USING ram lambs is allowing the Oppenheimer family to accelerate genetic improvement in their Poll Merino commercial flock at Petali, Walcha.
Martin and Cheryl Oppenheimer run a 4000 to 5000-head Poll Merino ewe flock alongside their Poll Merino and White Suffolk studs.
They’ve been using ram lambs for a few years with the White Suffolks, and with the Merino stud ewes since the early 2000s, but the accuracy of selection at such a young age held them back from using ram lambs in the commercial flock, until last year.
Objective selection has helped them determine lambs suitable for joining at six to eight months of age.
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“We can't mate them at the same rate as 1½-year-old rams that are at one per cent, but we join them at 2pc for the White Suffolks and 2pc to 3pc with the Poll Merinos,” Mr Oppenheimer said.
“If you go back to the 1980s, it was normal that the two to 2½-year-old rams were the youngest we'd use, and some people weren't mating ewes until 2½ years.
“Joining ram lambs happens a bit in the broader wool areas, but not so much in the finer operations.
“Part of the reason we can do this is using genetics that have extra growth – early growth from birth until six to eight months of age.
“The ram lambs can perform, as long as management allows them to express that growth, so that they're able to physically mate the ewes.”
The family runs sheep at a high stocking rate by district standards, around 15 dry sheep equivalent (DSE) for hectare, but imprint them as lambs, then manage feed to make sure they reach minimum weights of 45 kilograms for the Poll Merinos and 50kg for the White Suffolks prior to joining.
“The use of ram lambs is common in terminal operations, but it’s never been popular because of the low joining ratios,” Mr Oppenheimer said.
“For us it's a win-win situation – we can use our best new genetics once and sell them as one-year-olds the following year to clients, and they’re proven sires by that point. The slight downside is that, depending on the season, they're probably not going to be as well-grown as they would have been if they weren't mating.”
The ram lambs can perform, as long as management allows them to express that growth, so that they're able to physically mate the ewes.
The only other issue is the accuracy of selection at a young age, which the Oppenheimers are able to do using genetic data from mid-parent ASBVs.
“On the genomic side, we can take a tissue sample as early as we like, which is helping our selection accuracy,” Mr Oppenheimer said.
“Before, we were relying on minimal measurements at an early stage so we may not have been picking the right sheep, but now we’re backing up looks with genomic tests.
“Using the mid-parent EBV average of the sire and dam gives us a guide as to how the lambs will perform.
“The rate of genetic gain has increased, and we're seeing big changes in growth, fat, extra muscle and fleece weight.
“We’ve always had higher rates of genetic gain in the stud using AI rams, but now the commercial flock is much closer, and it allows us to use a more diverse set of genes in our commercial flock.”