Managing egg incubation to benefit chicken bone strength
The animal article of the month for April is ‘Incubation and hatch management: consequences for bone mineralization in Cobb 500 meat chickens‘
Following two field observations of newly hatched chicks that had soft bones and were having difficulty standing, we wanted to find out what causes soft bones and, what could be done to prevent this from occurring in the future. We also wanted to improve the standing ability of meat chickens. On reviewing the incubation conditions of the two batches of chicks with soft bones we were particularly interested in whether the incubation temperature could be effecting bone development in the chick embryo. We tested this theory in several studies using the Australian meat chicken breeder line in which the incidences of soft bones had been originally observed. We found that lower initial incubation temperatures delay chick hatch and, the later hatching chicks have higher bone mineral levels, indicating they have stronger bones, than earlier hatching chicks. Importantly, when 5 weeks old, the later hatching chicks could stand for longer than the earlier hatching chickens. 
As these initial studies involved a meat chicken breeder line, we then explored whether incubation temperature could also be used to improve the bone strength of the commercial Cobb 500 meat chicken, and, if the bone strength of the earlier hatching birds could be increased by giving them food soon after they hatched.
As with the parent line, Cobb 500 chicks that had been incubated with lower initial temperatures generally hatched later and they also had higher bone mineral levels than the early hatching chicks. We also found that we could increase the bone strength of the early hatching chicks by giving them access to food and water soon after they had hatched.
Following on from this we also observed that early hatching chicks are more likely to have the leg disorder tibial dyschondroplasia. 
Therefore, avenues to improve meat chick leg strength at hatch include incubating the eggs at lower temperatures in the early stages of incubation, which will delay chick hatch but will result in the chicks with stronger bones. Alternatively, if the chick has hatched early, the prompt provision of feed and water will improve its leg strength.
This article is freely available for one month: ‘Incubation and hatch management: consequences for bone mineralization in Cobb 500 meat chickens‘.
Author: W. Muir
 See publication doi:10.1371/journal.pone.0102682
 See publication doi:10.1017/S1751731116001105