Differences between sexes
The researchers found that the effects of sex were signiﬁcantfor all traits except pneumonia. The joint disorders were found to be highest in males, followed by castrates and females.
Slaughter remarks and growth
The results show that fast growing pigs have fewer incidences of the diseases, therefore leading to less pain and discomfort to the animals. However, results also suggest that the relationship between growth rate and joint disorders is more dependent on farm management.
Farms with better management and higher average growth rate could actually have lower incidences of joint disorders. About 42% of the pigs were from ‘Farm L’, that had lower growth rate and highest incidence of joint disorders; this might have contributed to the unexpected association of growth rate and joint disorders.
Estimates of heritability
The heritability estimates for pneumonia, pleuritis, pericarditis, liver lesions and joint disorders were 0.10, 0.09, 0.14, 0.24, and 0.17, respectively, the researchers wrote. These estimates were considered positive and could therefore be used to bring some improvement in animal welfare, according to the authors.
Genetic correlations with production traits
The research team also made estimates of genetic correlations with different production traits and carcass quality. Most of the correlations were low; in general, these correlations are not expected to be very high as they reﬂect lesions observed at slaughter mainly due to diseases that are more chronic in nature.
Nevertheless, these lesions are indicative of long term pain and suffering, therefore indicating poor animal welfare, the researchers wrote. The correlations were as expected for pneumonia, pleuritis and pericarditis, but, unexpected for liver lesions. The correlation between growth and overall slaughter remarks was negative, suggesting pigs with faster growth tend to have lower risks associated with these indicators of suboptimal health and welfare.
Creation of a selection index
The results obtained in the study suggest the existence of genetic variation for slaughter remarks and opportunities to reduce their prevalence through genetic selection. As a result, the team developed a selection index for identiﬁcation of genetically superior boars whose progeny are expected to have a lower risk of unfavourable slaughter remarks.
The index was calculated as sum of product of the breeding values with their respective economic weights. The economic values for the slaughter remarks were based on and adapted to the incidences of the slaughter remarks and current prices. This index is used to identify boars that can be used by producers to enhance animal welfare in their pig farms.
The welfare index allows routine genetic evaluations and selection of pigs to reduce the risk of unfavourable slaughter remarks. This is also an example of cooperation along the pork value chain, as efforts from value chain partners is required to enhance animal welfare.