ANGUS BEEF BULLETIN EXTRA

April 20, 2022 | Vol. 15 : No. 4

A Method for Selecting Replacements

Reproductive tract scoring allows cattlemen to judge whether females are ready for breeding.

Reliable Reproduction

Replacement heifers take a while to develop, so how do you know you’re choosing the right heifers to perform well in your herd? A management tool to assist those making selection decisions on yearling heifers is reproductive tract scoring (RTS). RTS is a subjective measurement that involves rectal palpation of a heifer’s reproductive tract (uterine horns and ovarian structures) and assignment of a reproductive tract score ranging from 1 to 5 (1 = immature; 5 = presence of a corpus luteum).

Since age at puberty is difficult to measure directly, RTS can estimate pubertal status. If performed before the onset of the breeding season, it can be a predictor of heifer reproductive performance. Heifers with poor breeding potential can be removed from the breeding group before any further costs are incurred.

The RTS system has been shown to be a repeatable measure between and within practitioners and to be moderately heritable.

An RTS of 1 refers to a prepubertal heifer. An RTS of 2 or 3 refers to a peripubertal heifer (transitional stage), and an RTS of 4 or 5 refers to a pubertal (cycling) heifer. The reproductive performance of heifers with an RTS of 1 or 2 is less than that of heifers with an RTS of 3 or greater. Heifers with an RTS of 1 or 2 are less likely to be cycling at the beginning of the breeding season and therefore are less likely to become pregnant. If they do become pregnant, they do so later in the breeding season, suggesting heifers with an RTS of 1 should possibly be eliminated from the breeding group.

It is worth mentioning that some heifers do not exactly fit a particular RTS score. It is up to the producer and/or practitioner to decide on which of the measures are to be given the most emphasis.

RTS should be estimated within a month prior to breeding so the score can be used as a culling tool. This is important because the RTS is an indicator of a heifer’s ability to conceive early during the first breeding season. If RTS is to be used to place pressure on age at puberty, the best time to evaluate the heifers is when approximately 50% of the heifers are thought to be cycling based on age, weight and occasional observations for estrus.

Another possible application of the RTS system is to assess the nutritional program. A cattleman can assign RTS 30-60 days before the start of breeding season and use the information to adjust rations if necessary. Heifers may need more feed to reach developmental goals. The beginning of breeding season could even be adjusted if necessary.

If your heifers are a little behind schedule this spring, consult with your veterinarian about RTS. The scores can be informative and beneficial in the selection and management of yearling replacement heifers.

Editor’s note: Mark Johnson is an Oklahoma State University Extension beef cattle breeding specialist. This article is reprinted with permission from the Cow-Calf Corner newsletter. Photo by Kasey Brown.




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