Abstract:
The accurate estimation of livestock weights
is important for many aspects of livestock management
including nutrition, production and appropriate
dosing of pharmaceuticals. Subtherapeutic dosing has
been shown to accelerate pathogen resistance which
can have subsequent widespread impacts. There are a
number of published models for the prediction of live
weight from morphometric measurements of cattle, but
many of these models use measurements difficult to
gather and include complicated age, size and gender
stratification. In this paper, we use data from the Infectious
Diseases of East Africa calf cohort study and additional data collected at local markets in western
Kenya to develop a simple model based on heart girth
circumference to predict live weight of east African
shorthorn zebu (SHZ) cattle. SHZ cattle are widespread
throughout eastern and southern Africa and
are economically important multipurpose animals. We
demonstrate model accuracy by splitting the data into
training and validation subsets and comparing fitted
and predicted values. The final model is weight 0.262 =
0.95 + 0.022 × girth which has an R2 value of 0.98 and
95 % prediction intervals that fall within the ±20 %
body weight error band regarded as acceptable when
dosing livestock. This model provides a highly reliable
and accurate method for predicting weights of SHZ
cattle using a single heart girth measurement which
can be easily obtained with a tape measure in the field
setting.
