1030 Recent Research in Egg Production. 



and Kirkpatrick,(34) w h noticed that small eggs were laid at 

 a time when the hen is laying most heavily. Brown/ 35 ) how- 

 ever, found with White Leghorns that there is nothing to indi- 

 cate that high production is responsible for any diminution in 

 the size of the egg, and Murphy (31) found that small eggs were 

 not always coupled with heavy production. 



In the Copenhagen trials* 14 ) it was observed that the weight 

 of the egg appeared to increase with the age of the hen, and it 

 is a matter of common observation that pullets lay smaller eggs 

 than do mature hens. It has been pointed out above that the 

 first egg laid in the cycle is usually the heaviest. 



Colour of the Egg.— Very little is known concerning the 

 causes which influence the colour of the egg shell. Tinted 

 egg shells are supposed to be due to products of hepatic origin 

 (bile pigments) secreted by certain glands of the oviduct. 



Laurie found in Australia that the tinting was less marked 

 in warm weather. Tinted shells, however, are undoubt- 

 edly chiefly a matter of breeding, although Lewis and 

 Thompson ( 37 ) in America have observed that some hens pro- 

 duce eggs varying widely in colour, while others show a 

 marked uniformity in this respect. 



The colour of the yolk is no doubt greatly influenced by 

 the food of the hen; thus Henriques and Hansen* 38 ) found 

 that hens fed on grains gave a light yellow yolk while grass 

 and herbs produced a dark yellow yolk, and a diet of worms 

 gave yolks of a reddish hue. Opperman( 39 ) in America, 

 who experimented with lots of forty White Leghorns, found 

 that feeding on yellow maize produced a rather deep yellow, 

 while wheat meal gave a very pale yolk. Hink,( 40 ) who fed 

 acorns to fowls, noticed that they produced yolk of a dirty brown 

 colour. 



From these experiments and from those quoted above on the 

 effect of egg production in reducing the yellow colour of the 

 legs and ear-lobes in certain breeds, it would appear that the 

 colouring matter of the yolk of the egg is derived from the 

 colouring matter of the fat of the body. The colouring of the 

 body fat is in turn derived mainly from the green colouring 



(34) Jour. Heredity, No. 3, 1916. 



(35) Jour. Bd. of Agric. and Fisheries, No. 3, 1916. 



(36) Jour. Dept. Agric., S. Australia, Nos. 9—10, 1915. 



(37) New Jersey Sta. Bept., 1915. 



(38) Skandin. Archi. f. Physiol., Vol. XIV., 1905. 



(39) Country Gentleman, No. 9, 1914. 



(40) Deutsche Landwirt. Tierzucht, No. 29, 1915. 



