Glycerol supplementation seems to h

Glycerol supplementation seems to have moderate metabolic effects: it did not modify plasma glucose, insulin, NEFA and BHB levels [29]. However, in another trial [30] 1 kg glycerol applied as a drench increased plasma glucose and insulin and decreased plasma NEFA concentration.
The sometimes contradictory results can be attributed to the different experimental conditions (e.g. dosage, duration and method of, application, lactation period, level of NEBAL, and certainly the body condition of cows).
The feed intake of cows is lower in early lactation, and therefore dietary fat supplementation in the early postpartum period alters energy status even though a more energy dense ration is fed. Increasing the caloric density of the ration by fat feeding might improve the reproductive parameters of cows. Improvement of the energy status of dairy cows has been found to influence reproduction by increasing the frequency of LH pulses, modulating the number of larger follicles, altering the size of the dominant follicle, and increasing progesterone concentrations during the luteal phase of the estrous cycle. Supplemental fat improves ovarian follicular dynamics, which is in a positive correlation with pregnancy rate. The use of fat in dairy cow diets usually increases the energy density of the ration and improves reproduction; however, these effects might be mediated by the fatty acid (FA) composition of the fat source. Polyunsaturated fatty acids (PUFA) can influence different levels of the hypothalamo-pituitary-ovarian axis, and they can locally stimulate follicular growth by altering hormone and metabolite levels. Fatty acids are precursors for ovarian steroidogenesis and for the synthesis of endometrial eicosanoids (PGF2α, PGE2). Different PUFAs are important mediators of uterine involution and the ovulatory processes. Feeding sunflower oil rich in linoleic acid (C18:2, n-6) promotes uterine involution.
Supplementation of linseed (α-linolenic acid, C18:3, n-3) or the feeding of fish oil containing a high amount of eicosapentaenoic acid (C20:5, n-3) and docosahexaenoic acid (C22:6, n-3) may inhibit endometrial PGF2α synthesis through mechanisms such as the decreased availability of its precursor, arachidonic acid. PUFAs of the n-3 family suppress luteolytic signals around the maternal recognition of pregnancy. This might improve the mechanism of embryo preservation and support embryonic survival in cattle.