duction, egg weight on any calendar date, body weight after six weeks 

 of production, fertility, hatchability, or laying house mortality. 



Progress reports from this station on some of the studies summarized 

 here have been presented (7,8,9). 



Experimental 



Throughout the studies to be reported, customary management practices 

 were followed. Starting, growing, and laying feeds were used, the change 

 being made at the usual times. For some experiments commercially mixed 

 branded feeds were used, for other experiments custom mixed New Eng- 

 land College Conference formula feeds were used. Whenever feed restric- 

 tion was practiced, sufficient feeder space was allowed so that all chickens 

 could eat at one time. All feeds used were of the type termed "high efficiency" 

 or "high energy*' at the time the experiment was conducted. 



Vaccination and immunization for disease control was according to 

 accepted practice for this area at the time. Drug medication, except in one 

 experiment specifically mentioned, was limited to the use of a coccidiostat 

 for coccidiosis control. 



Artificial light was used to maintain a minimum 14-hour day, regardless 

 of season of year or age of the chickens. This practice was based on re- 

 search at this station demonstrating that chickens hatched in the fall 

 months can be delayed in sexual maturity about two weeks, when grown 

 under conditions of uniform 14-hour light as compared to chickens sub- 

 jected to the conditions of natural daylight (10,11). Since we were in- 

 terested in delaying sexual maturity, it seemed logical to make use of 

 this management practice and determine what delay might be obtained by 

 the feeding program. 



Culling was not practiced at any time. On occasion it was necessary 

 to adjust pullet numbers to available housing space. This was done by 

 random selection and distribution of the pullets to be used. 



For determining pullet age at a particular production level, an average 

 of three days' egg production was used to determine the percentage egg 

 production. Average egg size to 50 percent egg production level was meas- 

 ured by weighing all eggs laid to this specific time and dividing by the 

 number of eggs weighed. In order to obtain the egg size distribution 

 throughout an experiment, the usual type of commercially manufactured 

 farm egg grader was used. Up to the point of 50 percent egg production 

 each day's eggs were graded. After the time of 50 percent egg produc- 

 tion, one week's eggs out of every four weeks' production was used (25 

 percent sample). The number of eggs per hen was figured on a hen-day 

 basis. 



Since the initial program for restricted feeding was of field origin, the 

 first two experiments (No. 1 and 3) were an attempt to evaluate this pro- 

 gram under controlled conditions. 



The first experiment was started in November, 1952, utilizing a com- 

 mercial strain of meat-type New Hampshire stock. One hundred and fifty 

 straight run chicks were randomized into each pen with the cockerels re- 

 moved at twelve weeks of age. The feeding treatments were as follows: 



