Effects of stray voltage on the physiology of stress, growth performance and carcass parameters in Romane male lambs
Résumé
The effects of permanent or random exposure to stray voltage on a water trough were evaluated in growing–finishing Romane male lambs between the age of 13 and 19 weeks. Ninety lambs were assigned during two 6-week experimental periods to one of three treatments, with 30 animals in each treatment (15 per experimental period). The treatments were permanent exposure to voltage (PERM, 3.5 V) on the water trough, random exposure to voltage (RAND, 3.5 V, 34 h/week) and no voltage exposure for the control group (CONT). No effects of voltage exposure were observed on production parameters: growth, average daily gain and water intake. The stress physiology seemed to be slightly modified with a lower plasma cortisol concentration at slaughter in PERM lambs compared to CONT lambs (P < 0.05) and a higher adrenal medulla weight in PERM lambs compared to CONT lambs (P < 0.05). However, no differences were observed between treatments in heart-rate, basal plasma cortisol concentration and tyrosine hydroxylase and phenylethanolamine-Nmethyl transferase activities. Carcass yield, temperature and the pH of the M. longissimus dorsi were not modified by voltage exposure during rearing. In the good carcass conformation class (R class in EUROP grading scheme), there were fewer fat carcasses (grade 4 of 5) in the PERM and RAND compared to the CONT group (P < 0.05). In conclusion, no major effects of voltage exposure were observed in male lambs on production, carcass parameters and stress physiology. Stray voltage could be considered as a mild stressor in growing–finishing lambs.