The effect of organic zinc and selenium supplementation on feed intake, digestibility, and rumen fermentation parameters in sheep

This study was conducted to evaluate the effect of dietary inclusion of zinc-methionine and seleno-methionine on feed intake, rumen fermentation and protozoa population in sheep. In Exp. 1, 20 Sanjabi rams were assigned to one of the four treatments as: 1) basal diet or control without Zn-met and Se-met ; 2) basal diet supplemented with 300 mg Se kg-1 of DM; 3) basal diet supplemented with 400 mg Zn kg-1 of DM;4)basal diet supplemented with 300 mg Se plus 400 mg Zn Kg-1 of DM . In Exp. 2, the fermentation parameters were studied by an in vitro gas test using the rumen fluid from control rams. The gas test was conducted for the treatments as: 1) basal diet or control; 2) basal diet supplemented with 300 mg Se/30 ml rumen fluid ; 3) basal diet supplemented with400 mg Zn/200mg of 30 ml RF; 4) basal diet supplemented with300 mg Se and 400 mg of Zn /200mg of 30 ml RF . In Exp. 1, metabolisable energy, organic matter digestibility, ammonia nitrogen and total short chain fatty acids were decreased by Zn-met and Se–met supplementation , however, the partitioning factor and microbial protein were improvedin treatments containing mineral supplement. In conclusion, the addition of Zn-met and Se-met had no useful effect on the rumen fermentation parameters of sheep, however, the protozoa population was increased. Also in this study, in vitro method was not a suitable index for evaluating the effect of mineral supplements on the in vivo rumen fermentation.