Proper macronutrient management is critical for livestock nutrition
When thinking about and developing livestock nutrition programs, producers should bear macronutrients in mind.
Macronutrients are, by definition, nutrients required in large amounts. When looking at livestock nutrition, water, energy and protein are essentials.
Water
Dr. Shane Gadberry, ruminant nutrition specialist with the University of Arkansas Cooperative Extension Service, explained that water is essential and required in large amounts, but often taken for granted because livestock often have free access from a pond, tank or stream.
If animals are not drinking enough water, either due to an insufficient supply or a contaminated water source, their feed intake, productivity and overall health will rapidly decline. According to the Noble Research Institute, a beef cow can drink up to 5 percent of its body weight per day; a high-producing dairy cow, up to 20 percent.
Energy
Energy is a vital macronutrient that is responsible for an animal’s health, maintenance and productivity. The amount of this macronutrient in livestock feedstuffs is derived from total digestible nutrients (TDN) found in fat and carbohydrates.
“Cattle get the majority of energy in the diet from carbohydrates, primarily fiber,” according to Dr. Eric Bailey, Beef Cattle Nutrition Extension Specialist with the University of Missouri Extension.
Since fiber and forage provide a great deal of energy, the quality of the forage animals are eating should be determined and addressed. Knowing the forge quality and the amount of energy it is providing will ensure that animals get enough of this macronutrient year-round.
“Energy deficiencies often occur in winter because stored forages can be low in energy while production and environmental conditions ramp up energy needs during this time,” Gadberry said.
Protein
According to Gadberry, while protein also contributes to energy like fat and carbohydrates, it is also considered independently since its components are important for microbial proliferation in the rumen.
“The combination of feed protein and microbial protein for ruminants take care of protein turnover in maintenance along with protein deposition in growth and fetal development,” he said.
Again, producers need to consider the amount of the macronutrient in the forage they are feeding. Fescue hay often has adequate protein.
“Tall fescue hay is unique relative to other forages used for hay in that energy is often limiting, but not protein,” Bailey explained. “Many of you have heard or seen article after article encouraging feeding supplemental protein to cattle when feeding hay. There is a lot of poor fescue hay put up around this state with 8 to 10 percent crude protein, which is not significantly limiting to cattle, depending on their stage of production (lactation, pregnancy, etc.). The reason protein supplementation is talked about frequently is that in warm-season forage systems, hay crude protein will commonly drop below 6 percent. When forage crude protein gets that low, it slows the rate at which rumen microbes ferment feed. When the rate of fermentation slows, feed stays in the rumen longer and they eat less overall.”
Putting It All Together
Livestock water supplies should be evaluated to ensure proper water intake. If producers suspect a contaminated water supply, testing should be done right away to determine the contaminate and a course of action. To ensure enough consumption of protein and energy, producers need to evaluate the levels of both, because if the amount of macronutrients in the nutritional program is found to be lacking, producers will need to provide an appropriate supplement.
“Assessing forages for nutritive value is very important as these conditions vary from farm to farm,” Gadberry said. “If the goal is to feed livestock to a target level of production, it is important to both understand nutrient requirements and nutrient supply. Putting the two together can help determine if and what is most limiting.”
County extension agents can assist producers with forage testing, analyzing feedstuffs for nutrient composition and interpreting results.
