Study on the Influence of Certain Factors on the Milk Urea Content in Sheep From the Bulgarian Synthetic Milk Population

A b s t r a c t: The concentration of milk urea (MU) can be used to evaluate crude protein in ration of sheep, which is particularly important for grazing animals whose assessment of intake is a major problem.Although the concentration of milk urea is mainly influenced by nutrients, its level could be influenced by some non-nutritional factors such as breed, season, pregnancy and stage of lactation, milkiness, milking time and somatic cell count.The aim of the study was to investigate the lactation stage and rainfall effects during the studied period on the average daily milk yield and milk urea level in sheep from the Bulgarian Synthetic Milk Population.The results from the current study show that the urea content of ewes' milk increases at the end of lactation (P < 0.001).During the active grass growth period there is an increase in milk urea level (P < 0.001 ).In early spring and autumn, as well as during periods with heavy rainfalls, sheep should be fed with high-quality cereal feed and simultaneously the level of nitrogen release to the environment should be monitored using milk urea level as indicator.It is highly imperative to develop appropriate nutrition strategies in order to provide the necessary nutrients for sustaining life and productivity, by using indicators of protein and energy levels, taking into consideration the impact of farming activities on the environment.