|Shea moore, Margaret|
Submitted to: Journal of Animal Science
Publication Type: Abstract only
Publication Acceptance Date: 6/1/1999
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Producers are reporting handling problems with pigs selected for lean gain. The objectives of this study were to determine if selected genetic lines of pigs respond differently to transportation stress. A randomized complete block design was used. Market-weight pigs from three genetic lines (high- lean-gain, HLG, n=14; moderate-lean-gain, MLG,n=11; low-lean-gain, LLG, n=12) blocked by location, were exposed to transportation stress prior to slaughter. Salivary samples were collected two weeks prior to transport to determine baseline cortisol levels. Pigs were mixed within each genotype and loaded into one of three pens (maximum of 5 pigs per pen) on a livestock trailer and transported for 2h. Behavior was video-recorded during transport. This was replicated three times until all pigs from each genotype were tested. Salivary samples were collected immediately after transport before unloading and again after the pigs had been moved from the etrailer to the holding pen in the abbattoir. There was a significant effec of genotype on the levels of aggression displayed (chi-squared=6.06,df=2, p<.05). HLG pigs were more aggressive (17 occurrences) during mixing than LLG pigs (6 occurrences). MLG pigs were not different from HLG or LLG pigs. Cortisol data were analyzed using mixed model analysis and assumptions of the model were met using a log transformation. Salivary cortisol levels were significantly elevated after transport (P<.0001) and after unloading (P<.0001) compared to baseline in all treatment groups but there was no effect of genotype on cortisol levels. In conclusion, pigs selected for lean gain show increased levels of aggression during mixing and transport. Salivary cortisol levels reflect the stress of transportation but do not differ among the genotypes tested.