Dietary supplementation with lysine (protein) in late pregnancy does not enhance mammary development in multiparous sows.

This project was conducted to determine if providing standardized ileal digestible (SID) Lys at 40% above estimated requirements (NRC, 2012), with the concomitant increased protein intake, from days 90 to 110 of gestation stimulates mammary development in multiparous sows. From day 90 of gestation, Yorkshire × Landrace multiparous sows (parities 2 and 3) were fed 2.6 kg/d of either a conventional diet (CTL, control, n = 17) providing 14.8 g/d of SID Lys or a diet providing 20.8 g/d of SID Lys via additional soybean meal (HILYS, n = 16). The diets were isoenergetic. Concentrations of IGF-1, glucose, free fatty acids (FFA), urea, and amino acids (AA) were measured in jugular blood samples obtained on days 90 and 110 of gestation. Sows were necropsied on day 110 ±â€…1 of gestation to obtain mammary glands for compositional and histological analyses. Backfat or BW changes of sows during late gestation were unaffected by treatment (P > 0.10), as was the case for fetal BW (P > 0.10). None of the variables measured in mammary tissue were altered by supplementary Lys (P > 0.10). Circulating IGF-1, glucose, and FFA did not differ (P > 0.10) between HILYS and CTL sows on day 110 of gestation, whereas concentrations of urea were greater (P < 0.01) in HILYS versus CTL gilts. Concentrations of Ile and Thr in plasma were also greater (P < 0.05), and those of Glu were lower (P < 0.01) in HILYS than CTL sows. These results demonstrate that feeding Lys (via protein) above current NRC recommendations during late gestation does not improve mammary development of multiparous sows. Hence, the use of a two-phase feeding strategy to provide more Lys (protein) to multiparous sows during this period is not necessary.

Results indicate that there is no advantage in terms of mammary development to feeding late-pregnant multiparous sows with 40% more lysine (via protein) than current recommendations (NRC, 2012). From days 90 to 110 of gestation, multiparous sows (parities 2 and 3) were fed 2.6 kg/d of either a conventional diet providing 14.8 g/d of standardized ileal digestible (SID) lysine or a diet providing 20.8 g/d of SID lysine via the inclusion of additional soybean meal. Diets were isoenergetic. Feeding supplementary SID lysine had no effect on mammary development at the end of gestation. Contrary to our previous report for gilts, mammary gland development is not improved by providing more lysine to multiparous sows in late gestation. Such information is crucial for developing the best feeding strategies to maximize milk yield. The use of a two-phase feeding strategy to provide more lysine (protein) as of day 90 of gestation is not necessary in multiparous sows.