The impact of pre-slaughter sensory enrichment on reducing cattle stress

Cattle can be exposed to pre-slaughter stressors that have negative impacts on cattle behaviour and welfare. Environmental sensory modifications (sight, sound, smell) can reduce stress, but they have not been investigated in a commercial beef processing setting. This study examined if environmental sensory modifications could reduce pre-slaughter cattle stress and alter cattle behaviour at a commercial beef processing facility. The study was approved by the Murdoch University Animal Ethics Committee (R3302/20) and meets the requirements of ISAE ethics. The following environmental conditions were tested individually; (1) reduction of intermittent plant noise (removal of safety siren), (2) masking abattoir odours with hay odours provided in the cattle race way, and (3) lights added to illuminate cattle race way, and (4) an acoustic sound wall enclosing the lead-up chute to the site of euthanasia reducing the noise levels from 100 to 72 dB hertz. Cattle of mixed sex (female= 240, male= 994), age (0-8 teeth) and breed that had been on a 100-day grain feeding program prior to slaughter were selected. The breeds consisted of Angus, Murray Grey, Simmental, Limousin, Red Angus, Droughtmaster, and Ultra Black. Cattle were not selected for breed type, age or sex in this study and hence was not included in the analysis. The environmental modifications were evaluated singularly. Each experimental group consisted of between 70-110 cattle with 20 focal cattle for subsequent blood collection, as such each control and treatment group had 20 focals included (Table 1). Three replicates of each treatment were repeated giving a total sample size of approximately 70-110 cattle including 60 focal animals per treatment. Blood samples were collected immediately post-slaughter and were analysed for glucose, lactate, magnesium, creatine kinase and aspartate aminotransferase. All carcasses were graded by qualified Meat Standards Australia (MSA) graders after overnight refrigeration and measurements included ultimate pH (pHu), with increased levels indicating pre-slaughter stress. Cattle behaviours were assessed by Qualitative Behavioural Assessment (QBA), in which observers scored the demeanour of the cattle using a fixed list of terms after viewing short video clips as they walked through the raceway leading to the site of euthanasia. The blood parameters and pHu as carcass variables were analysed using general linear models (GLM) to determine the impact of treatment, which was performed using the statistical package SAS. The QBA data was generated by the method of Principle Components Analysis (PCA), performed using the statistical package GenStat. Each of the assessed animals received a score on the two main PCA consensus dimensions that were generated, and these scores were analysed with a mixed‐model Analysis of Variance (ANOVA) to determine if there was an effect of treatment (fixed factor) on the transformed PCA dimension scores given to the animals. The QBA observers had a significant consensus in their scores when observing cattle demeanour (P<0.01). The cattle groups exposed to the hay-odour and reduction of intermittent the noise both had higher QBA scores than the controls, with the observers scoring them as less “frustrated” and less “agitated” (P<0.01). Ultimate pHu decreased (P<0.05) for the hay-odour group and reduction of intermittent plant noise group compared to the controls. Additionally, there was a negative association between pHu and the QBA scores for the cattle exposed to the hay treatment (P