Effects of early energy and protein restriction on growth performance, clinical blood parameters, carcass yield, and tibia parameters of broilers

This study was conducted to investigate the effects of dietary energy and protein dilution from age 8 to 14 d on growth performance, clinical blood parameters, carcass yield, and tibia parameters of broilers. Treatments were assigned in a completely randomized manner with factorial arrangement (4×4) including 4 levels of energy dilution and 4 levels of protein dilution. All birds were fed the same diet during the remaining period of time. The feeds were weighed every week, and the birds were weighed at 7, 14, and 42 d. At 14 d, blood samples were taken for clinical chemistry measurements, and 4 birds from each replicate were sacrificed to measure carcass yield and tibia parameters at 42 d. From 8 to 14 d, average daily feed intake (ADFI) of the 20% protein dilution group increased significantly compared with that of the 10% protein dilution group (P<0.05). The feed conversion ratio (FCR) of the group with 30% protein dilution and 15% energy dilution creased the most among all treatment groups. From 15 to 42 d, the ADFI and FCR of the 20% protein dilution group were greater than those of the 0 and 10% protein dilution groups (P<0.05), and the FCR of the 15% energy dilution group increased significantly (P<0.05). At 42 d, body weight (BW) of the 15% energy dilution group was less than that of the other groups (P<0.05). Significant interactions were observed in ADFI, FCR, and BW at 42 d of age between energy dilution and protein dilution (P<0.05). At 14 d, serum total protein levels of birds in the 20 and 30% protein dilution groups decreased significantly compared to that of the 10% protein dilution group (P<0.05). Blood urea nitrogen concentration of birds in the 20 and 30% protein dilution groups decreased significantly compared with those in 0 and 10% protein dilution groups (P<0.05). Triacylglycerol concentration of birds in the 20% protein and 10% energy dilution groups decreased significantly compared with that of the 0 dilution group (P<0.05). The carcass yields were unaffected by dilution of energy and protein (P>0.05). The bone breaking strength of the 15% energy dilution group decreased significantly compared with that of the 5% energy dilution group (P<0.05). This study suggested that dietary protein and energy reduced 10% from 8 to 14 d of age can not affect the growth performance and other indexes in broilers.