Dairy calf raisers and researchers are widely and collectively embracing the concept of maximizing early life nutrition to raise the most productive herd replacements. But how do you determine the correct recipe to do that precisely?
Cornell University Dairy Extension Specialists Margaret Quaassdorff and Casey Havekes shared a mathematical path with Calf-Tel to calculate calves’ nutritional needs to achieve growth goals.
They noted a common goal in the industry is to achieve a doubling of calves’ birth weight by 60 days of age. It’s a goal that’s doable, but it also requires an intentional effort in nutrient delivery.
Quaassdorff and Havekes noted that calves’ nutritional intake falls into two camps: maintenance, which is the baseline level of nutrients to keep the calf alive; and growth, which are the excess nutrients available to build tissue and add weight and stature growth to the animal.
Their calculations for necessary Metabolizable Energy (ME) require knowledge of the calf’s bodyweight (BW) and desired average daily gain (ADG) to hit growth targets.
Theinitial formula to determine a calf’s maintenance needs is:
MEmaintenance Mcals = 0.1 X BW (kg)0.75
Then, the additional nutrients required to achieve desired growth can be calculated with this formula:
ME growth Mcals = [0.84 X BW(kg)0.355 X (ADG(kg/day)1.20]
The results of both of these formulas are then added together to achieve the total daily energy requirement. For example, the first calculation (maintenance) for a calf weighing 41 kg (about 90 pounds) would be 1.61 Mcals of metabolizable energy per day.
With a desired growth goal of 0.8 kg/day, that same calf would need an additional 2.40 Mcals of metabolizable energy daily, for a sum total of 4.01 Mcals ME daily. It should be noted that these formulas are metric based, so conversions from pounds to kilograms, for example, should be made before doing the calculations.
Once the target metabolizable energy is known, the actual liquid ration formulation can be made. Most milk replacer formulations will have an energy value of about 4.2-5.0 Mcals/kg of dry matter. Holstein whole milk will have about 5.3 Mcals.
For example, a 28:20 milk replacer might supply 4.74 Mcals ME/kg DM. The 4.01 requirement should be divided by 4.74 to determine the amount required to meet 4.01, which would be 0.85. So, the calf would need 0.85 kg (1.88 pounds) of this milk replacer per day to meet both maintenance and growth goals.
It’s important to note that maintenance requirements go up in cold conditions – about 0.03 Mcals ME for each degree Celsius below the calf’s thermoneutral ambient temperature of 15°C.
That may not sound like much, but if the temperature drops to 0°C (freezing), that’s a 15-degree swing, creating a need for a additional 0.45 Mcals ME, which need to be added to the maintenance value. Otherwise, much of the “extra” energy provided for growth will be used up just keeping the calf alive.
A nutritionist or milk replacer supplier can assist with these calculations. Pinpointing exactly what calves need can result in beneficial and efficient growth, and in some cases produce cost savingsby avoiding overfeeding of nutrients.
