Supplementation of high levels of essential fatty acids using soybean oil in lactation diets benefits the subsequent reproduction of sows but can be detrimental to the performance of young sows if provided after weaning

This study investigated the potential impacts of increasing linoleic and α-linolenic acid intake during lactation and wean-to-breeding on subsequent reproduction of sows. A total of 309 sows (PIC Camborough L42) were balanced by parity (140 and 169 sows representing parity 1 to 2 [P1-2] and 3 to 9 [P3+], respectively) and assigned within parity to a 2 × 2 factorial arrangement. Factors included essential fatty acid (EFA) supplementation (control diets containing 1.2% linoleic and 0.15% α-linolenic acid or diets with 3.0% linoleic and 0.38% α-linolenic acid) and supplementation period (lactation or wean-to-breeding). Tallow (low EFA diets) or soybean oil (high EFA diets) were included at 4% in sorghum-soybean meal-wheat middlings-based diets to attain targeted EFA levels. High levels of EFA fed during lactation had no effect on feed intake or litter performance, but increased subsequent farrowing rate (P = 0.027; 82.1% vs. 70.4%), tended to reduce the proportion of sows removed (P = 0.070; 12.4% vs. 20.8%), decreased the number of total pigs born in the following litter (P = 0.072; 15.3 vs. 16.2), and increased total pigs born alive per 100 sows weaned (P = 0.062; 1,122 vs. 974), regardless of sow parity. Young sows (P1-2) consuming the high EFA diet during lactation displayed a shorter wean-to-estrus interval (P = 0.035; 4.2 vs. 4.6), but P3+ sows were unaffected. Increasing EFA intake for P3+ sows, but not P1-2 sows, resulted in more sows bred by d 5 (P = 0.028; 91.1% vs. 81.7%) and more mummies in the subsequent litter (P = 0.040; 0.32 vs. 0.16). Feeding increased EFA to P1-2 sows during the wean-to-breeding period decreased subsequent farrowing rate (P = 0.042; 72.0% vs. 87.7%), and increased removal rate (P = 0.003; 28.8% vs. 9.4%). Total pigs born alive per 100 sows weaned was reduced (P = 0.007) in P1-2 sows when supplemented with EFA during wean-breeding (939 vs. 1,149) but was not impacted in P3+ sows (1,131 vs. 982). Supplemental EFA in lactation diets benefited subsequent reproduction of sows, regardless of parity. Increasing dietary levels of EFA during the wean-to-breeding period to younger sows negatively impacted subsequent reproduction.