Comparison of the 7 & 7 Synch protocol and the 7-day CO-Synch + CIDR protocol among recipient beef cows in an embryo transfer program

Correlation between Pre-Ovulatory Follicle Diameter and Follicular Fluid Metabolome Profiles in Lactating Beef Cows

“…Average cow age (5.75 ± 0.34 years) was consistent with previous reports of mean beef cow longevity of approximately four to eight years, depending on production and geographical location [32,33]. Average body condition score (6.023 ± 0.26) and weight (623.3 ± 17.1 kg) of animals included in this study were as expected in beef cattle operations; however, the upper BCS range in our cohort extended to beyond the BCS range commonly observed in beef production scenarios [34]. Cows were 58.7 ± 0.56 days postpartum at the time of follicle aspiration.…”

Evaluation of the 7 and 7 synch protocol for control of the estrous cycle among beef cows prior to fixed-time artificial insemination with sex-sorted or conventional semen

“…In comparison with cows receiving the 7-day CO-Synch + CIDR protocol, cows receiving 7 & 7 Synch presented with significantly greater largest follicle diameter at the time of GnRH administration, with subsequent CL status and estrus expression suggesting a high ovulatory response to GnRH (Bonacker et al, 2020b). In addition, a subsequent embryo transfer trial observed a greater proportion of recipient cows expressed estrus and became pregnant to embryo transfer when treated with 7 & 7 Synch (Bonacker et al, 2020a). Based on these observations, the following experiment was designed to evaluate expression of estrus and pregnancy outcomes among multiple herds when using the 7 & 7 Synch protocol prior to FTAI.…”

“…Another approach to potentially address the challenge of variable ovulatory response to GnRH among beef cows may be to induce formation of a persistent follicle prior to GnRH administration. By administering PG and placing a CIDR in advance of GnRH administration, an increased proportion of cows present with a physiologically mature, LH-responsive follicle at the time of GnRH administration (Bonacker et al, 2020a;French et al, 2013;Small et al, 2009). This approach is of practical significance as a simple, one-step method for presynchronization, and early results with the 7 & 7 Synch protocol that incorporates this presynchronization approach have suggested improved control of the estrous cycle (Bonacker et al, 2020a(Bonacker et al, , 2020b.…”

“…The experiment was designed to evaluate the physiology behind inducing a persistent follicle as a presynchronization strategy. In this approach, later termed 7 & 7 Synch (Bonacker et al, 2020a), PG is administered on Day 0 concurrent with CIDR insertion, GnRH is administered on Day 7 and PG is administered on Day 14 concurrent with CIDR removal. Administrating PG concurrent with CIDR insertion induces luteolysis among cows with PG-responsive CL, resulting in circulating concentrations of progesterone to subluteal concentrations of CIDR-source.…”

“…Although formation of persistent follicle is generally detrimental due to premature resumption of meiosis of the oocyte (Kinder et al, 1996), intentional formation of persistent follicles is advantageous in this context as a means to enhance follicular maturity and thereby improve likelihood of ovulatory response to GnRH administration and subsequent emergence of a new synchronized follicular wave. Based on the hypothesis that the observed improvements in control over follicular wave development would result in increased synchrony among cows in timing of estrus expression, a subsequent large field trial was conducted to evaluate use of the 7 & 7 Synch protocol for control of the estrous cycle among recipient beef cows prior to embryo transfer (Bonacker et al, 2020a). A greater proportion of cows treated with 7 & 7 Synch expressed estrus compared to cows treated with the 7-Day CO-Synch + CIDR protocol.…”