Effect of omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation to lactating sows on growth and indicators of stress in the postweaned pig1,2

Abstract

Dietary omega-3 polyunsaturated fatty acids (n-3 PUFA) are precursors for lipid metabolites that reduce inflammation. Two experiments were conducted to test the hypothesis that enriching the sow diet in n-3 PUFA during late gestation and throughout lactation reduces stress and inflammation and promotes growth in weaned pigs. A protected fish oil product (PFO; Gromega) was used to enrich the diet in n-3 PUFA. In the initial experiment, time-bred gilts were fed a gestation and lactation diet supplemented with 0% (control; n = 5), 0.25% (n = 4), 0.5% (n = 4), or 1% (n = 5) PFO from 101 ± 2 d of gestation to day 16 of lactation. Adding 1% PFO to the diet increased the n-3:n-6 PUFA ratio in colostrum and milk compared with controls (P = 0.05). A subsequent experiment was performed to determine whether supplementing the sow diet with 1% PFO improved growth and reduced circulating markers of acute inflammation and stress in the offspring. Plasma was harvested from piglets (16 per treatment group) on day 0 (d of weaning) and days 1 and 3 postweaning. Pigs from the 1% PFO treatment group weighed more (P = 0.03) on day 3 postweaning and had a greater (P ˂ 0.05) n-3:n-6 PUFA ratio in plasma on each day sampled compared with 0% PFO controls. There was an overall treatment effect on plasma total cortisol (P = 0.03) and haptoglobin (P = 0.04), with lesser concentrations in pigs on the 1% PFO diet. Plasma corticosteroid-binding globulin (CBG) concentrations were not different between treatment groups but were less (P ˂ 0.001) on days 1 and 3 when compared with day 0. The resultant free cortisol index [FCI (cortisol/CBG)] was less (P = 0.02) on days 1 and 3 for pigs from the 1% treatment group compared with the controls. An ex vivo lipopolysaccharide (LPS) challenge of whole blood collected on days 0 and 1 was used to determine whether 1% PFO attenuated release of inflammatory cytokines (IL-1β, IL-6, and TNF-α). Blood from pigs within the 1% PFO treatment group tended (P = 0.098) to have a lesser mean concentration of TNF-α in response to LPS compared with blood from controls. These results suggest that providing a PFO supplement as 1% of the diet to sows beginning in late gestation and during lactation can increase the n-3:n-6 PUFA ratio in their offspring, which may improve growth and reduce the acute physiological stress response in the pigs postweaning.

Keywords: fish oil; lactation; pig; sow; supplementation; weaning stress.

Figure 1.

Colostrum concentrations of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (ARA) from sows receiving a corn-soybean meal based diet supplemented with 0% (n = 5), 0.25% (n = 4), 0.5% (n = 4), or 1% (n = 5) of a protected fish oil product (PFO; Gromega, JBS United Inc., Sheridan, IN) from days 101 ± 2 of gestation to day 16 of lactation and collected within 24 h of farrowing. ^a,bMeans ± SEM with different letters differ (P = 0.05).

Figure 2.

Plasma n-3:n-6 PUFA ratio measured in samples collected immediately prior to weaning (day 0), and on days 1 and 3 postweaning in pigs nursed by sows receiving a corn-soybean meal based diet supplemented with 1% protected fish oil (1% PFO, n = 16 pigs; Gromega, JBS United Inc., Sheridan, IN) or no supplement (0% PFO, n = 16 pigs) 1 wk prior to farrowing until day of weaning (31 ± 2 d of age). ^a–dMeans ± SEM with different letters differ by diet (P < 0.001), day (P < 0.001), and diet x day (P < 0.05).

Figure 3.

Body weight (BW) on day −7 preweaning and to day 3 postweaning in pigs nursed by sows receiving a corn-soybean meal based diet supplemented with 1 % protected fish oil (1% PFO, n = 16 pigs; Gromega, JBS United Inc., Sheridan, IN) or no supplement (0% PFO, n = 16 pigs) 1 wk prior to farrowing until day of weaning (31 ± 2 d of age) and provided ad libitum access to either the control or 1% PFO nursery feed consistent with their pre-weaning dietary treatment group. ^a–cMeans ± SEM with different letters differ for diet (P = 0.03) and day (P < 0.01).

Figure 4.

Plasma concentrations of cortisol and corticosteroid-binding globulin (CBG) in samples collected immediately prior to weaning (day 0), and on days 1 and 3 postweaning in pigs nursed by sows receiving a corn-soybean meal based diet supplemented with 1% protected fish oil (1% PFO, n = 16 pigs; Gromega, JBS United Inc., Sheridan, IN) or no supplement (0% PFO, n = 16 pigs) 1 wk prior to farrowing until day of weaning (31 ± 2 d of age). ^a–cMeans ± SEM with different letters differ by diet (P = 0.03) and day (P < 0.01).

Figure 5.

Free cortisol index (FCI) in samples collected immediately prior to weaning (day 0), and on days 1 and d 3 postweaning in pigs nursed by sows receiving a corn-soybean meal based diet supplemented with 1% protected fish oil (1% PFO, n = 16 pigs; Gromega, JBS United Inc., Sheridan, IN) or no supplement (0% PFO, n = 16 pigs) 1 wk prior to farrowing until day of weaning (31 ± 2 d of age). The FCI was calculated by dividing plasma cortisol concentrations (nmol/L) by corticosteroid-binding globulin concentrations at each day sampled. ^a-dMeans ± SEM with different letters differ by diet (P = 0.02), day (P < 0.001), and diet x day (P = 0.01).

Figure 6.

Concentrations of cytokines IL-6, TNF-α, and IL-1β from media containing whole blood and subjected to ex vivo lipopolysaccharide (LPS) or PBS treatment (Trt). Whole blood was collected on day of weaning (day 0) and 1 d postweaning from pigs receiving a corn-soybean meal based diet supplemented with 1% protected fish oil (1% PFO, n = 16 pigs; Gromega, JBS United Inc., Sheridan, IN) or no supplement (0% PFO, n = 16 pigs) 1 wk prior to farrowing until day of weaning (31 ± 2 d of age). ^a–dMeans ± SEM with different letters within measured cytokine differ.

Figure 7.

Plasma haptoglobin concentrations in samples collected immediately prior to weaning (day 0), and on days 1 and 3 postweaning in pigs nursed by sows receiving a corn-soybean meal based diet supplemented with 1% protected fish oil (1% PFO, n = 16 pigs; Gromega, JBS United Inc., Sheridan, IN) or no supplement (0% PFO, n = 16 pigs) 1 wk prior to farrowing until day of weaning (31 ± 2 d of age). ^a–cMeans ± SEM with different letters differ by diet (P = 0.04) and diet x day (P = 0.05).