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Genetic Evaluation of Milk Traits under Whole-Season Once-a-Day Milking
This study undertook an analysis of the test day records of grazing cows milked once a day (OAD) for their entire lactation, and assessed if a dedicated breeding program targeting OAD herds could help improve their performance. A cost-benefit analysis of alternative breeding schemes to identify bulls suitable to breed high-performing daughters under OAD was also undertaken. Regression of a calculated OAD economic index on the existing breeding worth index (assumes twice-a-day milking) demonstrated that only 60-70% of the value of genetic gain would be realized in OAD herds if mainstream industry sires were used. A breeding scheme for OAD that utilizes genomic information would be more beneficial as it provided higher rates of genetic progress and greatest net returns, while maintaining relatively low costs of implementation.
Keywords:
once-a-day milking
breeding strategy
genetic evaluation
