Prostaglandin F2α and its synthetic analogues, because of their luteolytic properties, have found wide application in the reproduction of domestic animals, including cattle, swine and horses. They are used to induce and synchronize heat, ovulation and parturition, as well as to improve the results of insemination and early-stage pregnancy termination. The ongoing discussions regarding animal welfare include the question of the lowest effective dose of hormones in individual species and how it could be reduced by selecting the optimal route of hormone administration. Intramuscular injection is the recommended method of administering prostaglandins to cows, pigs and mares. Due to the different sensitivities of these species to prostaglandins, the recommended therapeutic dose varies significantly from one species to another. The luteolytic effect also depends on the route of administration. Studies on alternative routes of injection report good therapeutic effects after administration of the hormone subcutaneously (SC), into intravaginal submucosa (IVSM), at the BAI-HUI acupuncture point or at the ischiorectal fossa (IRF). The injection site, the dose and the type of prostaglandin used may intensify negative effects, such as an increase in the heart or breathing rate and increased sweating.
The Ovsynch programme is one of the most frequently used procedures in managing dairy cattle reproduction. There are many studies evaluating the effectiveness of the Ovsynch programme. However, few of them assess the impact of factors that can lead to a decrease in the pregnancy rate and thus, reduce the success of the Ovsynch programme. This review aims to examine the impact of both individual and environmental factors on the likelihood of pregnancy. The risk factors described include: the body condition, age, number and stage of lactation, production level, occurrence of diseases and postpartum complications, functional status of the ovaries, oestrous cycle phase, temperature, season and year, and program start-up after calving. Possible modifications of the Ovsynch programme are presented in order to increase its effectiveness and to determine the best time to start it. Additionally, attention was paid to pregnancy losses during the Ovsynch programme which ultimately decrease pregnancy rates. The impact of this many factors on the efficiency of the Ovsynch suggests the need to adjust the synchronization program each time to the individual situation of the herd.
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