Duration of egg formation in hens selected for increased rate of lay under 23 h and 24 h light-dark cycles.
1. The intervals from oviposition to the next ovulation and the times spent by the ovum in various parts of the oviduct were examined, in hens selected for increased rate of lay over 5 generations under a 23 h light-dark cycle (23HS line) and kept in a 22 h light-dark cycle, and in hens selected under a 24 h light-dark cycle (24HS line) and kept in a 24 h light-dark environment. 2. The intervals from oviposition to the next ovulation were 13 min and 25 min in the 23HS and 24HS lines respectively. Times from ovulation to entry of the ovum into the uterus were 4 h 44 min and 4 h 43 min in the 23HS and 24HS lines respectively, and times spent by the ovum in the uterus were 19 h and 19 h 24 min in the 23HS and 24HS lines respectively. 3. It is concluded that the reduced oviposition interval in the 23HS line compared to the 24HS line was caused by the reduction in the interval from oviposition to the next ovulation and the time spent by the ovum in the uterus.
Naito
M
M
National Institute of Animal Industry, Tsukuba Norindanchi, Ibaraki, Japan.
Nirasawa
K
K
Oishi
T
T
D000818:Animals; D002645:Chickens / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D010057:Oviducts / Q000502:physiology; D010058:Oviposition / Q000502:physiology*; D010060:Ovulation / Q000502:physiology*; D010063:Ovum / Q000502:physiology; D013997:Time Factors