Author
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Perry Jr, George |
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SMITH, M - UNIVERSITY OF MISSOURI |
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LUCY, M - UNIVERSITY OF MISSOURI |
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Roberts, Andrew |
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Macneil, Michael |
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Geary, Thomas |
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Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only Publication Acceptance Date: 4/1/2003 Publication Date: 6/1/2003 Citation: PERRY JR, G.A., SMITH, M.F., LUCY, M.C., ROBERTS, A.J., MACNEIL, M.D., GEARY, T.W. EFFECT OF OVULATORY FOLLICLE SIZE AT TIME OF GNRH INJECTION OR STANDING ESTRUS ON PREGNANCY RATES AND EMBRYONIC/FETAL MORTALITY IN BEEF CATTLE. JOURNAL OF ANIMAL SCIENCE SUPPLEMENT ABSTRACT #211. 2003. v. 81(SUPPL. 1). p. 52. Interpretive Summary: Technical Abstract: Use of GnRH in AI protocols results in ovulation of a wide range of follicle sizes. Our objective was to determine the effect of ovulatory follicle size at GnRH-induced ovulation or standing estrus on pregnancy rates and embryonic/fetal mortality. Lactating beef cows (n = 273) received the CO-Synch protocol (100 ug GnRH, i.m. on d -9; 25 mg PG, i.m. on d -2; and 100 ug GnRH, i.m. on d 0 with timed AI) or were inseminated following detection of estrus using Heatwatch (electronic mount detectors). Ovulatory follicle size was determined by transrectal ultrasonography on d 0 (timed AI) or 12 h after detection in estrus. Pregnancy rates and fetal viability were determined by transrectal ultrasonography on d 27, 41, 55, and 68 after timed-insemination. On d 27 following GnRH-induced ovulation, there was a tendency (P = 0.07) for follicle size to effect pregnancy rates [13/45 (29%), 13/22 (59%), 18/39 (46%), 11/28 (39%), 13/20 (65%), and 7/19 (37%) for /= 15.5 mm follicles; respectively]; however, by d 68 embryonic loss in cows that were induced to ovulate /= 15.5 mm; respectively], nor were embryonic/fetal mortalities affected by ovulatory follicle diameter (P = 0.66). In summary, embryonic/fetal survival was decreased following GnRH-induced but not spontaneous ovulation of small ( |
