Breed and environmental factors of sows and their repeatabilities in central Mexico

Background: reproductive traits influence lifetime productivity of sows.Objective: to determine the effects of year and season of farrowing, parity number, and breed, on litter size at birth, weaning to service interval (WSI), farrowing to service interval (FSI), and to estimate their repeatabilities. Methods: data from years 1998 to 2008 from a farm in La Piedad, Michoacan, Mexico, were used. Sow breeds were Camborough 22 (PIC), Yorkshire (Y), F1 Landrace x Yorkshire (F1 LY), and ¼ Landrace x ¾ Yorkshire (LY3/4). The studied traits were total pigs born at birth (TPB, n = 45,798), number of pigs born alive (PBA, n = 45,798), WSI (n = 41,156), and FSI (n = 41,156). The statistical model for TPB and PBA included the effects of farrowing year, farrowing season, parity number, breed, and year/season interaction. The model for WSI and FSI included the above factors plus the linear and quadratic effects of lactation length. Results: the overall means for TPB, PBA, WSI, and FSI were 9.31 pigs, 8.60 pigs, 7.87 days, and 29.9 days, respectively. All effects included in the statistical models were significant (p