Estimation of genetic trends from 1977 to 2000 for stress-responsive neuroendocrine systems in the French Large White and Landrace breeds using frozen semen

An experimental design aiming at estimating realised genetic trends from 1977 to 1998-2000 in the French Large White (LW) and Landrace (LR) breeds was conducted by INRA and IFIP-Institut du Porc. Large White sows were inseminated with semen of LW boars born in 1977 (frozen semen) or in 1998 and animals from the 2nd generation were tested in station. Landrace sows were inseminated with semen of LR boars born in 1977 (frozen semen) or in 1999-2000, and produced animals tested in station.Urinary concentration of stress hormones (cortisol and catecholamines) and carcass composition traits (estimated carcass lean content (ECLC) and global adiposity) were measured. For the two breeds, selection carried out since 1977 led to an increase in ECLC and a decrease in carcass adiposity. Between 1977 and 1998-2000, urinary concentrations of stress hormones were unchanged in the LR breed, but were decreased in the LW breed. Moreover, for the animals generated from LW boars born in 1977, urinary cortisol levels were negatively correlated with ECLC. Therefore, in the LW breed, selection carried out for higher ECLC resulted in a decrease in cortisol production. Selection carried out for increased carcass lean content leads, in this breed, to large modifications in the functioning of the stress-responsive systems, thereby influencing a large range of physiological regulations.