Comparing a seaweed blend to pharmacological levels of zinc oxide in weaner pig diets: The benefit to pig performance and inflammatory response

After the ban of pharmacological zinc oxide (ZnO) in EU pig diets, alternative ways to improve health and growth performance of pigs after weaning are being sought. Seaweed blends have been an area of interest given their potential prebiotic effects. This work compared two levels of seaweed blend, added to a control diet and a diet with pharmacological levels of ZnO, on feed intake, growth, feed efficiency and the inflammatory response. A total of 240 pigs ((Large white x landrace) x Danish duroc) were weaned (8.5 ± 0.31 kg) into pens of five pigs per pen and allocated to one of four dietary treatments. Across treatment groups, pens of pigs were balanced for the sex ratio within a pen, a pig's litter of origin and weight at weaning. Pens of pigs were fed one of four diets: 1) positive control (PC) - standard diet with 3.1 g/kg ZnO; 2) negative control (NC) - standard diet without ZnO; 3) NC+5 g/kg seaweed blend (SWB); 4) NC+10 g/kg SWB, across three phases: days 0 - 7, 7 - 20 and 20 - 42 after weaning. Feed refusals per pen and individual pig weights were recorded on days 7, 20 and 42 to determine average daily gain (ADG), average daily feed intake (ADFI) and gain:feed (G:F) per phase. On day 20, six pigs per treatment were euthanised and dissected. Peripheral plasma samples were collected for ELISA analysis of Interleukin-6 (IL-6), IL-1β and IL-10 and the ileal mucosa was scraped for qPCR analysis of relative mRNA quantification of IL-6, IL-1β and tumour necrosis factor-alpha (TNF-α). During the first seven days after weaning, PC fed pigs tended to have higher ADG than other treatments (P<0.10) and higher G:F compared to NC (0.888 vs. 0.764, P<0.001, NC+5 g/kg SWB (0.888 vs. 0.753, P=0.019) and NC+10 g/kg SWB (0.888 vs. 0.762, P=0.034). Between 8-20 days, PC pigs tended to have higher ADFI than all treatments (P<0.10). Average daily gain between 8-20 days was not different for PC and NC+5 g/kg SWB pigs (0.368 and 0.308 kg/day) and G:F was higher for PC compared to both NC (0.830 vs. 0.721, P=0.021) and NC+10 g/kg SWB pigs (0.830 vs. 0.702, P=0.005). Between 21-42 days, there were no differences in ADG or ADFI. Gain:feed for PC (0.755) and NC+5 g/kg SWB (0.768) pigs were not different but were lower than NC (0.804, P=0.002 and P=0.038, respectively). There were no differences in mRNA levels of IL-6, IL-1β or TNF-α in the ileum. In plasma, PC and NC+5 g/kg SWB tended to have lower IL-6 concentrations compared to NC and NC+10 g/kg SWB (1.7 and 1.1 vs. 4.7 and 5.0 pg/ml; P<0.10). Given the intermediate performance of pigs fed 5 g/kg inclusion of SWB it could be beneficial to investigate this inclusion level further, or lower inclusion levels, given 10 g/kg did not show any beneficial effect.