Livestock owners often need to know the weight of their animals in order to determine proper feed rations, to adminster the proper dosage of a medication, or to track how individual animals grow and use their feed. Approved and properly calibrated livestock scales are the most accurate and consistent method for determining body weight. However, there are several methods that can be used to determine an animal’s weight when access to scales is not possible: visual observation or guessing, weigh tapes, and weight estimation formulas.
Visual observation is usually very inaccurate and not recommended for use when determining rations, medication dosages, or when an accurate weight is important.
Weigh tapes are specially marked tapes used to measure the heart girth and convert that measurement to a fairly accurate estimate of the animal’s body weight. Weigh tapes are easy to use and can be utilized effectively for monitoring purposes when used in a consistent manner by the same person. They can be purchased for cattle, sheep, goats, hogs and horses through various livestock supply companies.
With weight estimation formulas, a common tape measure is used to determine the heart girth and body length measurement. These measurements are then used to calculate the animal’s weight. The weight estimation formulas described below are usually more accurate than a weigh tape and almost always more accurate than visual observation in determining an animal’s weight.
Measure the length of body, from the point-of-shoulder (A) to the point-of-rump or pin bone (B).
Measure the circumference or heart girth (C). Measure from a point slightly behind the shoulder blade, down the fore-ribs and under the body behind the elbow all the way around. After these measurements are made in inches – use the following formula.
(Heart girth X heart girth X body length) ÷ 300 = weight in pounds.