Effects of Litter Size Above Functional Teat Count on Litter and Sow Performance

Larger litter sizes in commercial sows often exceed the number of functional teats, creating challenges in providing adequate nutrition to all piglets without increasing nurse sow use. Increasing litter size beyond teat count may help improve productivity efficiency. The objective of this study was to evaluate the effect of litter size relative to the number of functional teats on sow and litter performance in a commercial farm. A randomized complete block design was used with 3 Piglet Load (PL) treatments based on litter size relative to teat count: 1) 0 = equal number of piglets and teats, 2) +1 = 1 piglet above teat count, and 3) +2 = 2 piglets above teat count. A total of 426 parity 1 and 2 sows were used. Cross-fostering was completed within 24 h after farrowing to achieve treatments. Piglets falling behind were not removed from the litter. Litter weights were collected after cross-fostering and 1 d before weaning. Sow body weight and caliper score were measured at farrowing and weaning, and feed intake was recorded throughout lactation. Data were analyzed using R (version 4.5.0), with litter/sow as the experimental unit for sow and litter traits and individual piglets as the unit for mortality. Models included the fixed effects of PL and parity. No effects of PL treatment were observed (P > 0.05) for changes in sow caliper score, body weight, or average daily feed disappearance. Mean entry caliper scores were 15.16, 15.24, and 15.26 for the 0, +1, and +2 treatments, respectively, and declined by − 3.48, −3.55, and −3.38 points by weaning. Sow body weight loss averaged −25.6, −28.8, and −26.3 kg, respectively, and feed disappearance averaged 5.7, 5.7, and 5.8 kg/day across treatments. At the start of the trial, litter size differed (P < 0.05) among treatments (0 = 16.05, +1 = 16.81, +2 = 17.43 piglets). Pre-weaning mortality increased (P < 0.05) with greater PL (0 = 6.74%, +1 = 8.27%, +2 = 10.30%). At weaning, sows on the 0 treatment weaned fewer piglets (P < 0.05; 14.95) than +2 sows (15.65), with +1 sows being intermediate and not different (P > 0.05) from the other 2 treatments. Total litter weight at the start was greater (P < 0.05) for +2 than 0 litters, but average piglet weight did not differ (P > 0.05). By weaning, total litter weight was similar (P > 0.05) across treatments, but average piglet weight was greater (P < 0.05) for the 0 treatment compared with +1 and +2. These results suggest that increasing litter size up to two piglets above functional teat count did not impair sow performance but increased pre-weaning mortality and reduced individual piglet weaning weight.