Farm Table says:
What is the problem?
Female reproduction is an important profit driver in northern Australian beef production systems.
Low weaning rates are common, and are mainly the result of extended post-partum anoestrous intervals, particularly in Bos indicus cattle.
There is currently a lack of data on the genetics of lifetime reproductive performance in female beef cattle and its relationships with other production traits
What did the research involve?
The cows were part of a long-term project.
Data was used from a beef breeding experiment in northern Australia that investigated the genetics of whole herd profitability.
In brief, Brahman (BRAH) and Tropical Composite (TCOMP) steers and heifers were generated over 4 years at 8 cooperator properties and were the progeny of 54 Brahman and 52 Tropical Composite sires.
At weaning the heifer calves were allocated to one of 4 Queensland research stations, where they remained for the duration of the experiment.
Genetic analyses of heifer performance have been previously reported for early growth and body composition, adaptation and age at puberty.
This project reports on the lifetime reproduction of these females and the estimation of trait heritabilities and genetic associations with early-in-life measures, including measures of puberty.
All cows had a DNA sample and their reproduction records were used to develop genomic prediction from 50K and 800K genome scans as part of the CRC’s Gene Discovery project
What were the key findings?
Weaning rates in the project were low, particularly in Brahmans, and results showed it can be improved through selection by focusing recording on early-in-life female reproduction traits.
Traits associated with age at puberty and lactation anoestrus in first-lactation cows were highly variable and moderately to highly heritable in both genotypes.
Several male traits were identified, including semen quality traits, that could also be used as indirect selection criteria to improve female reproduction rates.
The project established that it is possible to select for improved female reproduction simultaneously with selection for steer traits (growth, carcass, meat quality and feed efficiency), however improvement in both will require recording and appropriate multiple-trait selection strategies.