Resumo

LOPEZ- SOLANO, E et al. Content of lactic urea in cow's milk in the humid tropics of Veracruz. Universidad y ciencia [online]. 2011, vol.27, n.2, pp.199-208. ISSN 0186-2979.

The production of lactic urea and the factors that affect it were evaluated. A weekly sample of milk was collected and the daily production of 20 fully lactating cows was recorded. A completely random design with a multiple factorial array was used. The response variable was the content of lactic urea, and the factors were the production levels and the milk protein. The mean amount of lactic urea in the milk was 12.46 mg dl^-1. There were no differences (p ≥ 0.05) among the production systems. The content of lactic urea related to a < 5kg (11.48 mg dl^-1)^b production level was significantly different (p ≤ 0.05) from the ≥ 5 production level, but the ≤ 10 kg (12.8 mg dl^-1)^a and > 10 kg (13.07 mg dl^-1)^a levels were statistically equal (p ≥ 0.05). The contents of lactic urea found in the < 3.0% (13.2 mg dl^-1)^a level of milk protein were different (p ≤ 0.05) from the concentration of urea found in the > 3.2% (11.97 mg dl^-1)^b level of milk protein. There were no significant differences (p ≥ 0.05) in the interactions between production and milk protein. The concentration of lactic urea in August (8.77 mg dl^-1)^d was statistically different (p ≤ 0.05) from that of february (12.48 mg dl^-1)^abc, june (13.57 mg dl^-1)^abc, July (14.05 mg dl^-1)^a, september (13.47 mg dl^-1)^abc, october (13.62 mg dl^-1)^ab, november (13.83 mg dl^-1)^a and december (14.29 mg dl^-1)^a. It is concluded that the levels of lactic urea found in the herd are adequate, and that these levels are affected by the production levels and the protein contained in the milk.

Palavras-chave : Proteins; lactic urea; milk; production systems.

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