Genetics or environment? Nature or nurture? Before you start placing blame on genes, it's important to know the heritability of the problem in question.

I sold show pigs to 4-H and FFA students the first week of April. Showing swine is near and dear to me since I probably wouldn't be farming today if it weren't for showing swine. Striving to improve on my placing at the Lafayette County Fair caused me to begin my lifelong study of genetics and improvement of livestock.

The Lafayette County, Wisconsin, swine show is an excellent learning opportunity. Show pigs are identified and weighed in April. There is a maximum entry weight. Students then have the responsibility of caring for the pigs until the show in July. After the show, each student is allowed to sell one show pig in the livestock auction. Local businesses and individuals support the students by purchasing these pigs for meat. Prices are usually well above market price, so the students are almost guaranteed to make money on their project.

Students are required to keep production and financial records on their livestock. Students learn accounting and marketing skills all in one fun project. Not everyone is successful, however. There is a minimum weight (220 pounds) to sell in the livestock auction. This requires an average daily gain of about 1.5 pounds per day (170 pounds of gain in 113 days). This is not difficult to accomplish with today's swine.

But to achieve this average daily gain, a pig needs clean feed and water, shelter, shade, and a way to cool off (sprinkler or wallow) when it gets hot. If a student fails to provide these ingredients every day, the pig may be too light to sell at the auction. This is a great learning experience about responsibility.

Recently I helped a family (who had never purchased from me before) deliberate whether a smaller pig (46 pounds) would be big enough by fair time.

They asked me how well my pigs gained weight; I told them average. Then I asked what their pigs have weighed at the fair in the past. I wanted to know because it's been my experience that most families tend to have similar results from year to year, even though the pigs are different. Some families always bring 300-pound pigs to the fair; other families always struggle to make their pigs the minimum weight.

This is easily explained because average daily gain is only moderately heritable. The difference between individual pigs that's due to their genetics is called heritability. Heritability is expressed from 0 to 1, with 0 being not heritable and 1 being completely heritable. Heritability for average daily gain in swine is about .3. This means that 30% of the variation in average daily gain is due to genetics.