The present work was conducted to study the effect of various stoking densities and dietary silymarin level in cock's diet to alleviate the negative effects of increasing stocking density on productive performance and physiological stress of Inshas cocks. A 3x3 factorial design experiment was performed including three stocking densities (10, 12 or 14 birds/m2) with three levels of silymarin (0, 250 and 500 mg/kg diet). A total number of 324 male chicks of Inshas local strain at 4 weeks of age were randomly distributed into 9 treatment groups and housed during the experimental period 4-16 weeks of age in wire cages having dimensions of 80 × 125 × 55 cm.
Results obtained showed that: There were significant negative effects (P<0.05) on live body weight, live body weight gain, feed consumption (except 4-8 Weeks), carcass , dressing , breast and thigh percentages relative to pre-slaughter by increasing stocking density at the different experimental periods. Mortality rate of chickens housed at 14 bird /m2 were significantly higher than those of birds housed at 10 bird /m2. Abdominal fat %, erythrocytes cells, leucocytes cells, heterophils (H) and H/L ratio were significantly (P<0.05) increased with increasing stocking densities (12 or 14 birds / m2). Tibia weight, tibia length, tibia calcium and tibia phosphorous (% of ash) were higher significantly (P≤ 0.05) higher for male chicks kept at 10 birds/m2 compared with other densities, followed by male chicks stocked at 12 birds/m2 then male chicks stocked at 14 birds/m2.There were insignificant differences for feed conversion and chemical composition of breast and thigh of cocks with different stocking densities.
Live body weight and weight gain values were almost significantly (P<0.05) improved with silymarin levels compared to the basal diet. Feed conversion in male chicks was significantly (P < 0.05) improved with dietary silymarin levels during the all experimental periods. Carcass, dressing, breast and thigh percentages relative to pre-slaughter, crude protein percentage of breast, serum total protein and globulin were almost significantly (P<0.05) increased while, abdominal fat% and ether extract percentages of breast and thigh, leucocytes cells and lymphocytes (L) serum AST and ALT were significantly (P<0.05) decreased with silymarin supplementation (500 mg silymarin/Kg diet) as compared with control group.
Body weight at 16 weeks of age and body weight gain during 4-8 and 4-16 weeks of age, feed consumption during 8-16 and 4-16 weeks of agewere significantly (P<0.05) influenced by interaction between stocking density and silymarin level.It is noted that mortality rate was lowered with silymarin levels at different stocking densities studied.Tibia measurements, its mineral contents and chemical composition of breast and thigh of cocks was not significantly affected by interaction between stocking density and silymarin level.Increasing stocking density to 12 birds / m2 gave the best net revenue and economical efficiency compared with that of 10 or 14 birds / m2. The best net revenue and economical efficiency were recorded with cocks fed 250 mg silymarin /kg diet and followed by 500 mg silymarin /kg diet as compared with control group.
In conclusion, increasing stocking density to 12 birds /m2 with levels 250 or 500 mg silymarin /kg diet improved most productive performance and some physiological traits of Inshas cocks.