Effects of Farrowing Induction on Some Farrowing Characteristics in the Pig − A Review

Several farrowing induction programs have been used to increase the proportion of sow farrowing during the work period and the rate of farrowing supervision, as well as to promote the success of cross-fostering and the practice of all-in all-out in swine production. The present overview aimed to evaluate the effects of farrowing induction on farrowing duration, birth interval, birth weight, dystocia/birth assistance, and stillbirth in pigs. The results showed that via different routes of administration, either natural or synthetic prostaglandins alone or in combination mostly with uterotonic drugs, including oxytocin and carbetocin, have been used for the induction of farrowing. Sometimes other drugs, such as dexamethasone, estradiol, xylazine, ergometrine, and AGN190851, were added. Vulvar and perinatal routes reduced the intramuscular dose of prostaglandins by 50% to 75%, while equal effects remained. A split dose of prostaglandin 6 h apart should be used because it may enhance complete luteolysis. Additionally, if uterotonic drugs are used following prostaglandin injection, they should be injected after the birth of the first piglets at the earliest timepoint to ensure full opening of the cervix. These two practices decrease the farrowing duration, the birth interval, and dystocia. Induction should not be conducted more than 2 days earlier than the expected farrowing date in order to keep the stillbirth rate and birth weight unaltered. This review also revealed that certain factors, such as the rate of farrowing supervision, natural differences in piglets’ birth weights, litter size, gestation length, and treatment with altrenogest before induction, may be confounding factors that possibly alter the effect of induction programs on certain farrowing characteristics.