follicular atrophy was evident. The injections must have 
affected the mechanism involved in maintehance of the ovarian 
follicle, probably by way of neural pathways. 
Two irradiation studies that deal directly in one 
case and indirectly in the other case with inhibition follow. 
Muller et al. (1960) irradiated in a single dose from 100 to 
1000 roentgens at the rate of 43 roentgens per minute fertile 
eggs and one, two, and three-day-old embryos. They then selected 
randomly a group of female chicks that hatched from these eggs 
to raise to mat rity. Egg production was generally lower from 
these birds during the first six months of their production. 
Those receiving 400 to 700 roentgens exhibited delayed maturity 
or complete inhibition of egg production. Regression analysis 
tebe an decrease to be 1.66 per cent for each 50 roentgens 
received. 
Quisenberry and Atkinson (1953) gave X-ray doses of 
50, 100, 200, 300 and 500 roentgens to White Leghorn cockerels 
of 6, 12, and 18 weeks of age. After recovery from post 
irradiation symptoms, they were mated to normal non-irradiated 
White Leghorn females. Of the embryos dying during the third 
week of incubation, females predominated. The per cent of 
third-week dead embryos was highly related to the amount of the 
X-ray dosage. They suggested that maybe a sex-linked lethal 
had been created by the irradiation. 
Now to cover some of the nutritional and pharmaceutiéal 
inhibitions of egg production. There is a tremendous amount of 
material in the literature on protein levels and energy ree 
quirement necessary for maximum egg production which I shall not 
go into here other than to say that birds need adequate protein 
levels and energy sources for maximum production. 
Feeding diets to birds which are deficient in various 
vitamins has a marked effect on egg production. It has been 
shown that a minimum requirement of vitamin A for maximum egg 
production for laying hens is 1200-1600 U.S.F. units per pound 
of diet (Hill et al., 1961), and 1200 U.S.P. units of stabilized 
vitamin A per pound of diet for turkeys (Stoewsand, et al., 1961). 
Sunde et al. (1950) showed that a ration lacking folie acid 
inhibited egg production completely by ten weeks in laying hens, 
and that 0.25 mg./kilogram of feed was a borderline level. 
Ringrose et al. (1961) demonstrated that niacin deficiency re- 
duced egg production, but not to zero. Niacin at 20 to 50 mg./ 
lb. of feed was necessary to give results equivalent to the 
controls. Ferguson et al. (1961) showed using Beltsville Small 
White turkeys (fed a basal casein-gelatin diet minus one vitamin 
at a time) that a riboflavin deficiency reduced production to 
zero in eight weeks, approached zero in the pyridoxine deficient 
group and suddenly dropped after 12 weeks in the pantothenic 
acid deficient group. In Single Comb White Leghorns, the minimum 
requirement of pyridoxine was approximately 2.3 ng./Kilogram of 
diet. Below that level production was markedly reduced. Wooten 
59 
