Hydroxy-selenomethionine is an effective selenium source for pregnant heifers and their calf

This study aimed to evaluate the efficacy of hydroxy-selenomethionine (SO) when compared to sodium selenite (SS) on Se status of pregnant heifers and their offspring. A total of 42 in-calf heifers were randomly assigned to one of three experimental diets offered in the 7 weeks preceding calving; a non-Se-fortified basal diet (NC); NC + 0.3 mg Se/kg DM as SS; NC + 0.3 mg Se/kg DM as SO. Blood samples were taken three weeks before calving. Colostrum was collected at birth and new-born calves were blood sampled within 24 hours. Plasma Se increased in heifers receiving Se supplemented diets (SO and SS) when compared to NC. Plasma Se was greater in SO when compared to SS (P<0.001). Similarly, colostrum Se was greater in Se supplemented heifers when compared to NC, and greatest in SO when compared to SS (P<0.001). Furthermore, calves born to Se supplemented dams had greater plasma Se when compared to NC, and calf plasma Se was greatest in SO when compared to SS born calves (P<0.001). Speciation revealed that the greater Se concentration in heifer plasma was a consequence of increased selenomethionine, whereas increases in colostrum Se were attributable to increases in selenocysteine (P