What is the problem?
Weaning period is considered a crucial event in the management of ewes and lambs, resulting in a number of significant challenges. Although multiple stresses significantly affected adaptive capability of ewes in terms of changes in physiological mechanisms insufficient knowledge are available to understand the adrenocortical and functional responses of lambs to adapt to weaning stress.
The main objective of the study was to evaluate the effect of weaning associated with maternal separation on circulating cortisol concentrations, respiratory rate and rectal temperature changes after the first 24 h weaning period and 2 weeks later in cross-bred lambs.
What did the research involve?
- thirty-four crossbred lambs were assigned randomly to two treatments: 17 (unstressed control group) were housed in standard farming conditions with their mothers, 17 lambs (treated group) were submitted to weaning and separation from maternal care
- both groups were studied and sampled 2 weeks before (weaning) in baseline conditions (T0), 24 h (T1) and 2 weeks (T2) after (weaning)
What were the key findings?
- in treated group lambs showed decreases of cortisol concentrations 24 h after and 2 weeks after weaning, compared to baseline values. Weaning effects were shown for cortisol changes in treated lambs
- the comparison between control and treated lambs showed lower cortisol concentration both 24 h after weaning and 2 weeks later in treated than control subjects
- treated lambs showed decreases of respiratory rate 24 h after and 2 weeks after, compared to baseline values, with a significant weaning effects for RR changes
- no significant changes were observed for RT at different times in treated lambs. Negative and significant correlations were observed between RR and RT for all measurement periods in control group
- these results showed that a short- and long-term perturbation of the post-weaning has measurable effects on adrenocortical and functional response of weaned lambs.
- results obtained showed that the ability of the adrenocortical gland to modulate cortisol concentrations was different in control and treated groups. The ability remained unmodified in unstressed animals, but significantly decreased in weaned lambs
- it was concluded that the presence of maternal care did not appear to influence cortisol concentrations
- the decreases of cortisol concentrations after weaning were the evident effect of persistent stress suffered by lambs both early and late phases of weaning