Photoperiodic sensitivity in domestic female birds

Abstract

Research works devoted to the photoperiodic sensitivity of domestic birds have been largely developed for half a century (between the thirties and the eighties) and have opened up the way to numerous applications in poultry practice. In the first part of the present paper, the main basic data concerning the perception and roles of photoperiod in birds are mentioned, namely: extraretinal (through the skull) perception of light and its consequences for the stimulating effect of different wavelengths; the double role of photoperiod, both stimulant of reproduction on a long term basis and daily synchronizer of the endocrine events which end up in ovulation and clutch formation; the apparently low involvement of melatonin into this mechanisms ; the notion of subjective day, underlaying the interrupted lighting programmes.

The second part of this paper is devoted to a summarized and updated presentation of the applications of these data to the laying hen, already largely exposed. The modulation of sexual precocity by manipulating daylength is still a classical component of the pullet rearing (at least outside the tropical zone). On an other hand, the sensitivity of the adult hen to daylength seems to have been reduced during the last three decades, inprobable relationship with the strong selection pressure exerted over the laying rate of this species. Some egg characteristics (such as egg-weight and eggshell thickness) can be improved by ahemeral lighting programmes longer than 24 h, or by short cycle symmetric programmes (without any main night period) which have been more used in the French context. Asymmetrical interrupted lighting programmes, keeping a main night period, can allow some productivity savings without any modification of the egg characteristics. Possible effects of these treatments on the hens’ welfare are also mentioned.