Estrus synchronization is a reproductive biotechnology used to improve artificial insemination or pairing through the manipulation of the estrous cycle at a desirable time. Employing this technique in captive pacas (Cuniculus paca L.) is important because it creates expectation of meeting the demand for paca meat and, consequently, reduces poaching. Thus, this research aims to verify the effect of a progestogen implant associated with two doses of eCG on the synchronization and induction of fertile estrus. Twenty-seven adult pacas were used, 18 non-pregnant females and nine males, divided into three groups. G1 and G2 females groups (treatments) received 1.5 mg Norgestomet and were injected intramuscularly, seven days later, with 0.13 mg of prostaglandin. After 24 hours the implants were removed and the animals immediately received 25 IU and 50 IU of ECG intramuscularly, respectively. The mating of the three groups took place on the same days. G3 females’ group (control) showed estrus on different days after D0. Females under treatment displayed estrus only after removing the implant (D8). G1, G2, and G3 pregnancy rates were 100%, 66%, and 50%, respectively. Regarding births per parturition, 100% of G1 and G3 produced one offspring, while 50% of G2 produced two. Progestogen in the form of subcutaneous implants was effective in mimicking the luteal phase of the estrous cycle. After removal, implants favored the occurrence of a fertile estrus. As a conclusion, further studies must be conducted in order to establish in-depth possible association between 50 IU of eCG, and the occurrence of twin pregnancies.

Perfect detection of estrus is crucial for good husbandry practice of cow. Estrus synchronization is the alternative strategy to bypass the critical problem of estrus detection. Synchronization program allows fixed timed artificial inseminations (FTAI) to evade the estrus detection. The most recently developed programs include protocols for re-synchronization following first or subsequent inseminations. These re-synchronization protocols may involve selected forms of hormonal intervention during the diestrus and pro-estrus periods following FTAI, or following pregnancy diagnosis by ultrasound from 28 days after FTAI. Almost all programs involve strategically timed treatment of prostaglandin F2α (PGF) and gonadotropin releasing hormone (GnRH). Treatment of an estradiol ester and progesterone supplementation per vaginum may be included in some programs. The basic program is the “Ovsynch” regimen. This mini-review discusses a number of key points related to external hormonal stimulation on ovarian follicular wave to improve pregnancy rate following timed AI.

To declare the interaction between IBR vaccination and the synchronization protocol, dairy heifers (n= 24), 12.5-14.0 months old, were equally and randomly assigned according to the timing of vaccination into pre-synch group (vaccinated 3 days before synchronization), in-synch group (vaccinated five days after the start of the synchronization), and control (given sterile water same as treated groups). Ovarian and uterine ultrasound examinations were done on Day -3, 5, 8, 19 and 43. Blood samples were collected for measuring estradiol and progesterone levels after vaccination. The effect of IBR vaccination on ovarian activity appeared on Day 5 (P= 0.07) through decrease in the mean diameter of the growing follicles in pre-synch group compared to in-synch group, and on Day 8 through reduction of the total and growing follicular numbers (P= 0.05 and 0.03, respectively) in in-synch group compared to other groups. Estradiol levels were significantly (P=0.03) higher on day 8 (day of insemination) in the pre-synch group than the other groups. The uterine changes were characterized by a significant decrease in uterine diameters on Day 5 in the pre-synch group compared with control. The ventral uterine diameter in-synch group decreased on Day 5 (P= 0.015) and re-increased on Day 8 (P= 0.007 compared to control group. In conclusion, administration of IBR vaccination prior to synchronization may possess some impacts on the ovarian and uterine activities without major adverse reactions on reproduction. Therefore, vaccination timing is recommended to be at least three days away from the beginning of the synchronization protocol.

Analysis of synchronization of oestrus of cows by means of Ovsynch and Pre-Synch methods was realized in the conditions of the Republic of Belarus. Research results showed that estrus synchronization by means of Pre-Synch method proved to be more efficient by means of higher percentage of fertilization after the first and second insemination in comparison with Ovsynch method. Treatment of cows with the substances Surfagon and Tetravit for synchronization of oestrus did not render negative effect on milk quality and safety.