title: The recruitment of ovarian follicles is enhanced by increased dietary intake in heifers.
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.
authors.affiliation: Roslin Institute (Edinburgh), Midlothian, UK.
authors.forename: C G
authors.initials: CG
authors.lastname: Gutiérrez
authors.forename: J
authors.initials: J
authors.lastname: Oldham
authors.forename: T A
authors.initials: TA
authors.lastname: Bramley
authors.forename: J G
authors.initials: JG
authors.lastname: Gong
authors.forename: B K
authors.initials: BK
authors.lastname: Campbell
authors.forename: R
authors.initials: R
authors.lastname: Webb
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000502:physiology; D002417:Cattle / Q000097:blood / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D004435:Eating / Q000502:physiology*; D004971:Estrus / Q000502:physiology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000502:physiology; D013006:Growth Hormone / Q000097:blood / Q000502:physiology; D006885:Hydroxybutyrates / Q000097:blood; D007328:Insulin / Q000097:blood / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000502:physiology; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000254:growth & development / Q000502:physiology*; D012044:Regression Analysis; D013997:Time Factors; D014463:Ultrasonography / Q000379:methods / Q000662:veterinary; D014508:Urea / Q000097:blood
chemical_list: D001786:Blood Glucose; D006885:Hydroxybutyrates; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D014508:Urea; D005640:Follicle Stimulating Hormone; D013006:Growth Hormone