Carroll, J.A., Ballou, M. 2011. Effects of changing milk replacer feedings from twice to once daily on Holstein calf innate immune responses before and after weaning. Journal of Dairy Science. 94:2557-2565. Interpretive Summary: Feeding dairy calves milk or milk replacer twice daily is labor intensive. A management strategy that decreases calf rearing costs due to reductions in time and labor is to only feed milk or milk replacer once daily. However, the effect of switching to once-a-day milk replacer feeding on the innate immune responses of Holstein calves is unknown. Therefore, a collaborative study among scientists from ARS' Livestock Issues Research Unit and Texas Tech University was conducted to determine the effects of switching Holstein calves to once-a-day feeding during the 4th week of life on innate immune responses and also evaluate whether there were any carry-over effects when the calves were weaned during the 7th week of life. The results of the study demonstrated that consolidating calf milk replacer into one feeding during the 4th week of life caused a transient neutrophilia, but did not suppress functional capacities of neutrophils. Once-fed calves did not have acute suppression of TNF-alpha secretion from whole blood cultures, but 21 d after changing the feeding frequency they were persistently lower through the end of the study. Overall, these data indicate that switching Holstein calves to once-a-day feeding during the 4th week of life was likely a mild and acute stressor, and the calves were able to cope rapidly to the change in feeding frequency. This information will be of interest to dairy producers and dairy cattle nutritionists that are seeking to reduce the cost associated with the management of young dairy calves.
Technical Abstract: The objectives of this study were to determine the effects of switching Holstein calves to once-a-day feeding during the 4th week of life (24 ± 2.3 d of age; once-fed n = 22; twice-fed n = 22) on innate immune responses, and also evaluate whether there were any carry-over effects when the calves were weaned during the 7th week of life. Whole blood was taken just before the change in feeding strategy (age 24 d), as well as 27, 31, 45, 48, 52 and 66 d of age, and was analyzed for circulating cortisol, haptoglobin, total leukocyte counts, neutrophil:mononuclear cells, and hematocrit percent. Whole blood was also stimulated with lipopolysachharide (LPS) for 24 h and supernatant tumor necrosis factor-alpha (TNF-alpha) concentration analyzed. Neutrophil L-selectin and Beta-integrin expression were analyzed via flow cytometry. Simultaneous neutrophil phagocytic and oxidative burst responses to a heat-killed Escherichia coli were quantified via dual-color flow cytometry. There were no differences between treatments on either the pre- or post-weaned performance. Once-fed calves tended (P = 0.07) to have more circulating neutrophils at 27 d of age, greater (P = 0.07) expression of L-selectin on neutrophils at 31 and 45 d of age, and greater (P = 0.06) intensity of phagocytosis at 45 d of age. Once-fed calves secreted less TNF-alpha when whole blood cultures were stimulated with LPS at 45 d of age when compared with Twice-fed calves (P < 0.05), and this tended (P = 0.09) to persist through the immediate post-weaning period. There were no differences in any of the other immune parameters after weaning between the pre-weaning feeding strategies (P > 0.10). Consolidating calf milk replacer into one feeding during the 4th week of life was likely a mild and acutely stressor, as evidenced by transient neutrophilia in the absence of suppressed functional capacities of neutrophils. Future research should address the mechanism and immunological significance of the persistent decreased TNF-alpha response in Once-fed calves.