SUPPLEMENTAL CHROMIUM AND NIACIN FOR STRESSED FEEDER CALVES

The effects of supplemental inorganic chromium (Cr) and (or) nicotinic acid (niacin) were compared with those of an organic source of Cr on performance, morbidity and blood metabolites were investigated of 135 crossbred steer calves, purchased at three sales in Ontario. Calves of 236-kg average weight were randomly assigned to control, 0.75 mg kg(-1) (dry matter) organic Cr from Cr yeast, 0.75 mg kg(-1) inorganic Cr from CrCl3 . 6H(2)O, 100 mg kg(-1) niacin, or CrCl3 . 6H(2)O + niacin for the 28-d stress and 28-d growing periods. During the first 2 wk Cr supplementation was doubled. The basal diet was 75% alfalfa silage, 23% high-moisture corn and 2% mineral and vitamin supplement. Treatments had no beneficial effect on overall morbidity. Inorganic Cr and niacin alone had no beneficial effect (P > 0.10) on performance. Inorganic Cr and niacin used together, however, tended to increase weight gain by 39% (P = 0.09) and feed efficiency by 47% (P = 0.08) during the 28-d stress period, with no improvement during the later growing period. Inorganic Cr together with niacin increased serum iron concentration (P = 0.01) and serum total iron-binding capacity (P = 0.01) of healthy calves but had no effect on these metabolites in morbid calves. This study suggested that supplemental inorganic Cr is not as effective as an organic source for ruminants. Supplemental inorganic Cr with niacin tended to improve performance of stressed calves, suggesting that niacin may be a Limiting factor for absorption and (or) use of inorganic Cr.