A study of the behavioural and physiological responses of the dairy cow (Bos taurus) to selected environmental features of the milking facility

Field: Agricultural and Biological Sciences (Life Sciences)

In general, the environment of milking facilities during routine milking activities exposes animals to a range of, potentially fear-provoking stimuli. This interaction between the environment and the animal is not always acknowledged in the design of milking facilities, or in animal handling practices, and consequently the behaviour, welfare and productivity of dairy cows may be compromised. In addition, the efficiency of animal handling and operator comfort during milking may also be adversely affected. This study examined the fear responses of dairy heifers to environmental stimuli that are commonly present in conventional milking facilities. Specifically, the behavioural and physiological impact of selected visual and auditory features of the milking facility environment was investigated. A critical requirement for this research was the development of rigorous methodologies to measure fear responses.\n\nTwo methodological techniques were used: aversion learning tests and preference tests. In each case, specific methods were developed that enabled measurement of those behaviours and responses most likely to impact upon efficiency of animal handling during milking, productivity, and the welfare of the animal. These included movement and avoidance behaviours, ease of handling, heart rate and cortisol concentrations. In addition, factors that were expected to affect these responses, such as learning (including past experiences) and social contact, were accommodated in the methodologies.\n\nUsing these methodologies, a range of experiments were conducted that assessed the behavioural and physiological responses of dairy heifers to each of the following environmental features: shadows, noise recorded from a conventional milking facility (85dB), confinement with visual restriction, the milking pit in a herringbone facility (visual cliff), and consistent and inconsistent floor contrasts. Results indicated that the noise stimulus was the most aversive for heifers, with increases in heart rate accompanied by prolonged increases in speed of movement, consistent with escape behaviour. When given the choice, heifers chose to avoid exposure to the noise. Exposure to the milking pit caused increases in heart rate and avoidance behaviour, with habituation of behavioural but not heart rate responses. Increases in heart rate were also observed during exposure to confinement with visual restriction, which were accompanied by reluctance to enter the confinement area, although this did not translate into a preference to avoid the visual confinement when given the opportunity. There were substantial habituation effects on both behavioural and heart rate responses. Exposure to changes in flooring contrasts also caused increases in heart rate, however there were no accompanying changes in behaviour, indicating that the heart rate response may have been a result of increased exploration, rather than a fear response.\n\nFrom these results it was concluded that of the stimuli examined, noise was the greatest stressor, however visual restriction during confinement, and exposure to the milking pit were also sufficiently fear-provoking to affect physiological stress indicators and to negatively impact on animal movement behaviours. The results of these experiments provide some information about individual animal responses to a range of environmental stimuli that are common in most conventional milking systems. In addition, the methodologies developed throughout this study provide a valuable assessment tool to benchmark environmental features of animal facilities and handling practices, that can assist in the design and planning of new and existing animal systems.