GROWTH PROMOTER

PURPOSE:To provide a safe and effective growth promoter, containing a kind of acyl based antibiotics as an active ingredient and having improving actions on the feed utilization rate for animals. CONSTITUTION:This growth promoter contains a compound of plusbacins of the formula [X is L-HyPro or L-Pro; R is CH3 or CH(CH3)2; (n) is 9-12] or its salt as an active ingredient. The daily dosage of this growth promoter is 0.1-5mg/kg, especially preferably 0.5-2.5mg/kg. In the case of using the compound of the formula by mixing thereof with a feed, its concentration is within the range of 0.5-100ppm, especially preferably 5-20ppm. The compound of the formula has antibiotic activities against harmful intestinal bacteria in animals, reduces the consumption of glucose and proteins in the intestine, suppresses the production of lactic acid, increases the production of volatile lower fatty acids which are an effective energy source, especially the production ratio of propionic acid, and on the other hand hardly affects the intestinal bacterial flora. This compound is obtained by culturing the bacteria having the activity of producing plusbacin, e.g. Pseudomonas sp. PB-6250 (FERM BP-2938) in a medium.