Factors influencing the content of urea in the milk of ewes

In total records of 363 East Friesian breed of sheep and 15 Lacaunes from 15 flocks located in Lower Austria, Upper Austria and Styria were available to investigate the influences on milk urea content. In one flock different groups of ewes were fed with low, medium and high amounts of energy and protein, but constant protein and energy ratio. The milk urea levels exhibited to statistically significant differences but the tendency of the feeding effect could be confirmed. Additional parameters influencing the urea content of milk of ewes are: herd specific factors, stage of lactation, mastitis, preservation and different analytical methods. The content of urea in milk is not suitable for assessment of the energy/protein-ratio of ewes with mastitis problems. Due to the special composition of sheep milk it is important to take account of the analytical method for determination of urea. Thus milk urea of one flock should be evaluated but not of individual sheep. In spite of these influence factors the determination of milk urea is a valuable tool for assessment of the energy and protein intake.