The aim of this work was to improve and validate the Oxylog portable
oxygen consumption meter for use with draught ruminants, and to test its
ability to estimate the energy expenditure of these animals in the field.
Few data were available on the energy costs of the various tasks that
draught ruminants perform and it was expected that the calorific factors
established during laboratory experiments may not necessarily reflect the
energy consumption during field work with farmers. This could have
important implications in the establishment of the nutritional requirements of
A review of the literature on the various techniques and instruments
available for the field measurement of energy consumption was carried out.
A new facemask for use with the Oxylog was designed and the Oxylog
equipment with this mask was validated against the open circuit gas analysis
system available at the Centre for Tropical Veterinary Medicine in Edinburgh.
It was found that the Oxylog, on average, overestimated oxygen consumption, as measured by the gas analysis system, by 1.5 %.
In the second experiment, carried out with buffaloes and oxen pulling
carts on the Unipalma oil-palm plantation in Meta, Colombia, the modified
Oxylog system was tested in the field. Technically, the method worked satisfactorily, although the small digital displays on the Oxylog were difficult to
read, and the measurements obtained generally agreed with the more established calculation methods of estimating energy consumption. It was concluded that the use of the modified Oxylog was an accurate and reliable
method for the estimation of energy expenditure in the field. Insufficient
time, however, was available to train the animals to wear the facemask and to
accustom them to the experimental procedures, hence, the acceptance of the
mask was low. The use of a constant value for the energy cost of walking
over various terrains and the difficulty in accurately defining the animals'
respiratory quotient, were also thought to have affected the results.
In the third experiment, the influence of soil consistency on the energy
cost of walking and the efficiency of working in Bunaji (Bos indicus) draught
bulls in the sub-humid zone of Nigeria was investigated. These experiments
were carried out in collaboration with the International Livestock Centre for
Africa. A dataviewer was designed to facilitate data collection. To ensure
that the respiratory quotient only varied between 0.8 and 1.0 the animals were
fed 3 kg of concentrates, 1 h before the start of the experiments so that they
were primarily metabolising carbohydrates. Eight experimental animals were
trained over a period of four weeks and the mask acceptance rate was 100 %.
The energy cost of walking on the different soils varied from 1.47 J/m/kg to
3.30 J/m/kg. Ploughing doubled or more than doubled the energy cost of
walking on the soils investigated. Although the consistency of the soil did not
influence the efficiency of doing work, both the speed of walking and work¬
ing, and the distance average draught force were affected. A simple method
to estimate the energy cost of walking based on the speed of walking on soils
of different consistencies was proposed. It was further established that it
would be more efficient to cultivate soils before they became inundated with
water, because as they became wetter more time, effort and energy were
needed for cultivation per unit area.
It was concluded that the modified Oxylog, although its use will be
largely restricted to trained animals being investigated by research organisations, is a useful and reliable tool in draught ruminant field calorimetry.