ABSTRACT
One thousand five hundred and forty Hybro HI-YR broilers were used in the study. One-day-old
chickens were allocated to four groups; in the pen trial each group comprised 5 replications with 56 birds,
in the digestibility trial there were 7 replications with 15 birds. The dietary treatments were as follows:
unsupplemented control wheat-barley diet or the same diet supplemented with 10 ppm avilamycin, 150
ppm or 300 ppm of plant extract (XT) containing capsaicin (1.98 g/100 g), carvacrol (4.95 g/100 g) and
cinnamic aldehyde (2.97 g/100 g). Performance was determined on days 21 and 48. After slaughter the
rectum content was collected for E. coli and Clostridium perfringens assay; slaughter yield and sensorial
evaluation of breast and thigh muscles were performed on 16 birds per group. In the digestibility trial,
on days 21 and 32 of life, after slaughter the apparent ileal digestibility of nutrients and amino acids was
estimated on 28 birds per group. In comparison with the control group, up to day 21 of life the administration
of feed antibiotic and 150 ppm or 300 ppm of plant extract enhanced body weight by 4.7, 5.4
and 8.1% (P