Factors Affecting Reproductive Performance in Swine

Abstract

Records from 10,976 litters of Yorkshire, Duroc, Chester White, Hampshire, Spotted and Landrace breeds and crossbreds were utilized from the Ohio Sow Records Program and American Yorkshire Sow Productivity Program from the years 1977 to 1982. Least-squares procedures were used to determine the effects of herd, breed, parity, year, and season on reproductive traits and sow productivity index (SPI). Differences (P<.01) were found among breeds for the litter traits and index except for survival rate. Landrace and Yorkshire had the largest total number born, pigs born alive, number of pigs after transfer, adjusted 21-d litter weight, SPI and adjusted SPI. There were differences (P<.01) in litter traits and index among herds within breed. There were parity effects on litter traits and index (P<.01). Performance in litter traits was better for sows in parities 3 through 6 than for gilts or other parities. There were year and season effects on several litter traits and SPI (P<.01) and season × year interactions for litter traits and index scores (P<.01). Results suggest that increasing the number of pigs nursed per litter would increase 21-d litter weight up through 13 pigs. The average increase in litter weight was 3.0 kg per pig after transfer, but the increase occurred at a declining rate over this range. Survival rate and average pig weight decreased with the increase in the number of pigs per litter. In estimating the adjustment factors for SPI, the differences in SPI for parity 1, 2 and 7 and above compared with the mature sow equivalent (parities 3 thru 6) were 16.4, 4.6 and 8.5 points, respectively.