Effects of dietary iron level on growth performance, haematological status and intestinal function in growing-finishing pigs.

This study investigated the different addition levels of iron (Fe) in growing-finishing pigs and the effect of different Fe levels on growth performance, haematological status, intestinal barrier function, and intestinal digestion. A total of 1,200 barrows and gilts [(Large White × Landrace) × Duroc]with average initial body weight (BW; 27.74 ±0.28 kg) were housed in 40 pens of 30 pigs per pen (gilts and barrows in half), blocked by body weight and gender, and fed 5 experimental diets (8 replicate pens per diet). The five experimental diets were control diet (basal diet with no FeSO4 supplementation), and the basal diet being supplemented with 150, 300, 450 or 600 mg/kg Fe as FeSO4 diets. The trial lasted for 100 days and was divided into the growing phase (27-60 kg of BW) for the first 50 days and the finishing phase (61-100 kg of BW) for the last 50 days. The basal diet was formulated with an Fe-free trace mineral premix, and contained 203.36 mg/kg total dietary Fe in the growing phase and 216.71 mg/kg in the finishing phase based on ingredient contributions. And at the end of the experiment, 8 pigs (4 barrows and4gilts) were randomly selected from each treatment (selected 1 pig per pen) for digesta, blood and intestinal samples collection. The results showed that the average daily feed intake (ADFI; P =0.025), average daily gain (ADG; P =0.020) and body weight (BW; P =0.019) increased linearly in the finishing phase of pigs fed with the diets containing Fe. On the other hand, supplementation with different Fe levels in the diet significantly increased serum iron (SI) and transferrin saturation (TAST) concentrations (P< 0.05), goblet cell numbers of duodenal villous (P<0.001) and MUC4 mRNA expression (P< 0.05). The apparent ileal digestibility of amino acids for pigs in the 450 and 600 mg/kg Fe groups were greater (P <0.05) than for pigs in the control group. In conclusion, dietary supplementation with 450-600 mg/kg Fe improved the growth performance of pigs by changing haematological status, and enhancing intestinal goblet cell differentiation and apparent ileal digestibility of amino acids.