This study was conducted to compare the effects of dietary eubiotics or intravenous amino acid infusions (IVAAI) as two different growth promoters on nutrient digestibility, rumen fermentation, performance, and blood biochemical parameters of buffalo calves in subtropical climatic conditions. Thirty male buffalo calves (284.40 ± 18.45 kg) were randomly distributed into three groups and fed a basal diet (BD) of concentrate feed mixture and roughages. The first group was fed BD and considered as the control, the second group was fed the BD supplemented with eubiotics at 1.0 kg/ton of concentrate, whereas the third group was intravenously infused with amino acid (IVAAI) injection at a dose of 2.0 ml/100 kg body weight. Results showed that the total gain and the average daily gain were improved (P < 0.05) with dietary eubiotics. The digestibility of some nutrients was increased (P < 0.05) with dietary addition of eubiotics. In addition, eubiotics stabilize (P < 0.05) the rumen pH, which reduce the risk of subacute ruminal acidosis but increased (P < 0.05) ruminal NH3-N and total volatile fatty acids. The rectal temperature was decreased (P < 0.05) with eubiotics supplementation. In conclusion, the use of eubiotics induced superior positive effects on the digestibility of nutrients, rumen fermentation, rumen enzymes, rumen protein concentration, growth performance, feed conversion, blood parameters and ameliorated the harmful effects of thermal stress of buffalo calves in comparison with intravenous infusion of amino acids.