effects two levels of energy and fattening periods on performance of chalishtori ram lambs

this study was investigate the effects of two levels of metabolism energy (me) and length of fattening periods on performance and growth characteristics of chalishtori male lambs. 64 ram lambs were weaning and intake diets with two levels of energy include: 2.5 and 2.3 mcal me/kg dm in 90 and 120 days fattening period. in this study used of completely random designs with 2×2 factorial methods (fattening periods and levels of energy). rations were isonitrogenous (14 %cpdm/d). at the end of each fattening period, 16 lambs were randomly selected (totally 32 lambs) and slaughtered. data were statistical analyzed by sas (2001) with glm method. the different levels of energy had no significant effects on lambs daily weight gain, but length of fattening period had highly significant effects on lambs daily weight gain (p<0.01). effect of fattening periods and levels of energy on daily feed intake and feed conversion ratio were significant (p<0.05). effect of fattening periods were significant on drip loss of lambs carcass in first 24 h in the chiller (p<0.05). in conclusion, 90 d fattening period was better, because they have higher daily weight gain, loser daily feed intake, better of feed conversion and so, 2.3 mcal me/kg dm because daily weight gain, feed efficiency, and drip loss were not significant between two levels of energy.