Do varied dietary omega-6 to omega-3 ratios affect the performance, nutrient digestibility, immune status and faecal microbiota of weaner pigs?

Abstract

The present study tested the hypothesis that altering the ratio of omega-6 (n-6) to omega-3 (n-3) fatty acids (FAs) in the diet will improve growth performance, nutrient digestibility and blood parameters of weaner pigs. In total, 90 crossbred weaner pigs ((Yorkshire × Landrace) × Duroc, 28 days old), with an average bodyweight (BW) of 6.53 ± 0.71 kg were used in a 6-week experiment. Pigs were blocked on the basis of BW and sex and randomly allotted to one of three dietary treatments (5 pigs per pen (2 barrows and 3 gilts); 6 pens per treatment). Treatments consisted of plant-derived n-6 and n-3 FAs (15:1, 10:1 and 5:1). The experimental period was divided into three phases: Phase 1; 28–35 days of age, Phase 2; 36- 49 days of age and Phase 3; 50–70 days of age. Supplementation of varied n-6:n-3 FA ratios in the diet of weaned pigs showed linear increases (P < 0.05) in BW and average daily gain during Phases 1 and 2. The feed:gain ratios reduced linearly (P < 0.05) during Phase 1 and tended to reduce (P = 0.08) during Phase 2 as the ratio of n-6:n-3 FA decreased from 15:1 to 5:1. However, the overall performance of weaners was not affected by the n-6:n-3 FA ratio. Dry matter and nitrogen (N) digestibility increased linearly (P < 0.05) and energy digestibility tended (P = 0.089) to increase linearly with the reduction of n-6:n-3 FA ratio from 15:1 to 5:1 during Week 3 and, in Week 6, dry-matter digestibility increased (P < 0.05) linearly, whereas energy digestibility tended to increase with a decreasing n-6:n-3 FA ratio in the diet. The high-density lipid cholesterol showed a significant (P < 0.05) linear increase at Week 3 and a tendency to increase at Week 6, but no significant effects on other serum lipids were observed. The dietary n-6:n-3 FA ratio did not have a significant effect on white blood cell, lymphocyte, immunoglobulin G and tumour necrosis factor-α concentrations or faecal microbial counts. In conclusion, the reduction of n-6:n-3 FA ratio from 15:1 to 5:1 in the diet did not affect the overall performance of weaning pigs. However, it showed a positive effect on the growth performance of pigs during Phases 1 and 2.