|Mulliniks, J -|
|Kemp, M -|
|Endecott, Rachel -|
|Cox, S -|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 21, 2013
Publication Date: March 11, 2013
Repository URL: http://handle.nal.usda.gov/10113/57082
Citation: Mulliniks, J.T., Kemp, M.E., Endecott, R.L., Cox, S.H., Roberts, A.J., Waterman, R.C., Geary, T.W., Scholljegerdes, E.J., Petersen, M.K. 2013. Does ß-hydroxybutyrate concentration influence conception date in young postpartum range beef cows? Journal of Animal Science. 91:2902-2909. Interpretive Summary: Changes in blood metabolites and metabolic hormones during early lactation, resulting from body weight loss after calving, can act as signals to allow or inhibit reproduction. Serum metabolite differences during early lactation were an effective means to segregate cows based on classification of young beef cows according to their conception date. This study indicates that elevated ß-hydroxybutyrate concentrations prior to breeding are related to or may have a detrimental effect on the interval to resumption of estrus in young beef cows and thereby prolong time of conception. A decreased concentration of ß-hydroxybutyrate resulted in an earlier conception date in young lactating beef cows. Therefore, ß-hydroxybutyrate concentrations prior to breeding may be a useful predictive indicator of days to resumption of estrus and conception date. In addition, chute-side measurement of ß-hydroxybutyrate concentrations may provide producers opportunity to manage cows differently to improve overall reproductive efficiency.
Technical Abstract: Cows in negative energy balance after calving often have reduced reproductive performance, which is mediated by metabolic signals. The objective of these studies was to determine the association of serum metabolites, days to first postpartum ovulation, milk production, cow BW change, BCS, and calf performance with conception date in spring-calving 2- and 3-yr-old beef cows grazing native range. In Exp. 1, cows were classified by conception date in a 60-d breeding season as early (EARLY; conceived in first 15 d of breeding) or late conception (LATE; conceived during the last 45 d of breeding). Beginning on d 35 postpartum, blood samples were collected twice/week for serum metabolite analysis and progesterone analysis to estimate days to resumption of estrous cycles. As a chute-side measure of nutrient status and glucose sufficiency, whole-blood '-hydroxybutyrate (BHB) concentrations were measured 14 ± 2 d prior to breeding. In Exp. 2, cows were classified by subsequent calving date resulting from a 55 ± 2 d breeding season as conceiving either early (EARLY; conceived in first 15 d of breeding) or late (LATE; conceived during the remaining breeding season). Blood samples were collected in two periods, 30 ± 4 d prior to calving and 14 ± 3 d prior to the initiation of breeding, to determine circulating concentrations of IGF-I and BHB. In Exp. 1, BHB and serum glucose concentrations were lower (P < 0.04) in EARLY cows than LATE cows. Serum insulin concentrations were greater (P = 0.03) in EARLY cows relative to LATE cows. Milk production and composition did not differ (P > 0.24) by conception date groups. In Exp. 2, cow age × sample period × conception date interaction (P < 0.01) occurred for serum BHB concentrations. Serum BHB concentrations were similar (P > 0.10) for 2-yr-old cows (in higher nutritional plane compared to exp. 1) regardless of their conception date classification and sampling period. However, pre-calving serum BHB concentrations were greater (P < 0.01) for LATE than EARLY in 3-yr-old cows with no difference (P = 0.86) at pre-breeding. Serum IGF-1 concentrations were greater (P < 0.01) for EARLY cows relative to LATE cows at pre-calving and pre-breeding. This study indicates that blood BHB concentrations during times of metabolic dysfunctions may provide a more sensitive indicator of energy status than body condition predicting rebreeding success in young beef cows as measured by interval to conception.