Pig Notes January 2012

The weaning to service interval, although a short period in the reproductive cycle of the sow is a very important period.  The length of the period influences both farrowing rate and numbers born.  The shorter the weaning to service interval:-

Analysis of WinPig data shows that the average weaning to service interval for sows is 5.4 days. As expected, the interval for first litter sows is longer; on average one and half days.  

The most fertile sows are those that are served three to five days after weaning.  A recent analysis of records from a large scale pig unit confirmed that this is indeed the case. On this unit sows are weaned on Thursday.  The records show that sows served on Monday and Tuesday of the following week, that is four and five days after weaning, had the highest farrowing rate (85 percent), whereas sows served six to 10 days after weaning had a farrowing rate between 74 and 77 percent.  The number of pigs born alive was also highest for sows served on Monday and Tuesday (11.5–12) compared to an average born alive of 11-11.5 for sows served towards the end of the week.

What influences weaning to service interval? The main influence is feed intake during lactation. If sows do not eat enough during lactation and loose body condition, especially body protein, they will be slower coming on heat. This is especially true for first litter sows. Due to their smaller body size they are often unable to consume adequate feed.  Feeding sows ad lib from weaning to service also encourages them to come on heat quicker. But remember the nutrient density of the diet fed from weaning to service will not compensate for inadequate nutrition during lactation.

Conception rate and farrowing rate are two figures that are often quoted by pig producers.  However, the two figures are often confused.

What is the difference between conception and farrowing rate?

Conception rate can be calculated at any stage throughout pregnancy and is the percentage of sows in pig relative to the number served.  For example, if 100 sows are served on the 1 January and six weeks later 95 are still in pig the conception rate is 95 percent.

Farrowing rate differs in that it is based on the number of sows that actually farrow.  Taking the same example of 100 sows served on 1 January, 115 days later 89 of these sows farrow; the farrowing rate is then 89 percent.  

If the farrowing rate for your unit is less than the target of 87+ percent investigate why sows served do not farrow. There are only five reasons why a sow does not farrow. They are:-

As temperatures continue to drop now is the time to check the temperature of your medicine fridge. Very often medicine fridges are kept in poorly insulated outbuildings or stores. If this is the case there is a risk the temperature in the fridge will drop to freezing or below. Vaccines stored in the fridge may be destroyed and pigs vaccinated using these vaccines may not be adequately protected against disease outbreak.

Also take a minute and think about the storage and handling of semen during cold weather. Semen is very sensitive to temperature fluctuation. The optimum storage temperature for semen is 17 degrees centigrade, with variation of no more than two degrees.  Think about where the semen is stored – is it too cold? Also think about the transfer of semen to the service area and storage in the service area. Semen is too valuable a commodity to store and handle incorrectly.