Carcass Quality In Sheep Research Articles

PSV-13 Incidence of infectious and non-infectious feet lesions and their association with carcass quality in sheep at a slaughter plant in Alberta

Abstract Infectious and non-infectious feet lesions (FL) in livestock have been associated with reduced welfare, production, carcass and meat quality. Currently, the incidence of FL in sheep and its relationship with carcass quality has not been documented in Canada. The objectives of this study were to determine 1) the incidence and type of lesions in Alberta sheep at slaughter and 2) the relationship between FL and carcass quality. A total of 4,487 sheep carcasses were assessed for FL at a slaughter plant in Alberta, Canada between October 2017 and March 2019. Approximately 300 sheep were evaluated monthly by two experienced observers who recorded common infectious (IN) and non-infectious (NIN) lesions. In addition, carcass information including hot carcass weight (HCW), and back fat thickness (BFT) were obtained from the slaughter plant records. Data were analyzed by multivariable regression models using SAS PROC GLIMMIX. Overall, FL incidence was 9.4% (7.0% having one lesion and 2.4% having more than one lesion). Infectious lesions accounted for 45.7% of all lesions [footrot (37.1%), interdigital dermatitis (7.3%), and contagious ecthyma (1.3%)], while NIN lesions accounted for 54.3% [overgrown horn (21.9%), injury (13.6%), laminitis (10.2%), and other lesions (8.6%)]. Sheep with IN had lower BFT (13.5 ± 1.32 cm, P = 0.0002) and HCW (51.5 ± 1.89 kg, P = 0.0189) than NIN (15.8 ± 1.51 cm and 54.7 ± 1.97 kg, respectively). For every 1 cm decrease in BFT and 1 kg decrease in HCW the odds of IN increased by 0.89 (P < 0.0001) and 0.98 (P = 0.0229), respectively. Based on our findings, foot lesions are a significant issue for the Canadian sheep industry and infectious lesions may have greater detrimental effect on carcass quality than non-infectious lesions. Further studies are necessary to understand the relationship of carcass quality and feet lesion.

Non-normality in carcass quality measurements and effects on the genetic evaluation of sheep

In order to estimate genetic parameters for four traits related to carcass quality in sheep (live weight, ultrasonic fat and muscle depth and in vivo conformation, assessed at 21 weeks of age), the validity was tested of the assumptions of homogeneity of variance and normality of residuals. Animals were of the Bluefaced Leicester breed, the most prevalent crossing sire breed used in the UK. The fit of the model and the distribution of the residuals were investigated when fitting a mixed (animal) model after applying Box–Cox power transformations to deal with scale-related non-normality. For ultrasonic fat depth, the log-transformation was shown to improve normality and decreased the correlation between flock means and standard deviations. The other traits did not show sufficient improvement to justify a transformation. For ultrasonic fat depth, the regression of both genetic and residual variance on sample means obtained by bootstrapping (sampling flocks) was positive whereas the regression of heritability on sample means was negative. The log-transformation made the association weaker and the regression coefficient changed sign for genetic variance only. The four traits all had moderately high heritabilities. Log-transforming ultrasonic fat depth caused the heritability to decrease from 0.43 to 0.30. Conformation had the lowest heritability (0.20) but had high positive correlations with the other traits, suggesting that improving conformation could lead to more muscling but may also increase the amount of fat in the carcass. The log-transformation had a major effect on ranking of individuals based on estimated breeding values, particularly for high selection intensities.