Effects of reducing dietary crude protein concentration and supplementation with either laminarin or zinc oxide on the growth performance and intestinal health of newly weaned pigs

Abstract

A 2 × 3 factorial experiment was conducted to examine the effects of reducing dietary crude protein (CP) concentration and/or supplementation with zinc oxide (ZnO) or laminarin on the growth performance and intestinal health in pigs reared under sanitary (Exp. 1) and unsanitary (Exp. 2) conditions, for 35 days post-weaning (PW). Pigs were assigned to: (T1) 21 % standard CP diet (SCP); (T2) SCP + ZnO; (T3) SCP + laminarin; (T4) 18 % low CP diet (LCP); (T5) LCP + ZnO; (T6) LCP + laminarin (n = 8 replicates/treatment). In Exp. 1 intestinal tissue and digesta were collected on day 9 PW. Under sanitary conditions, there was an effect of CP and additive on the incidence of diarrhoea in the first 14 days PW. Pigs offered the LCP diet had a higher incidence of diarrhoea than those offered the SCP diet (P < 0.01). Supplementation with laminarin or ZnO reduced the incidence of diarrhoea compared with the unsupplemented pigs (P < 0.001). Reducing CP downregulated nutrient transporter and upregulated inflammatory marker expression in the ileum and increased Enterobacteriaceae in the colon compared with the SCP diet (P < 0.05). In Exp. 2, reducing CP or supplementation with ZnO or laminarin improved overall (faecal score) FS (P < 0.001). There was a CP concentration x additive interaction on the incidence of diarrhoea in the first 14 days PW (P < 0.01). Pigs offered the LCP diet with ZnO had a lower incidence of diarrhoea compared with pigs offered the LCP or LCP LAM diets, however, there was no effect of additive on the on the incidence of diarrhoea in pigs offered the SCP diets. Supplementation with ZnO increased daily gains (P < 0.01) and there was a tendency for laminarin to increase daily gains. Laminarin supplementation increased the abundance of faecal Lactobacillus spp. relative to the unsupplemented and ZnO supplemented pigs (P < 0.01). In conclusion, the LCP diet did not compromise performance, likely due to the LCP diet providing sufficient concentrations of essential amino acids to maintain growth performance. However, it increased the incidence of diarrhoea between days 0−14 PW, reduced the expression of nutrient transporter genes and increased the expression of inflammatory genes under sanitary conditions. Thus, further investigation into the effects of lower CP diets are necessary. Laminarin and ZnO reduced the incidence of diarrhoea in the first 14 days PW under sanitary conditions. Under the unsanitary conditions, laminarin and ZnO also improved FS and performance, with both additives effective at either CP concentration. Thus, laminarin warrants further investigation as a dietary supplement for weaned pigs.