This study was conducted to determine the effect of different ratios of concentrate to forage in post-weaning period on performance and metabolic responses Holstein calves. For this purpose, forty-five Holstein female calves (70 d of age and 77.7 ± 4.44 kg body weight), were randomly assigned to 1 of the following 3 treatment differing in forage to concentrate ratio. All the diets were formulated and to be isonitrogenous but energy was more in high concentrate treatment. Calves were kept in individual pens for up to 120 days. Daily feed intake was recorded and body weight recorded at the beginning of the experiment (d 70), d 95 and the end of the experiment (d 120). In order to evaluate the environmental conditions, temperature and humidity of the environment were recorded by thermometer and moisture meter daily. The results of this study indicated that the feed intake (p 0.01), daily weight gain (p 0.01), feed efficiency (p = 0.01), was affected by the treatment and showed a significant difference in the third treatment compared to the others. Also, body weight was affected at d 95 (p 0.01) and d 120 (p 0.01), and was higher in the third treatment. Regarding the health index, the health score was lower for the first treatment (p 0.02) and the animals were healthier than others. Ruminal pH on d 95, 120 was lower than other treatments (p 0.02). Dry matter, neutral detergents fiber, fat and protein digestibility were not different between treatments. The results of this study indicated that feeding 20-80% (20% Alfalfa hay and 80% concentrate), after weaning period, can improve calf performance. Key words : calves, forage, concentrate, performance, weaning
