Behavioral and physiological adjustments by lambs in response to weaning stress

Abstract

Early weaning is a widely accepted approach for enhancing productivity. This practice always accompanies undesirable stresses in lambs. Lambs must adapt these emotional and physical stresses rapidly to be productive. To estimate the stress, due to early weaning, 14 Patanwadi lambs weighing 9-11 kg, aged 50 days, were randomly divided into two different groups, that is weaned (W) and unweaned (UW) group. Before the start of the experiment, each group was given a 10 days’ acclimatization period with their group members. On the 11th day of the experiment (60th day), the W group lambs were separated from their dams. After weaning, on day 1, the W group had 1.6% declines, whereas the UW group had 4% increases in the growth rate over their respective preweaned weight (the day before weaning). The body weight of W group, which was reduced drastically on day 1, started rising by the second day after weaning. All the physiological parameters such as respiration rate, pulse rate, and rectal temperature were significantly (P < 0.05) lower in the W group as compared with the UW group. Behavior and feed intake were recorded for three hours daily for the entire experimental period (0-3 days after weaning). The W group lambs spent significantly (P < 0.05) higher time in vocalization, rumination, and drinking. Their playing and idle lying time were significantly (P < 0.05) lower than the UW group. Feed intake and feeding behavior showed the W group spent significantly (P < 0.05) less time for significantly higher (P < 0.05) concentrate intake. The blood biochemistry studies revealed no significant (P < 0.05) variations between two groups for total protein, albumin, globulin, urea, BUN. The plasma cortisol levels were nonsignificantly (P < 0.05) higher in the W group. The comparable changes of body weight and blood biochemical levels indicated that weaning on the 60th day enables the lambs to cope with the weaning stress through the behavioral and physiological stratagem.