There have been extensive studies in sheep and cattle considering cobalt (Co) supplementation and its effects on vitamin B 12 concentrations in the body. However, there are limited studies on goats. The aim of this study was to compare two different sources of Co (sulfate v . glucoheptonate) at two different concentrations (0.25 and 0.5 mg/kg dry matter) in goat kid nutrition, and to evaluate the effects of these supplements on performance, serum vitamin B 12 , blood biochemistry and rumen volatile fatty acids. For this purpose, 30 weaned male goat kids were randomly allotted to five treatments. Serum vitamin B 12 increased during the trial in the Co-supplemented groups. Co supplementation increased serum glucose concentrations. On day 35, Co-supplemented groups had greater glucose concentrations compared with control. Propionic+iso-butyric acid concentrations increased only in the 0.5 mg Co glucoheptonate treatment ( P <0.05). Our results suggest that, despite the two sources of Co proving mostly similar, the main advantage of Co glucoheptonate compared with Co sulfate was in the ruminal synthesis of vitamin B 12 . However, although providing Co at National Research Council recommendation levels maintained vitamin B 12 above or at normal concentrations, Co supplementation of the Co sufficient basal diet increased vitamin B 12 and glucose concentrations.
