Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/14/2008
Publication Date: 6/24/2008
Citation: Roberts, A.J. 2008. Assessment of insulin-like growth factor-1 as an indicator of competence for rebreeding in first calf heifers. Western Section of the American Society of Animal Science Meeting Abstract. Interpretive Summary: Abstract only
Technical Abstract: Objective of this research was to evaluate whether concentrations of IGF-1 in circulation, BW and BCS measured before calving, after calving and immediately before breeding could be used as indicators of nutritional competency for time of rebreeding in first calf heifers. Heifers were artificially inseminated at about 14 mo of age and then exposed to bulls for the remainder of a 53-d breeding season. This breeding season resulted in a 71-d calving period that began on March 8. Blood samples, BW and BCS were obtained at 3 time points from 74 cows: February 25, which was 12-d prior to beginning of the calving period, 0 to 14 d after calving (date varied in relation to calving), and again on May 27 (before breeding). Separate regression analyses were run for each time point, using a model that included concentration of IGF-1, cow BW, cow BCS and day of calving as independent variables, and day of second calving the dependant variable. Birthday of second calf was influenced (P = 0.01; R*2 = 0.17) by birthday of previous calf (P =0.01; b = 0.31 +/- 0.12) and precalving concentration of IGF-1 (P =0.001; b = -0.20 +/- 0.06), but not by BW (P =0.4) or BCS (P =0.9). Regression analyses with postcalving (P = 0.17; R2 = 0.10) and prebreeding (P = 0.25; R*2 = 0.07) data accounted for less variation in birthday of second calf than precalving measurements of IGF-1. However, similar trends toward a negative relationship between IGF-1 and second calving day were observed with postcalving (P = 0.08; b = -0.07 +/- 0.04) or prebreeding (P=0.09; b = -0.07 +/- 0.04) measures of IGF-1. Results indicate the precalving concentrations of IGF-1 may be a useful indicator of nutritional competency for rebreeding in first calf heifers. Measures of BW and BCS did not appear to be indicative of time to rebreeding.