Mother-young spatial association and its relation with proximity to a fence separating ewes and lambs during enforced weaning in hair sheep (Ovis aries) Lucı ´a Galeana, Agustı ´n Orihuela * , Virginio Aguirre, Reyes Va ´zquez Facultad de Ciencias Agropecuarias de la Universidad Auto ´noma del Estado de Morelos, Av. Universidad 1001, Colonia Chamilpa, Cuernavaca, Morelos 62210, Mexico Accepted 30 October 2006 Available online 28 November 2006 Abstract 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 = 1.35x 0.38 ) 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 Æ 0.47, 1.5 Æ 0.39 and 0.42 Æ 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 72h of separation (2.00 Æ 0.30, 2.07 Æ 0.25 and 1.58 Æ 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 À0.27 (P = 0.10) while with the lamb’s proximity it was À0.38 (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. # 2006 Elsevier B.V. All rights reserved. Keywords: Mother-young separation; Sheep; Stress; Weaning www.elsevier.com/locate/applanim Applied Animal Behaviour Science 108 (2007) 81–88 * Corresponding author. Tel.: +52 7773172990. E-mail address: aorihuela@uaem.mx (A. Orihuela). 0168-1591/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2006.10.016