DRY MATTER INTAKE, MILK YIELD AND COMPOSITION OF HOLSTEIN COWS FED ORGANIC MINERALS
The aim of this study was to evaluate the effects of organic sources of minerals diet of dairy cows in mid-lactation on dry matter intake, milk yield and composition. Twenty Holstein cows with an average body weight of 625.30 ± 80.37 kg and DIM averaging 146.83 ± 67.34 were allocated to receive one of two diets: INO (inorganic): diet with addition of inorganic mineral sources; ORG (organic) diet with addition of organic mineral sources (zinc, cooper, selenium, chromium, manganese, cobalt, iron and sulfur; DSM Produtos Nutricionais, Brazil). The design was cross-over. Each experimental period had 14 d adaptation and 7 d for sampling. Samples of milk were collected on 16th, 17th and 18th days of each period to evaluate the composition. The cows were allocated in individualy barns type free-stall, fed ad libitum and intake were estimated by bromatological analyzes of feeds and orts. Increases in fat-corrected milk (P<0.05), fat yield (P<0.05) and protein (P<0.10) were observed in the animals receiving the diets containing organic mineral sources compared to those fed inorganic sources. This increasing in fat corrected milk shows an increased efficiency of energy use, most likely due to higher preparation of enzyme apparatus for metabolizing energy. Milk yield has not influenced by the treatments, showed a mean of 32.43 kg.d-1 and difference of 0.63 kg.d-1 of milk, which, together with the average increase of 1.4 g.kg-1 fat led to increase in fat yield (P<0.05). The protein content, although not statistically differ, was 0.8 g.kg-1 higher in diet with organic sources and result in increase 0.05 kg the protein yield (P<0.10). The dry matter intake average 21.27 kg.d-1 and no effect of experimental diets was observed. Organic minerals increases energy efficiency in dairy cows, increasing the secretion of milk solids without change the intake.
Keywords: Dairy cows, efficiency, milk fat