Whole-body protein turnover and nitrogen balance in growing pigs supplied with an antibiotic feed additive (Avilamycin)

Introduction   Antibiotic feed additives like Avilamycin (Maxus^®) exert a well-documented stimulatory effect on growth rate and feed efficiency in pig production (reviewed by, e.g., R oth and K irchgessner 1990; K amphues and M eyer 1992). The benefits to production performance seem to originate mainly from an enhanced gain of body protein as has been demonstrated in nitrogen balance trials with piglets and fattening pigs (R oth and K irchgessner 1993a,b; W indisch et al. 1998). However, the primary mode of action of antibiotic feed additives is not clarified completely. The growth-stimulating effect is assumed to originate from an enhanced absorptive capacity of the digestive tract for essential nutrients due to an improved microbial ecosystem in the gut (reviewed by, e.g., G reife and B erschauer 1988). However, metabolic effects may contribute to the higher protein accretion capacity also, as for example a reduced immune defense stress at the small intestine for example (discussed by, e.g., S chole et al. 1985). In order to elucidate possible metabolic effects of antibiotic feed additives it was the aim of the present study to combine a nitrogen balance experiment on Avilamycin-treated growing pigs with measurements on whole-body protein turnover.