Effect of Various Levels of Cottonseed Meal with Silymarin on Performance, Tibia Bone Characteristics and Some Blood Parameters of Broiler Chickens

Cottonseed meal (CSM) is a by-product of the separation of oil from cottonseed, which is limited in poultry feed due to its gossypol, cyclopropenoid fatty acids, high fiber and low protein quality. For this purpose, in the present study, the effect of different levels of cottonseed meal with silymarin on the performance and some blood parameters of broilers was investigated.

Treatments consisted of different levels of CSM (0, 12 and 24 percentage of diet) and 2 levels of silymarin (0 and 600 ppm) that was performed in completely randomized design with 2×3 factorial arrangement with 240 broiler chicks. Experimental diets for starter period (1 to 21 days) and grower period (22 to 42 days) were performed based on the requirements of the National Research Council. Feed intake (FI), body weight gain (BWG) and feed conversion ratio (FCR) were recorded weekly. On day 42 of breeding, blood samples were taken to evaluate blood lipid parameters. Breast weight, thighs, abdominal fat, total gastrointestinal tract, liver, spleen and bursa of fabricius were also measured at day 42 and the data were reported as a percentage of live body weight.

The results of this experiment showed that dietary supplementation of silymarin was more effective on increasing FI in birds that consumed 12% CSM at starter period. Supplementation of silymarin to the control diet significantly decreased FI at grower period and whole period of experiment (p<0.05). Improved BWG and FCR was related to the birds fed silymarin at 2 levels (0 and 600 ppm) without cottonseed meal (p<0.05). Highest relative weight of thigh was related to the birds that consumed diet without cottonseed meal and silymarin. Highest value of relative weight of breast was recorded for the birds that received diet with silymarin and without CSM that had significant difference to the diet contains cottonseed meal (with or without silymarin). Also, highest value of relative weight of gastro-intestinal tract was recorded for the birds that received diet with 12% CSM and silymarin. The plasma LDL level of birds fed diet with silymarin and without CSM were lowest that had significant difference to the other treatments (p<0.05). Also, dietary supplementation of silymarin at the lack of CSM increased but in CSM diets decreased significantly plasma triglyceride concentration (p<0.05).

The results of this experiment showed that supplementation of silymarin at 600 ppm to the CSM diets could not reduce negative effects of gossypol in broiler chickens.