The performance of sheep with differing haemoglobin and potassium blood types

Abstract

1. Records of sheep with differing haemoglobin and potassium blood types were examined in a large flock of Scottish Blackface sheep.2. Differences in reproductive performance, which would be subject to natural selection, and in growth rate, fleece characteristics, etc., which would be subject to artificial selection, were sought as an explanation for the gene frequencies observed in different breeds.3. No significant differences were found in any weights or measurements.4. The number of lambs produced by different types of ewe did not differ significantly, although there was some suggestion that haemoglobin heterozygotes produce a larger number of lambs at weaning.5. Study of the equilibrium of the population, however, showed that any heterozygote advantage, if it exists at all, can only be small.