Effects of diet and weight gain on circulating tumour necrosis factor-α concentrations in Thoroughbred geldings.

This research study investigates the link between weight gain, diet and levels of systemic inflammation in horses. It specifically examines how different types of diet can influence the levels of a particular inflammatory protein, tumour necrosis factor-α.

Study Design

• The study involved fifteen mature Thoroughbred geldings (neutered male horses) with an average initial weight of 519±12 kg and a body condition score (a visual and palpable assessment of an animal’s body fat and muscle mass) of 4.3±0.1.
• The horses were then divided to consume two types of diets: one that was high in non-structural carbohydrates (basically starch and sugar, similar to commercially available horse feeds), labelled as ‘CON’; and the another one where the energy source was replaced with fat and fibre, labelled as ‘FAT’.
• These diets were provided for 32 weeks. Within this period, excess calories (20 Mcal/day) were fed to promote weight gain.
• Whilst gaining weight, the horses were also subjected to light exercise – exercised twice daily at a walk.
• The horses’ weight and body condition score were monitored every two weeks. Blood samples were also taken every four weeks to assess circulating levels of tumour necrosis factor-α (also known as TNF, an inflammatory protein in the blood).

Findings

• The horses began the study with similar mean serum TNF concentrations. However, after 12 weeks of consuming the FAT diet, a decrease in circulating TNF was observed. This was generally maintained throughout the study, except at weeks 20 and 32.
• There was no direct correlation found between serum TNF concentration and body condition score as horses gained weight; this was true for both diet groups.
• Horses on the CON diet had higher TNF levels, suggesting increased systemic inflammation independent of weight gain.

Implications and Further Research

• The study indicates that diet influences the levels of inflammation in horses – the fact that the CON diet led to increased TNF implies a heightened state of systemic inflammation, not directly tied to changes in weight.
• Further research needs to be carried out with horses that are fed to maintain body condition rather than to gain weight, to better understand the various influences of diet on inflammation levels.