Status of the digestive system and tibiae of cropectomized hens at night.

Experiments were conducted to determine the effect of cropectomy on the total amount and calcium content of ingesta in the digestive tract of the laying hen at night, as well as to determine if any abnormal physiological changes had occurred in the cropectomized hens. Treatments were cropectomized, sham operated and unoperated control hens. The gizzards from cropectomized hens contained about twice as much feed at 7:30 p.m. as that of the controls. The gizzard weight, without contents, was also significantly heavier in cropectomized hens than that of the controls. At 7:30 p.m. total contents of the digestive system of cropectomized and control hens were 15.94 gm. versus 24.07 gm., respectively. The control birds also had 2.71 times more total calcium in the digestive system at 7:30 p.m. than the cropectomized birds. The contents of the small intestine of cropectomized birds had 17% more calcium at 7:30 p.m. than did that of the controls. However, by 5:30 a.m. the contents of the small intestine of the control birds had 3.17 times more calcium than did that of the cropectomized birds. No differences were found between treatments or between time periods in relation to tibia breaking strength, calcium content of tibia or percent tibia ash. The degree of dietary calcium deficiency at night appears to be greater with cropectomized hens, even though the gizzard compensates, in part, for the loss in storage capacity of the crop. It is hypothesized from these data that the crop is an important and necessary organ in the laying hen for supplying nutrients throughout the night when the hen is not consuming feed.