The addition of hydrolyzable tannin extract to milk affects calves' performance, health, blood metabolites, and pathogen shedding

Abstract

The purpose of this study was to determine what quantity of a hydrolyzable tannin extract (HTE) might be used in calf milk to increase growth performance, health, and metabolic condition, as well as shedding fecal bacteria. A total of 48 newborn Holstein calves were randomly allocated to one of four dietary treatments, which included daily in-milk HTE supplementation of 0 (HTE0), 2 (HTE2), 4 (HTE4), and 6 g (HTE6). Milk was offered from day 6–70 of the study, using an adjusted step up/step down milk feeding strategy of 4, 5, 6, 7, 6, and 3 L/d on days 6–20, 21–25, 26–30, 31–60, 61–65 and 66–70, respectively. On day 70, all calves were weaned, and the experiment was terminated on day 76 of calf age. During the investigation, the calves had free access to a starter diet and fresh water. The HTE was blended into milk and fed twice daily. Supplementation with HTE had no effect on starter intake or total DM intake. When compared to other treatments, calves fed HTE4 had higher average daily gain (ADG; P = 0.01) and final body weight (BW) (P = 0.04). Furthermore, calves fed HTE4 showed the greatest feed efficiency (FE) when compared to the other treatments (P < 0.01). The incremental levels of HTE lowered fecal score and diarrheic episode duration (P < 0.01). With the supplementation of HTE, the Escherichia coli population decreased linearly, although the lactobacillus population increased (P < 0.01). In comparison to other treatments, HTE4 supplementation resulted in the highest lymphocyte percentage and lymphocyte-to-monocyte ratio (P < 0.01). Albumin concentration was greatest when calves were fed HTE4 (P = 0.02). Further, plasma cholesterol concentration evolved quadratically (P = 0.03) with HTE supplementation so that calves fed HTE4 had higher cholesterol concentrations than HTE0 and HTE6 calves. Calves fed HTE had a linear increase (P < 0.01) in TAC on day 36, with HTE6 calves having greater TAC than HTE0 and HTE4 calves. In addition, on day 65, TAC changed quadratically as HTE levels increased (P < 0.01), with HTE2 and HTE4 calves having greater TAC values than HTE6 calves. In conclusion, our findings suggested that HTE supplementation with up to 4 g/d may increase growth performance and plasma antioxidant capacity, decrease the presence of pathogens in feces, and improve newborn calves' health condition.