The effect of weaning age on foal growth and radiographic bone density

Seven foals weaned at 4.5 months were compared to eight foals weaned at 6.0 months at three-week intervals before and after weaning to assess the effect of weaning and weaning age on growth and bone density. Average daily gain (ADG) declined (P < .01) in the first week after weaning in both weaning groups, and remained lower (P < .05) than preweaning gain in foals weaned at 6.0 months at three weeks' post weaning. Cannon circumference (CC) growth was depressed at three weeks (P < .05) and six weeks (P < .10) postweaning when foals were weaned at 4.5 months, but not when foals were weaned at 6.0 months. Withers height (WH) and radiographic bone density were not affected by weaning or weaning age. By 203 days of age, there were no differences in body weight, CC, WH or bone density between weaning groups. Therefore, weaning foals at 6.0 months of age seems to provide little growth advantage over weaning foals at 4.5 months of age. Radiographic analysis across treatments revealed that the medial density of the left third metacarpal (MCIII) was greater (P < .01) than the right MCIII, thereby suggesting that both forelimbs should be included when assessing dietary or exercise effects on radiographic bone density.