Farming Magazine - March, 2013


Dairy Nutrition: Forage to the Max

By John Hibma

Anyone who owns animals knows how much the price of feed has increased since the middle of 2012. For dairy farmers, figuring out how to feed cows and not go broke has been a real challenge. You're caught between the proverbial rock and a hard place, knowing that cutting back on purchased feed is almost a must, but realizing that if you do cut back, the milk revenue can quickly suffer much more than the amount of money you may save by reducing grain. Ask just about any dairy farmer and they'll all pretty much agree that if they could eliminate the grain bill, life would be a lot less stressful.

Getting cows to produce lots of milk on high-forage diets continues to be a challenge for the dairy industry. Cows certainly can produce impressive amounts of milk on high-forage diets when the forage is good and there's a consistent supply of it.

The most important factor to remember about high-forage diets is that forage is bulky and a cow is limited as to how much she can consume every day. Milk production is highly dependent upon feed intakes, meaning that the more a cow can eat, the more milk she tends to produce. High-forage diets tend to limit feed intakes, therefore limiting potential milk production.

The key metric for forage quality is the level of neutral detergent fiber (NDF). The more mature a forage is, the higher the level of NDF and the less digestible the forage is. As forage NDF (FNDF) increases in the diet, the cow's ability to ferment it in the rumen decreases. As fermentation is diminished, total energy coming from forage also diminishes. Research has shown that a cow can consume up to about 1 percent of her body weight as FNDF. A milk cow weighing 1,500 pounds will be limited to about 15 pounds of FNDF per day. (Some studies show that cows can consume as much as 1.5 percent of body weight.)

NDF percentages in forages (dry matter basis) tend to be in the 40s, 50s or 60s. Mature grass hay in New England nearly always measures greater than 60 percent NDF. Early-season grasses will be in the 50 percent range, and leafy alfalfa is down in the 40 percent range. Corn silage NDF levels generally average in the 45 percent range. These various NDF ranges will have a significant impact on how much forage a cow can consume and how much milk you can expect her to produce.

Another measure of forage quality is the NDF digestibility. The NDF digestibility varies greatly between forage types and also within forage types, depending on growing conditions. When sampling forages for quality, both an NDF value and an NDF digestibility value should be taken to get a complete idea of overall forage quality.

So the question is: Can a 1,500-pound Holstein produce, say, 70 pounds of milk on a straight forage diet? Her daily feed intake must be about 45 pounds of dry matter to meet both maintenance and milk production requirements. If the NDF level in the forage is 50 percent, that means the FNDF from that forage will be 22.5 pounds. That's 7.5 pounds more FNDF than the 1 percent of body weight that we said she was limited to. Therefore, this cow cannot consume enough dry matter in the form of all forage needed to support 70 pounds of milk per day.

From a practical standpoint, very few dairy farms in New England have access to forages with NDF levels in the 40 percent range, except for corn silage. Corn silage, of course, is problematic since it contains only half the protein required for milk production, as well as low levels of lysine, an important amino acid. Low-NDF grass and legume forages have much more protein and energy available for growth and milk production. It then behooves the dairy farmer to focus on growing or accessing grass and legume crop forages with low NDF levels.

When designing and implementing a milk cow ration that can maximize forages, first calculate the theoretical forage-fill for your cows. If you have access to hay, haylage and corn silage that averages 45 percent NDF (dry matter basis), you can feed about 33 to 35 pounds of dry matter with that forage. The remainder of the diet will have to be grains, byproducts and proteins necessary to meet nutrient requirements for the desired 70 pounds of milk production. However, if the forage changes and is suddenly over 50 percent NDF, this will have a dramatic impact on milk production if ration adjustments are not made.

The most significant challenge with forages is that they're constantly changing, and even if you do have some really high-quality forage, there's never enough of it. Both the dairy farmer and the nutritionist must be patient as they develop a feeding program that uses more forage. Forage must be analyzed more frequently. Dry matter intakes must be monitored more aggressively. You might have to buy a mixer box that can handle lots of forage.

It's always been a whole lot easier to compensate for changes in forage quality when you're feeding smaller amounts - that way the forage doesn't have as large of an impact on total nutrition in the diet. Grains and byproducts have done a good job of hiding and/or compensating for forage quality problems over the years. However, these days inexpensive byproducts have become about as scarce as a cheap cup of coffee.

There's no question that feeding higher-forage rations creates an opportunity for higher profits on dairy farms, with the current high grain prices. So long as physically effective fiber is not compromised in the ration, high-forage diets have been shown to improve rumen health, decrease cull rates, improve milk components, lower vet bills and decrease nitrogen release into the environment.

At the end of the day, the dairy farmer must determine if income-over-feed cost improves with changes in a diet or a feeding program. Every feedstuff must be evaluated on the basis of its cost and what it contributes to the diet and milk production. The key to implementing and maintaining a high-forage diet for dairy cows is understanding that forage production, forage inventories and herd diets will have to be managed much more aggressively.

The author is a dairy nutritional consultant and works for Central Connecticut Cooperative Farmers Association in Manchester, Conn.