Does coping style affect behavioral responses and growth performance of lambs weaned at different ages?

The objective of this study was to determine the relationships between coping style (CS), and physiological, behavioral characteristics and growth performance of lambs weaned at different ages. Male Karakaş lambs (n = 75, mean age = 30 d) obtained from a breeder farm were subjected to a 3-minute open field test. Of the 75 lambs classified by hierarchical clustering on principal components’ scores on open field test behaviors, 40 were assigned to 1 of 2 groups as proactive (Pro, n = 20) or reactive (Rea, n = 20). Pro (n = 10) and Rea (n = 10) lambs were selected randomly and weaned at 45 d (D45). The remaining 20 lambs (10 Pro, 10 Rea) were weaned at 75 d (D75). Lambs from Pro and Rea groups (Pro n = 5, Rea n = 5) were randomly assigned to each pen (n = 10). Blood samples were taken from lambs just before and 20 minutes after the start of open field test and at weaning (on 0, 1, 3, 5, and 7 d after weaning) to measure serum cortisol, glucose, lactate dehydrogenase, creatine kinase, total protein, and triglyceride concentrations. There was no significant effect of CS on blood parameters measured both in open field test and that measured at weaning (P > 0.05). CS had significant effect on live weight (LW) and average daily weight gain (ADWG) (P < 0.05). Reactive lambs had greater LW and ADWG than Pro lambs (P < 0.05). Weaning age (WA) had significant effect on LW and ADWG (P < 0.05). The ADWG were greater in D75 lambs than in D45 lambs (P < 0.05). CS did not have significant effect on behavioral variables measured at weaning, except for success index values. Rea lamb had greater index values than Pro lambs (P < 0.05). WA had significant effect on behavioral variables measured at weaning and those variables were higher in D75 lambs than in D45 lambs (P < 0.05). Partial correlations between open field test behaviors and those measured at weaning were not significant (P > 0.05). There was a significant positive partial correlation between aggressive behaviors and glucose (P < 0.05). The strongest partial correlations in the network were between creatine kinase and lactate dehydrogenase (r = + 0.78, P <0.05), and stereotypic behaviors and aggressive behaviors (r = + 0.67, P <0.05). Although the behavioral responses measured in the open field test are less time consuming than are those measured in ethological field studies, they do not reflect adequately the social behavior of lambs after weaning; however, WA had significant effects on social and stereotypical behaviors; therefore, to ensure social cohesion among lambs, it is important to identify the appropriate age for weaning.