Effects of tannic acid supplementation on growth performance, blood hematology, iron status and faecal microflora in weanling pigs

This experiment investigated the effects of dietary tannic acid (TA) supplementation on growth performance, hematology, plasma iron status, and faecal microflora in weanling pigs. One hundred and eighty male pigs (Landrace × Yorkshire × Duroc; 6.485 ± 0.66 kg; 21 ± 3 day) were randomly allotted to one of five treatments (4 pens per treatment; 9 piglets per pen) on the basis of initial body weight. The basal diet was formulated without any additional iron in the premix. The treatment diets were supplemented with 125, 250, 500 and 1000 mg TA/kg. The supplemental levels of TA were obtained by adding albumin tannate containing 500 g TA/kg to the diets. The trial lasted for 28 days. Faeces were collected on days 14 and 28 and the population of total anaerobic bacteria, Bifidobacterium spp., Lactobacillus spp., Clostridium spp. and coliform bacteria were counted. Two pigs from each pen were bled at days 7, 14, 21 and 28 of the experiment to determine blood hematology and plasma Fe status. An increase in TA concentration reduced linearly overall average daily gain (P < 0.001), feed efficiency (P = 0.021), faecal coliform count (day 14, P = 0.014) and tended to reduce feed intake (P = 0.088). The excretion of Fe in faeces was higher (linear, P = 0.005) in pigs fed TA diets. Total erythrocyte count, hemoglobin, hematocrit on days 21 and 28 and plasma iron concentration on day 21 were linearly reduced (P < 0.05) with increased levels of TA. Additionally, TA reduced the faecal coliform bacteria count (linear, P = 0.014) at day 14 and had no influence on the other faecal bacteria. It is concluded that inclusion of TA in the diet had a negative impact on performance, hematological indices and plasma iron status of pigs.