The recruitment of ovarian follicles is enhanced by increased dietary intake in heifers

J Anim Sci. 1997 Jul;75(7):1876-84. doi: 10.2527/1997.7571876x.

Abstract

The objective of this study was to determine whether dietary-induced changes in growth hormone (GH), insulin, and IGF-I alter the pattern of ovarian follicular development in heifers. Twenty-eight 2- to 3-yr-old Hereford-Friesian heifers were equally allocated (n = 7) to one of four dietary treatments: 1) Control (C) fed a maintenance diet as two meals per day; 2) twice maintenance (2M2) given as two meals per day; 3) twice maintenance (2M6) given as six meals per day; 4) feed-deprived (F) fed maintenance requirements as for C, changed to straw ad libitum for 3 d from a synchronized estrus. On d 4 (estrus = d 0) heifers were transferred to grass silage (ad libitum access) until the end of the experiment. Blood samples were collected hourly for 10 h on d 1 and 3 and daily for an additional 14 d. Follicular development was monitored daily by ultrasonography until d 14. The number of small follicles (< 4 mm) was increased (P < .05) by 37% on d 1 and 2 in 2M2 and 2M6 heifers, with no carryover effect of nutrition to the second follicular wave. Number of medium-sized (4 to 8 mm) and large (> 8 mm) follicles did not vary (P > .05) among treatments. The FSH concentrations were not different (P > .05) among treatments. Insulin concentrations were higher (P < .05) in 2M2 and 2M6 heifers than in C or F heifers, with no carryover after the diet was changed. Increase in number of small follicles was independent of changes in FSH and IGF-I, negatively associated with GH, but positively associated with circulating insulin. These results indicate that a short-term increase in nutritional plane can affect follicular recruitment in cycling heifers.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animal Nutritional Physiological Phenomena*
  • Animals
  • Blood Glucose / metabolism
  • Body Weight / physiology
  • Cattle / blood
  • Cattle / physiology*
  • Diet / veterinary
  • Eating / physiology*
  • Estrus / physiology
  • Female
  • Follicle Stimulating Hormone / blood
  • Follicle Stimulating Hormone / physiology
  • Growth Hormone / blood
  • Growth Hormone / physiology
  • Hydroxybutyrates / blood
  • Insulin / blood
  • Insulin / physiology
  • Insulin-Like Growth Factor I / analysis
  • Insulin-Like Growth Factor I / physiology
  • Ovarian Follicle / diagnostic imaging
  • Ovarian Follicle / growth & development
  • Ovarian Follicle / physiology*
  • Regression Analysis
  • Time Factors
  • Ultrasonography / methods
  • Ultrasonography / veterinary
  • Urea / blood

Substances

  • Blood Glucose
  • Hydroxybutyrates
  • Insulin
  • Insulin-Like Growth Factor I
  • Urea
  • Follicle Stimulating Hormone
  • Growth Hormone