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- Title
The effect of follicle age on pregnancy rate in beef cows.
- Authors
Abreu, F. M.; Geary, T. W.; Cruppe, L. H.; Madsen, C. A.; Jinks, E. M.; Pohler, K. G.; Vasconcelos, J. L. M.; Day, M. L.
- Abstract
The effect of the age of the ovulatory follicle on fertility in beef cows was investigated. Multiparous (n = 171) and primiparous (n = 129) postpartum beef cows in 2 groups (G1 and G2) received estradiol benzoate (EB; 1 mg/500 kg BW, intramuscular [i.m.]) 5.5 d (Gl; n = 162) and 6.5 d (G2; n = 138) after the final GnRH of a synchronization program (5d CO-Synch + CIDR) to induce emergence of a new follicular wave (NFW), followed by prostaglandin F2α (PGF2α; 25 mg, i.m.) administration either 5.5 d ("young" follicle, YF; n = 155) or 9.5 d ("mature" follicle, MF; n = 145) after EB. Estrous detection coupled with Al 12 h later (estrus-AI) was performed for 60 h (MF) and 84 h (YF) after PGF2α; cows not detected in estrus within this period received timed Al (TAI) coupled with GnRH at 72 and 96 h, respectively. Within the first 72 h after PGF2α, more (P <0.01) cows in the MF (76.3%) than YF treatment (47.7%) exhibited estrus, but through 96 h, the proportion detected in estrus (P < 0.05) and interval from PGF2α to estrus (P <0.01) were greater in the YF than MF treatment (88.6% vs. 76.3%, 78.9 ± 0.8 vs. 57.5 ± 1.6 h, respectively). Age of the ovulatory follicle at Al was greater (P <0.01) in the MF (9.32 ± 0.04 d) than YF (6.26 ± 0.02 d) treatment, but follicle diameter at Al and pregnancy rates did not differ between MF (13.1 ± 0.2 mm; 72.0%) and YF (12.9 ± 0.1 mm; 67.1%) treatments. Regardless of treatment, the diameter of the ovulatory follicle at Al and pregnancy rate were greater (P <0.01) with estrus-AI (13.1 ± 0.1 mm; 75.0%) than TAI (12.6 ± 0.2 mm; 55.4%). Cows in the MF treatment that initiated a second NFW after EB but before PGF2α (MF2; n = 47) were induced to ovulate with GnRH and TAI at 72h, when ovulatory follicles were 4 d old and 10.2 ± 0.2 mm in diameter. Pregnancy rate for TAI (51.1%) in MF2 did not differ from TAI pregnancy rate (55.4%) across the MF and YF treatments. In summary, the age of the ovulatory follicle affected interval to estrus and Al but did not influence pregnancy rate in suckled beef cows.
- Subjects
BEEF cattle breeding; FOLLICLE-stimulating hormone; CATTLE pregnancy; FERTILITY; PROSTAGLANDINS; ESTRUS
- Publication
Journal of Animal Science, 2014, Vol 92, Issue 3, p1015
- ISSN
0021-8812
- Publication type
Article
- DOI
10.2527/jas.2013-6760