| Autor: |
Mercadante, V. R. G., Kozicki, L. E., Ciriaco, F. M., Henry, D. D., Dahlen, C. R., Crosswhite, M. R., Larson, J. E., Voelz, B. E., Patterson, D. J., Perry, G. A., Funston, R. N., Steckler, T. L., Hill, S. L., Stevenson, J. S., Lamb, G. C. |
| Zdroj: |
Journal of Animal Science; November 2015, Vol. 93 Issue: 11 p5204-5213, 10p |
| Abstrakt: |
Two experiments were conducted to determine the effect of administering PGF2αat the initiation of the 7-d CO-Synch+controlled internal drug release (CIDR) fixed-timed AI (TAI) protocol on pregnancy rates of suckled beef cows and replacement heifers. Within location, cows were stratified by days postpartum (DPP), BCS, and parity (Exp. 1; n= 1,551) and heifers were stratified by BCS (Exp. 2; n= 999) and randomly assigned to 1 of 2 treatments: 1) CO-Synch+CIDR (100-μg injection of GnRH at CIDR insertion [d –10] with a 25-mg injection of PGF2αat CIDR removal [d –3] followed by injection of GnRH and TAI on d 0) or 2) PG-CO-Synch+CIDR (a 25-mg injection of PGF2αon d –10 of the CO-Synch+CIDR protocol). Follicle diameter and corpus luteum (CL) development were assessed on d –10 and –3, and pregnancy status was determined on d 30 to 35. Blood was collected on d –20, –10, –3, and 0 relative to TAI to determine concentrations of progesterone (P4). In Exp. 1, TAI pregnancy rates did not differ (P= 0.667) between treatments and were affected by BCS (P= 0.003) and DPP (P= 0.006). Concentrations of P4 were greater (P< 0.0001) on d –3 for CO-Synch+CIDR than for PG-CO-Synch+CIDR (4.1 ± 0.2 and 3.4 ± 0.2 ng/mL, respectively). Follicle diameter on d –3 differed (P= 0.05) between PG-CO-Synch+CIDR (13.4 ± 0.3 mm) and CO-Synch+CIDR (12.5 ± 0.3 mm) treatments. Cows with P4 > 2.5 ng/mL on d –10 had greater (P= 0.024) pregnancy rate to TAI (56.5%) compared with cows with 2.5 ng/mL < P4 > 1 (43.0%), whereas cows with P4 < 1 ng/mL were intermediate (51.6%). Cows with a CL on d –10 had greater (P= 0.012) pregnancy rates to TAI than cows without a CL (66.3 vs. 39.4%, respectively). In Exp. 2, TAI pregnancy rates did not differ (P= 0.316) between treatments. Concentrations of P4 differed (P< 0.0001) on d –3 with greater concentrations of P4 for CO-Synch+CIDR than for PG-CO-Synch+CIDR (3.75 ± 0.20 ng/mL and 3.60 ± 0.21 ng/mL, respectively). Follicle diameter was similar (P= 0.749) between treatments on d –10 and –3. Regardless of treatment, cyclic status tended (P= 0.062) to improve pregnancy rates to TAI (55 vs. 45%, for cycling and noncycling heifers, respectively). We concluded that addition of PGF2αto the 7-d CO-Synch+CIDR protocol decreased concentrations of P4 in cows and heifers and increased follicle diameter at CIDR removal in cows but failed to increase TAI pregnancy rates. |
| Databáze: |
Supplemental Index |
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