Doing the calculations shows that there are situations when market prices are very low and feed costs are high that it is more profitable to ship pigs lighter than the grading grid would suggest. This is because the value added to the hog by a gain in weight does not compensate for the cost of the feed it takes to make the weight gain, and considering that feed conversion tends to decrease as weight increases.

For example, Jaydee Smith has calculated that getting a hog from 107 to 130 kg (about 85.5 to 104.5 kg carcass weight) would currently increase carcass value by about $18 on the Ontario Heavy Grid, but it could well cost $24 in feed to do it.

It is important to know the target carcass weight range of the grading grid in use and the shipping weight needed to hit that target range, which depends on dressing percentage. Mistakes on the heavy end can be catastrophic given the compounded effect of feed costs and reduced index.

It is worth making whatever effort it takes to ship pigs at the right weight – once you've decided what that is. Shipping lighter could save feed, as well as reduce the amount of pork marketed.