The influence of protein quality on the effect of flavomycin on wool growth, liveweight change and rumen fermentation in sheep

Abstract

The feed additive flavomycin, a glycolipid antibiotic, was evaluated for its potential to improve wool growth in sheep fed two pelleted diets: one based on lucerne chaff and lupin grain and the other on wheat chaff and fishmeal. Seventy-eight weaner ewes, approximately 20 months of age and mean weight of 32 kg (s.e. � 0.3), were placed in individual pens and fed the pelleted diets at a level equivalent to 3.5% of the mean liveweight of the group. The experiment consisted of an initial period (8 weeks) during which all animals received their respective diets with no flavomycin, followed by an experimental period (9 weeks) during which the animals received their diets with flavomycin. Flavomycin was included at three different rates (l0, 20 and 40 ppm) in both diets (nine sheep/level) during the experimental period and twelve sheep were fed each of the unmedicated diets (no flavomycin). Feed intakes were measured daily and animals weighed weekly. Wool growth was measured for the initial and experimental periods by clipping a mid-side patch of about 100 cm2. In sheep fed the lucernellupin based diet, flavomycin increased liveweight gain ( P < 0.05) at 20 ppm but had no effect on wool production, whereas in those fed the hay/fishmeal diet, there was a linear decrease in liveweight gain (P < 0.001) (161, 151, 142, 130 g day-1) and a dose related increase in clean wool production (P<0.01) (12.9, 14.5, 15.2, 15.3 g m-2 day-1) with increasing rates of flavomycin (0, 10, 20, 40 ppm respectively). There was no significant effect of flavomycin on fibre diameter in the sheep fed either diet. The inclusion of flavomycin in both diets significantly increased the molar proportions of propionate in the rumen fluid and in sheep on the hay/fishmeal pellet it reduced the concentration of rumen ammonia. The time animals took to eat their ration was increased with the inclusion of flavomycin in the hay/fishmeal diet.