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Genetics of early and lifetime annual reproductive performance in cows of two tropical beef genotypes in northern Australia

journal contribution
posted on 21.08.2018, 00:00 by DJ Johnston, SA Barwick, G Fordyce, RG Holroyd, PJ Williams, Nicholas CorbetNicholas Corbet, T Grant
Reproduction records from 2137 cows first mated at 2 years of age and recorded through to 8.5 years of age were used to study the genetics of early and lifetime reproductive performance from two genotypes (1020 Brahman and 1117 Tropical Composite) in tropical Australian production systems. Regular ultrasound scanning of the reproductive tract, coupled with full recording of mating, calving and weaning histories, allowed a comprehensive evaluation of a range of reproductive traits. Results showed components traits of early reproductive performance had moderate to high heritabilities, especially in Brahmans. The heritability of lactation anoestrous interval in 3-year-old cows was 0.51 ± 0.18 and 0.26 ± 0.11 for Brahman and Tropical Composite, respectively. Heritabilities of binary reproductive output traits (conception rate, pregnancy rate, calving rate and weaning rate) from first and second matings were generally moderate to high on the underlying scale. Estimates ranged from 0.15 to 0.69 in Brahman and 0.15 to 0.34 in Tropical Composite, but were considerably lower when expressed on the observed scale, particularly for those traits with high mean levels. Heritabilities of lifetime reproduction traits were low, with estimates of 0.11 ± 0.06 and 0.07 ± 0.06 for lifetime annual weaning rate in Brahman and Tropical Composite, respectively. Significant differences in mean reproductive performance were observed between the two genotypes, especially for traits associated with anoestrus in first-lactation cows. Genetic correlations between early-in-life reproductive measures and lifetime reproduction traits were moderate to high. Genetic correlations between lactation anoestrous interval and lifetime annual weaning rate were -0.62 ± 0.24 in Brahman and -0.87 ± 0.32 in Tropical Composite. The results emphasise the substantial opportunity that exists to genetically improve weaning rates in tropical beef cattle breeds by focusing recording and selection on early-in-life female reproduction traits, particularly in Brahman for traits associated with lactation anoestrus. Journal compilation © CSIRO 2014.

Funding

Category 4 - CRC Research Income

History

Volume

54

Issue

1

Start Page

1

End Page

15

Number of Pages

15

eISSN

1836-5787

ISSN

1836-0939

Publisher

CSIRO Publishing

Peer Reviewed

Yes

Open Access

No

Acceptance Date

11/04/2013

External Author Affiliations

CRC for Beef Genetic Technologies; University of New England; Dept of Agriculture, Fisheries and Forestry; CSIRO Livestock Industries

Era Eligible

Yes

Journal

Animal Production Science