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

ABSTRACT

The objective of this study was to investigate the effects of dietary linoleic acid level and the ratio of linoleic acidlinolenic acid (LAALA) on the growth performance, expression of genes associated with lipid metabolism, and inflammatory status of grow-finish pigs. A total of 300 growing pigs (body weight [BW] = 41.1 ±â€…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 (231; HR), moderate (131; MR) or low (41; LR) dietary LAALA in a 2 × 3 factorial design. Diets were fed across three 28-d phases and were balanced for dietary metabolizable energy. Pigs were housed five pigs per pen in single-sex pens. Blood samples were collected on days 0, 21, 42, and 84, and synovial fluid was collected from the hock joint on days 0 and 84 for inflammatory marker analysis. Data were analyzed as repeated measures using PROC MIXED (SAS 9.4) with initial BW as a covariate, pen as the experimental unit, and LA level, LAALA, sex, phases, and their interactions as fixed effects. Compared to HLA, LLA pigs tended to have increased BW at days 56 and 84 (P = 0.088). There was no effect of LA × LAALA for growth performance. For the overall days 0 to 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 day 84 BW compared to gilts receiving the low and moderate LAALA (P = 0.006), which was a result of improved overall days 0 to 84 ADG compared to gilts receiving the MR diets (P = 0.023). Barrows fed LR had improved BW on day 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 days 0 to 84 ADG (P = 0.023). Overall, C-reactive protein (CRP), tumor necrosis factor-α (TNFα), and interleukin-6 were reduced in the plasma of pigs over time (P ≤ 0.037). Across all treatments, CRP and TNFα were reduced in the hock and carpus synovial fluid on day 84 vs. day 0 (P ≤ 0.049). In conclusion, LAALA ratios utilized in this study can be fed at varying linoleic acid levels without impacting growth or inflammation. Additionally, LAALA ratios can differentially impact the growth of gilts and barrows.

Previous research in lactating sows has reported that dietary inclusion of the essential fatty acids linoleic acid and linolenic acid is important for performance. Research in grow­finish pigs has shown an improvement in gilt growth performance when fed differing linoleiclinolenic acid ratios (LAALA); however, further research evaluating LAALA in diets with similar metabolizable energy is needed in growing pigs. In the present research, a 231 dietary essential fatty acid ratio increased the final body weight of gilts compared to a 131 or 41 LAALA, while barrows fed a 41 dietary essential fatty acid ratio had increased gain and final body weight compared to a 231 LAALA. Plasma and synovial fluid inflammatory markers were also reduced with time and were unaffected by dietary LAALA or linoleic acid inclusion. Dietary essential fatty acid ratio can differentially impact the growth of barrows and gilts, with no impact on systemic or joint inflammation.