The product P.G. 600 works to induce/synchronize heat in breeding females, particularly for sows experiencing delayed return to estrus after weaning.

It is also used to induce heat in replacement gilts entering the breeding herd. Concern today is the indiscriminate use of P.G. 600 in gilts with no known reproductive history, says Charlie Francisco, technical services veterinarian, Intervet Inc. P.G. 600 is marketed as an estrus control product.

Product Misuse

“Some producers are going in blindly and using P.G. 600, and if they don't get the response [they expect], they either put the blame on the product or they put the blame on the animal,” he explains.

If the gilt happens to be cycling, P.G. 600 won't help that estrus response and it may extend the anestrus period that follows. Instead of a 21-day return-to-estrus period, anestrus may extend out to 35 or 36 days. If the gilt had gone untreated, she probably would have been normal reproductively.

Profile Herds

The label claim for prepuberal gilts is for induction of fertile estrus. That means they have never had a heat cycle.

Producers need to profile their herds to understand when gilts are naturally coming into puberty, he says. Serum progesterone kits may be one way to detect the hormone activity that indicates cycling.

Gary Althouse, DVM, associate professor of reproduction at the University of Pennsylvania, tested the effectiveness of two serum progesterone assays. He found that both the Progestassay (Synbiotics Corp., San Diego, CA), and Target (BioMetallics, Princeton, NJ) assays were highly specific and sensitive for pig serum.

Observes Althouse: “A veterinarian can collect serum and run these tests at the farm or clinic. Both kits are simple to run and take only 15-25 min. to perform. The ability to run these tests sow-side should make them a practical aid when investigating herd reproductive problems and management programs.” Cost should be less than $15/test.

In skilled hands, real-time ultrasound may also be used to confirm that the gilt pool is truly non-cycling, says Francisco.

Another misuse of P.G. 600 in gilts is in “old maids” that have been in the gilt pool for an extended period of time, says Francisco. Heat cycle history may be largely unknown.

“Producers want to give them one last chance with P.G. 600, when frankly that class of gilts is probably not a good candidate for P.G. 600 or the breeding herd,” says Francisco.

He says the best use for P.G. 600 appears to be in gilts known to be prepuberal, along with good boar exposure methods. Administer P.G. 600 to a select group of gilts, not the leftovers. Also, consider high-risk, first- and second-parity sows, particularly during summer and seasonal anestrus periods. This helps reduce the cost of non-productive days for the breeding herd.