It’s a time-honored tradition — visually assessing potential replacement heifers to identify the oldest and largest candidates. But time has also proven that age and size can’t guarantee fertility.

Some producers may have recognized that continual selection of the heaviest heifers at weaning inadvertently increased cow size over time. On the other hand, consistently choosing lightweight heifers reaching puberty at an early age could decrease average age of puberty and increase the risk of mating with a co-pastured bull.

Until science perfects a definitive DNA fertility test, beef producers can pursue optimum reproduction results by obtaining a reproductive tract score (RTS) on potential replacement heifers 4-6 weeks before breeding season. RTS values can help predict reproductive performance of yearling heifers, especially for pregnancy rates in synchronized breeding and pregnancy rates at the end of the breeding season. Scores are ranked from 1 (immature) through 5 (cycling).

RTS values are gauged through rectal palpation of the uterine horns and ovaries. Sexual maturity of a 10- to 12-month-old heifer is gauged based on ovarian follicular development and palpable size of the reproductive tract. An RTS chart of standard values is used to assign a maturity rating (see table below).

RTS values are based on the size, length, height and width of the uterine horn, as well as the size of antral follicles.

• Heifers with small, toneless uterine horns and small ovaries rate an RTS of 1.

• Heifers with an RTS 2 are considered to be closer to cycling than those with a 1 rank.

• RTS 3 heifers are gauged to be on the verge of cycling based on slight uterine tone, in addition to the presence of follicles.

• An RTS 4 value presumes cycling, which is indicated by good uterine tone and size, as well as follicular growth.

• An RTS 5 heifer has all the characteristics of a 4, plus a palpable corpus luteum, the hormone-secreting structure that develops in an ovary after an ovum has been discharged.

repro tract score chart