Price and Bottorff (1954) and Price and Gingher (1956) present 
additional data on the effect of Enheptin upon egg production. 
Before leaving the inhibitions of egg production, it 
should be mentioned that in poultry most diseases will stop or 
reduce egg production and although I do not intend to go into 
the subject more deeply here, the same undoubtedly applies to 
wild birds. 
3 Additives and deficiencies in yolk formation detrimental to 
hatchability. 
Removal of necessary substances covers a number of 
vitamins and a few minerals. Hens maintained on a diet furnish- 
ing them with less than 1200 U.S.P. units of vitamin A per lb. 
of diet laid eggs with reduced hatchability (Stoewsand et al., 
1961). Lack of folic acid in the diet reduced hatchability to 
zero in six to ten weeks (Sunde et al., 1950, and Couch et al., 
1950). The minimum required for New Hampshire pullets for 
normal hatchability was found to be between 26 and 34 micro- 
grams per 100 grams of diet (Lillie et al., 1950), and for 
turkeys about 0.7 mg. of folic acid per kilogram of ration was 
required (Kratzer et ale, 1956). A more acute deficiency and 
even lower hatchability were produced when sucrose served as 
the carbohydrate instead of dextrin (Sunde et ale, 1950 b). 
Ringrose et al. (1961) reported that a niacin deficiency re- 
duced hatchability in three weeks and caused almost complete 
inhibition of hatch in six weeks in chickens. Ferguson et al., 
(1961), reported that niacin deficiency in turkeys reduced 
hatchability well below 25 per cent with most of the mortality 
occurring during the second week of incubation. Biotin de-=- 
ficiencies completely reduced hatchability in both chickens 
and turkeys in three to four weeks (Diechert et al., 1950) 
with highest mortality occurring during the first week of in- 
cubation, (Ferguson et al., 1961). The minimum requirement 
in turkeys for pantothenic acid is about 16 mg. per kilogram of 
ration, lower ratios caused a drop to zero in hatchability in 
seven weeks (Kratzer et al., 1955) with highest mortality of 
embryos during the first week of incubation (Ferguson et al., 
1961). <A lack of vitamin By; in diet has been shown by a 
number of workers to reduce hatchability to 14 per cent to 
49 per cent (Petersen et ale, 1950 and Carver et al., 1950); 
also Ferguson et al. (1961) showed in turkeys a similar de- 
pression and high firsteweek mortality. In pigeons, addition 
of both riboflavin and By5 increased hatchability by 14 per cent 
(Shultz et al., 1953). Lillie, Olsen and Bird (1951) showed 
that birds with normal high hatchability rates were less suscept-= 
ible to riboflavin or Byo diet deficiencies than birds with low 
hatchability rates. Pyridoxine deficiency caused reduced 
hatchability in hens when the diet was below 4.35 mg. of vitamin 
per kilogram of diet (Puller et al,, 1961), and in turkeys it 
caused high second=week mortality (Ferguson et al., 1961). 
62 
