Concentrados comerciais com diferentes teores de proteína bruta para vacas em lactação submetidas a dietas com palma forrageira (Opuntia fícus-indica. Mill)

Abstract

The objective of this study was to evaluate the effect of usage of commercial concentrates with different levels of protein in the diet of lactating Girolando cows on the nutrient intakes, performance and milk composition. Eight Girolando cows were used in the experiment. They averaged 545 ± 50 kg of living weight and 110 ± 14 days of lactation at the beginning of the experiment, with average production of 20 ± 3.2 kg / day, divided in two 4x4 latin squares. Diets were composed of giant cactus, native grass silage and concentrates trading with different protein levels 32, 39, 45 and 49% CP. Intake of dry matter (in kg/day, %BW, g/kgPV0,75), organic matter (OM), neutral detergent fiber (NDF kg/day and %PV), intake of total carbohydrates (TCH), ether extract (EE), non-fibrous carbohydrates (NFC) and total digestible nutrients (TDNI) were higher for animals with the 32% CP diet over the 39% CP diet. EE intake was lower for 49% concentrated diet. CP intake was not changed by the use of more concentrated protein. Apparent digestibility of DM, OM, CP, NDF and TC was higher in treatment with 49% concentrated in comparison to 39%. Milk production, total (kg/day) and corrected to 4% fat (kg/day) was lower for animals receiving 39% concentrated diet. Fat production was lower for treatments 39 and 49%. The 32% diet provided higher lactose and solids (kg/day) than the other treatments. Fat content was lower in the 49% diet, while the content of protein and lactose did not differ between treatments. Feed efficiency did not differ between treatments. Usage of concentrates with higher protein content promoted changes in consumption and digestibility of nutrients, as well as production and milk composition.