Low invasive estrous synchronization protocol for wild animals: an example with melengestrol acetate in brown brocket deer (Mazama gouazoubira)

Abstract

Deer are sensitive to stressful stimuli by handling and their reproductive physiology could be altered by these procedures, making it necessary to develop less invasive protocols for ART. Melengestrol acetate (MGA), a synthetic progestin administered orally, appears as an alternative for estrous synchronization protocols (ESP), such as reported in cattle. Firstly, we compared two MGA doses (0.5 and 1.0 mg/day/animal), which would have suppression effect in estrous behavior (EB). Eight females were randomly and equally distributed in Group 1 (G1) and Group 2 (G2), which received 0.5 and 1.0 mg/day/animal respectively for 15 days (D1 to D15). Two cloprostenol (CP) applications were performed on D0 and D11. Estrus detection (ED) was performed every day. All females from G1 displayed estrus during treatment period, whereas all females from G2 displayed estrus after treatment, suggesting a suppressive effect of 1.0 mg in the EB. Once the suppressive MGA dose (1.0 mg) was defined, we used this dose for assessing ESP. The same eight females received 1.0 mg/animal for eight days (D-8 to D-1), followed by 0.25 mg of estradiol benzoate on D-8 and 265 μg of CP on D0. Feces for fecal progesterone metabolites (FPM) measurement were collected from D0 until seven days after the last day of estrus. Seven females displayed estrus between 12 and 72 h after CP application, which was followed by a significant increase in FPM levels (except female MG6), suggesting the formation of corpus luteum. After ED, females were placed with a fertile male to assess the fertility of the protocol. Pregnancy was confirmed by ultrasound 30 days after mating in 3/6 individuals. Although the low effectiveness of MGA protocol, it should be considered as a promising alternative in deer ESP since this protocol has less stressful effect on the animal during reproductive management when compared to other ESP.

Transcervical artificial insemination in the brown brocket deer (Subulo gouazoubira): A promising method for assisted reproduction in deer

“…In the present study, 100% of females showed behavioral estrus approximately 44 hours after the end of the protocol. Similar success (100%) was previously reported for S. gouazoubira using the same oral progesterone 30 . Thus, the MGA-based estrus synchronization protocol is indicated for its high e ciency and for improving the welfare of the managed females, reducing stress sources, and offering more excellent safety to animals and technicians.…”

“…Due to a high-stress stimulus when handling the animal 7,38,42 , which may alter their physiological reproductive parameters 43 . With this regard, oral synthetic progestagens, such as melengestrol acetate (MGA), are an e cient option for estrus synchronization in deer species 30,44 and domestic ruminants [45][46][47][48] . In the present study, 100% of females showed behavioral estrus approximately 44 hours after the end of the protocol.…”

“…Estrus synchronization was based on the hormone protocol described by Tanaka et al (2020) 30 . All animals received two daily doses of 0.5 mg of melengestrol acetate (MGA, Premix ®; P zer.…”

Assisted Reproductive Technology in Neotropical Deer: A Model Approach to Preserving Genetic Diversity

“…Melengestrol acetate (MGA) can be administered to individuals with food at a dose of 1.0 mg/animal/day and is recommended to be divided into two periods of the day (morning and afternoon). The MGA-based protocol was applied in M. americana, M. nana, and M. nemorivaga, being used in a reproductive management routine for natural mating or artificial insemination procedures [94,95].…”

“…Using 250 IU of FSH dissolved in polyvinylpyrrolidone, less than one CL per animal was observed (0.80 ± 0.49) [102]. Another protocol tested a 700 IU of eCG and obtained 6.0 ± 1.7 CLs, while the application of 130 mg of FSH divided into eight equal doses resulted in 2.0 ± 0.3 CLs [94]. Despite obtaining better SOV responses in treatments where higher doses of eCG were used, this hormone caused a premature regression of the CL, indicating possible poor follicle quality [103].…”