Abstract A total of 90 weanling pigs (DNA 241 × 600; initially 5.97 kg BW) were used in a 14-d study using two groups (45 pigs/group) to evaluate the effects of low crude protein (CP) formulation strategies with and without pharmacological Zn from ZnO on growth performance and fecal dry matter in Enterotoxigenic Escherichia coli F18 challenged nursery pigs. Within group, pigs were balanced for sex, stratified by weight, and allotted to one of five dietary treatments in a generalized randomized block design with 9 pigs per treatment. Diets were corn-soybean meal-based and formulated as: High CP (20.7% CP, 1.35% SID Lys), Low CP (17.9% CP, 1.17% SID Lys), Low CP+AA (17.9% CP, 1.35% SID Lys, similar SID AA:Lys ratios to High and Low CP treatments by increasing crystalline AA addition), Low CP+ZnO (17.9% CP, 1.17% SID Lys, approx. 3,000 mg/kg Zn from ZnO), and Low CP+AA+ZnO (17.9% CP, 1.35% SID Lys, approx. 3,000 mg/kg Zn from ZnO). Following weaning (∼19 d of age) pigs were group housed by treatment (4 or 5 pigs/pen) and provided their respective treatment. Following the 7-d acclimation period, pigs were moved to individual pens and continued their respective treatment diet. Inoculation occurred on d 0 with 1´107 CFU/mL F18 ETEC administered via orogastric gavage. The isolate used was an F18 fimbrial type, with genes for heat labile enterotoxin (LT), heat stable toxin A (STa), heat stable toxin B (STb), and shiga toxin type 2e (Stx2e). Performance measures were collected on d 0, 7, and 14 to calculate ADG, ADFI, and G:F. On d 0, 3, 7, 10, and 14 fecal samples were collected from each pig for fecal dry matter analysis. 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 in overall G:F. There was a treatment×day interaction for fecal dry matter (DM; P 0.0001). On d 0 and 14, there were no differences in fecal DM between treatments. On d 3, fecal DM was greater (P 0.05) for pigs fed diets containing ZnO. On d 7, pigs fed Low CP+AA+ZnO had greater (P 0.05) fecal DM compared to pigs fed the Low CP diet. On d 10, pigs fed Low CP had greater (P 0.05) fecal DM compared to pigs fed High CP. 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.
Squires et al. (Wed,) studied this question.
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