Inheritance of the horned, scurred, and polled condition in cattle
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The results of this study from mating registered Angus, polled Hereford, and Hereford sires to nonregistered Angus and horned Hereford dams are in general agreement with the previously proposed hypothesis that four independent loci control the inheritance of horns and scurs in cattle. Observations on 830 progeny produced from mating Angus, polled Hereford, and Hereford sires to Angus and horned Hereford dams can be explained by assuming that all cattle are homozygous for the gene for horns (H), which is epistatic to the gene for scurs (Sc). The gene for polled (P) is completely epistatic to H in both sexes. The gene for African horns (Ha) is epistatic to polled (P) in males, but these results indicate that the gene is probably not epistatic to polled in fe males. The gene for scurs is sex-influenced with incomplete penetrance in males with ScSc females scurred and P-ScSc and PpScsc males scurred, i.e., males that are heterozygous for scurs must also be heterozygous for polled for scurs to be expressed. One polled Hereford sire that was classified as nonscurred and sired horned progeny also sired two scurred female progeny. This sire was likely misclassified in regard to scurs and his most likely genotype was PpScsc. On the basis of these results, avoidance of use of sires with scurs should result in increased frequency of the gene for polled in the polled Hereford breed. These results showed a frequency of 0·1 for the gene for scurs in the sample of Angus sires used. The frequency of the gene for scurs was 0·19 in nonscurred polled Hereford sires that did not produce horned progeny. The frequency of the gene for scurs averaged 0·34 in the sample of horned Hereford dams that produced male progeny in this experiment.The results from this study showed a higher frequency of scurs, scurs of larger size, and a higher frequency of bumps to be associated with shape of poii in descending order from flat, round, peaked, and extremely peaked. Thus, presence and size of scurs and presence of bumps are not independent of shape of poll. Selection of cattle with a peaked poll should contribute to a reduction in the percentage of scuffed animals produced. © 1978 AMERICAN GENETIC ASSOCIATION.
author list (cited authors)
LONG, C. R., & GREGORY, K. E.