Location: Range and Livestock ResearchTitle: Impact of body condition score on reproductive performance in young postpartum range cows grazing native range) Author
Submitted to: Western Section of Animal Science Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 4/10/2009
Publication Date: 6/15/2009
Citation: Mulliniks, J.T., Cox, S.H., Kemp, M.E., Endecott, R.L., Waterman, R.C., Petersen, M.K. 2009. Impact of body condition score on reproductive performance in young postpartum range cows grazing native range. Western Section of Animal Science Proceedings #15. Journal of Animals Science 87(E-Suppl 3):141. Interpretive Summary: n/a
Technical Abstract: Body condition score (BCS) is used as a management tool to predict reproduction of young beef cows. Therefore, the objective was to determine the effects of BCS at calving on pregnancy rates, days to first estrus (DTFE), nutrient status assessed by blood metabolites and calf body wt change in 315, 2- and 3-yr-old cows grazing native range over 5 yr at the Corona Range and Livestock Research Center, NM. Palpable BCS (1 – 9) were determined by experienced technicians prior to calving. Cows were assigned to one of four BCS treatments: Thin (T; BCS = 3.5 to 4.25), Thin-Moderate (TM; BCS = 4.5), Moderate-Fat (MF; BCS = 4.75 to 5.25), or Fat (F; BCS = 5.5 to 7.0). Postpartum supplementation was terminated each year when cows reached BW nadir. Cows were weighed weekly and serum was collected 2×/wk for progesterone analysis to estimate DTFE. Year effects were also evaluated, with years identified as either above (AA) or below (BA) average rainfall. Data were analyzed as a 4 × 2 factorial. A calving BCS × rainfall interaction occurred for DTFE (P = 0.01). In AA years, all BCS groups achieved DTFE within 86 d postpartum with F cows cycling the earliest at d 68 postpartum. In contrast, during BA years, cows with a higher BCS (MF and F) took up to 61 days longer postpartum to reach DTFE compared to cows in a thinner BCS (T and TM). Pregnancy rates did not differ between BCS (P = 0.45; 90, 95, 90, 90 for T, TM, MF, and F, respectively). Calf birth weight had a tendency to increase linearly (P = 0.11) with decreasing BCS. However, calf weaning weight was not affected by BCS (P > 0.20). Results suggest that BCS interacts with rainfall and may not be a consistent indicator of reproductive performance in young beef cows.