Efeito de níveis crescentes de uréia na dieta de vacas em lactação sobre produção, composição e qualidade do leite / Effects of dietary urea levels for dairy cows on milk yield, composition and quality

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The aim of this study was to evaluate the effects of three different dietary levels of urea on milk yield and composition, and milk protein composition. Nine lactating Holstein cows were used in a 3X3 latin square arrangement, with 3 treatments, 3 periods of 21 days each and 3 squares. The treatments were: A) NRC-based (NRC, 2001) diet to provide 100% of crude protein (CP), as well as, rumen undegradable protein (RUP) and rumen degradable protein (RDP) requirements, by using soybean meal and sugar cane; B) 0,75% urea inclusion; partially substituting soya meal from diet C) 1,5% urea inclusion, partially substituting soya meal from diet. Energy and protein levels of treatment diets comply with NRC (2001), and were isoenergetic and isoproteic. No statistical differences were observed among treatments, when results were analyzed by simple polynomial regression in relation to dry-matter intake, milk yield, 3,5% FCM, protein and fat yield, and somatic cell count (Log SCC). Cryoscopy, pH, milk density and alcohol stability, fat, lactose, urea, total solids and solids with no fat were not influenced by treatments. The protein composition, crude protein, true protein, casein, whey protein, non-casein nitrogen, milk urea nitrogen, as well as, true protein:crude protein and casein:true protein ratios were not influenced by the substitution of soybean meal by urea in ration. Results indicate that the use of urea up to 1,5% in DM does not alter milk yield and its composition.

ASSUNTO(S)

casein milk yield milk urea nitrogen nitrogênio uréico do leite urea caseína uréia milk composition produção de leite composição do leite

ACESSO AO ARTIGO

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