Farm Table says:
As a result of the high – 30% – lamb losses between birth and weaning in Australian Merino Sheep, the ability to select sheep with a genetic propensity towards lamb survival would be an incredibly desirable one.
This particular study described analyses undertaken on a mixed bloodline genetic flock that represented the major Merino strains across the Australian sheep industry.
The progeny of 421 sires and 3,666 days – a total of 14,123 lambs born between 1975 and 1983 – were used for the analysis. The flock were maintained at the NSW DPI Agricultural Research Centre in Trangie and were predominately run on native grasses, with some rotation onto Lucerne. Lambing occurred between July and August and lambs were identified within 12 hours of birth, tagged with their dam, and weighed. A maternal bond score was assigned and testing occurred through to 110 days.
The results suggested indicated that lamb survival beyond the first week of birth is largely beyond the control of the ewe.
Overall, the study found:
- Very low heritability for lamb viability (0.03)
- Very low heritability for the performance of the dam or ewe rearing ability (0.07)
However, an estimated repeatability score of at least 0.10 was recorded. This means that multiple records on the rearing ability of a ewe throughout her life can increase selection accuracy. Culling ewes that have a poor rearing ability can improve current generation improvement. Despite the repeatability and moderately heritable nature of maternal bond score and lamb birth weight, the correlation with lamb survival was basically zero. As a result, the traits should not be used as an indirect selection criteria for merino lamb survival.
The study notes that they have “produced some of the most precise estimates of genetic parameters for lamb survival in the Australian Merino”.