Reproductive Tract Scoring Replacement Heifers
Livestock Update, July 1998
John Hall, Animal and Poultry Sciences, Virginia Tech
Reproductive tract scoring or RTS is a useful tool for measuring the physiological readiness of replacement heifers for breeding. Colorado State researchers developed this tool several years ago. The technique involves palpating the reproductive tract of the heifer, assessing the development of the tract and assigning a score of 1 to 5. Heifers with RTS of 1 are immature or infertile while those with an RTS of 5 are cycling. RTS of 2, 3, and 4 fall in between these two extremes (Table1). RTS 4 heifers are probably cycling or will be in a few weeks. Heifers are usually given RTS exams between 12 and 14 months of age.
Table 1. Reproductive tract scoring system and it relationship to reproductive performance
|Score||Uterine Horns||Ovaries||Pregnant to Synch %||Total Pregnant %|
|1||Immature, < 20 mm diameter, no tone||15 mm x 10 mm x 8 mm, no structures||2.6||26.2|
|2||20 - 25 mm diameter, no tone||18 mm x 12 mm x 10 mm, 8 mm follicles||22.6||74.2|
|3||20 - 25 mm diameter, slight tone||22 mm x 15 mm x 10 mm, 8 - 10 mm follicles||39.5||76.2|
|4||30 mm diameter, good tone||30 mm x 16 mm x 12 mm, > 10 mm follicles, possible corpus luteum||54.6||94.1|
|5||> 30 mm diameter, good tone||> 32 mm x 20 mm x 15 mm, corpus luteum present||55||85.0|
Reproductive tract scores are highly correlated with subsequent reproductive performance (Tables1 & 2). The RTS measurements on table 1 were taken immediately before heifers were estrus synchronized. The RTS measurements in table 2 were taken 45 days before the breeding season. The closer that a heifer is to breeding the higher her RTS needs to be for her to breed early in the breeding season. For example, 12-month-old heifers that have score of 3, 4- or 5 should be expected to conceive early in the breeding season. However, 14-month-old heifers need to have scores of 4 or 5.
Table 2. Results from a Buckingham County, Va. farm
|Reproductive Tract Score|
|Number of Heifers||5||8||12||5|
|Total Percent pregnant (no. preg)||100 (5)||75.0 (6)||66.7 (8)||60.0 (3)|
|Total Percent open (no. open)||0 (0)||25.0 (2)||33.3 (4)||40.0 (2)|
|Percent pregnant to AI||60.0||50.0||16.6||33.3|
|Average days pregnant (including opens)||80.6||54.2||40.25||48.6|
|Average days pregnant (only heifers that conceived)||80.6||72.3||60.4||81.0|
This year I did RTS on several groups of heifers in Buckingham County. One herd had complete records this spring and these are summarized in Table 2. The 30 heifers were synchronized and artificially inseminated 45 days later and bred with a clean-up bull for 70 days. Jim Myers and the cooperator kept track of the breeding performance of these heifers, and Dr. Andy Meadows performed the ultrasound pregnancy diagnosis and fetal aging. As seen in Table 2, heifers with RTS of 4 and 5 had very good conception rates to AI and overall. In addition, these heifers conceived earlier in the breeding season as indicated by the "Average Days Pregnant Column".
Reproductive tract scoring is a useful tool and should be used on replacement heifers along with body weights to make decisions about retaining heifers for breeding. Please contact me if you have herds that want to make use of RTS with their heifers.