Use of Altrenogest at Weaning in Primiparous Sows

Administration of altrenogest for heat synchronisation in gilts after weaning their first litter increased the numbers of total piglets and piglets born alive in the subsequent litter in a study by North Carolina State University researchers.
calendar icon 22 July 2014
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Treating primiparous sows with altrenogest for seven days after weaning increased not only the subsequent total number of piglets born but also the number of piglets born alive and the number of sows returning to oestrus after cessation of altrenogest treatment, according to Drs Perle E. Boyer and Glen W. Almond of North Carolina State University.

In their paper in Journal of Swine Health and Production, they also concluded that farrowing rates were not affected by treatment.

The authors explain in their introduction that altrenogest (Matrix; Intervet/Schering-Plough Animal Health) is a synthetic progestin, which is widely used in the pork industry on a worldwide basis. The product is approved for use in sexually mature gilts that have had at least one oestrus cycle. It is administered orally for 14 days in North America and up to 18 days in Europe in order to inhibit oestrous cyclicity of gilts and synchronise the subsequent onset of oestrus.

As part of the seasonal infertility complex, Boyer and Almond continue, primiparous sows may experience a decrease in the number of pigs in their second litter compared to their first litter. Primiparous sows are also more susceptible to summer infertility than sows of higher parity. One method used to avoid the reduction in litter size during the second parity is to extend the weaning-to-service interval. In addition, administration of exogenous gonadotropins at the time of weaning has been used to induce oestrus although farrowing rates and litter sizes may be negatively affected by the use of exogenous gonadotropins


Boyer P.E. and G.W. Almond. 2014. Use of altrenogest at weaning in primiparous sows. J Swine Health Prod. 22(3):134–137.

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July 2014

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