Measures of behavioural reactivity and their relationships to carcass and meat quality in sheep.

Abstract

The ability to measure behaviour and knowledge of the relationships between temperament, stress and productivity in livestock can be utilised in improving livestock production systems, minimising stress and maximising ease of handling and efficiency of production. This research aimed to further the understanding of behavioural reactivity in sheep and investigate links between reactivity, carcass composition and meat quality. This was achieved with a combination of experimental trials and interviews of livestock transporters. Evidence to support the concept of temperament and behavioural reactivity was gathered across the studies. Repeatable differences between sheep were demonstrated, with moderate to strong correlations between some behavioural tests and links between reactivity and physiological indices of stress. Heritability estimates of up to 0.20 were reported; combined with significant breed effects on reactivity this provides evidence of an inherent genetic component of behavioural reactivity. Sheep experience was rated as very important by livestock transporters. Age and experience, although confounded, also appeared to be important in the experimental trials. Older, more experienced lambs were less reactive and their behaviour more repeatable than when measured at a younger age. Although all of the behaviours investigated contributed to overall reactivity, restrained and unrestrained tests are only weakly correlated, indicating that these tests measure distinctly different components of behaviour. A consistent finding in the literature review and experimental chapters was greater reactivity in ewes compared to wethers, although livestock transporters indicated that sex was of minimal importance and ewes and wethers were behaviourally indistinguishable when handled as a mob. Few phenotypic or genetic relationships were found between the behaviours and carcass traits in initial analysis of an industry research flock dataset. However, in an experimental trial behavioural reactivity was related to carcass quality, albeit opposite to the relationship expected, with higher reactivity being associated with better loin pH. Lambs that were more reactive at behavioural testing appeared to be stressed in lairage, most likely as they were moved to the stunning area, triggering lactic acid production, resulting in lower loin pH 24 hours post slaughter. Methodological advances were made during this research. The first of these was in regards to the measurement of flight speed, validating this behavioural test in sheep and assessing the appropriate distance for use in this species. This thesis also assessed the usefulness of face cover score and hairline position as indicators for a variety of measures of behavioural reactivity. The results give strong evidence against the future use of facial hair patterning as an indicator for behaviour in this species. These results show that behavioural reactivity on farm, combining flight speed and restrained tests and measured later in life (after weaning), can be used to predict the reaction of the sheep at slaughter. The complex phenomenon of reactivity was successfully divided into its components, significantly advancing the understanding of behaviour in sheep. Further work is necessary to confirm these results in a variety of flocks and to establish the links between individual behavioural tests and stress. Greater understanding of the relationships between the behavioural and physiological responses to stress will improve both farm productivity and animal welfare.