title: Comparison of 4- versus 5-day Co-Synch + controlled internal drug release (CIDR) + timed artificial insemination protocols in dairy heifers.
abstract: The objective of this study was to compare the pregnancy rate after timed artificial insemination (P/TAI) in dairy heifers treated with 4- versus 5-day Co-Synch + controlled internal drug release (CIDR) protocols. A total of 120 Holstein heifers were randomly assigned to one of two groups. The heifers received an intravaginal CIDR insert containing 1.38 g of progesterone for 4 days (Monday-Friday 4-day Co-Synch + CIDR; n = 60) or 5 days (5-day Co-Synch + CIDR; n = 60). At the time of CIDR removal, 25 mg of PGF2α was injected intramuscularly, and 72 hours after CIDR removal, the heifers received 100 μg of GnRH intramuscularly and were artificially inseminated. Artificial insemination was performed by an experienced technician, using commercial frozen-thawed semen from a single sire. Pregnancy diagnosis was performed by ultrasonography per rectum 32 days after TAI. Categorical data were analyzed using proc logistic and the chi-square test, whereas continuous variables were analyzed using the t-test of Statistical Analysis Systems. Heifers in the 4-day Co-Synch + CIDR group had an acceptable P/TAI32 (55.0%, 33 of 60), which was not different (P = 0.35) from that observed in the 5-day Co-Synch + CIDR group (63.3%, 38 of 60). Progesterone concentration at CIDR insertion or estradiol concentration at TAI did not influence the pregnancy outcomes. Interestingly, estradiol concentration at TAI was greater in the 4-day Co-Synch + CIDR group compared to the 5-day Co-Synch + CIDR group (P < 0.01). In conclusion, the Monday to Friday 4-day Co-Synch + CIDR protocol resulted in adequate P/TAI in dairy heifers, which was similar to that of the 5-day Co-Synch + CIDR protocol. This novel protocol might represent a promising hormonal treatment for TAI in dairy heifers, facilitating their reproductive management routine, while maintaining an adequate fertility.
authors.affiliation: Department of Population Health, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, USA. Electronic address: palomnr@uga.edu.
authors.forename: Roberto A
authors.initials: RA
authors.lastname: Palomares
authors.affiliation: Department of Large Animal Medicine, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, USA.
authors.forename: Heidi J
authors.initials: HJ
authors.lastname: Fishman
authors.affiliation: Department of Population Health, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, USA.
authors.forename: Arthur L
authors.initials: AL
authors.lastname: Jones
authors.affiliation: Department of Large Animal Medicine, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, USA.
authors.forename: Maria S
authors.initials: MS
authors.lastname: Ferrer
authors.affiliation: Department of Large Animal Medicine, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, USA.
authors.forename: Mathews
authors.initials: M
authors.lastname: Jenerette
authors.affiliation: Department of Large Animal Medicine, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, USA.
authors.forename: Aimee
authors.initials: A
authors.lastname: Vaughn
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003692:Delayed-Action Preparations; D005260:Female; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D016015:Logistic Models; D011247:Pregnancy; D018873:Pregnancy Rate; D011374:Progesterone / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology; D011372:Progestins / Q000008:administration & dosage* / Q000494:pharmacology; D013997:Time Factors
chemical_list: D003692:Delayed-Action Preparations; D011372:Progestins; D011374:Progesterone
keywords: Controlled internal drug release; Dairy heifer; Monday to Friday 4-day Co-Synch; Timed artificial insemination