A preliminary genetic analysis of breech and tail traits with the aim of improving the welfare of sheep

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.

Genetic parameters for breech cover, wrinkle and wool coverage scores and their implications for Merino sheep breeding programs and flock management

“…The low heritability estimates for MBCOV, YBCOV and ABCOV (0.01-0.16) in the current study, while lower than published estimates which range from 0.23 to 0.55 (Scobie et al, 2007(Scobie et al, , 2008Edwards et al, 2009;Greeff and Karlsson, 2009;Smith et al, 2009;Brown et al, 2010;Bird-Gardiner et al, 2014;Greeff et al, 2014), indicate that achieving a permanent decrease in breech cover is possible through selection. The phenotypic variance for BCOV in this study ranged from 0.43 to 0.55 across the three stages of assessment from marking to adult, which was similar to that reported by both Brown et al (2010) and Smith et al (2009) but greater than that of Greeff et al (2014) and Bird-Gardiner et al (2014).…”

Dag score is negatively correlated with breech bareness score of sheep

“…Lambs were presented to the observers in random order within lambing mobs, and lambing mobs were also presented at random. The lambs were scored for breech bareness on a 1--5 scale according to the method of Scobie et al (2007), where higher values indicated greater bareness. Dags were scored on a 0--5 scale with higher values indicating more dags according to the method of Larsen et al (1994).…”

“…Breech bareness score at weaning has been shown to be heritable and negatively correlated with dag score in a small flock of composite sheep selected for short tails and bareness of the breech and belly (Scobie et al 2007). The published work of Scobie et al (2007) was undertaken on a research farm and those traits were largely obtained from exotic breeds.…”

“…The published work of Scobie et al (2007) was undertaken on a research farm and those traits were largely obtained from exotic breeds. We have now tested the hypothesis that increased bareness of the breech will reduce dagginess in commercial sheep available to farmers, by making observations on the purebred and composite flocks of two ram breeders.…”

Mulesing and Animal Ethics

“…Positive research outcomes in Australia on Merino sheep (e.g., Greeff and Karlsson 2005;Greeff et al 2008) and in New Zealand with Merino cross-bred sheep (Scobie et al 2007) suggest that breeding and selecting breech strike resistant sheep may be a long term replacement for mulesing in the future that reduces chemical use and labor requirements in flystrike control (James 2006). James (2006, p. 14) points out that it is ''unlikely that breeding alone will be able to confer the degree of protection provided by surgical mulesing.''…”