Dairy cow behaviour and estrous expression : effects of disease and management

Management of modern dairy farms spend a considerable amount of time ensuring that every cow produces a calf every year, that all cows stay healthy. Despite these laudable goals, fertility and disease continue to be two of the major challenges facing the dairy industry. In this thesis I address both of these areas in an attempt to improve the health and welfare of dairy cattle and to aid farmers in the early identification of sick cows and identifying ways of improving fertility on their farms. My first aim was to assess changes in rumination and feeding behaviour associated with diseases common after calving (Chapter 2). The results indicate that monitoring rumination and feeding behaviour during the time around calving is helpful in the detection of cows with metabolic problems. The second aim focused on understanding how stocking density affects estrous expression and biomarkers of stress (Chapter 3). The results from Chapter 3 showed only mild effects of short-term exposure of lactating dairy cows to housing conditions where there is insufficient lying space for all cows to lie down at the same time, suggesting that many dairy cows are relatively resilient to short-term sub-optimal housing conditions. Lastly, I examined how standing and lying time, in general and around estrus, are affected by stocking density (Chapter 4). This chapter showed that even a short-term increase in stocking density to 133% (cow to stall ratio of 4:3) can have detrimental effects on the standing behaviour of healthy lactating dairy cattle and that individual standing times can be an indicator for the onset of estrus, particularly in understocked cows. In summary, this body of work shows how an improved understanding of behaviour can identify cows at risk for disease, that the choices made by farmers regarding how much lying space cows are given can affect standing and lying behaviour, and that changes in standing behaviour can be used detect estrus in dairy cows.Land and Food Systems, Faculty ofGraduat