The value of reproductive tract scoring as a predictor of fertility and production outcomes in beef heifers1

Abstract

outcomes in beef heifersThe value of reproductive tract scoring as a predictor of fertility and production doi: 10.2527/jas.2008-1579 originally published online Mar 13, 2009; 2009.87:1934-1940 ABSTRACT:In this study, 272 beef heifers were studied from just before their first breeding season (October 15, 2003), through their second breeding season, and until just after they had weaned their first calves in March, 2005. This study was performed concurrently with another study testing the economic effects of an estrous synchronization protocol using PG. Reproductive tract scoring (RTS) by rectal palpation was performed on the group of heifers 1 d before the onset of their first breeding season. The effect of RTS on several fertility and production outcomes was tested, and the association of RTS with the outcomes was compared with that of other input variables such as BW, age, BCS, and Kleiber ratio using multiple or univariable linear, logistic, or Cox regression. Area under the curve for receiver operating characteristic analysis was used to compare the ability of different input variables to predict pregnancy outcome. After adjustment for BW and age, RTS was positively associated with pregnancy rate to the 50-d AI season (P < 0.01), calf weaning weight (r = 0.22, P < 0.01), and pregnancy rate to the subsequent breeding season (P < 0.01), and negatively associated with days to calving (r = 0.28, P < 0.01). Reproductive tract scoring was a better predictor of fertility than was Kleiber ratio and similar in its prediction of calf weaning weight. It was concluded from this study that RTS is a predictor of heifer fertility, compares well with other traits used as a predictor of production outcomes, and is likely to be a good predictor of lifetime production of the cow.

Evaluation of pre-breeding reproductive tract scoring as a predictor of long term reproductive performance in beef heifers

“…Other researchers demonstrated that cows that calve early during the first calving season, calve early during subsequent seasons as well and have increased lifetime production (Lesmeister et al, 1973, MacGregor and Casey, 1999, Pence et al, 2007, Stevenson et al, 2008. In a previous report (Holm et al, 2009) we therefore hypothesised that heifers with higher RTS before the start of the first breeding season are likely to calve early during subsequent breeding seasons compared to their herd mates with lower RTS. It was further hypothesised that such heifers will have increased survival in a seasonal breeding system with a strict culling policy based on reproductive failure.…”

“…The farming system and breed type have been described previously (Paterson et al, 1980, Schoeman and Jordaan, 1998, Holm et al, 2008, 2009, 2014. In brief, the Bovelder is a South African composite beef breed, and Johannesburg Water Northern Farm is a semi-intensive system using irrigated ryegrass, kikuyu and clover pastures with additional maize or sorghum silage.…”

“…This shift occurs at a specific critical BW (as a proportion of adult BW) and critical age which varies amongst animals (Pence et al, 2007). Various factors affect the age at puberty in individuals, and RTS provides an indirect measure of pubertal development (Andersen et al, 1991, Pence and BreDahl, 1998, Holm et al, 2009). Weaknesses of RTS include imperfect repeatability, subjectiveness and inconsistent associations with reproductive outcome (Rosenkrans andHardin, 2003, Holm et al, 2009).…”

“…Short term reproductive performance may be predicted by RTS (Andersen et al, 1991, Pence et al, 2007, Holm et al, 2009) and we hypothesised that RTS may predict long-term survival in restricted bred heifers due to its association with pregnancy outcome and days to calving after first breeding, combined with reports that heifers calving early tend to calve early in subsequent seasons and have increased lifetime production (Lesmeister et al, 1973, Pence et al, 2007, Stevenson et al, 2008, Cushman et al, 2013. To the knowledge of the authors, a long-term study of the performance of heifers by RTS category has not been reported.…”

Growth and reproductive performance of 14- to 15-month-old Hereford heifers

“…Heifers with RTS>3 and average BW of 264.08±29.00 kg, which corresponded to 52.82% of mature cow weight, presented 62.9% pregnancy rate (Table 6). High RTS at the beginning of the breeding season is positively associated with pregnancy rate, weaning weight, repeated pregnancy rate, and longevity in the herd (Holm et al, 2009). These authors also state that RTS is the best predictor of heifer fertility and that age has a stronger effect on RTS than BW and BCS.…”