Producers now have access to a new Australian Sheep Breeding Value to drive genetic gain for reproduction

Maternal and Merino sheep producers now have a new Australian Sheep Breeding Value to drive genetic gain for reproduction, with hopes the addition will lead to better reproductive rates amongst the nation’s flock. The Weaning Rate (WR) ASBV replaces the Number of Lambs Weaned (NLW) breeding value. It uses an improved method to calculate the predicted number of lambs weaned per ewes joined for maternal and Merino animals. Meat and Livestock Australia sheep genetics senior development officer Emma McCrabb said the new WR breeding value could help farmers select for rams that would maximise the reproductive rates of their flock this spring ram season. “Traditionally, we had the single reproduction trait, NLW, but we’ve been able to break it down into its three component traits: conception, litter size and ewe rearing ability,” she said. “We then balanced these three components to produce the Weaning Rate breeding value, which describes how many lambs a ram’s daughter will wean.” Animal Genetics and Breeding Unit Principal scientist Andrew Swan led the development of the value and said the method would provide improved analysis and information to drive better genetic gains for producers. “WR will provide more transparent information to producers because it provides a net overall reproduction breeding value derived directly from component traits,” he said. “With NLW, trait values can be the result of any one of the components — for example, a value of zero lambs weaned could occur because the ewe didn’t conceive at all in the first place. “Or, because she had one of two lambs but none of them survived to weaning.” Mr Swan said the new reproduction analysis would allow ram breeders to focus on the three component traits separately to increase genetic gain and maximise reproduction. The new weaning rate ASBV would complement it as a simple tool for ram buyers to use in purchasing decisions. “Breeders can have more confidence that it’s accurate and the results are more detailed,” he said. Ms McCrabb said maternal and Merino sheep producers should keep an eye out for the new WR value when purchasing sires in the upcoming sales. “WR is not only an ASBV but it’s now included in our selection indexes for maternal and Merino breeds,” she said. “For maternal and Merino ram buyers turning up on sale day, keep in mind WR will be in the catalogue instead of NLW and looks a bit different — while NLW used to be expressed as a percentage, WR is presented as a decimal and is expressed in the units of lambs. “It’s an adjustment for producers, but it’s an improved model and it uses breeders’ data in a more accurate, detailed way.”