The effects of dietary essential fatty acid ratios and linoleic acid level in grow-finish pigs.

The objective of this study was to investigate the effects of dietary linoleic acid level and the ratio of linoleic acid:linolenic acid (LA:ALA) on the growth performance, expression of genes associated with lipid metabolism and inflammatory status of grow-finish pigs. A total of 300 growing pigs (BW = 41.1 ±6.3 kg) were randomly assigned to either a high (30 g/kg; HLA) or low (15 g/kg; LLA) dietary linoleic acid level with a high (23:1; HR), moderate (13:1; MR) or low (4:1; LR) dietary LA:ALA in a 2 × 3 factorial design. Diets were fed across three 28-day phases and were balanced for dietary metabolizable energy. Pigs were housed 5 pigs per pen in single-sex pens. Blood samples were collected on d 0, 21, 42, and 84, and synovial fluid was collected from the hock joint on d 0 and 84 for inflammatory marker analysis. Data were analyzed as repeated measures using PROC MIXED (SAS 9.4) with initial body weight as a covariate, pen as the experimental unit, and LA level, LA:ALA, sex, phases, and their interactions as fixed effects. Compared to HLA, LLA pigs tended to have increased BW at d 56 and d 84 (P = 0.088). There was no effect of LA × LA:ALA for growth performance. For the overall d 0 - 84 growth period, pigs fed HR had increased ADG compared to MR, with pigs receiving LR performing intermediate of MR and HR. Gilts receiving HR diets had increased d 84 BW compared to gilts receiving the low and moderate LA:ALA (P = 0.006), which was a result of improved overall d 0 - 84 ADG compared to gilts receiving the MR diets (P = 0.023). Barrows fed LR had improved BW on d 56 compared to MR and HR and higher final BW compared to HR, with MR performing intermediately (P = 0.006). This was a result of greater d 0 - 84 ADG (P = 0.023). Overall, C-reactive protein (CRP), tumor necrosis factor-α(TNFα), and interleukin-6 (IL-6) were reduced in the plasma of pigs over time (P ≤ 0.037). Across all treatments, CRP and TNFαwere reduced in the hock and carpus synovial fluid on d 84 vs. d 0 (P ≤ 0.049). In conclusion, LA:ALA ratios utilized in this study can be fed at varying linoleic acid levels without impacting growth or inflammation. Additionally, LA:ALA ratios can differentially impact the growth of gilts and barrows.