title: Long-term follicular dynamics and biochemical characteristics of dominant follicles in dairy cows subjected to acute heat stress.
abstract: The objective of this study was to examine the quality of successive dominant follicles (DFs) after induced heat stress. Non-lactating dairy cows expressing estrus at normal intervals were allocated randomly to heat stress (HS; n=8) and control (C; n=8) groups. Cows received GnRH (100 microg, i.m.) on Day 0, a progesterone CIDR-B device on Day 4 and prostaglandin (PGF(2alpha); 25mg, i.m.) on Day 7 upon removal of the CIDR device. The DF and follicles >5mm were aspirated on Day 8, and GnRH (100 microg) injected following aspiration, to initiate a new follicular wave. In this manner, a DF was aspirated every 8 days (one "follicular cycle") for 10 cycles. After the first follicular cycle, HS cows were placed in environmental chambers for 7 days during the second follicular cycle (8h per day at 43.3 degrees C set point and 16h per day at 24 degrees C for 4 days, and 8h per day at 43.3 degrees C set point and 16h per day at 32.2 degrees C set point for 3 days; relative humidity, 40%) and thereafter maintained outdoors with control cows at a mean ambient temperature (18.5 degrees C; range 12.7-26 degrees C). Rectal temperature increased (P<0.001) in HS as compared with C cows (39.28+/-0.01 degrees C versus 38.78+/-0.01 degrees C). Concentrations of estradiol (E(2); 1662+/-189 versus 1493+/-188ng/ml) and progesterone (P(4); 44.7+/-5 versus 54.1+/-5.1ng/ml) in follicular fluid (FF) of DF did not differ between C and HS treatments, respectively. Total FF protein concentration was greater (P<0.05) in HS (99.7+/-2.3mg/ml) than in C (92.7+/-2.3mg/ml). Heat shock protein 90 (Hsp 90) in FF was not altered by heat stress. IGF-II ligand blots were conducted with FF samples (n=79) from four HS and four C cows. There was a predominance of IGFBP-3 in 76 of 79 FF samples, indicating healthy follicular status, and only three FF samples had the lower molecular weight IGFBP-2 indicative of a poor quality follicle. Plasma P(4) and E(2) concentrations did not differ between C and HS groups. The number of class 1 and 3 follicles increased during and just after heat stress, but the number of class 2 follicles did not differ between C and HS cows. Heat stress appeared to induce a decrease in follicular dominance, but GnRH-induced follicular cycles resulted in development of healthy preovulatory follicles in both groups.
authors.affiliation: Department of Animal Sciences, University of Florida, Gainesville 32611-0920, USA.
authors.forename: A
authors.initials: A
authors.lastname: Guzeloglu
authors.forename: J D
authors.initials: JD
authors.lastname: Ambrose
authors.forename: T
authors.initials: T
authors.lastname: Kassa
authors.forename: T
authors.initials: T
authors.lastname: Diaz
authors.forename: M J
authors.initials: MJ
authors.lastname: Thatcher
authors.forename: W W
authors.initials: WW
authors.lastname: Thatcher
mesh_terms: D000818:Animals; D001831:Body Temperature; D002417:Cattle; D002418:Cattle Diseases / Q000503:physiopathology*; D015237:Dinoprost / Q000008:administration & dosage; D004958:Estradiol / Q000032:analysis / Q000097:blood; D005260:Female; D015571:Follicular Fluid / Q000737:chemistry; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D018841:HSP90 Heat-Shock Proteins / Q000032:analysis; D018882:Heat Stress Disorders / Q000503:physiopathology / Q000662:veterinary*; D006813:Humidity; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000032:analysis; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000032:analysis; D006080:Ovarian Follicle / Q000473:pathology / Q000503:physiopathology*; D011374:Progesterone / Q000008:administration & dosage / Q000032:analysis / Q000097:blood; D011506:Proteins / Q000032:analysis; D013696:Temperature
chemical_list: D018841:HSP90 Heat-Shock Proteins; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D011506:Proteins; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol; D015237:Dinoprost