Essential nature of fatty acids for the modern lactating sow

Abstract Text: Supplemental lipids are of keen importance in sow nutrition due to their high energy density and provision of essential fatty acids (EFA, linoleic and α-linolenic acid). In previous research, we demonstrated that lipid supplementation during lactation moderately improved (choice white grease) or decreased (animal-vegetable blend) sow performance, but greatly improved subsequent reproduction. We hypothesized that this benefit was due to EFA from supplemented lipids, because they are precursors of hormones important for reproduction. The objective of the present study was to determine the impact of supplemental EFA during lactation on the subsequent reproduction of sows. In Exp. 1, 50 lactating sows were assigned randomly to a 2 x 2 factorial arrangement of diets plus a control diet without added lipid. Factors included linoleic (2.1 and 3.3%) and α-linolenic acid (0.15 and 0.45%), obtained by adding 4% of mixtures of canola, corn, and flaxseed oils to diets. The balance of EFA was estimated by subtracting the amount secreted in milk from the calculated absorbed dietary EFA. For sows consuming low levels of EFA, the balance of EFA was relatively low (15.1 and 1.0 g/d, for linoleic and α-linolenic acid, respectively). Supplemental EFA greatly increased the balance of EFA (P<0.05; 33.6 and 8.6 g/d), which had a positive effect in the subsequent reproduction, as demonstrated in Exp. 2. In this experiment a total of 480 lactating sows (equally balanced by parity 1, and 3 to 5, P3+) were used to define the minimum levels of EFA for optimal subsequent reproduction.  Sows were assigned randomly to a 3 x 3 factorial arrangement plus a control diet without added lipid. Factors included linoleic (2.1, 2.7 and 3.3%) and α-linolenic acid (0.15, 0.30 and 0.45%), obtained as in Exp. 1. The effects of linoleic acid on P3+ sows were influenced by level of α-linolenic acid. For diets containing less than 0.45% α-linolenic acid, increasing linoleic acid tended to improve farrowing rate (P=0.07; 75, 85, and 85% for 2.1, 2.7, and 3.3% linoleic acid, respectively). Increasing linoleic acid linearly increased the subsequent litter size for parity 1 and P3+ sows (P=0.03; 13.2, 14.1, and 14.0 pigs). These results demonstrate that EFA supplementation during lactation directly affects subsequent reproduction, and that this phenomenon is increasingly important with advancing sow age. We estimate that provision of 100 g/d of linoleic acid to lactating sows will ensure adequate consumption of this fatty acid and prevent a potential negative balance.

Keywords: essential fatty acids, lactating sows, subsequent reproduction