Effect of Low- and High-Sulfur-Containing Amino Acid Inclusion in Diets Fed to Primiparous Sows in Late Gestation on Pre-Partum Nitrogen Retention and Offspring Pre- and Post-Weaning Growth Performance

Twenty-seven gestating primiparous sows (203 ± 9.1 kg initial body weight on d 89 ± 1 of gestation) were selected to determine the effect of standardized ileal digestible (SID) sulfur-containing amino acid (SAA) intake during late gestation on whole-body nitrogen (N) retention and subsequent litter performance. Primiparous sows were assigned to one of two experimental diets that provided SAAs at 63 or 200% of the estimated requirements during late gestation (0.29 and 0.92% SID SAAs, respectively; n = 15 and 12, respectively). The diets were isoenergetic, and the SID Lys was 0.80% in both diets. Each gilt received 2.50 kg of the assigned diet between gestation d 90 and farrowing. Common lactation and nursery diets were provided to all primiparous sows after farrowing and offspring after weaning, respectively. Gilt whole-body N balance was determined between d 107 and 109 of gestation using total urine collection and fecal grab sampling. After farrowing, litters were standardized to 13 piglets and were not offered creep feed. Whole-body N retention was greater in primiparous sows fed the diet containing 0.92 vs. 0.29% SID SAAs in late gestation (27.2 vs. 19.3 ± 1.8 g/d; <i>p</i> < 0.05), but the number of piglets born alive, litter birth weight, subsequent piglet growth rates, and litter size at weaning were not different between the treatment groups. The post-weaning growth performance of the offspring was not influenced by maternal dietary treatment in late gestation. At farrowing, the post-absorptive plasma concentration of Tau was greater (<i>p</i> < 0.01) for primiparous sows fed 0.92 vs. 0.29% SID SAAs in late gestation, and offspring from primiparous sows fed 0.92% SID SAAs tended to have greater plasma homocysteine (Hcys; <i>p</i> = 0.066). Post-absorptive plasma AAs Ile, Leu, Val, and Tyr were greater (<i>p</i> < 0.05), and Ser tended to be greater (<i>p</i> = 0.071) in sows fed 0.92 vs. 0.29% SID SAAs. For the offspring, there were no diet effects on any of the dispensable and indispensable AA concentrations in plasma at birth, at weaning, or 3 and 6 weeks post-weaning. The primary finding is that the sow has a remarkable ability to buffer dietary AA imbalances, ensuring fetal growth even when SAA intake is below the current requirement estimates. While sufficient supplemental SAA intake is essential for the sow's well-being, excessive SAA levels may not confer additional advantages in terms of sow or piglet growth and the production of vital metabolites. This research emphasizes the importance of meticulously balanced diets for pregnant sows to simultaneously support maternal growth and nitrogen retention, which may also have an impact on the synthesis of biomolecules linked to improving health outcomes for the offspring.