Journal
BIOLOGY OF REPRODUCTION
Volume 64, Issue 6, Pages 1624-1632Publisher
OXFORD UNIV PRESS INC
DOI: 10.1095/biolreprod64.6.1624
Keywords
fertilization; follicle; follicular development; gene regulation; granulosa cells; growth factors; IGF receptor; insulin; IVF/ART; oocyte development; ovary; ovum; theca cells
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Heifers were assigned either low or high (HE) levels of energy intake and low or high concentrations of dietary crude protein. The effect of these diets on the plasma concentrations of insulin, insulin-like growth factor (ICF)-I, and urea on follicular growth and early embryo development is described. We propose that the observed dietary-induced changes in the ovarian IGF system increase bioavailability of intrafollicular IGF, thus increasing the sensitivity of follicles to FSH. These changes, in combination with increased peripheral concentrations of insulin and IGF-I in heifers,offered the HE diet, contribute to the observed increase in growth: rate of the dominant follicle. In contrast to follicular growth, increased nutrient supply decreased oocyte quality, due in part to increased plasma urea concentrations. Clearly a number of mechanisms are involved in mediating the effects of dietary energy and protein on ovarian function, and the formulation of diets designed to optimize cattle fertility must consider the divergent effects of nutrient supply on follicular growth and oocyte quality.
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