TeamMate : a longitudinal study of health in working farm dogs on the South Island of New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Epidemiology, School of Veterinary Science, Massey University, Manawatu, New Zealand
Working farm dogs are crucial to the smooth running of sheep and beef farming operations in New Zealand, with specific types of dogs having been developed that are uniquely suited to the conditions of the country. Despite their importance to the economy of New Zealand, few studies have been carried out to examine health and welfare in these dogs, and none have examined the occurrence of new cases of disease or risk factors related to death, euthanasia or retirement.
This thesis presents data from the TeamMate project, which was a longitudinal study of health in working farm dogs on the South Island of New Zealand. The study was designed to supplement and fill gaps left by previous studies and ran from early 2004 to late 2018, collecting data during five data collection rounds. In total, data from 1930 examinations of 641 working farm dogs were collected, with 124 dog owners and staff from 11 veterinary clinics involved. Data was collected through clinical examinations of dogs carried out by veterinarians, and by asking dog owners to provide information about husbandry and workload pertaining to each dog. The data was used to produce four research chapters, each of which focused on a different aspect of health in working farm dogs.
The first research chapter detailed the study design and methodology of the TeamMate study and reported on population data, husbandry practices and prevalence of clinical abnormalities recorded on dogs’ enrolment to the study. Dogs were enrolled if they were at least 18 months old and in full work on farm. The data on population and husbandry largely confirmed previous research, with an almost even mix of the two most common types of dogs (Heading dogs and Huntaways) and males and females. Dogs found to be generally lean, were usually fed a combination of meat and commercial dog food and were housed in outdoor kennels. Clinical abnormalities defined as any abnormality irrespective of clinical significance, were recorded in 74% of dogs. The most common abnormalities involved the musculoskeletal system (42% of dogs), skin (including scars and callouses; 42%) and oral cavity (including worn and broken teeth; 35%).
The second research chapter investigated whether conventional body condition scores (BCS) are appropriate when applied to lean, athletic dogs such as working farm dogs, which they have been poorly validated for. BCS was found to be correlated with a predicted measure of body fat mass, but the effect was too weak to be useful for indicating meaningful differences in body condition between dogs. The ratio of the predicted lean body mass to skeletal size has been proposed as an alternative to BCS when assessing body condition in lean, athletic dogs such as working farm dogs. However, the equation used to predict lean mass in working farm dogs was developed using only 20 dogs and not been validated on a new set of dogs with known lean mass. Both BCS and the lean mass ratio should be validated for use in lean athletic dogs, and further investigation should be carried out to determine whether they are associated with health outcomes in working farm dogs.
The third research chapter focused on the occurrence of new instances of musculoskeletal abnormalities in 323 working farm dogs that were disease-free on enrolment to the study and had at least one follow-up examination. During the follow-up period, 184 dogs (57%) developed at least one musculoskeletal abnormality during 4,508 dog-months at risk, corresponding to approximately 4 dogs with recorded abnormalities per 100 dog-months at risk. Abnormalities in the hip and carpus were the most commonly observed. Two-thirds of dogs that experienced a musculoskeletal abnormality were observed to have a second abnormality. No major differences were observed between sexes or types or dogs. Considering the high prevalence and incidence of musculoskeletal abnormalities in this population, further research into the impact of musculoskeletal disease on the health, welfare and working ability of working farm dogs is strongly recommended.
The fourth and final research chapter investigated the factors that affected dogs’ risk of being lost from the workforce. Data was included from 589 dogs where information was available on whether or not the dog had died, been euthanised or been retired from work. Eighty-one dogs (14%) were lost during the course of the study, the majority of which had died or been euthanised. A multivariable logistic regression model was used to estimate the risk dogs dying, being euthanised or being retired from work. After accounting for age, the presence of lameness was found to have a significant effect on the risk of loss (P = 0.04, odds ratio (OR) = 1.9). This study expands our knowledge about the impact of clinical abnormalities on the overall health of working farm dogs. Further research into the underlying issues that cause lameness in these dogs should be prioritised.
The results of this study can be used to inform and prioritise further research, and will contribute to an increased understanding of how to ensure optimal health, welfare and working ability in working farm dogs.