Extending the laying cycle of laying hens- can egg quality be sustained?

Extending the production cycle in laying hens and producing 500 eggs in a single laying cycle until 100 wk of age appears to be a realistic goal to reach by 2020. Field reports suggest that this might be feasible even today, in 2017. However, results of a field study conducted in 2014 on Belgian layer farms and observations in (long term) studies conducted at ILVO and EPC in Belgium suggest that there are considerable differences between layer hybrids regarding their potential for an extended laying cycle. Results of the field study indicated that laying hens were kept in production on average until 80 wk of age, but end of lay ranged between 74-92 wk. Egg quality was assessed at 60 wk and at the end of the laying period. Although internal and shell quality declined, and variability between eggs increased, egg quality was still acceptable at end of lay. Flocks were depopulated before decreasing shell quality could cause economic losses. This suggests that some commercial flocks in 2014 might have already had a potential to be kept beyond 80 wk of age. However, there are several bottlenecks in extending the production period of layer flocks: not only egg quality, but also persistency and bone quality declines as hens become older. Genetic selection programs address these problems by including new traits as selection criteria (e.g.: clutch length, dynamic stiffness) and new molecular breeding methodologies (genome-wide studies and identification of quantitative trait loci). However, improved genetic potential of highly prolific layer hybrids can only be realized in the filed if nutrition and management are both optimized in extended production cycles. In fact, extended production cycle starts at day 1 of rearing. Growth during rearing and the early laying period determine for a great part, how a flock will perform and how long the laying hens can be kept in production. Initial pullet weight at the onset of lay is related to total egg output, and growth during this period determines how egg size will increase during the start of lay. Perhaps in extended production cycles more robust birds with higher bone Ca reserves having a delayed start of lay could maintain persistency and eggshell quality for longer. Therefore, adjusted lighting programs might need to be applied already during rearing if the goal is to keep hens in production until 100 wk of age. From onset of lay, maintaining gut health and the integrity of the intestinal segments, with special attention to the duodenum – the main site of Ca and P absorption – is a pre-requisite for maintaining eggshell quality in extended laying cycles. In addition, there might be a potential to improve Ca utilization and consequently shell quality in aged laying hens in alternative feeding systems, such as split feeding, where nutrient supply better matches requirements during the daily egg formation cycle compared to in conventional systems where one diet is fed during the day. Results of long-term studies at EPC indicate that split feeding can have a potential not only to improve feed efficiency but also to decrease cracked eggs % in the last phase of the production cycle. In general, an overall strategy is needed which includes different nutritional aspects and management practices to tackle specific problems related not only to egg(shell) quality but also to health and welfare problems (such as bone integrity, gut health) to successfully extend the production period.