Non-invasive Corticosterone Monitoring in Laying Hens with Different Egg Production Rate

The process of egg production has to be regarded as severe metabolic stress to the hen. Elevated corticosterone concentrations have been described to precede oviposition for one to two hours, but may be masked by the diurnal changes in levels of glucocorticosteroids (corticosterone, cortisol). Increased corticoid levels were discussed either to be involved in the local induction of the process of ovulation and/or oviposition, or as result of those processes. The objective of the study was to investigate the relation between egg production rate and overall level of secretion of glucocorticosteroids determined as contents in feces. First, a method for determining glucocorticoids in feces was developed. Then, the diurnal rhythm of secretion of corticosterone and cortisol in feces was determined. In the third step, feces were collected and egg production was recorded daily in 16 Bovans Goldline laying hens during a 35 days period. Eight hens showed low to moderate and 8 hens high laying performance. Corticosterone concentrations in feces were about twofold higher than those of cortisol (20.0 and 10.1 ng/g fresh matter for corticosterone and cortisol respectively, p ≤ 0.01) and reached a diurnal maximum in the morning samples. Corticosterone concentration was lower with less variation during the experiment in ‘good’ performing hens, whereas, it was significantly higher and more variable in ‘bad’ layers. Furthermore, corticosterone content in feces decreased in ‘good’ performing hens and increased in ‘bad’ performers during the experimental period. It was concluded that the capacity of hens to buffer stress is the key to a high laying rate.