The aim of this thesis was to assess the influence of genotype and management on the health, welfare and fertility of dairy cows in pasture-based milk production systems. Hence, the effects of genetic selection for improved fitness using the Irish Economic Breeding Index (EBI) was evaluated in terms of dairy cow behaviour, health, immune function and reproductive performance (experiment 1). Additionally, a typical Irish pasture-based system was compared to one in which cows were kept indoors in cubicles and fed a total mixed ration for the duration of lactation in order to elucidate the perceived benefits of pasture-based systems for dairy cow welfare (experiment 2). Similar measurements were used as for experiment 1. High EBI cows had better locomotion, fewer cases of clinical lameness and less severe hoof disorders than low EBI cows. Results from the first experiment also indicate that selection in contrasting environments and/or breeding goals play a role in the expression of immuno-physiological mechanisms of dairy cows; in addition it may reflect an innate energy conserving adaptation to survival in pasture-based environments. Thus, these effects should be considered when breeding cows in pasture-based systems. The second experiment, showed that a pasture-based system facilitated better expression of behaviour (e.g. lying time) and had a positive impact on the welfare of cows by reducing the severity of hoof disorders and the risk of lameness thus resulting in an overall improvement in locomotion ability. Furthermore, although pasture-based cows were at greater risk of nutritional/metabolic stress, they were in a less intensive system resulting in reduced energy output (e.g. milk production). The ability of the cow to monitor her biometric status in the early lactation period allows a readjustment in milk energy output such that energy intake from pasture is adequate for milk production as well as maintaining the health, fertility and welfare status of the cow. Overall, while pasture-based milk production systems are considered to be more welfare-friendly than ones in which cows are housed for the majority of the production cycle this, is based on certain provisions. These include the cows have been selected for and in a pasture-based enviroment. The findings of this thesis could strengthen the potential competitive advantage Irish dairy producers will have over their European counterparts, should legislation be created to ensure access to pasture for dairy cows.
|Translated title of the contribution||The influence of genotype and management on health, welfare and fertility of dairy cows in pasture-based milk production systems|
|Number of pages||167|
|Publication status||Published - 2008|