Sources of variation in milk urea nitrogen in Paraná dairy cows

Revista Brasileira de Zootecnia

Doska, Maria Cecília²  Valloto, Altair Antônio¹  Horst, José Augusto¹  Silva, Delma Fabíola Ferreira da²  Rossi Junior, Paulo²  Almeida, Rodrigo de² 

[1] UFPR, Curitiba

关键词: dairy cattle;    nutrition;    protein     Introduction As a result of environmental and genetic improvements and the development and implementation of new technologies in the dairy industry;    currently dairy cows produce larger amounts of milk and its components;   

DOI  :  10.1590/S1516-35982012000300032

学科分类：兽医学

来源: Universidade Federal de Vicosa

【 摘 要 】

The present study was conducted to determine the relationship between milk urea nitrogen (MUN) and milk yield, fat and protein contents, breed and season effects, parity and days in milk in dairy cows from Paraná State, Brazil. A total of 127,428 test-days from 16,013 dairy cows belonging to 96 herds enrolled in an official milk recording program were analyzed. Multivariate mixed model methodology was used to determine the relationship between MUN and the fixed effects and the covariable milk production. Milk urea nitrogen averaged 14.45±4.60 mg/dL. Positive and intermediate association between MUN and milk yield (r = 0.34) were found. Holstein cows showed lower MUN adjusted means than crossbred, Jersey, and Brown Swiss cows: 14.18 vs. 15.49, 16.12, and 17.62 mg/dL, respectively. First-lactation cows showed higher MUN values than second-lactation and older cows: 16.16 vs. 15.95, and 15.45 mg/dL, respectively. MUN test-days collected during the winter were higher than those collected in the other seasons. The effects of the lactation stage on MUN were significant, with the highest MUN values observed in the sixth month of lactation. High-producing dairy cows showed higher milk urea concentrations but several environmental factors may contribute to reduce this important parameter of diet utilization efficiency.

【 授权许可】

CC BY-NC