The handling of cattle pre-slaughter and its effects on carcass and meat quality

Abstract

Almost all cattle are eventually slaughtered for meat. Because the slaughtering industry is becoming centralised into fewer, larger plants, marketing times have increased, particularly for animals sold through live auctions or those reared under extensive systems. During marketing, cattle are subjected to various stressors which elicit specific behavioural and physiological responses. Typical stress responses such as elevation of heart rate and body temperature and increased circulating corticosteroid levels are seen. The natural patterns of behaviour of cattle, particularly their following and herding instincts, can be exploited to facilitate handling. Increased use of young bulls for beef production in many countries has highlighted the importance of good design of handling facilities. Pre-slaughter handling can affect both carcass and meat quality. Losses in carcass yield are caused by both mobilisation of tissues to provide energy for maintaining the vital functions of the body and the dehydration which often accompanies the inevitable period of food and water deprivation together with the stress of transport. The size and onset of these losses are as yet poorly defined for cattle, possibly because of the large influence of variation in environmental conditions. Reported losses in yield after a 48 h fast range from < 1% to 8%. Transport leads to losses over and above those attributable to fasting; time, rather than distance, being the important factor. Bruising is frequently a large problem in extensively reared cattle unused to handling. Bruised tissue is trimmed, reducing yield as well as often leading to downgrading. The major influence of pre-slaughter handling on lean meat quality is through the potential effect on muscle glycogen stores. If depleted by chronic stress the extent of postmortem acidification is reduced leading to the production of dark cutting beef (DCB). This is prone to spoilage and has poor organoleptic qualities. The major cause of DCB is mixing unfamiliar animals promoting agonistic behaviour, particularly in young bulls. Pre-slaughter handling practices which encourage mixing therefore increase the incidence of DCB. Prolonged transport is also a factor and there appear to be seasonal influences although the reasons are unclear.