Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2009
Publication Date: 10/2/2009
Citation: Holl, J.W., Rohrer, G.A., Brown Brandl, T.M. 2010. Estimates of Genetic Parameters Among Scale Activity Scores, Growth, and Fatness in Pigs. Journal of Animal Science. 88:455-459.
Interpretive Summary: The amount of interaction between pigs and humans has decreased as a consequence of increased herd size and reduction in labor. As fewer opportunities for contact exist, there is a greater chance that animals may perceive contact as stressful, resulting in increased potential for animal and human injury. Therefore, the potential for genetically selecting pigs for reduced susceptibility to fear was studied. Three generations of pedigreed pigs from a USMARC composite pig population were scored for scale activity while being measured for ultrasonic backfat and weight at 22 wk of age. The score ranged from 1 (calm) to 5 (highly excited). A mode of inheritance was inferred from the data using two types of statistical models. In addition, genetic associations were identified between scale activity and backfat, and scale activity and weight. In conclusion, selection for more docile animals would be expected to result in faster growing, fatter pigs.
Technical Abstract: Genetic parameters for scale activity score were estimated from generations 5, 6, and 7 of a randomly selected, composite population composed of Duroc, Large White, and two sources of Landrace (n = 2,186). At approximately 156 d of age, pigs were weighed (WT) and ultrasound backfat measurements (BF1, BF2, and BF3) collected. While pigs were in the scale, a scale activity score (AS) was assigned, which ranged from 1 (calm) to 5 (highly excited); where 58.1%, 28.5%, 8.9%, 4.0% and 0.5% were scored as 1, 2, 3, 4, and 5, respectively. Statistical model effects were year-week of measurement, sex, covariates of age for AS and WT for BF1, BF2, and BF3, and an animal direct genetic effect. Two statistical models were investigated. Model 1 was a five-trait linear mixed model. Model 2 was a five-trait threshold-linear mixed model, where AS was treated as a categorical trait. Estimated heritabilities using Model 1 were 0.23, 0.54, 0.56, 0.52, and 0.48 for AS, WT, BF1, BF2, and BF3, respectively. Model 1 estimated genetic correlations between AS and WT, AS and BF1, AS and BF2, and AS and BF3 were -0.38, -0.11, -0.12, and -0.16 respectively. Estimated heritabilities using Model 2 were 0.30, 0.56, 0.59, 0.55, and 0.52 for AS, WT, BF1, BF2, and BF3, respectively. Model 2 estimated genetic correlations between AS and WT, AS and BF1, AS and BF2, and AS and BF3 were -0.38, -0.15, -0.18, and -0.24, respectively. Results indicated AS had a heritable genetic component and genetic correlations were slightly stronger in the combined threshold-linear model. Estimated genetic correlations between AS and backfat measurements adjusted to a common weight were negative for both models. Therefore, selection for more docile animals would be expected to result in faster growing, fatter pigs.