Walstra looked for ways of increasing the adaptive capacity of laying hens, so as to enable them to respond to pathogens more effectively. She hatched eggs at the optimal eggshell temperature of 37.8 degrees Celsius, after which the chicks had immediate access to food and water. They were then kept in a free-range barn with a dust bath for seven weeks.
Another batch of eggs was hatched at temperatures of between 36.7 and 38.9, did not get immediate access to food and drink, and were kept in a cage. These conditions are common in the poultry sector. When the chicks were exposed to an intestinal parasite at the age of 53 days, the chicks in the first group were affected much less severely. “All the chicks fell ill, but the first group lost less weight than the second group”, says Walstra.
Poultry farmers obtain more resilient laying hens if more care is taken at the hatchery over the temperature in the hatching machine and the living conditions for the young chicks, concluded Walstra. It can be difficult to make the second improvement because standard hatcheries do not have space for chicks to free-range before they are delivered to the poultry farmers.
Walstra calls her experimental research a first step towards an alternative method of improving animal health without using drugs. She does add that the resistance of the laying hens is also influenced by the conditions in the barn, the virulence of the pathogens concerned and the poultry farmer's management.
Source: Wageningen University
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