Tannic Acid in Liaoning Cashmere Goat Diets: Effects on Growth Performance, Digestibility, Nitrogen Metabolism, Rumen Fermentation and Blood Parameters

The aim of this study was to investigate the effects of dietary supplementation with tannic acid (TA) on the growth performance, nutrient apparent digestibility, nitrogen metabolism, rumen fermentation and blood indices in Liaoning cashmere goats. Twenty-four Liaoning cashmere goats with an initial body weight of 23.78±1.25 kg were equally divided into four dietary treatment groups: TA0 (Con group), 0 g/kg dry matter (DM) TA; TA2, 2 g/kg DM TA; TA4, 4 g/kg DM TA; TA8, 8 g/kg DM TA. The results showed that dietary TA supplementation had no effect on growth performance of goats (P>0.05), but increased the apparent digestibility of crude protein (P<0.05). The addition of 4 g/kg DM TA increased the content of total protein, albumin and creatinine in serum (P<0.05). Moreover, the concentrations of propionic acid, butyric acid, valeric acid and microbial crude proteins in rumen were significantly higher in the 4 g/kg DM TA group compared to the Con group (P<0.05). Furthermore, dietary 4 g/kg DM TA reduced urinary urea nitrogen and nitrogen excretion but increased nitrogen deposition and nitrogen deposition rate significantly (P<0.05). Thus, adding 4 g/kg DM of TA to the basal diet modulates nitrogen metabolism, improving the crude protein apparent digestibility and protein utilization without affecting the growth performance of goats.