NZERF Research Grants in 2004

PROGRESS REPORT: AN INVESTIGATION OF STIFLE AND HOCK OSTEOCHONDRITIS DISSECANS (OCD) DEVELOPMENT IN THE NEW ZEALAND THOROUGHBRED
Dave Keenan
Matamata Veterinary Services

The New Zealand thoroughbred industry relies heavily on the successful breeding and selling of young stock to international and domestic markets. The ultimate measure of success of New Zealand Thoroughbreds is success on the racetrack

Lameness is the most common reason for wastage (and lack of success) in thoroughbred racehorses worldwide. Osteochondritis dessicans (OCD) is common in the thoroughbred population and is an important contributor to lameness and therefore wastage. Consequently, it is now international protocol for horses to undergo radiographic examination prior to both private sales and public auctions (a radiograph repository system has been in place at NZ yearling sales since 2003 and is now in place for weanling sales also). The presence of radiographic evidence of OCD lesions is deemed detrimental to the future racing career, and to the saleability, of the individual.

There is no data available on the developmental patterns or risk factors associated with OCD in Thoroughbreds. Therefore, it is in the interests of the NZ thoroughbred industry to investigate the dynamics of OCD in the developing foal in order to identify risk factors and to be aware of the normal developmental patterns of the disease. This study aims to provide a better understanding of how such lesions develop and/or regress. This will enable us to offer management strategies to breeders in order to minimise the disease.

i.e. the objectives of the study include identifying management factors, which may predispose yearlings to having OCD lesions when presented at yearling sales.

FURTHER DEVELOPMENT OF A SIMPLE NON-INVASIVE METHOD FOR ASSESSING STRESS IN HORSES
Professor Cliff Irvine
Lincoln University

The aim of this project is to develop a way to assess the stress levels of horses by measuring the concentrations of the stress hormone, corticosterone, in faeces. During stress, the adrenal gland releases cortisol and corticosterone into the bloodstream. These hormones are then excreted in urine and faeces unchanged and in several metabolised forms. In a previous project, funded by the Equine Research Foundation, we began evaluating a commercially-available corticosterone assay kitset for measuring stress hormone metabolites in horse manure. The initial results were very promising and this project is intended to complete the validation of this assay method. Specifically, we are investigating: (a) the homogeneity of distribution of corticosterone within and between faecal balls, and (b) the time course of the increase in corticosterone in faeces after an acute rise in secretion into blood. This information is important because it will (a) tell us how much manure needs to be sampled to get a representative result and (b) enable us to relate changes measured in faecal corticosterone to the experiences of the horse.

MICROBIOLOGY OF THE INTENSIVELY MANAGED EQUINE – WHAT MICROBES ARE RESPONSIBLE FOR ACIDOSIS?
Dr. Simon Hoskin
Massey University

Horses evolved to eat large quantities of low quality grasses (high fibre and low digestible energy). In modern equine management we commonly feed large quantities of grain to meet the energy demands of the racing or competition horse. Often part of the grain is not digested in the stomach and is fermented in the horses hindgut by microbes such as bacteria. This fermentation produces a highly acidic hindgut (acidosis), which is a digestive disturbance that has serious consequences for the health, performance and well-being of intensively managed equine athletes. Acidosis can contribute to laminitis, colic and azoturia (“tying up”).

In cattle, gut acidosis occurs in the rumen (forestomach) and is initiated largely by the bacterium Streptococcus bovis which rapidly ferments soluble carbohydrates to lactate leading to acidosis. This starts a chain reaction allowing rapid growth of other lactate-producing bacteria and even more acid is produced. It is thought that similar events occur in the equine hindgut and that Streptococcus bovis is probably also the initial culprit. However, almost nothing is known about the bacterial population of horses grazing pasture in New Zealand and how the bacterial population in the hindgut changes in the transition to a grain-based diet. Gaining this knowledge will allow further studies to identify possible mechanisms for controlling growth of “bad” bacteria that cause acidosis and identifying animals that are at risk of developing diseases such as laminitis.

This project aims to identify what bacteria are present in the hindgut of NZ pasture-fed horses by the use of both microbiolgical and molecular-based techniques and to determine how the populations and species of bacteria changes as inputs of grain are increased. This will be based on collection of faecal samples, so the first step is to confirm that bacterial counts obtained from faecal samples are representative of the bacteria present in the caecum and colon.