Flavomycin's (RTM) influence on lactational responses and nutrient utilization in dairy cows.

Abstract

A lactation trial (N = 34, multiparous; 29, primiparous) and a metabolic trial (N = 3), using lactating Holstein cows, were conducted to determine the effects of feeding varying amounts (0, 30, 60, 90 and 0, 75, 150 mg/d, respectively) of bambermycins (Flavomycin®) on production responses, reproduction and health, rumen fermentation patterns, and ruminal protein and fiber digestion in lactating cows. Flavomycin increased milk yields and milk fat and protein yields in multiparous cows (P < .05). Although dry matter intake (DMI) was increased in cows receiving Flavomycin, efficiency of milk production was also increased. Primiparous cows receiving 60 or 90 mg/d Flavomycin had fewer days open and a shorter calving interval than cows not fed Flavomycin (controls). Body condition score (BCS) and body weight (BW) of all cows were not affected significantly by feeding Flavomycin. Acetate:propionate ratios were significantly lower for cows fed Flavomycin compared to controls. Digestibilities of dry matter, crude protein, and acid detergent fiber were not affected significantly by Flavomycin. Total tract digestibility of neutral detergent fiber was significantly lower for cows fed 75 mg/d Flavomycin compared to controls. Cows receiving 75 mg/d Flavomycin had a higher (P < .05) proportion of bacterial crude protein in duodenal digesta than control cows. Flavomycin appears to be beneficial for increasing milk production efficiencies in multiparous lactating cows, but the mechanism of action remains to be clarified.