Epsilon Open Archive

Abstract

This thesis describes the effects of forage-only and forage-oats diets, different levels of crude protein intake, road transport and different housing systems on body weight, fluid shifts, metabolic response and exercise response in trained Standardbred horses. A total of 28 horses participated in the research.

Body weight was significantly higher on the forage-only diet (mean 496 kg) than the forage-oats diet (mean 492 kg) in one study, but a 12 h feed deprivation period diminished the small increase in body weight on the forage-only diet. The forage-only diet resulted in lower plasma protein concentration, indicating greater potential to use an internal fluid compartment to maintain plasma volume. In another study assessing these two diets and transportation, there were no differences between the diets (forage-only 502 kg, forage-oats 501 kg). There was also no effect of high crude protein intake (160% of recommended level) on response to exercise, but the intake was high enough to increase plasma urea. High protein intake also increased water excretion through faeces and urine and thereby exerted an unnecessary load on the racing horse. Overall, the forage-only diet decreased exercise-induced effects on extracellular fluid regulation.

Aerobic energy supply was elevated during exercise following a period of road transport and forage-only diet further increased the usage of fat (acetate) as energy substrate. However, this positive effect on aerobic energy supply needs to be studied further in terms of transport timing and duration, in order to confirm whether this can be used as an efficient part of pre-race preparations

It was found that keeping the horses in an active group housing system had positive effects on appetite and recovery of energy balance and post-race joint swelling compared with housing in a conventional box stall system.

In conclusion, this thesis demonstrates that a forage-only diet and a free-range housing system are good management options for racing Standardbred horses and can form part of a sustainable horse management system that supports performance, health and animal welfare.