The effects of depriving feed to facilitate transport and slaughter in sheep – a case study of cull ewes held off pasture for different periods

Abstract

AIM: To determine the ability of sheep to mobilise their body reserves after being deprived of feed prior to transport for slaughter.

METHODS: A total of 240 3- and 4-year-old cull ewes were held off pasture for 0, 9, 18 or 30 hours (n=60 per group) then transported 1 hour by road, unloaded and washed, held in lairage for 3 hours then slaughtered. Blood samples were collected from a subsample of 60 unfasted ewes 1 week earlier, and from all ewes at exsanguination to determine concentrations of serum metabolites indicative of adaptation to fasting. In addition, several attributes of carcass quality were measured.

RESULTS: At slaughter, increased time off pasture prior to transport resulted in no change in glucose concentrations in serum (p=0.140). There were differences (p<0.001) between the group fasted for 30 compared with 0 hours in mean concentrations of free fatty acids (0.98 (SD 0.32) vs. 0.58 (SD 0.23) mmol/L), β-hydroxybutyrate (0.69 (SD 0.17) vs. 0.42 (SD 0.11) mmol/L), triglycerides (0.29 (min 0.13, max 0.83) vs. 0.22 (min 0.06, max 0.96) mmol/L) and urea (10.17 (SD 1.80) vs. 6.94 (SD 2.03) mmol/L). Different periods of feed deprivation had no effect (p>0.05) on carcass weights (mean 22.7, min 13.2, max 32.9 kg) or dressing out percentages (mean 40.9, min 27, max 49%). Meat ultimate pH was unaffected (p>0.05) by the period of feed deprivation but meat became darker (p<0.05) and had reduced redness (p<0.001) with increasing time off feed.

CONCLUSIONS: The results suggest that sheep in variable body condition adapted to the periods of feed deprivation by mobilising their energy reserves without any evidence of metabolic depletion (e.g. depleted blood glucose or high meat pH). However, being deprived of feed they probably experience a degree of hunger.

KEY WORDS:

• Sheep
• slaughter
• fasting
• transport
• animal welfare
• carcass quality

Acknowledgements

The Ministry for Primary Industries (formerly the Ministry of Agriculture and Forestry) is thanked for commissioning this study through its Operational Research Programme. In addition, the authors are indebted to the helpful interest and advice provided by Hazel Johnston and Kate Littin. The work has generated a tremendous amount of goodwill from many individuals and organisations involved in sheep farming, transport and processing industries, without whom the project could not have been undertaken in the way that it was. We are especially indebted to Graeme Orviss, Neil Smith, Jack Burne, Murray Pedersen, Tui Strickland and staff at Silver Fern Farms Takapau, for processing the animals, and Kay Ward for assistance with sample collection. Thanks also to Bushetts Transport, Gribbles Veterinary, AgResearch Grasslands Animals Ethics Committee, and Geoff Cuthbert (Mint Technology) for their invaluable assistance.

Notes

*Non-peer-reviewed