Standardized ileal digestible linoleic acid requirement of modern lactating sows: A dose-response study

Continued genetics and management improvement necessitates the verification of nutrient requirements for prolific and high-producing modern sow. Therefore, the objective of this study was to determine the standardized ileal digestible (SID) linoleic acid (LA) requirement of lactating sows using dose-response estimation methods. A total of 100 healthy Yorkshire × Landrace sows (parity two to four; initial body weight 245.0 ± 15.8 kg) were randomly assigned to five treatment groups with 20 replicates per group. The five diets contained 1.47%, 1.91%, 2.32%, 2.74%, or 3.15% SID LA. The experimental period lasted 28 d from d 107 of gestation until weaning. Reproductive performance of sows were not affected by dietary SID LA levels (P > 0.05); however, piglet weaning weight linearly increased with increasing SID LA levels (P = 0.044). A linear-broken relationship between litter weight and SID LA concentration was observed, litter weight on d 14 increased with SID LA until reaching a plateau at 2.36% of SID LA (P = 0.005), reaching a plateau at 2.15% of SID LA on d 21 (P = 0.083). The contents of immunoglobulin A in colostrum (P = 0.061) and immunoglobulin M in milk (P = 0.088) showed a trend towards a quadratic polynomial relationship with SID LA levels, immunoglobulin M content in milk peaked at 2.41% of SID LA (P = 0.038). In addition, the tumor necrosis factor-α content in plasma of piglets on d 7 of lactation showed a quadratic polynomial relationship with SID LA levels (P = 0.041). The content of immunoglobulin G on d 21 of lactation in sows linearly increased with higher SID LA levels (P < 0.001). The level of total antioxidant capacity of piglets on d 21 showed a quadratic polynomial relationship with SID LA levels (P = 0.001), which peaked at 2.23 g/kg of SID LA (P = 0.002). The glutathione peroxidase activity of piglets on d 7 increased linearly with the increase of SID LA, and reached a plateau at 2.07% of SID LA (P = 0.002). In conclusion, using broken line and quadratic regression model, the SID LA requirement for modern lactating sows ranged from 2.07% to 2.43% (133-156 g/d) to achieve optimal litter weight, milk immunoglobulin, and antioxidant capacity of sows and piglets.