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The study of factors influencing animal intake can provide a better understanding of the dynamics of the pasture ecosystem and serve as a basis for managing livestock in a more efficient way. We measured different sward surface heights of tall fescue in the process of short-term intake rate of sheep. There was a significant effect of sward surface height on herbage mass (P P P = 0.02), bite mass (P = 0.01) and short-term intake rate (P = 0.03) of sheep. There was a quadratic fit between time per bite and bite mass (P = 0.006). Multivariate analysis showed that the short-term intake rate and bite mass were positively correlated (r = 0.97), bite rate and total jaw movement rate were positively correlated but both were negatively correlated with time per bite. The sward surface height of tall fescue corresponding to the maximum short-term herbage intake rate was 22.3 cm. The underlying processes were driven by the bite mass, which was influenced by the leaf lamina bulk density and its consequences upon time per bite. This sward surface height can be adopted as a pre-grazing target for rotational stocking systems to optimize sheep nutrition on pastures.

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.

Avaliaram-se os efeitos da ureia protegida na produção e composição do leite, utilizando-se 34 vacas da raça Holandesa, com 128±60 dias em leite e produção de 41,6±6,7kg/dia no início do experimento, distribuídas em blocos por produção de leite, ordem de lactação e dias em lactação. As variáveis produção de leite, porcentagens e produções de gordura, proteína, lactose e sólidos totais do leite, contagem de células somáticas e nitrogênio ureico no leite foram mensuradas aos 30 e 60 dias do experimento. Os dados foram analisados por procedimento de modelos mistos com o modelo contendo como covariável as observações obtidas antes da adoção das dietas experimentais e os efeitos fixos de período, de tratamento e a interação de período versus tratamento. Os tratamentos (T) foram compostos por dietas isoenergéticas e isonitrogenadas com 1,66 EL L e 18,35% de PB, definidas como: T1= 11,4% farelo de soja e T2= 0,4% ureia encapsulada + 9,0% farelo de soja. Não foram observadas diferenças (P>0,05) nas produções diárias de leite e de sólidos, de nitrogênio ureico no leite e da contagem de células somáticas. A dieta com ureia protegida reduziu (P0.05) on the daily production of milk and solids, milk urea nitrogen, and somatic cell count. The slow release urea diet reduced (P