Superovulation of Holstein heifers under heat stress with FSH-P or Folltropin

THERIOGENOLOGY SUPEROVULATION OF HOLSTEIN HEIFERS UNDER HEAT STRESS WITH FSH-P OR FOLLTROPIN R. D. Page, J. E. Jordan and S. K. Johnson Department of Animai and Dairy Science University of Georgia Athens, Georgia 30602 USA The objective of this study was to compare the superovulatory response of Holstein heifers to FSH-P (Schering Corp, Kenilworth, NJ) and Folltropin (Vetrepharm, London, Ontario, Canada) under relatively cool, spring temperatures during April and May (Phase and I), and under heat stress, summer temperatures during July August (Phase II). Heifers were treated with a 4-day declining dose scheme of each hormonal preparation beginning on day 9-12 of their estrous cycles. A total of 32 mg FSH-P and 35 mg equivalent of Folltropin were administered. Cloprostenol (Haver, Shawnee, KS) was administered in 3 doses of .25 mg each beginning 48 h after the initial hormone injection. All heifers were bred artificially 12 and 24 h after the first observation of standing heat. Mean environmental temperatures recorded for the period starting with the initiation of the injection scheme until the day the animal was flushed were as follows: Phase I, spring, mean temperature 67.7"F with mean low daily temperature of 55.D"F; Phase II, Sumner, mean temperature 80.3"F with mean low daily temperature of 69.1"F. The high relative humidity (x=62%) raised the mean apparent temperature (Heat Index) during Phase II to 83°F. Corpora Lutea and unovulated follicles were estimated by rectal palpation. Cool temp (X=67.70~) N CL Follicles Embryos Ova % Fertile Transferable

FSH-P 20 lD.7ab 1.2a 4.8ab 0.8ab 88% ab 3.lb

Folltropin 20 lo-lab 1.6a 4.7ab 1.8b 73% b 3.3b

Heat stress (x=80.3'F)* SE FSH-P Folltropin LSM 20 20 9.8b 13.la k1.15 1.6a 1.4a t .39 3.5b 7.la f .D99 0.5a 0.6a f .D42 95% a 89% ab f. 6% 2.9b 6.3a 2 -85

a,b numbers in a row with different letters are significantly different (PO.O5). However, under heat stress conditions, the superovulatory response of Holstein heifers to Folltropin yielded more CL and more fertilized embryos (P
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JANUARY1989VOL.31NO.l