24 N. H. Age. Experiment Station [Bulletin 262 



of the timber, the distribution of age classes, the delimitation of the 

 boundaries between owners, and the division of the area into land uses. 

 (Purnell Fund) 



Measuring Vitamin A Requirements 



Although more than one per cent, cod-liver oil in the ration now 

 appears to retard the growth of chicks, research has not yet shown how 

 much oil is needed to meet their vitamin A requirements. As much as 

 three per cent, has already been given. Four and five per cent, will 

 be tried during 1932. Since the number of units of vitamin A in the 

 oil is definitely known, an exact measure should soon be made. Then 

 other feeds carrying vitamin A can be substituted for the growth- 

 retarding oil ; for instance, alfalfa-leaf meal or yellow corn meal. 



The determination of the vitamin A requirements of chicks is im- 

 portant. Healthy chicks cannot withstand a deficiency of this vitamin 

 for more than a few weeks of the initial growth period. 



In the experimental work in 1931, several groups of chicks were 

 used. One was fed the New England college conference ration, an- 

 other a ration entirely lacking in vitamin A, others a vitamin A de- 

 ficient ration with one, two, and three per cent, cod-liver oil. Each 

 lot was weighed weekly. All made similar growth the first six weeks, 

 but the group given the conference ration, which includes one per cent, 

 of cod-liver oil, forged ahead and finished the experimental period far 

 in advance of the others. The group getting three per cent, oil was 

 greatly slowed down in development. Kidney injury was also noticed 

 in all groups, except the one of the conference ration. Each group 

 was given the same irradiation from an ultra-violet lamp each day to 

 insure sufficient vitamin D. The work was done by A. E. Tepper, H. 0. 

 Stuart, T. B. Charles. (Purnell Fund) 



Comparison of Brooder Temperatures 



High brooding temperature in the heated-room type of battery 

 brooder produces greater growth and means smaller loss in both light 

 and heavy breeds of chicks, according to trials with starting tempera- 

 tures of 90 and 95 degrees, which were reduced five degrees each week 

 during a six-weeks' period. 



Under the lower temperatures the heavier breeds of chicks — New 

 Hampshire Reds and Barred Plymouth Rocks — made slower gains per 

 week and were lighter at the end of six weeks Hum the same breeds 

 under the higher temperatures. The mortality of the lower-tempera- 

 ture group was seven per cent., as compared with only two per cent, for 

 the higher temperature. 



The lighter breeds responded similarly, although they were a bit 

 slower in starting under the higher temperatures. By the end of the 

 third week they were ahead of the lower-temperatures group and held 

 this lead throughout the remainder of the period. A. E. Tepper, H. 0. 

 Stuart, T. B. Charles. (Purnell Fund) 



