Effect of nursery diet protein quality and fish oil supplementation on growth performance, immune response, and gut morphology in starter pigs

Abstract Text: Previous research has demonstrated that diet quality affects growth performance and immune response of starter pigs. This study was conducted to assess the interactive effects of feeding dietary protein quality and oil types on growth performance, immune response and gut morphology in starter pigs. Newly-weaned pigs (21 d age; BW = 6.25±0.83 kg) were randomly assigned to 4 dietary treatments (3 pens/treatment; 10 pigs/pen), as a 2 x 2 factorial design, with differing diet protein quality (High vs. Low; animal vs. soybean protein), and 5% oil (Fish vs. Corn). Pigs were fed according to a three phase program; diets fed for 7, 14 and 21 d, respectively. On d 6 and 20 post-weaning, 12 pigs per treatment were vaccinated with 0.5 mg ovalbumin (OVA), 0.5 mg killed C albicans (CAA), and 0.5 mg Quil A adjuvant in 1 ml saline. Blood samples were collected at d 20 and 34 for determination of anti-OVA antibodies, and d 22 and 28 for haptoglobin (Hp) analysis. The delayed type hypersensitivity (DTH) reaction was evaluated on d 17 and 48, using intradermal injection of OVA and CAA in the ear, and ear thickness was measured at 6h post- injection. Per treatment 6 pigs were euthanized at 2, 4 and 8 wks post-weaning and jejunum samples were collected to evaluate morphology. Data were analysed as a Mixed model procedure of SAS. There were no significant interactions (P>0.10) between main effects. During the 6 wk starter period, ADG was greater (P<0.05; 422 vs. 385 g) for pigs on High; High and Fish fed pigs had greater feed efficiency (G: F) (P<0.05; 0.750 vs. 0.721, 0.775 vs. 0.695). Diet did not affect (P>0.10) primary or secondary antibody immune response to OVA. At d 17, DTH response to OVA was greater (P<0.05) in pigs fed Low diets. At d 48, DTH response to CAA tended to be lower (P<0.10) for pigs fed Low and Fish diets. The vaccination protocol increased (P<0.05) serum Hp and these were lower in pigs on Fish (P<0.05; 0.40 vs. 0.25 g/L). Diet did not impact villus height or villus height:crypt depth ratio; crypt depth was greater (353 vs. 275, 345 vs. 282 μm; P<0.05) at wk 4 in pigs fed Low and Corn. Diet protein quality appears strongly related to growth performance, while fish oil improves feed efficiency and attenuates haptoglobin response of starter pigs.

Keywords: fish oil, protein quality, starter pigs