CAUSES OF MILK FAT DEPRESSION IN DAIRY COWS

Fat is typically the most variable component in milk, and is affected by many physiological and environmental factors. In dairy cattle, both the concentration and composition of milk fat are influenced by the diet. Concentration is reduced by feeding diets that contain large proportions of readily-fermentable carbohydrates (starch) and unsaturated fat. Conversely, the percentage of fat in milk can be increased by feeding rumen-inert fats. Milk fat depression is due to changes in rumen biohydrogenation of unsaturated fatty acids and the passage of specific intermediates of biohydrogenation out of the rumen (e.g. trans-10, cis-12 conjugated linoleic acid) that subsequently reduce milk fat synthesis in the mammary gland. Low milk fat tests typically occur as a result of several concurrent diet or management factors rather than as a result of a single factor. Low rumen pH is a key change in the rumen environment that may lead to flux of fatty acids through alternate pathways of ruminalbiohydrogenation. In this situation, high concentrate/low forage diets or dietary supplements of plant oils or fish oils cause a dramatic decline in milk fat secretion, whereas yields of milk and other milk components remain unchanged. If the feeding of unsaturated fats reduces the numbers or activity of fiber-digesting bacteria in the rumen, then feed intake can decrease, milk production can decrease, and milk fat concentration can decrease. This review contains the information about the milk fat depression which is caused by improper feeding. And also its huge economic losses in farm animals.