Bos indicus x Bos taurus (n=251) and Angus (n=323) cows received a progesterone containing device called an Eazi-BreedTM CIDR® for 7 d with a prostaglandinF2a (PGF2a) injection at CIDR removal. At CIDR insertion half the cows received a GnRH injection and half did not. Upon CIDR removal, half the cows in both GnRH and No-GnRH groups were equally divided into two AI treatment groups: 1) injectio...

The objective of the experiment was to compare follicular dynamics, ovulatory response to GnRH, and synchrony of estrus and ovulation among estrous-cycling and prepubertal beef heifers synchronized with a controlled internal drug-release (CIDR)- based or GnRH-PGF(2alpha) (PG) protocol. Estrous-cycling beef heifers were randomly assigned to 1 of 4 treatments (C1, C2, C3, C4), and prepubertal bee...

The CIDR is an intravaginal progesterone insert, used in conjunction with other hormones to synchronize estrous in beef and dairy cows and heifers. The CIDR was developed in New Zealand and has been used for several years to advance the first pubertal estrus in heifers and the first postpartum estrus in cows. The CIDR is a “T” shaped device with flexible wings that collapse to form a rod that c...

This experiment was designed to test the hypothesis that delayed insemination of nonestrous cows would increase pregnancy rates when using sex-sorted semen in conjunction with fixed-time artificial insemination (FTAI). Estrus was synchronized for 656 suckled beef cows with the 7-d CO-Synch + controlled internal drug release (CIDR) protocol (100 μg GnRH + CIDR [1.38 g progesterone] on d 0, 25 mg...

The objective of the experiment was to examine the necessity of adding a GnRH injection to a 14-d controlled internal drug release (CIDR)-based protocol for synchronization of estrus in beef heifers that were prepubertal or estrous-cycling at the initiation of treatment. The hypothesis tested was that the addition of GnRH in a CIDR-based estrus synchronization protocol would increase the synchr...

The objective of this study was to evaluate the effect a low dose hCG or FSH on follicle growth and pregnancy per artificial insemination (AI) in crossbreed beef heifers subjected split-time AI program. All (n = 386) were 7-d Co-synch protocol an intravaginal controlled internal drug release (CIDR) device (GnRH CIDR insertion; 7 days later PGF2α, removal, application tail head estrus detection ...

The objective of this study was to determine the effect on pregnancy outcome of either inseminating heifers twice (at 48 and 72 hours after withdrawal of a controlled internal drug release insert (CIDR) containing progesterone) or once (56 hours after CIDR withdrawal) following a seven-day CIDR synchronisation protocol. Dairy heifers (n=267) from five farms, with an age range of 388-736 days, w...

AIMS This study aimed at elucidating the effects of recombinant human follicle stimulating hormone (r-hFSH) on the ovarian follicular dynamics, progesterone, estradiol-17β profiles, and pregnancy of dairy cows. MATERIALS AND METHODS Three groups (G, n=5 cows) of multiparous dairy cows were used. G1 (C) control cows were given controlled internal drug release (CIDR) and prostaglandin F2α; G2 (...

The objective of the experiment was to compare follicular dynamics, ovulatory response to GnRH, steroid hormone concentration patterns, and synchrony of estrus and ovulation among estrous-cycling and anestrous postpartum beef cows following treatment with long-term progestin-based protocols. Beef cows (n = 40) were assigned to treatments based on age, days postpartum, BCS and estrous cyclicity ...