PROTEIN REQUIREMENTS OF CHICKENS AT VARIOUS 

 STAGES OF GROWTH AND DEVELOPMENT* II 



A. E. Tepper, R. C. Durgin,^ T. B. Charles, 

 S. R. Shimer and H. A. Davis 



PREVIOUS work on this problem has been reported in Station 

 Bulletin 312, covering the results of investigations in the period 

 April, 1935 to August, 1938. Work reported in this bulletin was con- 

 ducted from April, 1939 to August, 1940. 



In the earlier studies of protein requirements of chicks described 

 in Bulletin 312, chicks were raised to 70 weeks of age with meat 

 scraps, dried skimmilk and fish meal as the protein sources in their 

 rations. Results showed that increase of protein up to 18 or 20 per 

 cent in the ration improved growth in the first 12-week period of 

 age. Per cent of protein fed had no apparent relationship to body 

 weight, while there was a definite relation between total feed con- 

 sumed and body weight. Birds receiving the protein mixture and 

 fish meal supplements were heavier at twelve weeks of age than were 

 the meat scrap or dried skimmilk fed groups. Birds receiving lower 

 protein feeds (range 15 to 19 per cent) were more efficient in use of 

 feed in the 12 to 23 week age period. Birds receiving fish meal as 

 their only animal protein, laid better than other birds, had a lower 

 feed cost per dozen eggs, and were earliest in sexual maturity. The 

 per cent of protein fed had no significant relation to size of eggs, or 

 age of laying first (tgg. Fish meal in the ration did not produce any 

 discernible flavor or odor in meat or eggs. 



EXPERIMENTAL METHODS 



The previous work described in Bulletin 312 was conducted with 

 all birds grown and maintained in batteries and laying cages through- 

 out the experimental period. It was deemed wise to change this 

 method to growth and maintenance of birds in floor pens to allow 

 a comparison of the two methods of management as they may be 

 influenced by percentage and type "~of protein fed the birds. This 

 report is prepared in a form similar to that of Bulletin 312 for di- 

 rect comparison. 



April 6, 1939 twelve groups of 60 New Hampshire day-old chicks 

 were started under electric brooders on floor pens and raised to 16 

 weeks of age. At six weeks of age all groups were reduced in num- 

 ber by approximatel)' one half. At twenty-three weeks of age, each 

 group was further reduced to fifteen females and two males each 

 and continued as a breeding unit for future fertility and hatchabil- 

 ity studies through a period terminating at 70 weeks of age. The 

 weights reported after six weeks of age apply to females only. 



*A cooperative project between the Poultry Husbandry and Agricultural and Biological Chem- 

 istry departments. 

 ^Resigned, December 31, 1940. 



