This past week I spent some time reviewing the literature regarding the impact of weaning age on pig growth to slaughter weight. With profits returning to the swine industry, many producers are debating whether to invest in additional farrowing capacity so they can wean older pigs into their production flows.
The debate on the appropriate weaning age is not simple, as weaning age not only impacts the pigs that are weaned, but also impacts the subsequent performance of the females that weaned pigs.

The potential impact on female productivity has big implications for farrowing sites as it impacts the number of females needed to fill a given number of farrowing crates and the overall number of pigs weaned. In general, as weaning age declines (goes from 21 days to 17 days as an example), the subsequent litter size is reduced by 0.1 pigs per day of age decline. In addition, as the return to estrus tends to lengthen and there is some evidence of a reduction in conception rates.

On the weaned pig side of the wean age equation, the data is more confusing. In looking at performance results for 8 studies that followed the weaned pigs to slaughter weight, there was no consistent decrease in the days to final weight. In some of the trials, when pigs were weaned at an older age, they grew faster. In other trials, pigs reached a constant final weight in the same number of days from birth, regardless of wean age. Weaning an older pig does not automatically mean a younger pig at a constant slaughter weight.

What has confused a lot of people in looking at the wean age data is that pigs in the trials are most often weighed on the same day post-weaning, and performance has been reported as performance since weaning. In every instance, the older pigs have grown faster and attained a given final weight sooner than the younger pigs. This makes it appear that older pigs at weaning have a performance advantage over younger pigs, when in fact this isn’t always the case.

One of the questions that must be considered by a production system is where do you want to house pigs – on the sow in farrowing rooms or in wean-finish production facilities. If it takes the same number of days to attain a 270 pound sale weight, the question of weaning age then becomes, what age makes the most sense given the options for where I can house pigs, and what is the impact on sow productivity?

As a person who has been involved in starting weaned pigs for over 30 years, older pigs arriving at a production facility are always an advantage, in my opinion. A truck load of 22 day old pigs vs a load of 17 day old pigs means a lot fewer 5 to 7 pound pigs to deal with.