MOST female pig’s will show signs of heat at about six months of age but it’s often advisable to leave them for another couple of months before you consider serving them.
Best, long term results are achieved by starting off with a good strong healthy pig, in good body condition, which is capable of withstanding any hardship that pregnancy might endure. This will ensure a long a healthy life for your sow So what are the signs of a sow coming on heat? A young gilt (a female sow which has not yet reared litter of piglets) will often show signs of coming on heat two or three days before she is on heat. This will be apparent by her vulva swelling up and becoming a deep red in colour. This is a generalization though and might be more difficult to spot in dark coloured pigs.
This swelling up and deepening in colour does happen in sows which have already had a litter but can be less obvious and more difficult to observe compared to gilts.
As the pigs actually come on heat they will often become more excitable and more vocal.
If there is a boar nearby then the female pig will almost certainly show some interest with him.
When she is actually ready for serving other signs of heat can include ears being pricked up. If you have a breed such as a Large White where their ears tend to be pricked up anyway then their ears will be very up right, almost curled over and touching at the top. Other breeds which have lopped ears will be less obvious but their ears will often twitch and rise slightly.
The main way of knowing if your pig is on heat though is with standing heat. When a sow is ready for service she will stand rock solid, often observed with a faraway look in her eyes, waiting for the boar to mount her.
Because natural service can take up to fifteen minutes this means that she will have to be prepared to stand still for quite a length of time. If you observe other pigs riding a sow then you know she is ready for the boar. The pig which is on heat is not the one on top but the sow which is standing underneath.
If you want to test this yourself, and it is easier if you have a boar in a next door pen, then quietly approach your sow and gently stroke her back. You may notice her ears prick. She will probably stand steady. Push down harder on her back and see if she still stands still.
If you feel confident then you can jump onto her back, if she will allow. I have often stood on a sow’s back and she will not budge but do beware because sometimes she might decide she has had enough and decide to run off with you on her back. Standing heat is the best, sure way of knowing if your sow is ready for service.
If you have just the one sow and are having a problem observing her coming onto heat then you can synchronise your pig using hormone progesterone which is added to her feed. This will in effect stop her coming onto heat. Once she has the hormone removed she will come onto heat approximately five days later. To find out more about these products you will first need to speak with your vet.
There is a lot of talk about when best to serve your sow and some people say either after twenty four hours or as she is going off heat but I always advise to serve as soon as she is standing and then every twenty four hours until she goes off heat.
The reason for serving her as soon as she will stand is because the reality is that you do not know for sure how long she has really been on heat. Also some pigs can have quite a short heat while others can have a long heat so it could be possible to miss ovulation.
Most sows stay on heat for two to three days on average. Take a note of her service because 115 days (on average) later she should farrow. An easy way to remember how long a pig is pregnant for is ‘three months, three weeks and three days’.
If your pig does not become pregnant or if she is not served at all then she will come back on heat three weeks (21 days) later. The main way of knowing if your pig is pregnant is by using either a scanner or ultra sound. Both of these methods however require specialist equipment which needs experience to operate.
The other method is to record the service date and between 18 – 24 days later put the sow in with the boar. If she has not held to pregnancy then hopefully she will show signs of heat again.
As your pig progresses throughout her pregnancy she should be kept well fed, but not allowed to become fat. A couple of weeks before farrowing you might notice that her belly has become noticeably bigger. About a week before farrowing her udder will start to swell and her vulva will start to slacken a bit.
Actual signs that farrowing are getting closer is indicated by the fact that her nipples will start to become very swollen. You can, using thumb and finger, often draw a jet of milk if you try. The sow will usually let you stroke her swollen udder.
About twelve hours before she will farrow she will start to make a nest by picking up leaves, twigs or by rooting up the ground. Any material will be deposited in the nest area. This behaviour by sows always fascinates me, as they have such a focussed and intent expression on their faces You know by this preparation that it is also time for you to prepare for the imminent birth of the piglets.