Effects Of Corn Particle Size On The Laying Hen Performance

To determinate the optimal corn ground particle size for the laying performance,a 2×6 factorial experiment was conducted,in which the two feeding model included feed intake ad libitum and restrictedly and six ground particle sizes of corn were 600,800,1000,1200,1500 and 1800 microns.The restricted feed was supplied as much as 90%of voluntary feed intake.Totally 2880 laying hens aged 41 weeks were allocated to 12 treatments.Each treatment had 10 replicates with 24 hens in 8 cages per replicate.The trial lasted 8 weeks.The results indicated that the feed intake difference between the two feeding model was great significant(P＜0.001).In contrast to voluntary feeding,restricted feeding decreased laying rate(P=0.035 and 0.280,in 2^nd and whole period respectively),egg mass(P=0.198,P＜0.001 and P=0.280,in 1^st,2^nd and whole period,respectively),egg weight(P＜0.001,in 1^st,2^nd and whole period) and ABWG (P＜0.001),and increased ratio of E/F(P＜0.001,P=0.035 and P＜0.001,in 1^st,2^nd and whole period, respectively) and percent of eligible egg(P=0.027,0.064 and 0.027,in 1^st,2^nd and whole period, respectively).Egg special gravity,egg shell pressure,haugh unit and egg yolk ratio were not affected by feeding model.Compared to voluntary feeding,restricted feeding increased PBI(3.20 g/kg BW VS 3.33 g/kg BW,P=0.079),GBI(13.66 g/kg BW VS 13.85 g/kg BW,P=0.437),DBI(6.37 g/kg BW VS 7.45 g/kg BW,P＜0.001),JBI(8.24 g/kg BW VS 9.86 g/kg BW,P＜0.001),IBI(4.73 g/kg BW VS 5.92 g/kg BW,P＜0.001) and GIBI(36.19 g/kg BW VS 40.40 g/kg BW,P＜0.001) and decreased GS(1.83 VS 1.67, P=0.121).Feed intake(P＜0.001,P=0.002 and P＜0.001,in 1^st,2^nd and whole period,respectively) and laying rate(P=0.042,P=0.085 and P=0.062,in 1^st,2^nd and whole period,respectively) increased as the granularity of ground corn increasing from 600μm to 1500μm treatment,and then decreased.The size of corn particle affected significantly the egg weight at each period.Egg weight touched the peak at 1500μm treatment in 1^st and whole period,and then 1000μm treatment in 2^nd period.Egg mass was as the same trend as feed intake and laying rate according to corn particle size(P=0.011,P=0.072 and P=0.024,in 1^st,2^nd and whole period,respectively).Egg/feed ratio,percent of eligible egg were not affected by corn particle size and reached the peak at 1500μm.traetment.Corn particle did not affect the egg special gravity and eggshell pressure.As time went on,the effect of corn particle on egg special gravity attenuated and on eggshell pressure intensified.Corn particle size affected significantly haugh Unit at 5^th week,haugh unit at 800μm treatment was the top and higher significantly than the one at 1200μm treatment.The rest were no significant difference.Egg yolk ratio was affected by corn particle at 5^th(P=0.044) week with the top one at 800μm treatment which was higher significantly than the one at 1200μm treatment,6^th(P=0.090) week with no significant difference,7^th(P=0.022) and 8^th(P=0.022) week with the top one at 800μm and 1500μm treatment.PBI,DBI,JBI and GIBI were not affected significantly by corn particle.With the granularity of corn particle increasing,GBI(P=0.003) increased and IBI(P=0.004) and GS(P＜0.001) decreased.In the present experiment,corn.particle size and feeding model were no significant interaction for all observations.The optimal corn particle size was the corresponding granularity at 1500μm treat-ment(1495μm) when voluntary feeding,and the one at 1200μm(1238μm) treatment when restricted feeding.