The effect of thyme extract on growth performance, digestive organ weights and serum lipoproteins of broilers fed wheat-based diets

The effect of the thyme extract and wheat form of the diet on performance, digestive organ weights and serum lipoproteins was studied in 320 male day old (ROSS 308) chicks. From 1 to 42 d of age, 8 diets arranged factorial with 4 thyme extract level (0.0, 0.2, 0.4 and 0.6%) and 2 wheat forms (ground <em>vs</em> whole) was used. Each treatment was replicated 4 times (10 birds per replicate). Thyme extract had no significant effect on body weight gain, feed intake and feed conversion ratio irrespective of wheat form used over whole trial period (1-42 d). From 1 to 21 d of age, broilers fed the whole wheat diet grew faster than the broilers fed ground wheat based diet (609.06 <em>vs</em> 573.34 g). Relative abdominal fat and gizzard weight was significantly higher (P&lt;0.05) in birds fed the whole wheat diets. Two-way interaction between thyme extract and wheat form were observed for total cholesterol, LDL-cholesterol, HDL-cholesterol and very-low-density lipoprotein (VLDL) in the experiment. The results showed that the extract had no effect on performance of broilers irrespective of wheat form used. Relative gizzard weight was higher (P&lt;0.05) in birds fed the whole wheat diets, but an increase in abdominal fat should be taken into account for carcass quality and processing. The predominant effect of thyme extract on lowering lipid levels in broilers fed on wheat based diets was on triglyceride rather than on cholesterol concentrations