Reducing the Interval from Presynchronization to Initiation of Timed Artificial Insemination Improves Fertility in Dairy Cows

• Published in: Journal of dairy science Vol. 90; no. 9; pp. 4212 - 4218
• Main Authors: Galvão, K.N., Sá Filho, M.F., Santos, J.E.P.
• Format: Journal Article
• Language: English
• Published: Savoy, IL Elsevier Inc 01.09.2007; American Dairy Science Association; Am Dairy Sci Assoc
• Subjects: animal fertility; Animal productions; animal reproduction; Animals; artificial insemination; Biological and medical sciences; calving interval; Cattle - physiology; corpus luteum; dairy cow; dairy cows; Dinoprost - administration & dosage; Estradiol - administration & dosage; Estradiol - analogs & derivatives; estrus synchronization; Estrus Synchronization - methods; Female; Fertility; Food industries; Fundamental and applied biological sciences. Psychology; gonadotropin-releasing hormone; Gonadotropin-Releasing Hormone - administration & dosage; Insemination, Artificial - methods; Insemination, Artificial - veterinary; Lactation; Milk and cheese industries. Ice creams; Ovary - diagnostic imaging; Ovulation; Parity; Pregnancy; presynchronization; reproduction; Terrestrial animal productions; Time Factors; timed artificial insemination; Ultrasonography; Vertebrates; dairy cow; presynchronization; timed artificial insemination; reproduction; Farming animal; Dairy cattle; Vertebrata; Reproduction; Mammalia; Fertility; Dairy industry; Artificial insemination; Artiodactyla; Ungulata; Interval
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2007-0182

The objective was to determine if reducing the interval from presynchronization to the first GnRH injection (G1) of a timed artificial insemination (AI) protocol improves pregnancy per AI. One thousand two hundred fourteen Holstein cows, at 37±3 d in milk (DIM), were stratified by parity, DIM, and milk yield in the first month postpartum and randomly assigned to control (n=412), 2 injections of PGF2α at 37±3 and 51±3 DIM, then enrolled in a timed AI protocol 14 d later; PShort (n=410), 2 injections of PGF2α at 40±3 and 54±3 DIM, then enrolled in a timed AI protocol 11 d later; or PShortG (n=392), same as PShort, but with an injection of GnRH 7 d before G1. All cows received the same timed AI protocol (d 65, G1; d 72, PGF2α; d 73, 1mg of estradiol cypionate; d 75, AI). A subset of 1,000 cows had their ovaries examined by ultrasonography at G1 and 7 d later when PGF2α of the timed AI was given to determine presence of corpus luteum (CL) and ovulation to G1. Pregnancy was diagnosed on d 38 after timed AI, and pregnant cows were reevaluated for pregnancy 4 wk later. Altering the interval between presynchronization and G1 did not affect the proportion of cows with a CL at G1, but GnRH 7 d before G1 increased the proportion of cows with a CL. Ovulation to G1 was greater for 11 compared with the 14 d interval, but GnRH did not improve ovulation. The increased ovulation to G1 when the interval was reduced from 14 to 11 d was observed only in cows with a CL at G1, but treatment did not affect ovulation in cows without a CL at G1. Treatment affected the pregnancy per AI on d 38 and 66 after insemination, and they were greater for the 11 compared with 14-d interval, but addition of GnRH did not improve pregnancy per AI. Cows ovulating to G1 had greater pregnancy per AI regardless of whether or not they had a CL at G1. Reducing the interval from presynchronization to initiation of the timed AI protocol from 14 to 11 d increased ovulation to G1 and pregnancy per AI in lactating dairy cows.