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Apparent balance of essential fatty acids for the prolific lactating sow
The objective of this study was to determine the effects of supplementing diets with essential fatty acids (EFA, linoleic, C18:2n-6; and α-linolenic acid, C18:3n-3) on sow milk composition in order to estimate the balance of EFA during lactation. Fifty sows, balanced by parity (1 vs. 3 to 5) and nursing 12 pigs, were randomly assigned 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%); resulting in 4 different n-6:n-3 (primarily from EFA) fatty acid ratios: 5, 7, 14 and 22. Concentration of EFA was obtained by adding 4% of different mixtures of canola, corn and flaxseed oils to diets. Diets were corn-soybean meal based with 12% wheat middlings and contained 3.39 Mcal ME/kg and 3.29 g SID Lys/Mcal ME. Milk samples were collected from each sow on d 10 of lactation. Data were analyzed using the mixed procedure of SAS. No diet by parity interactions were detected (P>0.05). Supplemental EFA did not impact milk concentrations of protein (P=0.26), lactose (P=0.48), or Ca (P=0.80). Supplemental α-linolenic acid tended to reduce milk fat content (P=0.07; 6.5 and 5.9% for 0.15 and 0.45% α-linolenic acid, respectively). Supplemental EFA increased milk concentration of both α-linolenic (P<0.05; 0.75 and 1.18 g/kg of milk) and linoleic acid (P<0.01; 9.9 and 13.8 g/kg of milk for 2.1 and 3.3% linoleic acid, respectively) in a dose-related manner. Supplemental linoleic acid tended to increase the concentration of arachidonic acid secreted in milk (P=0.08; 0.39 and 0.47 g/kg of milk), but concentration was reduced with 0.45% α-linolenic acid (linoleic × α-linolenic acid interaction, P<0.05). The balance of EFA was estimated by subtracting the amount secreted in milk from the apparently absorbed dietary EFA. For sows consuming control diet, the balance of EFA was relatively low (18.1 and 1.3 g/d, for linoleic and α-linolenic acid, respectively) and similar to the balance for sows consuming diets with low levels of EFA (15.1 and 1.0 g/d, for 2.1% linoleic and 0.15% α-linolenic acid, respectively). Supplemental EFA greatly increased the balance of EFA (P<0.05; 33.6 and 8.6 g/d for 3.3% linoleic and 0.45% α-linolenic acid, respectively). In conclusion, supplemental EFA alters milk fat composition and greatly increased the apparent balance of EFA during lactation. The latter may be beneficial for subsequent reproduction of prolific lactating sows because EFA are precursors of hormones important for reproduction.
Keywords: dietary lipids, essential fatty acids, lactating sows