Calf removal improves conception rates to the Ovsynch and CO-Synch protocols.

Beef cows (n = 473) from two locations were stratified by breed, postpartum interval, age, and AI sire and were randomly allotted to one of four treatments for synchronization of ovulation. Ovulation synchronization protocols included the Ovsynch protocol with (n = 114) or without (n = 123) 48-h calf removal from d 7 to 9 (d 0 = 1st GnRH injection) or the CO-Synch protocol with (n = 119) or without (n = 117) 48-h calf removal from d 7 to 9. The Ovsynch protocol included administration of GnRH (100 microg; i.m.) on d 0, PGF2alpha (25 mg; i.m.) on d 7, GnRH (100 microg; i.m.) on d 9, and timed insemination on d 10. The CO-Synch protocol included administration of GnRH (100 microg; i.m.) on d 0, PGF2alpha (25 mg; i.m.) on d 7, and GnRH (100 microg; i.m.) with timed insemination on d 9. Blood samples were collected from all cows on d -10 and d 0 for analysis of serum progesterone. Cows with at least one serum progesterone concentration greater than 1 ng/mL were considered to be cyclic at the time of treatment. Conception rates of cows that received the CO-Synch + calf removal, Ovsynch + calf removal, CO-Synch, or Ovsynch protocol (63, 61, 54, and 52%, respectively) were not different (P = 0.50). Conception rates were not different (P = 0.80) among CO-Synch- and Ovsynch-treated cows; however, both estrual status and 48-h calf removal affected conception rates. Conception rates of cyclic cows (66%) were greater (P = 0.01) than those of anestrous cows (53%), regardless of which synchronization protocol was used. When data were pooled across synchronization protocol, conception rates of cows with 48-h calf removal (62%) were greater (P = 0.09) than conception rates of cows without calf removal (53%). The CO-Synch + calf removal protocol induces a fertile ovulation in cyclic and anestrous cows, requires handling cattle just three times, results in high conception rates from timed insemination, and should be a useful program for synchronization of ovulation in beef cows.

[1]  S. Edwards.  The effects of short term calf removal on pulsatile LH secretion in the postpartum beef cow. , 1985, Theriogenology.

[2]  J. Yelich,et al.  Synchronization of estrus in suckled postpartum beef cows with melengestrol acetate, 48-hour calf removal and PGF2alpha. , 1995, Theriogenology.

[3]  J. C. Whittier,et al.  Effects of a Timed Insemination Following Synchronization of Ovulation Using the Ovsynch or CO-Synch Protocol in Beef Cows , 1998 .

[4]  J. Whittier,et al.  OVARIAN AND ESTROUS RESPONSE OF SUCKLED BEEF COWS TO SELECT SYNCH ESTROUS SYNCHRONIZATION PROTOCOL , 2000 .

[5]  M. Ellersieck,et al.  Pituitary and ovarian responses to gonadotropin releasing hormone, calf removal and progestogen in anestrous beef cows. , 1983, Journal of animal science.

[6]  G. L. Williams,et al.  Evidence for maternal behavior as a requisite link in suckling-mediated anovulation in cows. , 1993, Biology of reproduction.

[7]  J. Lynch,et al.  Twice daily suckling but not milking with calf presence prolongs postpartum anovulation. , 1999, Journal of animal science.

[8]  J. Stevenson,et al.  Restricting calf presence without suckling compared with weaning prolongs postpartum anovulation in beef cattle. , 1996, Journal of animal science.

[9]  T. Kiser,et al.  The effect of calf removal on estrous response and pregnancy rate of beef cows after SYNCRO-MATE-B treatment , 1980 .

[10]  G. L. Williams,et al.  Patterns of tonic luteinizing hormone release and ovulation frequency in suckled anestrous beef cows following varying intervals of temporary weaning. , 1989, Domestic animal endocrinology.

[11]  R. Schalles,et al.  Effect of forty-eight-hour calf removal, once- or twice-daily suckling and Norgestomet on beef cow and calf performance. , 1986, Theriogenology.

[12]  G D Niswender,et al.  Pregnancy rates of postpartum beef cows that were synchronized using Syncro-Mate-B or the Ovsynch protocol. , 1998, Journal of animal science.

[13]  M. F. Smith,et al.  Hormone treatments and use of calf removal in postpartum beef cows. , 1979, Journal of animal science.