Abstract A total of 1,005 sows and their litters were used to evaluate the effect of initial litter size relative to functional teat count on sow and litter performance. Sows were blocked by parity (1, 2 to 4, or 5+) and functional teat count (≤ 13, 14 to 15, or ≥16) categories and allotted to one of four treatments with 251 or 252 replications. Treatments consisted of 1 less pig than functional teats (-1), same number of pigs as functional teats (0), 1 more pig than functional teats (+1), or 2 more pigs than functional teats (+2). Pigs were individually weighed after cross-fostering and before weaning. Pigs born 0.9 kg were fostered onto sows not included in this study. Replacement pigs were not added to litters after a removal or mortality. Sow body weight (BW), caliper score, and backfat depth were collected at farrowing house entry and weaning (d 22). Parity category, treatment, and their interaction were fixed effects in the model along with teat category. As litter size relative to functional teat count increased, sows lost more BW and caliper units, but culling rate due to non-conception decreased (linear, P ≤0.038). Litter size and weight increased (linear, P 0.001) as initial litter size relative to functional teat count increased at d 2 and weaning. Litter average daily gain (ADG) exhibited a quadratic relationship (P = 0.045) where -1 and + 2 sows had numerically greater litter ADG compared to 0 and + 1 sows. Mean pig weaning BW (linear, P 0.001) and pig ADG decreased (quadratic, P = 0.042) and removals and mortality (d 2 to weaning) increased (linear, P 0.001) as initial litter size relative to functional teat count increased. Pigs weaned per sow per year (PSY) increased (linear, P 0.001) as initial litter size relative to functional teat count increased. Wean-to-estrus interval (WEI) exhibited a quadratic relationship (P = 0.049) where 0 sows had longer WEI compared to + 2 sows with -1 and + 1 sows intermediate. Subsequent farrowing rate did not differ; however, subsequent liveborn increased (linear, P = 0.017) and total born tended to increase (linear, P = 0.061) as previous litter size relative to functional teat count increased. In conclusion, sows with 1 less pig than functional teats after cross-fostering had the lowest piglet mortality and sow BW loss and greatest piglet weaning BW. However, sows with 2 more pigs than functional teats after cross-fostering had the greatest number of pigs weaned per litter, litter WW, and PSY.
Jenkins et al. (Fri,) studied this question.