Freitas-de-Melo, A., Ungerfeld, R. 2020. The sex of the offspring affects the lamb and ewe responses to abrupt weaning. Applied Animal Behaviour Science 229, 105008.
Female lambs have a stronger attachment with their mothers and show a greater susceptibility to stressors than male lambs. Male lambs grow faster than female lambs do, achieving a greater nutritional independence from their mothers. Our hypothesis was that female lambs and their mothers are more susceptible to stress of abrupt weaning than male lambs and their mothers. The objective of this study was to compare the behavioral and physiological responses of female and male lambs and their mothers to abrupt weaning. Thirty single lambs from 30 multiparous Corriedale ewes (16 females and 14 males) were weaned at 90 days of age. Body weight of the lambs was recorded at birth, before and after abrupt weaning. Behavioral activity, blood proteins and hematocrit of the lambs and their mothers were also determined before and after weaning. At the day of weaning, ewes that reared male lambs were observed pacing more times than those that reared female lambs (P < 0.0001). Male lambs grazed and ruminated more frequently (P ≤ 0.0001), and had greater average daily gain from 84 to 95 days of age (P = 0.03) than female lambs. While albumin concentration increased in female lambs after weaning (P < 0.0001), it did not change in male lambs. Male lambs coped better with abrupt weaning than female lambs, as they were probably in a more advanced stage of independence from their mothers, being thus separated when their attachment with their mothers was weaker than that of female lambs. The responses of ewes that lost male lambs were slightly greater than of those that lost female lambs.