The present study was conducted to determine the effects of forage source (alfalfa hay or corn silage) and forage offering method for alfalfa hay (total mixed ration or free choice provison) on starter intake, average daily gain (ADG), feed efficiency, nutriant digestability, rumen fermentation and nutritional behavior of Holstein dairy calves. For this purpose, fifty six Holstein dairy calves (8 females and 6 males per treatment ) were used in a completely randomized design. At d 3 of age, calves were randomly allocated to one of the four treatments consisting of: control (CTR, starter without alfalfa); total mixed ration with 10 % alfalfa hay (TM-AH); (total mixed ration with 10 % corn silage (TM-CS); free choice alfalfa (AH-F). All calves were weaned at d 56. All diets were formulated to be isoenergetic and isonitrogenous according to the Cornell Net Carbohydrate and Protein System version 5.1. Statistical analyses were performed using PROC MIXED in SAS. Results of the present study indicated that daily starter intak in calves fed with corn silage was higher ( P 0/01 ) in comparison to other groups during the pre-weaning, post-weaning and entire periods. Average daily gain did not differ among treatment during the pre-weaning, post-weaning and entire trial. There were significant differences among treatments for feed efficiency during the pre-weaning ( P 0/04 ), post-weaning( P 0/004 ) periods however; there were significant differences among treatments over the entire trail (P 0/016) . Dry matter digestability was lower for TM-CS calves compared with other groups during the pre-weaning( P 0/03 ). There were no significant differences for rumen fermentation parameters among treatments. The ruminal concentration of N-NH3 decreased over time and calves recieved CTR diet had higher ( P 0.01 ) ruminal concentration for N-NH3 than calves fed forage treatment at week 7. In general results of the present study indicate that forage feeding and free-choice provision of alfalfa hay improves intake and performance of dsiry calves without impairing digestibilities nutrients. Kay word: dairy calves, alfalfa, corn silage, digestibilities, free-choice provision of feed
