THE EFFECTS OF THE STRESS OF WEANING AND TRANSIT ON PERFORMANCE AND METABOLIC PROFILE OF BEEF CALVES OF DIFFERENT GENOTYPES

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Abstract
Feeder calves of Bos indicus or Bos taurus breeding, reared under the same management and environmental conditions, were subjected to the stressors of weaning, assembly and transport to determine if genotype of the calf had a significant impact on stress responsive parameters. These responses were measured by monitoring changes in body weight, poststress dry matter intake and selected metabolic factors. Calves lost 11 kg or 8.1% of their weaning body weight during assembly and transit. Genotype was not related to weight changes during assembly and transit; however, Hereford × Brahman calves gained less (P < 0.05) weight during the 28-d post-transit period than Angus × Brahman or Angus × Hereford calves. Serum glucose, urea nitrogen, total protein, potassium and sodium concentrations were altered (P < 0.05) by weaning or transport and were generally higher (P < 0.05) in the half Brahman calves than the Angus × Hereford calves. Within the context and conditions of this experiment, genotype was not related to the metabolic response of the beef calf to the stresses associated with weaning and transport. However, genotype was found to influence basal nonstressed metabolic values indicating that poststress metabolic measurements alone may be misleading as an indication of the physiological response to stress. Key words: Cattle, stress, genotype, glucose, protein, urea