PHOTOPERIODISM IN FEMALE DOMESTIC FOWL 771 



lighting resulted in higher egg production than did the same daily 

 ration given continuously. 



In the experiments of Piatt (1953) noted previously, red light was 

 used to divide the dark period. No direct comparison can be made, 

 however, between Piatt's results and effects of red light used to 

 lengthen the natural day. 



High-intensity light for one or a few short periods (5 to 20 sec) 

 during the night has been shown to stimulate or maintain high egg 

 production in the hen (Staffe, 1950, 1951; Weber, 1951), an effect 

 comparable with those of more conventional forms of intermittent 

 lighting, though intensity possibly plays a role here not usually en- 

 countered. 



Within limits, a given total daily light ration is apparently more 

 effective in stimulating or maintaining egg production in the hen when 

 applied intermittently than it is as a single photoperiod. As far as 

 ovarian response is concerned, the effect appears to be similar to that 

 observed in wild birds. As Farner et ah ( 1953a,b) suggest, the greater 

 effectiveness of intermittent lighting in the hen may be explained by 

 the "carry-over period" of gonadotropic activity after the cessation of 

 a photoperiod. 



(c) Intensity and wavelength. According to Roberts and Carver 

 (1941; also Dobie et al. 1946), no significant differences were ob- 

 served in production under light intensities of 1.0 to 31.3 ft-c at feed 

 troughs, "provided the hens receive 13 hr of Mazda light per day." 

 Nicholas et al. (1944) reported no effect on production of intensities 

 ranging from 0.5 to 38.0 ft-c. The minimal intensity for the mainte- 

 nance of even high production is obviously quite low. 



Curiously, no study of the effects of wavelength comparable to that 

 of Benoit and Ott (1944) in the immature male duck has been made 

 in the hen. Scott and Payne (1937) found that early morning use of 

 unfiltered white light, or red light only, stimulated early egg produc- 

 tion in the turkey, but blue or blue-green light failed to do so. The 

 greater effectiveness of red (i.e., long) wavelengths is in accord with 

 results in the duck (Benoit and Ott, 1944). It seems generally as- 

 sumed that the response of the fowl is similar; certainly red lights of 

 low (?) intensity stimulate or maintain high production (cf. Piatt, 



