Knowing how much forage your pasture produces combined with how much food your animals eat can tell you how many animals they can sustainably raise, according to the National Grazing Lands Coalition.
Levi Trubenbach, Ph.D, nutritionist with the Livestock Nutrition Center, is often asked: “How much should I be feeding my cows?”
“It is a valid question with meaningful tradeoffs,” he says. “On one hand, we want to minimize the largest variable cost in a cow-calf business, while, on the other hand, we yearn for maximum reproductive efficiency. The truth is finding yourself on either side of this delicate balance can have profound impacts on financial performance.”
- Defining Nutrient Requirements – The first step in designing any cow supplementation program is to define nutrient requirements. The first question Trubenbach asks is, “What stage of production are they in?” Generally, what we need to know is an average timeframe during which cows are expected to calve, rebreed and wean a calf so we can estimate nutrient requirements through the current or future months. Immediately after calving, milk production increases demands for nutrients beyond basic maintenance needs. Approximately eight weeks post-calving, milk production peaks, declining slowly until calves are weaned. In a typical production system, cows rebreed approximately 80 to 90 days after calving, resulting in additional nutrient demands for fetal and maternal support tissues. While gestational nutrient requirements are relatively low during the first two trimesters, these requirements increase exponentially during the last two months of pregnancy. At peak lactation, protein and energy requirements can be 80% to 100% greater than the period immediately following weaning.
- Estimating Nutrient Intake – Step two is determining nutrient intake, which is determined primarily by forage quality in two ways: its effects on dry matter intake and its relationship with nutrient concentrations. In general, the higher the forage quality, the more cows will eat of it, and the more nutrients are supplied per unit of intake.
- Nutrient Balance – Once we have defined nutrient requirements and estimated supplies, the final step in our process is to calculate nutrient balance, which is nutrient supply less demand, with a negative balance suggesting deficiency and a positive value representing excess.
Learn more from Trubenbach on this topic at the Livestock Nutrition Center. Also, download the Forage Consumption Estimates to find out how much an animal should eat per day, month and year. Figures are based on a daily air-dry matter intake of 2.2 to 3 percent of body weight, depending on the nutritional demands for the type and class of livestock and wildlife. Wildlife values are based on the nutritional needs of average-sized breeding females.