Feeding supplemental fat to dairy cows no longer has energy density as a primary consideration in the ration. Essential fatty acids, notably linoleic (omega-6) and linolenic (omega-3) acids have direct effects on physiological processes such as cellular membrane integrity, hormonal pathways, and immune function. Clearly, they are important to uterine health, and that is accompanied by earlier ovulations PP and more cycles during the voluntary waiting period. decline in fertility and there is increasing evidence to assume that reduced oocyte and embryo quality are two major players in this “disappointing fertility syndrome” nutrition has the potency to alter the micro-environment of the oocyte and the embryo, making it more hostile to optimal fertilization and pre implantation embryonic growth .Data reviewed shows that supplementation with different sources of lipids and fatty acids improve reproductive performance of the female ruminant. However, it is important to consider that the optimum response will be achieved when under nutrition status of the female is not extremely severed. A nutrient balance (protein: energy) in the ration consumed by the animal is fundamental to obtain maximum benefit from supplementation with fat, The feeding of additional energy in the form of fat reduces the cow’s negative energy status so that she returns to oestrus earlier after calving and therefore conceives sooner. Cows fed fat produce or secrete more progesterone, a hormone necessary for the implantation and nutrition of the newly formed embryo. Specific individual long chain fatty acids found in some fats inhibit the production or release of prostaglandin by the uterus. This prevents the regression of the corpus luteum (CL) on the ovary so that the newly formed embryo survives. Based on the experiments done at this time, it appears that dietary fats may increase the size and the life span of the CL. The larger size of the dominant follicle in fat-supplemented cows may result in a larger CL. More CL cells produce more progesterone. Greater progesterone should improve implantation and nutrition of the embryo. In addition, certain fatty acids such as linoleic acid and those found in fish may partially suppress secretion of Prostaglandin by the uterus at the time of conception so that the CL is not regressed and embryo survival is potentially enhanced.

Keywords: Essential fatty acid; Fertility; Nutrient-balance; Embryonic growth; Oestrous; Microenvironment.