Effect of hCG administration on day 7 of the estrous cycle on follicular dynamics and cycle length in cows

The Induction of a Secondary Corpus Luteum on Day 12 Post‐Ovulation can Delay the Time of Luteolysis in High‐Producing Holstein Cows

“…In contrast, previous studies showed that hCG‐induced CLs were smaller than spontaneous CLs (Rajamahendran and Sianangama ; Fricke et al. ; Sianangama and Rajamahendran ,b; Diaz et al. ).…”

“…However, most studies did not specifically assess the relationship between CL2 formation and P4 increase. The present study demonstrates that CL2 formation is clearly involved in the P4 increase after hCG treatment, even if some authors attribute to the induced CL a reduced ability to produce steroids (Fricke et al 1993;Sianangama and Rajamahendran 1996b). In the absence of saline-treated group, the present study was not designed to assess the respective contributions of CL1 vs. CL2.…”

“…). Treatments with hCG or GnRH during early luteal phase (Days 5–7) usually raise circulating P4 concentrations but do not prevent the risk of premature luteolysis because the induced CL usually regresses before or at the time of CL1 luteolysis (Howard and Britt ; Sianangama and Rajamahendran ; Stevenson et al. ; De Rensis et al.…”

“…Another strategy to enhance cow fertility is to inject LH-like molecules, such as hCG or GnRH, to luteinize a growing follicle, inducing a secondary corpus luteum (CL2) as well as directly stimulating P4 production by the primary corpus luteum (CL1) (Thatcher et al 2002). Treatments with hCG or GnRH during early luteal phase (Days 5-7) usually raise circulating P4 concentrations but do not prevent the risk of premature luteolysis because the induced CL usually regresses before or at the time of CL1 luteolysis (Howard and Britt 1990;Sianangama and Rajamahendran 1996b;Stevenson et al 2008;De Rensis et al 2010). To delay luteolysis, induction of an accessory CL later in the luteal phase may be needed.…”

Roles of hCG in Advancing Follicular Growth to Ovulation after Concurrent Injections of and GnRH in Postpubertal Holstein Heifers Bearing a CL

“…This trial was meant to evaluate the effects of hCG in advancing follicular development to ovulation in dairy heifers with progesterone levels similar to concentrations observed in early diestrus [27]. Other researchers observed alteration of the follicles dynamic in nonbred lactating cows receiving hCG on day 7 of the estrous cycle [28]; in that study, the time of emergence of the second wave of follicular growth was advanced in the group of cows receiving hCG treatment. Additionally, administration of hCG 7 days post insemination was suggested to improve embryo retention in cattle by boosting plasma progesterone concentration as a consequence of inducing formation of an accessory corpus luteum [29].…”