Spontaneous intake of essential oils during the early rearing phase of chicks and long-term effects on performance and transcriptome regulation

To mitigate the effects of stressful factors during the perinatal period in broiler chicks, we have tested their ability to drink spontaneously essential oils (EO) in addition to water. Chicks were either immediately placed in the rearing facility (C group), or submitted to a 24h-delayed period before their placement (S group) mimicking transport delay in commercial conditions. In experiment 1, half of each group had only access to water and the other half to water and one EO (cardamom, marjoram or verbena) from D1 to D13. In experiment 2, half of each group had only access to water and the other half was offered water and the 3 EO simultaneously.

In experiment 1, EO intake was higher in S group than in C group from D1 to D6 whatever the EO. In experiment 2, from D1 to D6, the marjoram intake was the highest compared to the other EO whatever the treatment. EO intake did not allow to overcome the reduced growth in S group but tended to overcome the reduction of the relative percentage of Pectoralis major muscles. Transcriptome analysis of blood cells showed long-term effects of the delay to placement on gene expression at slaughter age. Overexpression of transcription factors in S group was related to oxidative stress in males and to oncogenesis in females. EO intake reduced the overexpression of several genes involved in oxidative stress and inflammation in S groups.

In conclusion, chicks are able to make spontaneous choices for EO according to their post-natal experience. These choices had a few beneficial effects on their performance, and long-term regulatory effects on blood transcriptome which could participate to maintain chicken welfare and health.

This study was supported by a grant from the Integrated Management of Animal Health metaprogram of INRA for the 'GISA – WHELP' project (www.gisa.inra.fr/en).

Fig. 1: Spontaneous Intake of essential oils by chicks placed immediately after hatching in rearing facility (C group) or submitted to a 24h-delayed period before thcir placement (S group)