Effect of virginiamycin and sodium bicarbonate on milk production, milk composition and metabolism of dairy cows fed high levels of concentrates

摘要: Milk production and composition were measured for 63 days in 153 Holstein–Friesian cows offered either 7, 10 or 13 kg/day (as fed) of a rolled, 74% barley/26% lupin grain mixture together with no feed additive, 300 mg/day virginiamycin (VM) plus 200 g/day sodium bicarbonate (VM + NaHCO3). All fed 1 pelleted mineral supplement containing the additives. The grazed as single herd on perennial ryegrass–subterranean clover pasture silage available during periods shortage. Rumen fluid was analysed pH volatile fatty acids, blood plasma glucose, beta-hydroxy-butyrate, urea D- L-lactic acid, faeces dry matter pH, both urine milk sodium. incidence bloat all treatments low. There main effect dietary additive treatment intake, but at highest level, VM NaHCO3 ate more than those additive. significant differences between production, composition, cell count, liveweight condition score. Mean daily covariance-corrected yields protein (kg), content (g/kg) respectively, significantly (P<0.01) greater 11 (28.0, 0.86, 30.6) 14 (28.7, 0.88, 31.0) concentrate compared 8 (26.4, 0.78, 29.7). fat lower from (32.0) (35.9) (34.7) kg/day. feeding levels yield somatic count. Covariance-corrected score higher levels. interactions level parameters. No recorded different concentration total rumen concentrations glucose L-lactate. molar proportions acetate butyrate lower, propionate valerate offered. ratio to It concluded that inclusion virginiamycin, bicarbonate, high rations cannot be recommended improving grazing dairy already adapted barley grain.