The effect of flavophospholipol (Flavomycin (R)) on milk production and milk urea nitrogen concentrations of grazing dairy cows

Mills production and milk composition responses to supplementation of Holst ein-Friesian cows grazing kikuyu pasture in summer and a combination of ann ual ryegrass and maize silage in winter with 64 mg/d flavophospholipol were determined. There was no difference in the average mills yield over the fi rst 100 days of lactation between the control group (19.8 kg/day) and the F lavomycin supplemented group (20.5 kg/day). Milk production over the full l actation of 300 days was also not influenced by Flavomycin addition (contro l: 5 525 kg; treatment: 5 627 kg). There was no difference between the cont rol and treatment group in average butterfat percentage (3.55% vs. 3.62%), butterfat yield over 300 days (195.3 kg vs. 201.2 kg), average protein perc entage (3.12% vs. 3.14%) or protein yield over 300 days (170.2 kg vs. 178.5 kg). Flavomycin addition only reduced the mills urea nitrogen (MUN) concen trations during the third week of April (treatment: 16.0 +/- 0.8 mg MUN/dl; control: 18.6 +/- 0.4 mg MUN/dl) and the second week of September (treatme nt: 16.0 +/- 1.2 mg MUN/dl; control: 19.6 +/- 0.9 mg MUN/dl). Cows grazing nitrogen-fertilized pastures displayed great variation in weekly and monthl y milk urea nitrogen concentrations which frequently exceed 18 mg MUN/dl.