Efficacy of avilamycin on the incidence and severity of diarrhea associated with pathogenic Escherichia coli and the subsequent growth performance of nursery pigs.

A total of 3,329 commercial crossbred barrows and gilts were used to compare the efficacy of avilamycin on incidence and severity of diarrhea and growth performance of pigs naturally infected with Escherichia coli. An incomplete block design was used with a 2 × 4 factorial arrangement of treatments: 1) Stocking density (Single: 0.67 sq. m/pig vs. Double: 0.33 sq. m/pig) and 2) Nursery medication program [Nonmedicated control fed for 56 d (CON) vs. 80.5 mg/kg avilamycin fed for 21 d (AVI21) vs. 80.5 mg/kg avilamycin fed for 42 d (AVI42) vs. 55.1 mg/kg carbadox fed for 21 d (CAR21)]. Subjective diarrhea scores were collected weekly on each pen according to a 3-point scale. Pigs were weighed on days 0, 21, 42, and 56 of the study. Pigs had ad libitum access to feed and water throughout the study. Diets were formulated to meet or exceed NRC (2012) recommendations. Fecal swabs from pigs were collected and confirmed the presence of hemolytic E. coli within the first two weeks of study. During the first 21 d, feeding AVI21 and AVI42 lowered (P < 0.05) diarrhea severity compared to controls, with CAR21 being intermediate. In the second 21 d, feeding AVI42 lowered (P < 0.05) diarrhea incidence and severity compared to the other treatments. In general, feeding medication resulted in lower maximum diarrhea scores compared to nonmedicated controls. For the overall study period (day 0 to 56), there were no (P > 0.05) stocking density × nursery medication program interactions for growth performance measures. A significant interaction (P < 0.05) was observed for day 0 to 42; feed conversion did not differ between double and single stocking density treatments for AVI42, whereas for CON, AVI21, and CAR21, feed conversion was lower in the single stocking density treatment. For the overall study period, there was no effect (P > 0.05) of nursery medication program on final BW, ADG, ADFI, or incidence of morbidity and mortality. Overall G:F was improved (P < 0.05) for pigs fed avilamycin compared to carbadox, with controls being intermediate. Double stocking resulted in lower overall ADFI (P < 0.05) and improved G:F (P < 0.05) compared to single stocking, but increased overall morbidity and mortality and diarrhea severity, incidence, and overall scores (P < 0.05). The results of this study demonstrate relatively similar performance with improved feed conversion and improvements in diarrhea incidence and severity for pigs fed avilamycin compared to carbadox.