Improving reproductive efficiency through the use of reproductive tract scoring in a group of beef replacement heifers

Abstract

This study investigated the potential improvement in reproductive efficiency through reproductive tract scoring (RTS) of heifers 30-60 days prior to breeding. Between 2000 and 2004, the RTS of 1986 heifers (mean age of 395 days) were determined in two locations in Georgia, USA as part of the Heifer Evaluation and Reproductive Development (HERD) project. These heifers were of similar age and were managed using comparable nutrition and management protocols. The Kaplan-Meier product-limit method was used to analyse the number of days from the start of the breeding period to conception for heifers with different RTS classifications. RTS was significantly associated with both time to conception and the proportion of heifers that conceived during the breeding period. The mean time to conception for heifers in the combined RTS 1 and 2 category (37.8 days) was significantly longer than for heifers with scores of 4 (19.7 days) or 5 (15.8 days), but not significantly different from heifers with RTS of 3 (29.2 days). The estimated percentages of heifers that would have conceived during a uniform 70 day breeding period were 94.6% of RTS 5, 91.2% of RTS 4, 87.6% of RTS 3, and 70.5% of RTS 1 and 2. This study indicates that reproductive tract scoring can be used to assist producers in the selection of heifers that will conceive at a higher rate and breed earlier during the breeding season.