A 2 × 7 factorial experiment was conducted to examine the effects of a fat soluble vitamin premix (FSVP, 0 and 1.2 mL/bird/injection) on performance indices and hematological variables in broiler chicken with different growth rate (x̄-3SD, x̄-2SD, x̄-1SD, x̄, x̄+1SD, x̄+2SD and x̄+3SD) using 364 male Ross 308 broiler chicks. Body weight (BW) of the birds at marketing age (42 d) was not follow the same pattern as their BW at age of 21 d. The birds receiving a FSVP achieved greater body weight, ate more feed and converted the feed with a greater efficiency than the untreated birds. Heart percentage was significantly lesser in the birds with initial body weight close to the population mean compared with the birds having a lesser or a greater BW than the population mean. Injection of FSVP increased heart weight by 20.48 percent and decreased plateletcrit (PCT) by 33.3 percent. Step-wise multivariate regression analysis showed that heart percentage explained 38.37, 39.07 and 8.57 percent of the variation in BW (42 d), feed intake and feed conversion ratio (21 to 42 d), respectively. Hemoglobin concentration and red cell distribution width (RDW) were the next two variables that collectively explained about 10 percent of the final BW (42 d) variance. It was concluded that birds showing a body weight of x̄-3SD at early ages cannot exhibit greater growth rate in later ages probably due to intrinsic limitations. No hematological parameter, excluding heart percentage seems to have a significant influence on intra-flock variance in performance indices in broiler chickens. Manuscript profile