Environmental and breed factors associated with lifetime and per year productivity of sows in a commercial farm in Michoacan, Mexico

The objective of this study was to determine the effects of some environmental and breed group factors on lifetime and per year productivity of sows. A retrospective study was carried out from 1998 to 2007 using information of a production system with 2,400 sows, in La Piedad, Michoacan, Mexico. Data from 6,063 sows belonging to the breed groups PIC Camborough 22, Yorkshire (Y), F1 Landrace (L) x Y (F1 LY) and 3/4Y1/4L were used. The response variables were the number of pigs born alive per sow per year (PBY) or per productive lifetime (PBL), number of pigs weaned per year (PWY) or per productive lifetime (PWL), kg of pigs weaned per sow per year (KWY), kg of pigs weaned per sow per lifetime (KWL) and productive lifetime (PLT) of sows. The statistical model included the fixed effect of year of first farrowing (1998-2007), season of first farrowing (spring, summer, fall, winter), breed group of the sow, number of pigs born alive at first farrowing (10 pigs) and year by season interaction. Means and standard deviations estimated for PBY, PWY, KPY, PBL, PWL, KWL and PLT were 21.4±3.71 pigs, 18.2±4.04 pigs, 107.5+25.8 kg, 48.3±22.7 pigs, 41.4±3.71 kg, 243.7±122.9 kg and 805.6±338.8 days, respectively. All factors studied had effect on all traits (P < 0.05), except, breed group on PBY, and season on PWY and KWL. The interaction of year by season was not significant only for PBY. Sows farrowing from 2005 to 2007 and in the fall season had the poorest performance. The best performance per year or productive lifetime corresponded to the 1/4L3/4Y breed group, except for PBY where no differences were found. Also, the 1/4L3/4Y sows stayed longer in the herd. The sows with the smallest litter size at first parity (≤ 6 piglets) had the worst performance