Diet-Induced Hyperlipidemia in Cattle Modifies the Intrafollicular Cholesterol Environment, Modulates Ovarian Follicular Dynamics, and Hastens the Onset of Postpartum Luteal Activity1

Abstract

Three experiments were conducted with female cattle during the postpartum period and during the estrous cycle to examine the effects of diet-induced hyperlipidemia on lipoprotein-cholesterol and triglyceride (TG) metabolism, ovarian follicular dynamics, and incidence of postpartum luteal activity. Dietary-lipid effects were examined independently of metabolizable energy intake. Feeding a high-lipid (HL) diet (8% total lipid) for the first 3 wk of the puerperium (Experiment 1) increased (p less than 0.0001) the concentration of total cholesterol and high-density lipoprotein-cholesterol (HDL-CH), but not TG, within follicular fluid (FF) of estrogen-active (E-A) and inactive (E-I) follicles. Increases (1.4- to 1.7-fold) were similar in proportion to those observed in peripheral blood serum, but absolute concentrations were about 45% of that in serum. Greater than 95% of the cholesterol in FF was HDL-CH, with a greater (p less than 0.06) proportion of HDL-CH sequestered by E-A compared to E-I follicles. The HL diet increased (p less than 0.06) the number of medium-sized (3.1-9.9 mm) follicles present at ovariectomy 19-21 days postcalving and increased (p less than 0.03) concentrations of FF androstenedione in E-I follicles 5-fold. Granulosa cells from preovulatory follicles (Experiment 2) of heifers fed HL diets secreted 2.1- to 3.5-fold greater (p less than 0.03) quantities of pregnenolone and progesterone in vitro. Finally, feeding HL supplements to postpartum range cattle for 30 days increased (p less than 0.05) the incidence of ovarian luteal activity by 18% (Experiment 3). Shifts in lipid metabolic status modify reproductive potential in cattle, independently of dietary energy intake.

The consequences of metabolic changes in high-yielding dairy cows on oocyte and embryo quality

“…The saturated fatty acids in particular are bound on LDL, while the unsaturated ones are preferentially bound on albumin (Chung et al, 1995). Because LDL are absent in FF, these findings could account for the differences in concentration and composition of NEFA in FF compared to serum early post partum (Wehrman et al, 1991).…”

Effect of a supplement rich in linolenic acid added to the diet of post partum dairy cows on ovarian follicle growth, and milk and plasma fatty acid compositions

“…Improvements in pregnancy rate at 45 d post insemination [5], ovarian follicle growth [6] and steroidogenesis [7] have all been reported. It has been suggested that the mechanism involves enhanced ovarian activity through the following: improved energy status [8], increased availability of cholesterol for steroid synthesis [9] and increased circulating insulin concentrations [10].…”

Supplementation of dairy cows with docosahexaenoic acid did not affect ovarian activity

“…Older studies often reported the positive influence of additional fat on ovarian activity, increased size of preovulatory follicles, and reduced pregnancy losses (Lucy et al 1991(Lucy et al , 1993Beam and Butler 1997;Ambrose et al 2006). Fat supplementation increased the concentration of total cholesterol in follicular fluid; this was associated with the fact that granulosa cells collected from follicles of supplemented cows showed increased progesterone secretion in vitro (Wehrman et al 1991). Ruminants treated with supplemental fat often had small increases in plasma concentrations of progesterone ).…”