3/19/2023 0 Comments Animal unit calculatorManagement practices such as rotational grazing versus season-long grazing, pasture water systems or higher stocking densities may be used to increase forage consumption and minimize forage losses due to factors such as trampling and spoilage. ![]() As a result, the total forage disappearance on pasture will exceed the daily forage intake values listed in Table 2. Weathering and forage senescence (aging) can also contribute to forage losses on pasture. Animals will trample and spoil feed as they travel throughout a pasture. Other factors such as animal age, physiological stage (dry, lactating) or supplementation level will also affect the level of pasture consumption.įor a more accurate stocking rate, adjustments should be made for both forage consumption and for other losses that occur within a grazing system. Forage growth in extensive grazing systems will provide more mature forage and, therefore, a lower level of forage consumption. ![]() Typically, early season growth or forage re-growth in managed grazing systems will provide the highest quality and, therefore, higher consumption rates. * 10 lb of milk supplies about 25% of the energy needed for daily gain of 2.0 lb per day in a 300 lb calf Table 2 Calculating AUM (nutrient requirements of beef cattle, 1996)Īverage 1,000 lb cow producing 10 lb milk per dayĮxtra energy needed by the calf from grazing* As a result, anticipate a higher level of forage intake in pastures composed of primarily vegetative growth versus more mature growth. As forage plants mature, digestibility decreases. One of the main factors that affects consumption rates is forage quality. However, in pasture environments forage consumption rates can vary from as low as 1.5 per cent of body weight to as high as 3.5 per cent of body weight. Animal Unit Equivalent (AUE) based on metabolic weight (live animal weight 0.75).Īnimal unit equivalent yx 0.75(% of 1,000 lbs)Īs shown in Table 2, the definition of the AUM provides an estimate of forage consumption to meet the metabolic requirements of cattle while on pasture. Rather, the requirement changes at a different rate than does the animal weight. Table 1 from the Dickinson Research Extension Center, North Dakota State University, shows that the change in metabolic requirement is not linear in relation to the weight of the animals. Therefore, cows in the 1,200 to 1,400 pound weight range would be equivalent to from 1.11 to 1.21 of the basic Animal Unit. The larger calves consume proportionately more as well. Cows in this weight range need from 23.0 to 25.6 pounds of DM, or 14 to 27 per cent more than the 1,000 pound cow. The Animal Unit does not accommodate the change in frame size of cattle where most crossbred beef cows weigh from 1,200 to 1,400 pounds. These aspects must then be considered along with the forage production and desired residue levels on the land. To establish accurate stocking rates, adjustments must be made to this basic definition of an AUM to arrive at reasonable forage disappearance rates, which include consumption levels, trampling and wastage by the cattle. These are equivalents established by the discussions of various agencies specializing in range management. For example, a mature bull is the equivalent of 1.3 AU, a yearling steer or heifer is 0.67 AU and a weaned calf is 0.5 AU. ![]() Various other types of stock are assigned AUM equivalents based on size and consumption. It is assumed that such a cow nursing her calf will consume 26 pounds of dry matter (DM) of forage per day (20 lbs for the cow and 6 lbs for the calf). The quantity of forage needed is based on the cow’s metabolic weight, and the animal unit is defined as one mature 1,000 pound cow and her suckling calf. Animal Unitsīy definition, the AUM is the amount of forage needed by an “animal unit” (AU) grazing for one month. Such an understanding can help in determining stocking rates to produce the maximum returns without causing damage to the available grassland resources. To get the best production from the grass resource, it is important to understand how the AUM is defined.
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