How is sow estrus timing controlled with exogenous progesterone?

Use exogenous progesterone (altrenogest or allylrenone) to control sow estrus timing.

Hormone management (III)

In our previous articles, we have been focusing on how to help sows come into estrus. In this article, we will explain how to use the "side effect" of progesterone (altrenogest or allylrenone) to delay sow estrus.

In principle, delaying sow estrus may sound a bit absurd, but under certain special circumstances, delaying estrus is still very useful.

Delaying cyclic estrus

From the earlier introduction, we know that when the ovarian corpus luteum is present, progesterone concentrations are high, and this inhibits sow estrus.

Levels of the main hormones during the sow estrus cycle

There are currently some synthetic progesterone products on the market that, when given to pigs, can inhibit follicular development and ovulation. Using this method, we can achieve delayed estrus in sows.

These products need to be administered at a fixed time every day. A relatively common product is allylrenone (Regumate®), which is an oral formulation given to pigs through feed.

When administration of the progesterone product to the pig is stopped, the progesterone level in the pig's body declines accordingly.

Exogenous progesterone no longer blocks follicular development, the estrus cycle continues, and the sow will come into estrus again after 5-6 days.

In the above case, we achieved a 30-day estrus cycle (estrus was delayed by 9 days).

Delaying postpartum estrus in sows

We have seen how to use progesterone to delay synchronized estrus in sows, and the same method can also be used in weaned sows.

In this example, assume the sow is weaned at 24 days, but we want this sow's estrus to be delayed by another week (entering the next week's estrus sequence).

When the sow receives allylrenone, its state is as if it were still pregnant, with high progesterone levels blocking ovulation, similar to the normal estrus cycle.

As we discussed earlier, after the exogenous progesterone product is stopped, progesterone concentrations decline, and follicular development and ovulation resume immediately.

5-6 days after the interruption of exogenous progesterone, the sow will come into estrus, just as after weaning.

In this case, the sow was weaned at 24 days, but through our intervention, the sow achieved the effect of 31-day weaning in terms of timing. Estrus was delayed by one week.

Special reminder!

If you want to achieve a one-week delay in sow estrus, it is recommended to start treatment at the minimum dose one day before the sow is weaned, rather than starting treatment on the day of weaning.