Relationships among dietary lipid intake, serum XXXX and ovarian function in Holstein heifers.

@entity251 @entity1420 @entity53 @entity134 @entity3774 @entity165
Experiments were performed to determine whether serum concentrations of total @entity165 (TC) undergo cyclic changes during the estrous cycle of dairy heifers and to assess the relationship between serum concentrations of TC and ovarian @entity134 hormones. The effects of a hypercholesterolemic diet upon luteal @entity1420 secretion also were determined. Experiment 1 involved five dairy heifers exhibiting normal estrous cycles. Serum concentrations of TC, @entity1420 , @entity251 and @entity53 -17 beta were determined in blood samples collected throughout a complete estrous cycle. A transient decline in TC was observed during the luteal phase of all heifers beginning on d 2 and reached a nadir 6 d after estrus. Highest mean concentrations of TC occurred between d -2 and +2 (96.3 +/- 8.2 mg/dl), which were markedly higher (P less than .05) than the lowest mean concentrations (76.3 +/- 10.3 mg/dl) observed on d 6. Concentrations of serum TC were negatively correlated (r = -.40; P less than .01) with @entity1420 between d 2 and 9. Serum TC was not correlated with @entity251 or @entity53 -17 beta. In Exp. 2, seven cycling Holstein heifers were fed a control diet for 70 d (Stage I), a diet containing 15% whole sunflower seed as a source of supplemental dietary lipid for 70 d (Stage II) and then the control diet for 70 d (Stage III). Diets were isocaloric and isonitrogenous. All heifers were synchronized with @entity3774 after wk 5 in each of the three feeding stages.(ABSTRACT TRUNCATED AT 250 WORDS)
