For Consumers >

This site provides technical and program information for veterinarians and farmers. If you are a consumer looking for general information, please visit the IMPROVEST®(gonadotropin releasing factor analogdiphtheria toxoid conjugate) Consumer Resource Center.

Frequently Asked Questions


IMPROVEST® gives you a safe and effective alternative to physical castration to manage boar taint. Meat from male pigs can have an offensive smell when cooked. While these naturally developing odors are completely safe, research shows that a high proportion of consumers, especially women, can easily detect them,12,13 making their control a necessity to protect the quality experience of eating pork.

   What is it and how does it work?

This FDA-approved product is a protein compound that works like an immunization, using the pig’s own immune system to temporarily provide the same effect as physical castration, but much later in the male pig’s life. About a month before going to market, male pigs are given IMPROVEST®, which stimulates their immune system to prevent them from producing the off-odor substances.
It’s important to realize that IMPROVEST® is NOT a hormone or growth promotant. It’s not added to the feed or genetically modified. And, it is not chemical castration. It’s a protein compound that provides a temporary immune response to manage the unpleasant aromas of boar taint.

   Who benefits from the use of IMPROVEST® ?

For farmers, IMPROVEST® offers a safe and effective alternative to physical castration of male pigs to reduce off odors in cooked pork.[1] By eliminating the need for physical castration, the animals grow with all the inherent advantages of intact males. They convert feed to meat more efficiently, and the risk of piglet mortality associated with physical castration is eliminated. Studies also show that following administration of IMPROVEST®, pigs are less aggressive than intact males, behaving similarly to barrows.1,2

For Americans who eat pork, they can enjoy the same high quality pork with the knowledge that it was raised using fewer resources. As intact males, the pigs convert feed into meat more efficiently – they eat less feed, create less manure, and produce more pork. Less waste and more pork means an incremental reduction in the carbon footprint compared to barrows.6

   Is this technology used in other countries?

Yes. This type of immunological technology is approved in more than 60 other countries around the world, including the European Union, Australia and Japan, under the related global brand IMPROVAC. IMPROVAC has been used successfully by farmers in some countries for more than 10 years.

To see the list of countries click here >

   How is IMPROVEST® given to pigs?

IMPROVEST® is administered via injection at the base of the pig’s ear, and is not added to the pigs’ feed. IMPROVEST® is protein based and must be given as two injections to create the immunologic response needed to control the unpleasant aromas.

   Is IMPROVEST® a hormone?

No. It’s a protein compound that works like an immunization and has absolutely no hormonal activity. It uses the pig’s own immune system to temporarily provide the same effect as physical castration to manage substances that can cause unpleasant aromas in pork from male pigs.

   Is it chemical castration?

No. IMPROVEST® is an immunological product, meaning it uses a pig’s natural immune system to temporarily reduce the substances that cause the unpleasant aromas in pork.

   Is it safe, are there residues in the meat?

It is safe. There are no residues in the meat from IMPROVEST® that could affect human health, according to the FDA. In its approval of IMPROVAC (related global brand), the European Union’s regulatory authority stated that meat from pigs given IMPROVAC "would not contain any potentially harmful residues" and that the consumption of pork from these pigs therefore "poses no risk to the consumer."14

   Why must I wait to market my pigs between three to 10 weeks after the second dose?

That allows time for the pig’s natural substances (androstenone and skatole) that cause the unpleasant aromas to clear the pig’s system to ensure a high quality pork eating experience. That’s why the label says pigs should not be sent to market prior to three weeks after the second dose, allowing adequate time for the reduction in the substances responsible for off odors in pork. Marketing pigs on the IMPROVEST® program more than 10 weeks after the second dose may increase the risk of odors in the pork.

   Can this product be used on any size farm?

Yes, this product is size-neutral. IMPROVEST® can be used by, and brings benefits to, any size farm.

   How will raising intact males affect management practices on my farm?

Use of IMPROVEST® requires a significant change because intact male pigs have different nutritional requirements, which brings new management considerations.

As the product is introduced to an operation, Zoetis will work with veterinarians and their producer clients to help them adopt nutritional guidelines and best handling practices to optimize growth for intact males on the IMPROVEST® program.

Product availability will increase gradually as the experience of working with intact males expands. This gradual approach also provides the time needed to ensure a coordinated food chain effort and gives processors and packers time to integrate and optimize this into their systems, as well.

Zoetis wants to ensure the best IMPROVEST® program experience for everyone – from farmers to meat packers and processors, retailers and, ultimately, to consumers.

   How does this impact the environment?

The efficiencies gained by allowing male pigs to grow longer as intact males before IMPROVEST® is administered has the potential for an incremental reduction in the carbon footprint.6

The environment is of significant importance to the pork industry and its customers.7 The environmental impact of U.S. pork production is relatively low (0.33% of the total U.S. greenhouse gas emissions).8 Incremental reductions in these emissions remain a high priority.

   Can I use this with other types of pigs?

IMPROVEST® should not be used with female pigs, barrows or male pigs intended for breeding.

   What is gonadotropin releasing factor – diphtheria toxoid conjugate?

It’s the generic name for the active ingredient in IMPROVEST®. Let’s break it down:

  • Gonadotropin Releasing Factor (GnRF) – This is a compound that all mammals produce naturally as they mature, including pigs. IMPROVEST® does not contain the naturally occurring GnRF. Rather, it contains an incomplete version of it, which makes it inactive.

  • Diphtheria toxoid (DT) – This is the same as the standard diphtheria vaccine that has been safely used in global childhood vaccination programs since the 1930s. It is simply a protein that contains natural amino acids. It is used as the carrier (conjugate) protein for the incomplete GnRF molecule.

  • Conjugate – Means "to join together." The two compounds need each other to produce the immunological response in the pig. Together, they act as an immunization to control the substances that create the unpleasant aromas that can occur in pork from male pigs.

   What are the most important safety considerations for IMPROVEST®?

Special care should be taken to avoid accidental self injection during administration of IMPROVEST®. Accidental self injection could negatively affect reproductive physiology of both men and women. Therefore, pregnant women should not administer IMPROVEST® and women of childbearing age, as well as men, should exercise extreme caution when administering the product. There is no risk, however, of these effects on an individual who consumes pork from pigs given IMPROVEST®.

Important Safety Information - Pregnant women should not administer IMPROVEST. Women of childbearing age, as well as men, should exercise extreme caution when administering this product. Exercise special care to prevent accidental self-injection because of negative effects on reproductive physiology in both men and women. However, there is no risk associated with consuming pork from animals administered this product. IMPROVEST should not be used in female pigs, barrows, or male pigs intended for breeding.