Responses to Repeated Deprivation of Lying Down on Feed Intake, Performance and Blood Hormone Concentration in Growing Bulls
Repeated deprivation of lying down was used as a model to study the effect of long-term stress on performance, meat quality and metabolic changes in young bulls. Sixteen Danish Friesians were included and assigned to either control treatment or deprivation of lying down from 07:00 to 14:00 and 15:00 to 22:00 every day for 10 weeks. Feed intake was recorded daily. Blood was taken weekly to study changes in hormone and metabolite concentrations. On days 5 and 55 of the treatment, the sensitivity of the pituitary to growth hormone-releasing factor was tested. Repeated deprivation of lying down did not affect voluntary feed intake or meat quality. Likewise, feed efficiency and daily intake did not differ statistically, but numerically the reduction was in accordance with the hypothesis that long-term stress depresses performance. Between-animal variation appears to be markedly increased for traits such as daily gain and feed conversion ratio, indicating individual adaptation to long-term stress. Stressed animals tended to have lower circulating levels of insulin-like growth factor-I but no effect was observed on the sensitivity of the pituitary.