Effects Of Low Protein Diet In Ideal Amino Acid Pattern On Laying Performance And N Excretion Of Laying Hens

Recently, the costs of feedstuff are more and more in the livestock breeding industry.Lots of protein sources depending on imports and the increasingly serious environmentalnitrogen pollution caused by livestock indicate the necessity of using low-protein diets in theproduction. The aim of this study was to examine the effects of dietary crude protein (CP)with synthetic amino acid supplementation on egg performance, egg qualities, bloodparameter, N excretion and greenhouse gases in laying hens of21to34weeks of age and toexplore the feasibility of using low protein dietary in the production of laying hens.Trial1focus on the effects of dietary crude protein levels on egg performance and eggqualities in laying hens. Hy-Line Grey layers (n=540,20weeks old) were randomly allottedinto one of five dietary treatments, which had17.00%,16.50%,16.00%,15.50%and15.00%CP level in the same dietary energy of11.00MJ/kg.Each treatment contained6replicates of18hens in6cages. The trial lasted for14weeks. Average daily feed intake and daily egg masswere maintained well during the feeding trial while egg production, egg weight and egg/feedwere significantly affected by the protein level of dietary (P<0.05). As the CP level decreased,there was improvement in egg production and egg/feed, in contrast, egg weight and averagedaily protein intake were significantly decreased during this study (P<0.01). All of the eggquality parameters were significantly affected during the feeding trial (P<0.01) except eggshell thickness. There were no significant effects on egg components (P>0.05). Albumenheight of17.00%CP level group was significantly higher than the other four groups (P<0.01).The egg shell strength of16.50%CP level group was lower than the groups of16.00%,15.50%and15.00%CP levels (P <0.01), when the egg shell strength of17.00%CP levelgroup was similar to the other four groups. The Haugh unit of17.00%and15.00%CP levelgroups was similar to each other and their value was dramatically higher than the other threegroups (P <0.01). The dietary CP levels also significantly effected on the yolk color of layinghens (P <0.01). In conclusion, the low dietary protein with synthetic amino acidsupplementation at a constant standardized ileal digestible amino acid pattern can maintainedthe layer performance well. Trial2focus on the effects of dietary crude protein levels on blood parameter, Nexcretion and greenhouse gases in laying hens. Hy-Line Grey layers (n=540,20weeks old)were randomly allotted into one of five dietary treatments, which had17.00%,16.50%,16.00%,15.50%and15.00%CP level in the same dietary energy of11.00MJ/kg.Eachtreatment contained6replicates of18hens in6cages. The trial lasted for14weeks. As CPlevel decreased, the concentration of plasma uric acid was trend to decline (P=0.053). Thedietary CP level has no effect on the concentrations of blood ammonia among treatments (P>0.05). The average daily excretion of dry matter had a trend to reduce (P=0.09). N excretionwas reduced significantly as CP level decreased (P <0.01).Dietary CP level did notsignificantly affect CO₂and CH₄emission, but a decreasing trend of CH₄emission did exist.The results indicated that feeding low protein diet with synthetic amino acid supplementationat a constant standardized ileal digestible amino acid pattern can reduce the concentration ofplasma uric acid and decline N excretion while the CH₄emission had a decreasing trend.