The effect of environmental factors and husbandry practices on stress in goats

Abstract

The welfare of animals is an emotional topic and even farm animal welfare is becoming more and more of relevance with a public consciousness on “How we treat the animals we eat”. Regardless the reason why goats are being kept, their wellbeing remains an important factor to ensure satisfactory results and production. Typical stressors such as transport, shearing, isolation and heat exposure are topics that have been extensively researched for its stress impact factor. Routine handling procedures used in the general management of a goat flock is not generally regarded as a form of abuse or stressful and very little researched has been conducted on it. These routine procedures do however have the potential to cause stress and especially short term stress in the goat. The effect of stress can be determined by the concentration of the corticoid hormone, cortisol, in the body. The aim of this study was to determine the serum cortisol concentration after routine handling procedures, heat exposure, food deprivation and water deprivation as well as the cumulative effect of these potential stressors in South African unimproved indigenous goats. A series of blood samples were collected at 0-; 15-; 30-; 45-; 60- and 90 minutes into a vacuum serum tube from the jugular vein after venous occlusion. Analysis of the serum was done by chemiluminescent enzyme immunoassay with the SIEMENS Immulite® 1000 automated Immunoassay Analyzer for quantative measurement of cortisol in serum. The experimental design was a completely randomized design with stressors as treatment and animals as replication. The data was analyzed as a one-way Analysis of Variance (ANOVA) with the repeated measurements over time as a subplot factor. The effect of four potential stressors; handling, exposure to heat, food deprivation and water deprivation, on the serum cortisol concentration have been investigated in this study. The results indicated a significant increase in circulating cortisol when animals were handled in contrast to environmental stressors that did not involve handling such as heat exposure and food and water deprivation, where the cortisol levels stayed below the basal level. This large and infrequent increase in circulating cortisol can modify the cell mediated immune response in such a way that the response to a specific antigen challenge is compromised rendering the goat susceptible to stress related diseases such as pasteurellosis and coccidiosis. Routine procedures such as vaccination and deworming are performed under typical commercial farming situations and are important for the maintenance of good health in the flock. It is not the handling as such that is a stressor but more so the way of handling. During this study the goats was subjected to repeated blood sampling without eliciting a stress response because the animals were gentled during the procedure. The correct and proper handling of goats during routine procedures needs to be promoted as an important part of disease prevention and it should enjoy the same attention as deworming, vaccination and dipping do. The relationship of elevated cortisol concentrations and stress related diseases need further research.