Establishment Of The Dynamic Prediction Model For Energy Requirement Of Pink-shell Laying Hens During Peak Production

The various versions of the standards for pig and poultry feeding are static averages of the nutritional requirements of groups at different stages of production which cannot reflect the specific effects of specific physiological states,environmental conditions and management levels on animal nutritional requirements.Therefore,an important direction for the development of livestock and poultry nutrition needs research is to achieve dynamic assessment through modeling.In this study,we developed dynamic prediction equations for energy（metabolizable energy ME and net energy NE）requirements of powder-shelled hens using the factorization method to help hens consume energy accurately and save energy and reduce carbon.Study 1,the dynamic prediction equations for energy demand of powder-shelled hens during peak laying period were derived based on the adiabatic metabolism method and the comparative slaughter method.In the first trial,32 healthy Jing Tint 6 hens of similar weight at31 weeks of age（95% ± 5% egg production）were placed in a new 16-pack poultry respiratory calorimetry device,with 2 hens in each compartment.The initial body weight,final body weight,oxygen consumption,and CO2 exhalation were recorded during the 5-day acclimatization period and the 3-day fasting period.In the second trial,20 healthy Jing Tint 6 hens of similar weight at 31 weeks of age（95% ± 5% egg production）.6 of which were killed without bloodletting and the remaining 14 were weighed and reared until 39 weeks of age,then weighed again and executed without bloodletting to determine body deposition energy.During the rearing period,eggs were collected to measure egg deposition.After respiratory calorimetry,the experimental chickens’ dietary heat production,or net energy requirement for maintenance（NEm）was 368.36 k J/kg W^0.75?d.Based on the above results,study 1 established a peak NE demand prediction model with body weight,daily weight gain,and egg production as independent variables.The dynamic prediction model for the NE requirement of laying hens was as follows: NER（k J/d）= 368.36 W^0.75（kg）+ 14.26 BWG（g/d）+ 5.39 EM（g/d）.Study 2 was based on the gradient feeding restriction method,comparative slaughter method,and regression method to derive the dynamic prediction equation of energy demand during the peak egg-laying period of pink-shelled hens.In the first experiment,10 healthy Jing Tint 6 hens of similar body weight at 44 weeks of age were selected to determine the metabolizable energy level of the diet using the whole manure collection method.In the second experiment,60 hens with similar body weights at 38 weeks of age（95%±5% egg production）were randomly divided into 6 groups of 10 hens each.One group was selected for execution without bloodletting,and the remaining five groups were respectively weighed and fed in a graded manner at 100%,85%,70%,55%,and 40% of the free feeding rate.At 46 weeks of age,the animals were weighed again,and executed without bloodletting to measure the body deposition energy.During rearing,feed intake and egg production were counted while eggs were collected to determine egg deposition energy.Considering ME intake of tested hens as the dependent variable and metabolic body weight,daily weight gain and daily egg production as the independent variables in direct regression analysis,a dynamic prediction model of ME requirement of peak laying hens was established as follows: MER（k J/d）= 611.93 W^0.75（kg）+25.90 BWG（g/d）+ 10.85 EM（g/d）.A linear regression analysis was performed with ME intake as the dependent variable and body deposition energy and egg deposition energy as the independent variables to obtain the maintenance metabolic energy requirement of 626.55 k J/kg W^0.75?d,growth metabolic energy requirement of 26.83 k J/g and egg laying metabolic energy requirement of 10.43 k J/g for the test hens,and a dynamic prediction model of ME requirement for peak laying hens was established as follows: MER（k J/d）= 626.55 W^0.75（kg）+ 26.83 BWG（g/d）+ 10.43 EM（g/d）.Using heat production of test hens（HP = MEI-REg-REe）as the dependent variable and ME intake as the independent variable,an exponential regression analysis was performed to find the dietary heat production of test hens,i.e.,the net energy requirement for maintenance（NEm）of 377.73 k J/kg W^0.75?d.Combining the body deposition energy and egg deposition energy,the dynamic prediction model of NE requirement of peak laying hens was established as follows: NER（k J/d）= 377.73 W^0.75（kg）+ 13.62 BWG（g/d）+ 5.49 EM（g/d）.