Physical traits, performance data, and reproductive tract maturity score can be used to predict fertility and likelihood of early conception in beef replacement heifers consigned to a heifer development program in the southeastern United States

Brent C. Credille Food Animal Health and Management Program, Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, GA

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 DVM, PhD, DACVIM
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Jason D. Duggin Department of Animal and Dairy Science, College of Agricultural and Environmental Sciences, University of Georgia, Athens, GA

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 MS
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Arthur L. Jones Food Animal Health and Management Program, Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, GA

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 DVM, MS
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Grace Nyhuis Department of Animal and Dairy Science, College of Agricultural and Environmental Sciences, University of Georgia, Athens, GA

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Pedro L. P. Fontes Department of Animal and Dairy Science, College of Agricultural and Environmental Sciences, University of Georgia, Athens, GA

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R. Lawton Stewart Jr Department of Animal and Dairy Science, College of Agricultural and Environmental Sciences, University of Georgia, Athens, GA

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Roy D. Berghaus Food Animal Health and Management Program, Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, GA

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 DVM, PhD, DACVPM

Abstract

OBJECTIVE

To identify growth and reproductive measurements that can be used to select heifers with the potential to be more reproductively efficient.

SAMPLE

A total of 2,843 heifers consigned to the Georgia Heifer Evaluation and Reproductive Development program between 2012 and 2021 with a mean (min, max) age of heifers at delivery of 347 days (275, 404).

PROCEDURES

Reproductive tract maturity score (RTMS), weight at delivery as a percentage of target breeding weight, hip height 3 to 4 weeks after delivery, and average daily gain during the first 3 to 4 weeks after delivery were evaluated as potential predictors of the variables of interest.

RESULTS

The model-adjusted odds of pregnancy were 1.40 to 1.67 times higher for heifers with an RTMS of 3, 4, or 5 when compared to heifers with an RTMS of 1 or 2. For every 2.5-cm increase in hip height and every 1-month increase in age at the beginning of the breeding period the model-adjusted odds of pregnancy were 1.10 and 1.16 times higher, respectively. The model-adjusted pregnancy hazard rate for heifers with an RTMS of 3, 4, or 5 was 1.19 to 1.25 times higher than that of heifers with an RTMS of 1 or 2. For every 2.5-cm increase in hip height, the model-adjusted hazard rate for pregnancy was 1.04 times greater.

CLINICAL RELEVANCE

Physical traits related to animal maturity and attainment of early puberty can be used to select heifers that are more likely to become pregnant early in their first breeding season.

Abstract

OBJECTIVE

To identify growth and reproductive measurements that can be used to select heifers with the potential to be more reproductively efficient.

SAMPLE

A total of 2,843 heifers consigned to the Georgia Heifer Evaluation and Reproductive Development program between 2012 and 2021 with a mean (min, max) age of heifers at delivery of 347 days (275, 404).

PROCEDURES

Reproductive tract maturity score (RTMS), weight at delivery as a percentage of target breeding weight, hip height 3 to 4 weeks after delivery, and average daily gain during the first 3 to 4 weeks after delivery were evaluated as potential predictors of the variables of interest.

RESULTS

The model-adjusted odds of pregnancy were 1.40 to 1.67 times higher for heifers with an RTMS of 3, 4, or 5 when compared to heifers with an RTMS of 1 or 2. For every 2.5-cm increase in hip height and every 1-month increase in age at the beginning of the breeding period the model-adjusted odds of pregnancy were 1.10 and 1.16 times higher, respectively. The model-adjusted pregnancy hazard rate for heifers with an RTMS of 3, 4, or 5 was 1.19 to 1.25 times higher than that of heifers with an RTMS of 1 or 2. For every 2.5-cm increase in hip height, the model-adjusted hazard rate for pregnancy was 1.04 times greater.

CLINICAL RELEVANCE

Physical traits related to animal maturity and attainment of early puberty can be used to select heifers that are more likely to become pregnant early in their first breeding season.

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