Effects of crude protein and zinc oxide on growth performance, fecal consistency, and health parameters of nursery pigs

Abstract

Two experiments were conducted to evaluate the effects of crude protein and zinc oxide on the health and growth performance of both healthy and Enterotoxigenic Escherichia coli-challenged nursery pigs. In the first experiment, a total of 360 weanling pigs (DNA 241 × 600; 5.44 ± 0.03 kg BW) were used to investigate the effects of feeding varying levels of dietary CP (low, medium, high) with 110 or 3,000 mg/kg of ZnO on nursery pig growth performance, fecal dry matter, and circulating Zn in a 42-d growth trial. During the experimental period (d 0 to 25), increasing CP decreased ADFI (linear, P = 0.011) and tended to reduce ADG (linear, P = 0.100) and tended to improve G:F (quadratic, P = 0.052). Pig fed pharmacological Zn had increased ADG, ADFI, and G:F (P ≤ 0.002). Overall (d 0 to 42), pigs fed increasing CP had a decrease in ADG and ADFI (quadratic, P ≤ 0.098) with no effect on G:F. Pharmacological Zn tended to increase overall ADG (P = 0.066). For fecal DM, a Zn × day interaction was observed (P = 0.015) where fecal DM for pigs fed basal Zn level improved from d 10 to 25, but remained similar for pigs fed pharmacological Zn. Plasma Zn was greater on d 10 and 25 (P < 0.0001) for pigs fed 3,000 mg/kg Zn. In summary, CP × Zn interactions were limited, and thus the main effects of each feeding strategy were independent. In experiment 2, a total of 90 weanling pigs (DNA 241× 600; initially 6.59 ± 0.40 kg BW) were used in a 14-d study using two groups (45 pigs/group) to evaluate the effects of low CP formulation strategies with 110 or 3,000 mg/kg of ZnO, on growth performance, fecal dry matter, and health parameters in Enterotoxigenic Escherichia coli F18 (ETEC) challenged nursery pigs. Diets were corn-soybean meal-based and formulated as: High CP, Low CP, Low CP +AA, Low CP+3,000 mg/kg Zn from ZnO and Low CP+AA+3,000 mg/kg Zn from ZnO. Overall, pigs fed Low CP+AA+ZnO had greater (P < 0.05) ADG compared to pigs fed the High CP, Low CP, or Low CP+AA treatments. Feed intake was greater (P < 0.05) for pigs fed Low CP+ZnO and Low CP+AA+ZnO compared to pigs fed the High or Low CP diets. There was no evidence of a difference (P = 0.640) in overall G:F. There was a treatment × day interaction for fecal DM (P < 0.0001). In summary, inclusion of ZnO, particularly when combined with elevated amino acid levels in a low CP formulation, enhanced growth performance in ETEC F18-challenged pigs relative to a low CP diet.