This will sound pretty simple, because it is. The majority of insects (like alfalfa weevil) do not like to eat “sweet” plants. They attack low sugar content plants (like alfalfa). If you are having trouble with alfalfa weevil, it has two causes: (1) low sulfur soils inhibit the “energy” value of alfalfa, (2) alfalfa even in its optimal state is not that high a “sugar” forage. The biological solution to scaring away weevil is: plant it with “high energy” grass varieties. Straight alfalfa is really an obsolete forage concept.
Your cows’genetic encoding is to eat grass. As we switched her to corn-based diets we had to find the forage that would produce lots of protein to balance, and alfalfa (plus soybean meal) became the focus… but as costs of corn/soybean culture have risen, the energy superiority of grass (also a protein source) is coming into play. BUT—you have to select grass genetics just like you select corn and alfalfa, for the total nutrient package they bring. This is why Byron Seeds offers a different perspective on forages.
Ants, on the other hand, like sugar. If you want to tell whether a corn has the sugar content needed to give you more complete fermentation and higher digestibility as a silage, lay fresh cut stalks next to an anthill—and see which corn variety the ants pick first. In most cases, it will be Masters Choice corn, the independent corn company that won the World Dairy Expo corn superbowl this fall (2009).