Effects of Increased Feed Allocation from Breeding to Day 50 of Gestation on Sow, Litter, and Subsequent Reproductive Performance of Sows Differing in Body Condition at Weaning

Abstract Optimizing gestation feeding programs based on post-weaning sow body condition is essential to ensure farrowing and lactation success. As genetic selection continues to enhance sow productivity traits (e.g., total born and litter weaning weight), historical nutrient recommendations may no longer meet the requirements of the modern sow. This study aimed to evaluate the effects of three gestation daily feed allocations (Low, Medium, and High) across two body condition score (BCS) categories (Thin and Ideal) on sow and litter characteristics, farrowing and weaning performance, and subsequent reproductive performance. The study was conducted at a commercial sow research facility within the Carthage System (Carthage, IL, USA). At breeding, sows (N = 3,068; weaned from March to June 2024) were categorized by caliper score into Thin scores 9–12 (BCS 2) or Ideal scores 13–16 (BCS 3) groups and randomly assigned to one of three daily feed allocations within BCS category: 1) Low = 2.7 and 1.9 kg/d, 2) Medium = 3.2 and 2.3 kg/d, and 3) High = 3.6 and 2.6 kg/d for Thin and Ideal sows, respectively. All gestation diets were identical across treatments and formulated to meet or exceed nutrient requirements according to NRC (2012) guidelines. Sows remained on their assigned feeding treatment until relocation from stalls to pens at approximately day 50 of gestation. Data were analyzed using R (v4.5.0). Sow was the experimental unit, and the model included the fixed effects of gestation feed allocation, BCS category, and parity group (Immature = parities 1–2; Mature = parities ≥ 3). In both Thin and Ideal BCS categories, increasing gestation feed allocation resulted in higher caliper and subjective BCS measurements at days 21, 50, and 112 of gestation (P ≤ 0.05). Greater feed allocation also increased sow body weight at day 50 in both BCS categories (P ≤ 0.05). However, increased gestation feeding levels did not affect farrowing, weaning, or subsequent reproductive performance metrics for either Thin or Ideal sows (P 0.05). Across maturity groups, Ideal sows exhibited higher conception and farrowing rates, produced more total and liveborn piglets, and had shorter wean-to-first-service intervals than Thin sows (P 0.05). Among Mature sows, however, Ideal body condition was associated with a higher stillborn percentage and fewer piglets weaned (P 0.05). Overall, increasing gestation feed allocation improved sow body condition during gestation but did not translate into improved reproductive performance. Sows with Ideal body condition at weaning demonstrated greater reproductive efficiency than Thin sows in general; however, additional feed within a BCS category provided no productivity advantage. Therefore, managing gestation feed levels to maintain, rather than maximize, body condition may optimize feed efficiency, sustain reproductive performance, and reduce unnecessary feed costs in commercial production systems.