Abstract:
The area of naturally bare skin around the perineum was scored at weaning in lambs (n = 2152) from a composite flock of New Zealand crossbred sheep. Breech bareness was scored on a range from 1, where wool was growing right to the edges of the anus, to 5, where a large bare area surrounded the perineum. Bareness on the under surface of the tail was measured on a linear scale at tail docking. Dag score (degree of breech soiling) was recorded at weaning, on a scale of 0?5, where an increasing score indicated more dags. Dag score was taken as a measure of the risk of flystrike in the breech. Female lambs tended to have slightly greater (P < 0.001) breech bareness score (mean score 2.7) than males (mean score 2.6), whereas mean dag score of females was lower than that of males (0.45 v. 0.53; P < 0.05). Breech bareness score had a heritability of 0.33 � 0.06, and the length of bare skin under the tail had a heritability of 0.59 � 0.06. The genetic correlation between breech bareness score at weaning and length of bare skin under the tail at docking was positive (0.35 � 0.10). These 2 traits had phenotypic correlations with dag score of ?0.17 � 0.02 and ?0.03 � 0.03, respectively, and genetic correlations with dag score of ?0.30 � 0.13 and 0.03 � 0.12, respectively; negative values indicated a favourable relationship. Tails were removed at docking, so the phenotypic correlation of about zero between tail data and dag score at weaning was of little utility. Our results suggest that selecting for these 2 bareness traits could reduce dag formation and the associated risk of breech strike.