Feeding the Prolific Sow for Success, Part II: Late-gestation Phase Feeding Across Multiple Cycles Enhances Prolificacy

Abstract Evaluating nutritional impact over only one reproductive cycle may miss cumulative effects on long-term performance. This study assessed the effect of late-gestation nutrient enrichment across consecutive cycles. Seventy sows (parity 0–5) at 70 ± 2 days of gestation were allotted by parity, body weight, previous reproductive performance, and hemoglobin to a control (CON; n = 35; 11% CP, 0.52% SID lysine, industry-standard organic trace minerals, and vitamins) or a nutrient-enriched late gestation diet (LGPHASE; n = 35; 16% CP, 0.87% SID lysine, 2× CON industry-standard organic trace minerals and vitamins except selenium, plus 500 mg/kg vitamin C). The LGPHASE diet was fed from day 70 to 110 of gestation. Treatments were repeated in the subsequent reproductive cycle. A common lactation diet was fed in both cycles. Reproductive performance was analyzed using PROC GLIMMIX (SAS 9.4). Treatment, cycle, and their interaction were included as fixed effects. Sow was included as a random effect to account for repeated measurements across cycles. Only sows that completed both reproductive cycles were included in the analysis. Retention to Cycle II was 60% for CON (21/35) and 80% for LGPHASE (28/35) females. Farrowing duration was shorter in LGPHASE sows compared with CON sows in both Cycle I (286 vs. 373 min; P = 0.006) and Cycle II (275 vs. 353 min; P = 0.018), with no cycle effect within either treatment. Piglet birth weights did not differ between treatments in either cycle and no cycle effect was observed within treatment. The number of total born and liveborn pigs increased from Cycle I to Cycle II in LGPHASE sows (P = 0.024 and P = 0.031, respectively), whereas no cycle-to-cycle differences were observed in CON sows. In Cycle II, LGPHASE sows produced more total pigs born (19.24 vs. 16.84; P = 0.041) and liveborn pigs (17.70 vs. 15.00; P = 0.015) than CON sows. While piglet weights at weaning were greater in CON litters than LGPHASE litters in Cycle I (6.14 vs. 5.43 kg; P = 0.023), no differences were observed between treatments in Cycle II. Weaning weights did not change across cycles in CON, whereas LGPHASE litters weaned heavier pigs in Cycle II compared with Cycle I (6.25 vs. 5.43 kg; P = 0.017). LGPHASE sows tended to wean more pigs per litter than CON sows in both Cycle I (13.70 vs. 12.87; P = 0.084) and Cycle II (14.21 vs. 13.56; P = 0.102). In conclusion, nutrient-enriched late-gestation feeding shortened farrowing and improved sow recovery, with greater benefits extending into the subsequent parity through larger litter size, more pigs weaned, and fewer sow removals—supporting improved sow health, welfare, and economic returns.