Effect of feed level and supplementary rumen protected lysine and methionine on growth performance, rumen fermentation, blood metabolites and nitrogen balance in growing Tan lambs fed low protein diets

•Rumen protected lysine and methionine improved average daily gain in Tan lambs.•Digestibility of nutrients decreased linearly with an increase in feed level.•Rumen protected lysine and methionine improved nitrogen-retention.•Rumen protected lysine and methionine improved microbial protein synthesis.