Abstract
Abstract Weaning is a stressful event often associated with changes in physiological characteristics, increased restlessness, reduced feed intake, and poor performance. This study was designed to evaluate the effects of melatonin on behavioral and physiological responses of weaned beef calves. Angus beef calves (n=36) at 7-mo of age were stratified by dam parity, body weight, calf sex and randomly allocated to receive either 24mg melatonin implants (MEL) or physiological saline (CON). A subset of calves were fitted with accelerometers on the hind leg to monitor activity levels for 7 days after weaning. Blood samples, rectal temperature, chute score and body weight measurements were collected on d 0, 7 and 14 after weaning. Activity of MEL calves was significantly (P < 0.05) lower than CON. The MEL calves had lower (P < 0.05) chute score on d 7 and 14 compared to CON. There was no marked effect of melatonin on rectal temperature and hematological parameters, however, platelet showed significant (P < 0.05) difference with MEL recording higher values compared to CON. Average daily gain (ADG) was 1.67 and 2.35kg/d in CON and MEL, respectively. We concluded that although no differences in ADG, hemogram, and rectal temperature were observed, melatonin treated calves had reduced behavioral stress response associated with weaning.
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