Effect of interval between induction of ovulation and artificial insemination (AI) and supplemental progesterone for resynchronization on fertility of dairy cows subjected to a 5-d timed AI program

Abstract

Objectives were to investigate 2 intervals from induction of ovulation to artificial insemination (AI) and the effect of supplemental progesterone for resynchronization on fertility of lactating dairy cows subjected to a 5-d timed AI program. In experiment 1, 1,227 Holstein cows had their estrous cycles presynchronized with 2 injections of PGF(2α) at 46 and 60 d in milk (DIM). The timed AI protocols were initiated with GnRH at 72 DIM, followed by 2 injections of PGF(2α) at 77 and 78 DIM and a second injection of GnRH at either 56 (OVS56) or 72h (COS72) after the first PGF(2α) of the timed AI protocols. All cows were time-inseminated at 72h after the first PGF(2α) injection. Pregnancy was diagnosed on d 32 and 60 after AI. In experiment 2, 675 nonpregnant Holstein cows had their estrous cycles resynchronized starting at 34 d after the first AI. Cows received the OVS56 with (RCIDR) or without (RCON) supplemental progesterone, as an intravaginal insert, from the first GnRH to the first PGF(2α). Pregnancy diagnoses were performed on d 32 and 60 after AI. During experiment 2, subsets of cows had their ovaries scanned by ultrasonography at the first GnRH, the first PGF(2α), and second GnRH injections of the protocol. Blood was sampled on the day of AI and 7 d later, and concentrations of progesterone were determined in plasma. Cows were considered to have a synchronized ovulation if they had progesterone <1 and >2.26 ng/mL on the day of AI and 7 d later, respectively, and if no ovulation was detected between the first PGF(2α) and second GnRH injections during resynchronization. In experiment 1, the proportion of cows detected in estrus at AI was greater for COS72 than OVS56 (40.6 vs. 32.4%). Pregnancy per AI (P/AI) did not differ between OVS56 (46.4%) and COS72 (45.5%). In experiment 2, cows supplemented with progesterone had greater P/AI compared with unsupplemented cows (51.3 vs. 43.1%). Premature ovulation tended to be greater for RCON than RCIDR cows (7.5 vs. 3.6%), although synchronization of the estrous cycle after timed AI was similar between treatments. Timing of induction of ovulation with GnRH relative to insemination did not affect P/AI of dairy cows enrolled in a 5-d timed AI program. Furthermore, during resynchronization starting on d 34 after the first AI, supplementation with progesterone improved P/AI in cows subjected to the 5-d timed AI protocol.

Prostaglandin F2α or estradiol benzoate to induce ovulation in timed artificially inseminated dairy cows

“…given 24 hours after CIDR removal in 5d-GnRH-based protocols has provided controversial results. Two doses of PGF in the 5d TAI protocols improved luteolysis and pregnancy rates in dairy cows (Bisinotto et al, 2010;Santos et al, 2010), and heifers (Lima et al, 2013). However, Garcia-Ispierto & Lópes-Gatius (2014) did not observe similar beneficial effects on dairy cows.…”

“…However, based on the results of a previous study (Martinez et al, 2005) and on the foundational nature of the current work, we were not encouraged to risk using TAI in a large number of cows without treating them with an ovulation inducer. Considering that 55 to 65% of the cows are still not pregnant after the first postpartum AI (Bisinotto et al, 2010), the substitution of EB by PGF as the ovulation inducer in a TAI protocol provided satisfactory fertility in dairy cows (~40%). The acceptable pregnancy rates, obtained in both EB and PG groups (Table 1), is an evidence that ovulation probably occurred in a synchronous manner in both groups.…”

“…Although the effects PGF given 24 hours after the progesterone device removal on hastening luteolysis has been studied (Bisinotto et al, 2010;Santos et al, 2010;Lima et al, 2013;Garcia-Ispierto & Lópes-Gatius, 2014), to our knowledge, no study was performed to investigate whether PGF can induce ovulation by itself in TAI protocols for dairy cows. From a commercial perspective, the major significance of such studies is the possibility of developing a new method to induce ovulation in dairy cattle, reducing the use of estradiol in TAI protocols.…”

“…The mechanism by which PGF may affect fertility, when it is used in TAI protocols, could act either by anticipating luteolysis (Bisinotto et al, 2010;Santos et al, 2010;Lima et al, 2013), or by improving uterine environment for early conception development (Neglia et al, 2008;Gabriel et al, 2011;Garcia-Ispierto & Lópes-Gatius, 2014;Ambrose et al, 2015). Furthermore, incomplete luteolysis has been reported as a negative factor that impairs fertility of a TAI protocol .…”

Physiological and practical effects of progesterone on reproduction in dairy cattle

“…This has been clearly shown in numerous studies using timed AI programs (Souza et al, 2007;Brusveen et al, 2008;Bisinotto et al, 2010b;Giordano et al, 2012b and. In addition, studies on cows that receive AI after detection of estrus, have generally reported that minor elevations in P4 near AI are also detrimental to fertility (De Silva et al, 1981;Waldmann et al, 2001;Ghanem et al, 2006), although some studies did not obtain this result (Erb et al, 1976;Plym Forshell et al, 1991).…”