Analysis of Environmental Effects in Production and Reproduction Traits of Purebred Berkshire in Japan

The purpose of this study is to reveal environmental factors that affect production and reproduction traits of boars, sows and piglets and to add information regarding significant factors in pig production. Records of 2963 purebred Berkshire (1537 males, 1426 females) produced from December 1994 to January 2002 at Okayama prefectural animal husbandry and research center (Okayama Research Center) in Japan were analyzed. The number of Berkshire pigs maintained at Okayama Research Center was approximately 400 pigs each year. Animals from same litter were raised together in a pen from birth to 60 days of age; selection was then carried out based on their phenotypic performance. Among traits of sows, service sire effect (SSI) was not significant in any of the traits, whereas dam effect (DAM) was significant in all of traits, suggesting that both permanent environmental effects and maternal genetic effects have a marked effect on these traits. Management methods need to take into consideration the influence of seasons, which have a significant effect on the reproductive traits of boars and sows and as well as on all traits of body weight and weight gain except on Weaning Weight (WW), which was significant when birth year effect was excluded from the statistical model. The results indicated the necessity of including both the maternal genetic effect and the permanent environmental effect in analytical models.