Urea concentration in goat milk: importance of determination and factors of variability

Abstract

The optimal concentration of urea in cow's milk is known and is often used to assess the balance of energy and protein in diets. While in goat (and sheep) milk it is not controled nor defined. Main determinants of urea formation in milk are the amount of crude protein intake and the ratio betwwen protein and energy proportion in diet. Goat diet with excessive amount of crude protein and energy unbalanced diet cause the excess of nitrogenous substances in rumen along with release of ammonia and rise in concentration of urea in blood and milk, which adversely affects the production, milk coagulation propreties, environmental pollution and reproductive capabilities of goats. However, besides diet, there are other factors that influence milk urea concentration: breed, stage of lactation, parity, season, body mass, litter size, production and chemical composition of milk. Numerous studies conducted on cow milk included the influence of sources of variability listed above, while there are only few studies available for goat milk due to its less economic importance, seasonal polyesterity and different way of breeding and keeping goats. The aim of this paper is to comparatively and critically combine the previous research results on the importance of determining the milk urea concentration as well as on individual sources of variability of urea concentration in goat milk.

Keywords

• goat milk
• milk urea concentration
• feeding
• stage of lactation
• parity
• milk production