Behavioral and hormonal effects of 2 weaning methods in trotter mares

Abstract

Given the paucity of published data on the effects of artificial weaning on mares, the aim of the present study was to investigate the behavioral and hormonal effects of two different weaning methods in trotter mares. In stud 1 (10 mares, S1), weaning was performed around 5 months post-partum, two foals/week, and mares put to paddock after separation. In stud 2 (12 mares, S2), weaning was performed around 7 months post-partum, all foals on the same day, and mares put into indoor individual stalls for two days after separation. Behavioral observations and saliva and hair sampling for radioimmunoassay cortisol levels assessment were done on day -7, day 0 (weaning day), day 7, and day 30. Milk was sampled on day -7 and day 0. On field, behavioral observations were done using instantaneous scan sampling every two minutes for one hour on each day of observation. Behavioral data were analyzed using Friedman ANOVAs, Mann-Whitney U-tests, and Generalized Linear Mixed Models. Cortisol data were analyzed using repeated-measure ANOVAs. Spearman correlations were used to assess correlations. Mares in both studs ate the least on day 0 (P < 0.001). On day 0, vocalizations and locomotion were higher than in any other day (P = 0.003 and P = 0.045, respectively) and higher than in the other stud (both P < 0.001) in S1 and S2, respectively. Saliva cortisol concentrations showed weak, but significant, correlations with eating, stall pacing, pawing, and vocalizing. Results suggest that artificial weaning could be a stressor for mares in both groups. Mares whose foals were weaned earlier did not show more stress-associated changes in behavioral or endocrine parameters than those whose foals were weaned later, but housed more restrictively for two days after weaning.