Approximation of forage demands for lactating beef cows of different body weights and frame sizes using the Large Stock Unit

Author: M.C. Mokolobate, M.M. Scholtz, F.W.C Neser & G. Buchanan
Year: 2015
Issue: 1
Volume: 8
Page: 34 - 38

Producing efficient beef cattle in a commercial cow-calf enterprise is an issue of utmost importance. The rapidly increasing costs of feed as a result of effects of climate change and other inputs alongside with low market prices are responsible for a considerable and urgent need for cattle that utilize available resources more efficiently. Since the cow-calf production system in South Africa is largely extensive, it is important to find a standardized measure of feed intake in the sector. A measure, Large Stock Unit, with the official definition as the equivalent of an ox with a live weight of 450 kg which gains 500 g per day on grass pastures that have a mean digestible energy of 55%. To maintain this performance 75MJ metabolizable energy per day is required. This is similar to the Animal Unit used in North America. Tables with the feed requirements of cows of different weights and frame sizes were used to develop regression equations to estimate Large Stock Units. It is important to note that the Large Stock Unit equivalent of cows with the same body weight but different frame sizes is different. Furthermore, the relationship between cow weight and Large Stock Unit is not linear. For example, the Unit of a small frame cow of 450 kg is 1.32, whereas that of a large frame cow of 450 kg is 1.6. Similarly the 450 kg small frame cow will require 12 kg of grass per day and the 450 kg large frame cow 15 kg of grass per day, a difference of 25%. High stocking rates is a fairly general practice in South Africa, resulting in the overutilization of the natural resource. The information from this study can be used for the correct estimation of grazing capacity and stocking rates that will ensure sustainability of the farming enterprise, and thereby restoring or maintaining the rangeland biodiversity.

Keywords: Stocking rate
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