Nitrogênio Ureico no Leite (NUL) e no Plasma (NUP) de vacas leiteiras suplementadas com níveis crescentes de proteína bruta no concentrado

Abstract

The pasture production system is an alternative low cost alternative in the production of dairy cattle and it is possible to use concentrated supplementation to better meet the nutritional requirements of the animals. Thus, the objective of this study was to evaluate the protein efficiency use in different crude protein contents at concentrate 12; 14; 16 and 18% based on dry matter (DM) in the dairy cows diet. The experiment was conducted at the Regional Agribusiness Technological Development Hub Alta Mogiana, in Colina-SP. The experiment was carried out with 16 holstein-Zebu crossbred dairy cows, in the initial lactation third , maintained in a 4x4 latin square grass pasture cv. Tanzania (Panicum maximum), fertilized and irrigated, managed under intermittent stocking. There was no significant difference (P>0.05) In the levels of fat, protein, lactose, total solids and dry defatted milk extract with increasing levels of crude protein (12; 14, 16 and 18%) in the concentrate supplied to dairy cows under grazing. The values of milk urea nitrogen (NUL) and plasma urea nitrogen (NUP) obtained, had a linear increasing effect (P<0.05) in the diets according to the crude protein increase (CP) levels, where Level with 18% of CP obtained values higher than recommended by the literature, signaling excess CP in the diet. The level with 14% CP in the diet showed the best use of dietary nitrogen by the animals, reducing the cost of the diet and, consequently, optimizing the production of the animal.