1026 Recent Research in Egg Production. [Feb., 



that there is a definite rhythm in the recurrence of these 

 cycles. 



Patterson < 15 ), who investigated this rhythm, has attempted 

 to apply it to the selection of the highest producing hens. 

 He found that hens which had a cycle of 4 eggs or more in 

 March produced on the average 156 eggs per year, whereas 

 hens having a cycle of 2 eggs or less averaged only 110 eggs 

 in the year. 



It is interesting to note that Atwood and Weakley ( 16 ) dis- 

 covered that the first egg laid in the cycle is usually the 

 heaviest, and that the eggs decrease in weight until the cycle 

 has ended. 



Bloodiness. — A probable cause of the lowering of the produc- 

 tivity is the onset of broodiness. This is largely a breed charac- 

 teristic. Kirkpatrick and Card( 17 ), who investigated this point, 

 found that the percentage of broody hens in the various breeds 

 was as follows : — 



White Leghorn, 9-7 per cent.; Rhode Island Reds, 65-6 per 

 cent.; and Wyandottes, 69-6 per cent. They calculated that 

 the average number of days lost by each broody hen in the year 

 was 53. 



Goodale*' 18 ) estimated that broodiness reduces a hen's pro- 

 duction by about 40 per cent. 



In this connection it is suggestive that Pearl and Boring^) 

 have discovered in the ovaries of fowls certain bodies which 

 they consider resemble the corpora lutea of mammals. 



Pearl and Surface^ ) found that they could inhibit egg- 

 laying in a fowl by giving doses of the corpora lutea of cows. 

 These authors, however, disagree with Clark( 21 ), who claimed 

 to increase the egg production of fowls by administering pituitary 

 substance with the feed. 



In the Copenhagen*! 4 ) laying trials it was noticed that 

 within any one breed broodiness was more pronounced in the 

 best layers. As this result appears to conflict with the inves- 

 tigations of Goodale and the fact that " sitting " breeds are 

 frequently better winter layers, it would appear that further 

 research is required as to the effect of broodiness on egg pro- 

 duction. It may be that some relation may exist between 



(15) Jour. Amer. Ass. Instr. and Invest. Poultry ' ffusbaridry, Nos. 2 and 3. 1916. 



(16) West l r i>yi,>iu Sta. Bui, 1917. 



(17) Connecticut Storrs Sta, Bui., 1917. 



(18) Massachusetts Sta. Rept., 1915. 



(19) Amer. Jour, of Anatomy. No. 1. 1918. 



(20) Jour. Biol. Chemistry, No. 2, 1914. 



(21) Jour. Biol. Chemistry, No. 3, 1915. 



