These products are usually under the direct control of your veterinarian i.e. POM (prescription only medicines) products. As a general statement the use of hormones that act on the ovaries to stimulate oestrus should be avoided because the stage of the oestrus cycle cannot be accurately determined. However at specific times their use can be advantageous. Hormones used in the pig include the following:

Prostaglandins
See also chapter 8; Controlled farrowings.

These are substances that following injection, cause the corpus luteum to regress. The corpus luteum is present in the ovaries during the middle period of the oestrus cycle and during pregnancy. Its removal may either initiate oestrus, abortion or farrowing depending on the stage of the reproductive cycle. There are three uses:

1. Given within 36 hours post-farrowing to improve subsequent fertility and litter size.
2. To resolve endometritis or womb infection.
3. To synchronise farrowing by injecting the sow from day 113 of pregnancy. Farrowing usually commences within 24 hours.

Prostaglandins are potentially hazardous to women and should never be handled by them. Fig 4-15 shows a format recommended for their control and use on the farm

Milk let down products
These are hormones produced by the anterior pituitary gland at the base of the brain. Their action is to release milk from the mammary gland and cause contractions of the uterus. They may be given to promote the farrowing process provided there are no mechanical obstructions. They are also useful in promoting milk flow when the udder is congested. Specific uses are discussed in chapter 7.