| In this study, by measuring the production performance、nutrient retention、eggs quality、blood biochemical index and tibia quality of Hy-line laying hens，discuss theappropriate level of calcium and phosphorus in low-energy diet.Experiment1: Effect of different calcium、phosphorus levels on production performanceand nutrient apparent metabolic rate of laying hens in low energy dietsThe1050Hy-Line hens were randomly divided into10treatment groups (5replicates of21hens per treatment), the experiment lasted for56days.The energy was10.89MJ/kg in diet, the calcium levels were as follows:3.0%,3.5%,4.0%,and the availablephosphorus levels were as follows:0.28%,0.32%,0.36%, the control group was designedaccording to GB(2004). The results showed that:(1) when the calcium levels varied from3.0%to4.0%and available phosphorus levels varied from0.28%to0.36%in diet, thelaying rate、average egg weight、egg production、average feed intake and survival ratehave declined and cracked egg percentage has increased with the improvement of calciumlevel but no significant difference(P>0.05); average egg weight、egg production、averagefeed intake、feed/egg ratio and survival rate raised at first and then decreased and crackedegg percentage contrary but no significant difference(P>0.05).(2) the apparentdigestibility of dry matter、crude ash and calcium had no significant difference (P>0.05)when the calcium levels varied from3.0%to4.0%and available phosphorus levels variedfrom0.28%to0.36%in diet. the apparent digestibility of crude protein, group3.0%calcium content was significantly higher (P<0.05) than group4.0%, the apparentdigestibility of total phosphorus, group4.0%was significantly higher (P<0.05) thangroup3.5%and had no significant difference (P>0.05) with group3.0%; the apparentdigestibility of crude protein and total phosphorus, group0.32%available phosphoruscontent was significantly higher (P<0.05) than group0.28%and had no significantdifference (P>0.05) with group0.36%.(3) the analysis indicated that the calcium levels3.0%and available levels0.32%(energy was10.89MJ/kg) was the best among thetreatment groups for the laying performance and nutrient apparent digestibility.Experiment2: Effect of different calcium、phosphorus levels on egg quality of laying hensin low energy diets This study was conducted to determine the influence of dietary calcium andphosphorus levels on egg quality in low-energy diet. Four eggs were selectedRandomly from each repeated to determine the egg quality at the end of study,eggshell was collected and died for testing the calcium and phosphorus in the eggshell.The results showed that:(1) egg specific gravity、eggshell weight percentage andeggshell relative thickness, group3.0%calcium content was significantly higher(P<0.05) than group3.5%and had no significant difference(P>0.05) with group4.0%,the change of phosphorus in diet has no significant effect on egg quality; thecalcium and phosphorus interaction had significant effect (P<0.05) on Haugh unit、eggshell weight percentage and eggshell relative thickness.(2) the calcium in theeggshell has increased when the calcium levels varied from3.0%to4.0%, the calciumin the eggshell has raised at first and then decreased when the available phosphoruslevels varied from0.28%to0.36%, the change of calcium and phosphorus in diet hasno significant effect on the phosphorus in the eggshell(P>0.05).(3) the analysisindicated that the calcium levels3.0%and available phosphorus levels0.32%(energywas10.89MJ/kg) was the best among the treatment groups for the egg quality.Experiment3: Effect of different calcium、phosphorus levels on tibia quality and serumBiochemical parameters of laying hens in low energy dietsThis study was conducted to determine the influence of dietary calcium andphosphorus levels on blood biochemical index and tibia quality in low-energy diet.chosefive chick from each treatment according to the average weight at the8:00am in thesecond day of the feeding trial, and extracted blood from four chick’s vein, and thencollected the serum in order to testing the content of calcium, phosphorus and the activityof AKP in serum.Then extracted the right tibia from three chicks to testing the content ofash, calcium and phosphorus in tibia. The results showed that:(1) tibia quality、thecontent of serum phosphorus and the activity of AKP in serum had no significantdifference (P>0.05)When the calcium levels varied from3.0%to4.0%and availablephosphorus levels varied from0.28%to0.36%in diet; the content of serum calcium,group3.0%calcium content was higher than group3.5%(P>0.05) and group4.0%(P<0.05); the content of serum phosphorus, group0.32%available phosphoruscontent was significantly higher (P<0.05) than group0.36%.(2) the content of calcium,phosphorus in serum was higher than the other treatment groups when calcium andphosphorus levels in diet were3.0%、0.32%, the content of ash, calcium and phosphorusin tibia was higher than the other treatment groups when calcium and phosphorus levels in diet were3.5%、0.36%.(3)when energy was10.89MJ/kg in diet, the analysis indicatedthat the calcium levels3.0%and available phosphorus levels0.32%was the best amongthe treatment groups for the blood biochemical index,and the calcium levels3.5%andavailable phosphorus levels0.36%was the best among the treatment groups for the tibiaquality. |
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