An experiment was conducted in weanling pigs (Landrace x Yorkshire x Duroc) to evaluate the effects of dietary iron levels on growth performance, hematological status, liver mineral concentration, fecal microflora, and diarrhea incidence. One hundred and forty-four piglets (initial BW 5.96 +/- 0.93 kg) were randomly allotted to one of the four dietary treatments on the basis of their body weights. The basal diets for each phase (phase 1: days 0 to 14; phase 2: days 15 to 28) were formulated to contain minimal Fe and then supplemented with gradient levels of Fe (0, 50, 100, and 250 mg/kg) from ferrous sulfate. Feces were collected on days 14 and 28 and used for the analysis of microbial count and trace minerals. Eight piglets from each treatment (two piglets per pen) were bled at 0, 7, 14, 21, and 28 days to determine their hematological and plasma Fe status. In addition, two piglets from each pen (eight piglets per treatment) were killed at days 14 and 28 to determine liver mineral concentrations. Pigs fed supplemental 250 ppm Fe showed lowest overall average daily gain (linear, p = 0.036). Diarrhea incidence was linearly increased (p < 0.001) with supplemental Fe level. On days 14, coliform population in normal feces was increased (p = 0.036) linearly with supplemental Fe level, and there were higher (p = 0.043) coliform population and lower (p < 0.001) Bifidobacterium spp. in the diarrhea feces. Supplemental Fe linearly (p < 0.05) improved the total red blood cells, hemoglobin, plasma, and liver (p = 0.109) Fe status of pigs and also increased (linear and quadratic, p < 0.001) the fecal excretion of Fe on days 14 and 28. It is concluded that increasing the dietary iron levels in piglets improved their hematological status and liver Fe content; however, higher dietary Fe levels might also be associated with the increased diarrhea incidence.

This study investigated the effects of tannic acid (TA) in the diets for weanling pigs prepared with/without supplemental Fe on performance, hematology, fecal microflora and diarrhea incidence. Limestone and calcium phosphate used in Experiment 1 and 2 were of semi-synthetic and feed-grade quality, respectively; while the trace-mineral premix used in both the experiments was prepared without any added Fe source. In Experiment 1, 108 weaned pigs (Landrace × Yorkshire × Duroc, initially 6.46 ± 1.04 kg BW) were allotted to 3 treatments including control (diet added with FeSO4 and antibiotic), T1 (diet devoid of FeSO4 and antibiotic) and T2 (T1 diet added with 125 mg/kg TA). Each treatment had 4 replicates with 9 pigs in each pen. Feeding of T1 diet had a negative effect on the performance and plasma Fe status of pigs, while addition of TA to T1 diet resulted in performance of pigs comparable to pigs fed the control diet, reduced diarrhea incidence but had a negative influence on the hematological and plasma Fe indices. Additionally, pigs fed T2 diet had fewer (p<0.05) total anaerobic bacteria, Clostridium spp. and coliforms than pigs fed T1 diet, and greater number of Bifidobacterium spp. and Lactobacillus spp. in feces when compared with pigs fed control and T1 diets. In Experiment 2, 144 weaned pigs (Landrace × Yorkshire × Duroc, initially 6.00 ± 1.07 kg BW) were allotted to 4 dietary treatments including control (diet added with FeSO4 and antibiotic) and diets devoid of supplemental Fe added with antibiotic (An), TA and both (AnTA). Each treatment had 4 replicates with 9 pigs in each pen. Addition of An, TA or both to diets devoid of supplemental Fe did not have any effect on performance, blood hematology and plasma Fe but resulted in reduced (p<0.05) diarrhea incidence and lower (p<0.05) fecal coliform population than pigs fed the control diet. These results suggest that TA has a negative influence on blood hematology and plasma Fe status when diets are inadequate in Fe; however, TA reduced diarrhea incidence and might have antimicrobial activity.