Necessary forage requirements for dairy cattle and their nutrient needs will depend on the lactational stage of the cow. “On well-managed pasture, a mature lactating cow can consume more than 40 pounds of dry matter in forage in a day,” said Dr. Andrew Fidler, instructor for the Department of Animal Sciences at the University of Arkansas. “Even with that amount of intake, however, the cow may not be ingesting all the nutrients required to maintain body condition and fertility in the face of high milk production. Energy in the form of easily digestible carbohydrates is usually the limiting factor, and is most often provided in the way of supplemental grain by most American dairy grazers.”
When all cows are fresh and producing higher amounts of milk, cattle will need higher quality forage. “Milk cows need as much quality and nutrition as possible,” said Ted Probert, southwest regional dairy specialist for the University of Missouri. “The best way to provide this is through rotational grazing and managing forage quality.”
Producers must provide forage that the cattle will consume readily in the quantity sufficient to meet the nutritional needs. Probert also added that the fiber level will increase as forages mature, especially when seed heads are produced. As fiber levels increase, forages become less digestible.
Cool-season forage species’ provide most of the nutrient needs for animals’ however as we enter the summer months we recommend adding a warm-season component such as sorghum-sudan, millet or crabgrass to supplement growth and availability of quality forage, Probert added.
It is also essential to remember that fiber content varies widely in pastures throughout the year. “During heavy spring growth, effective fiber content may be too low and cows may benefit from supplemental hay or high-fiber byproducts,” Fidler said. “Many minerals, with the exception of Potassium (K), will probably also be too low, and should be supplemented to cows on pasture.”
Forages need to be harvested in their vegetative state, via cow or machine, and usually 6-8 inches in height depending on species. “This maximizes the carbohydrate and protein content of the forage,” Fidler said.
Rotational grazing helps to allow the forages to reach the greatest potential of quality and quantity by allowing for regrowth before cattle have the opportunity to graze it.
There are a lot of variables in the role of managing pasture to achieve optimal quality and quantity – pasture species, weather, soil, fertilization, grazing pressure and etc. Fidler said, “Knowing when your pasture species is at it’s maximal nutritional quality is the important thing, and knowing how to get it there, let the cows harvest it, and then getting it back to that point, that’s the ‘art’ of it.”
