Effects Of Corn Type And Particle Size On Growth Performance And Carcass Composition In Broiler Chickens

A study was conducted to evaluate the effects of corn type and particle size on growthperformance, carcass composition and blood responses in Ross308broilers, which were feda corn-soybean meal-based diet in a pellet form. A completely randomized experimentaldesign with a2×2factorial arrangement (corn type and particle size), each with6replicatesof45birds, was applied. Corn types include flour and flint corns, while particle size was1.5or3.0mm of diameter. The whole experimental period was divided into3phases: starter (1to12d), grower (13to28d), and finisher (36to42d). The dietary content of flour and flintcorns as well as the nutrient composition was the same in each growing period. The resultsare as follows:(1) In starter (1-12d) period, chickens ate more flour and smaller corns (P <0.05).Compared with the larger diameter of3.0mm, feeding smaller corn particle size (1.5mm)resulted in increases in body weight gain (P <0.01). In finisher (29-42d) period, broilerchickens fed flint corns had superior body weight gain and feed efficiency to those fed flourcorns (P <0.05). In grower and finisher period (13-42d), a significant interaction betweencorn type and particle size existed for feed conversion ratio (P <0.05). At13-28d of age,the superiority of flint corns to flour ones for feed efficiency of birds was observed withparticle size being1.5mm of diameter, while at29-42d of age, this was found with particlesize being3.0mm of diameter. When the whole growing period was considered, the feedintake of broiler chickens fed corns with a smaller particle size (1.5mm) was significantlyhigher than those fed corns with a larger particle size (3.0mm, P <0.05). Birds fed flintcorns had superior body weight gain (P <0.05) and feed efficiency (P <0.01) those fedflour corns.(2) In starter period (12d), the thigh muscle yield of broiler chickens tended to beincreased by corns with a smaller particle size (1.5mm, P=0.09). In finisher period (42d),it was significantly increased by flint corns (P <0.05). The abdominal fat content of birdswas slightly (P=0.05) and significantly (P <0.05) decreased by flint corns, respectively, at12and42d of age. In finisher period (42d), feeding a larger corn particle size (3.0mm)tended to increase the abdominal fat yield (P=0.09).At12(P <0.05) and42d (P <0.01) of age, feeding a smaller corn particle size (1.5mm) significantly reduced the percentage of proventriculus. At42d, the relative weight ofgizzard was flour corns> flint ones and3.0mm particle size>1.5mm ones. The percentageof intestine tended to be increased by feeding3.0mm corn particle size in both12(P=0.07) and42(P=0.09) d of age, relative to feeding1.5mm granularity. At12d, the relativeweight of bursa of fabricius tended to be flour corns> flint ones (P=0.05) and1.5mmparticle size>3.0mm ones (P=0.06).(3) At12d of age, plasma concentrations of urate tended to be increased by flint corns(P=0.08). At the end of the growing period (42d), plasma levels of triglyceride wassignificantly decreased by flour corns (P <0.05) and feeding a smaller corn particle size (P<0.01). In addition, the birds fed flint corns tended to have a higher plasma glucose content(P=0.11).The results of the present study indicate that the flint corns have a greater advantagethan flour ones in increasing body weight gain, improving feed efficiency and decreasing fatdeposition. But regarding internal organ growth, such as gizzard and bursa of fabricius, theflint corns are inferior to flour ones. The effect of corn particle size was most obvious on thedevelopment of digestive system, and feeding a larger size is beneficial to promote thegrowth of proventriculus, gizzard and intestine.