Stochastic model to estimate egg production in broiler breeders

The objective of this study was to develop a stochastic model to allow the prediction of individual biological responses of yellow follicle numbers (YF) and egg production rates (EGGs) of broiler breeders to changes in body weight (BW) on the basis of existing experimental data. The model was based on commercial modelling software. The first step was to model the relationship between YF with BW. Linear regression between BW and YF at all ages was assumed using relationships derived by Hocking (1993, 2004). Therefore, at any age, the model’s predicted value of YF is: YFexp = YFr + (YFal-YFr)*PrBW, where PrBW = (BWexp-BWr)/(BWal-BWr), YFr and BWr are theoretical YF and BW in restricted fed hens respectively and YFal, BWal are YF, BW in ad libitum fed birds. BWexp is experimental BW from data on restricted hens. An equation of sequence length was constructed and included as a variable affecting YFexp and allowing a pause during the cycle of production. EGGs was determined by two equations based on the YFexp present in the hen: if YFexp≤6 the relation used was: YFexp/6; if YFexp>6 the equation used was: 1-((YFexp-6)*0.5)/6, where 6 is the number of positions in the hierarchy of yellow follicles and 0.5 is the rate of egg production (number/hen d-1) from multiple ovulation. The estimates obtained by simulation for YF, BW and EGGs show similar behaviour to that observed in several published experiments. In conclusion, the model simulates the production of broiler breeder eggs with acceptable and high precision