Mother-young spatial association and its relation with proximity to a fence separating ewes and lambs during enforced weaning in hair sheep (Ovis aries)

This work examined the changes in mother-young spatial association with increasing age of lambs and proximity to a fence separating ewes and lambs during artificial weaning. Twenty-five St. Croix white hair ewes and their twin lambs were used. During the first part of the study the distance between the lambs and their mothers from days 35 to 63 postpartum was recorded. In phase two, lambs were separated from their dams by a wire fence at weaning (when lambs were 64 days of age) but with full view of their mothers. The distance between mother and young increased progressively as the experiment advanced (y = 1.35x0.38) and was not influenced (P > 0.05) by the sex of the lamb or distance of the sibling from their mother. After weaning, no difference (P > 0.05) was observed in the average number of times/h of observation ewes were observed at <1 m from the fence line between 24, 48 and 72 h after separation (2.17 ± 0.47, 1.5 ± 0.39 and 0.42 ± 0.16, respectively). However, a significant (P < 0.05) decline was observed at 72 h in comparison with 24 h after separation. In contrast, no difference (P > 0.05) was observed in the average number of times/h of observation that lambs were observed in proximity to the fence line at 24, 48 and 72 h of separation (2.00 ± 0.30, 2.07 ± 0.25 and 1.58 ± 0.21, respectively), or between 24 and 72 h (P > 0.05). The correlation between the ewe-lamb distance before weaning and the number of times the ewe was observed close to the fence was −0.27 (P = 0.10) while with the lamb's proximity it was −0.38 (P < 0.05). It was concluded that lambs that had a close spatial association with their mother (35-63 days postpartum) before weaning, are more likely to approach a wire fence separating them from their mother during enforced weaning at 64 days of age.