Effects of hydrolyzed yeast on weanling pig growth performance, fecal dry matter, and stress-related blood antioxidant criteria.

A total of 360 weanling pigs (241 × 600, DNA; initially 5.4 ± 0.01 kg) were used to evaluate the effects of a hydrolyzed yeast product (HY) on growth performance, fecal dry matter (DM), and stress-relevant blood antioxidant criteria. Pens of pigs were randomly allotted to one of six dietary treatments in a generalized randomized block design with 5 pigs per pen and 12 pens per treatment. Pigs were blocked with 4 replications of light (4.3 ± 0.01 kg), medium (5.4 ± 0.01 kg), and heavy (6.5 ± 0.01 kg) weight pens per treatment. Diets were corn-soybean meal-based and consisted of a negative control (NC) diet, a positive control (PC) diet which was the NC diet + 55 mg/kg carbadox, the PC diet with 0.04% HY, and the NC diet with either 0.04%, 0.08%, or 0.12% HY. Linear and quadratic contrasts were tested within increasing levels of HY in diets without carbadox. The main effect of carbadox was evaluated by comparing the average of 0% and 0.04% HY in the presence and absence of carbadox. Treatment diets were fed in three phases from day 0 to 10 (phase 1), day 10 to 24 (phase 2), and day 24 to 45 (phase 3). On day 10 and 24, fecal samples were collected from the same three initially randomly selected pigs in each pen to determine fecal DM and fecal scores. Blood samples were collected on day 10 and 45 from the same representative pig in each pen for total antioxidant capacity (TAC) and superoxide dismutase (SOD). Overall (day 0 to 45), final weight increased (P < 0.05) while average daily gain (ADG) and average daily feed intake (ADFI) tended to increase (P < 0.10) for pigs fed diets containing carbadox compared to pigs fed diets without carbadox. Gain:feed ratio (G:F) increased (P = 0.017) when 0.04% HY was added to the negative and positive control diets. On day 10, increasing HY in diets without carbadox increased fecal DM (linear, P = 0.005). Additionally, pigs fed carbadox had increased (P < 0.05) fecal DM on day 10 and 24 compared to pigs not fed carbadox. There were no treatment differences observed on day 10 for TAC; however, TAC decreased (linear, P = 0.008) on day 45 as HY increased in the diet. Increasing HY tended to decrease (linear, P = 0.095) serum SOD activity on day 10 while no treatment differences were observed on day 45. In summary, pigs fed carbadox had increased overall ADG and fecal DM. Increasing HY inclusion did not affect growth performance; however, fecal DM was improved during the early nursery period. Additionally, feeding 0.04% HY improved overall G:F.