Mike Hutjens thinks dairymen and their nutritionists should be using computer programs that do more than spit out balanced diets.

He's excited about ration formulation models that “give predictions of what a cow's rumen might be doing to forages or high-moisture corn or starch.”

Computer models can adjust dry matter intake, says the University of Illinois extension dairy nutritionist. “Once you play games with dry matter intake, then everything changes — rates of passage, fluid rates, digestibility, residence time in the rumen, bacterial activity and/or pH.

“If you don't use a model, you're assuming that a cow producing 160 lbs will handle feed the same as a cow producing 60 lbs.”

Models can look at NDF digestibility, protein solubility and degradation rates. “Some of these programs will look at such things as soluble fiber, which is very important in alfalfa. They'll look at sugars and a lot of different carbohydrate fractions,” Hutjens says.

Before you pick a program, decide how sophisticated a model you need, how quickly you'll need its results and what you can afford, he says. Students in his nutrition classes must know the basics of three popular ration models: CPM-Dairy, developed by Cornell University, the University of Pennsylvania and the Miner Agricultural Research Institute; the 2001 NRC, from the National Research Council; and AminoCow, a privately developed program from Degussa, a German-based corporation.

Spartan is a fourth program that may warrant consideration next year. It's currently under revision to add a model to its ration-balancing capabilities. Developed by Michigan State University, the current spreadsheet program lists feeds and nutrients, calculating ration nutrient levels compared to standard requirements. “It puts out a really nice report,” Hutjens says. “If you are simply going to ask the question, ‘What does my ration look like?’ then just use Spartan.”

If your dairy nutritionist has convinced you that you need a ration-formulating model, here are his thoughts on the ones he's most familiar with:

CPM-Dairy — “It has been updated, so it's probably one of the most sophisticated models,” Hutjens says. “Some of the newer updates will have a fatty-acid model that allows you to look at fat quite differently. It's a little more complex to run than other programs and will take more time to get your output than AminoCow will. It's also the most expensive of the three programs.”

NRC — The price is right: around $50-60, yet it takes a while to get results. “The plus side to the 2001 version of NRC is that it has a whole menu of different outputs, such as mineral, amino acid and heifer outputs.

“But there is no balancing; you need a second program. A lot of farmers and nutritionists are using Spartan to get the basic program results, then put those results, by hand, into NRC to do all the magic. Then they take it out of NRC and put it back into Spartan, because they like how it outputs.”

AminoCow — “It's basically a Spartan with a model integrated into it. It's a very simple spreadsheet type of approach and very simple to use.

“The limitation is, it's a private program,” says Hutjens, because it was developed by a commercial firm rather than a university or organization. “This one could be inexpensive because, in many cases, it's being provided at training workshops,” he adds. According to Degussa, AminoCow offers a full nutrient profile, including amino acid content.