Preferred speed and cost of transport: the effect of incline.

This article investigates how the preferred speeds of trotting horses change when they’re moving on level ground compared to an inclined surface. The researchers observe that the horses’ preferred speed, which they define as a frequently preferred range within their full speed capabilities, drops slightly when they’re moving uphill. The paper also discusses how this behavior impacts the animals’ energy consumption.

Understanding Preferred Speed and Cost of Transport

• The article begins by defining preferred speed as the behavioral tendency of animals, specifically horses in this case, to use a set of speeds that is in the middle of their total speed capability. This term is important as it is crucial in understanding how horses expend their energy when trotting at different inclines.
• The paper then moves on to discuss the potential explanations for this behavior. It highlights two possible motivations – minimizing musculoskeletal stress and maximizing energetic economy. By changing their speed, the horses might exert less pressure on their skeletal structures and utilize their energy more efficiently.

Investigating Changes in Preferred Speed and Energy Consumption

• To investigate the changes in preferred speed, the researchers conducted an experiment where they made horses trot on level ground and an 11.8% incline. They observed that the preferred trotting speed dropped from an average of 3.29 m/s on level ground to an average of 3.05 m/s on the incline.
• They then measured the horses’ oxygen consumption at various trotting speeds on a treadmill to examine how their energy consumption changes with speed. They observed a curvilinear relationship, which means that their energy consumption rates rise and fall as their speed changes.

Implications of the Findings

• The findings confirm the hypothesis that changes in preferred speed result in changes in the cost of transport (C(T)), which is an indication of how efficiently an animal uses its energy.
• The experiment showed that the speed at which energy consumption was at its lowest was very close to the preferred speed on level ground. This minimum C(T) speed also decreased on an incline, closely mirroring the previously discussed decrease in preferred speed when moving uphill.
• These observations suggest that animals naturally adjust their speed to minimize energy consumption based on the conditions of their environment.