Behavioral and physiological characterization of weaning stress in foals

Abstract

Behavioral and physiological responses to weaning stress were studied in 21 foals assigned to one of five treatments: abrupt, total separation of mare and foal, no preweaning creep feed (TSNC); total separation but with creep feed (TSC); partial separation of mare and foal allowing fenceline contact, no creep feed (PSNC); partial separation but with creep feed (PSC); and control (CON), no separation of mare and foal, with creep feed. Behavioral parameters included vocalization frequency and time spent standing still or walking for each foal. Weight gain and feed intake were recorded. Physiological characters included adrenal response curve areas, glucocorticoid responses, peak and basal glucocorticoid values, tri-iodothyronine (T(,3)) and thyroxine (T(,4)) values, and blood chemistry constituents for each foal. The TSNC foals spent more time walking and less time standing still than foals on other treatments. Foals on TSC and PSNC treatments spent more time standing still than walking. The PSC and CON foals were not different in locomotor patterns and spent more time standing still and less time walking than foals on other treatments. Foals on PSNC, PSC and CON treatments vocalized less (P < .05) than TSNC or TSC foals.</p> On partial separation treatments, creep fed and non-creeped foals consumed similar amounts of feed during wk 1 postweaning. On total separation treatments, non-creeped foals consumed more feed than creep fed foals. These high feed intakes resulted from foals observing their dams during feeding and their subsequent interest in pelletted feed. Foals without creep feed gained more weight immediately after weaning than creep fed foals, reflecting higher feed intakes. Foals in the total separation treatments generally had higher glucocorticoid characters than other treatments, suggesting they were more stressed at weaning. The PSNC, PSC and CON treatments did not differ (P < .05) in any glucocorticoid character. Total separation treatments had higher (P < .05) values than partial separation treatments for all glucocorticoid characters. Foals without preweaning creep feed had lower (P < .05) basal glucocorticoid concentrations than foals with creep feed. Concentrations of T(,3) and T(,4) ranged from 12-137 ng/dl and 1.2-6.2 (mu)g/dl, respectively. No treatment differences were found in thyroid hormone levels in this study. Blood chemistry constituents did not reflect weaning stress in foals in this study