42 N- H. EXPERIMENT STATION [Bulletin 310 



Performance requirements, birds must lay a minimum of 200 stand- 

 ard-sized eggs in a laying year. (Miscelloneoiis Income) 



Poultry Approval 



During the year 1938-39 New Hampshire poultrymen had 20.500 

 birds handled and selected by R. C. Durgin. selecting agent. This 

 process of selection and culling is called "approval." Both Poultry 

 Approval and Xew Hampshire Record of Performance regulations 

 comply with the provisions of the National Poultry Improvement 

 program. (Miscellaneous Income) 



Selective Breeding as a Control of Ruptured Egg Yolk 



This project which was carried on by R. C. Durgin. C. L. Martin, 

 M. S. Cover, A. E. Tepper, T. B. Charles and C. A. Bottorfif endeav- 

 ored to develop both susceptible and resistant lines to the condition 

 known as ruptured egg yolk. Post-mortem records maintained by 

 this department indicate this condition to be one of the major causes 

 of adult mortality. 



During the sjiring of 1939. one hundred ninety-eight chicks were 

 pedigree-hatched from families which showed a low incidence of 

 this condition. Two hundred twelve chickens were hatched from 

 families which showed a high incidence of ruptured egg yolk. From 

 these chicks we have housed five families of 63 birds from the low 

 mortality mating and five families of 58 birds from the high mortal- 

 ity group. From this beginning it is hoped that we may be able to 

 develop two distinct lines, one showing a high and the other a l<^w 

 incidence to ruptured egg yolk condition. (Pumell Fund) 



Controlling Moisture in Poultry Litter 



The principal reason for work on this project has been the prob- 

 lem encountered by poultrymen generally of wet litter in pens of 

 laying hens. \'arious efforts have l^een made to control this situa- 

 tion through insulation, ventilation, change in type of litter, and 

 other measures without a satisfactory solution having as yet been 

 found, report T. B. Charles. W. T. Ackerman, R. C. Durgin, G. M. 

 Foulkrod. .\. E. Tepper and B. J. French. The first year's operation 

 involved the recording of temperature, humidity, litter moisture, and 

 air movement conditions as existing in ]">ens of various types of con- 

 struction. Pen temi'jeratures in unheated houses from the last of 

 November to the first of May (the jKM-iod when this problem is most 

 acute) were an average of 8.3 degrees higher than the outside air. 

 In the coldest period, a differential of 13 degrees was reached, while 

 in the warmer spring conditions this was reduced to 5 degrees. 

 These factors arc of value in considering the effectiveness of natural 

 draft ventilation. 



Humidity records showed an average of 59 per cent moisture in 

 ('Utside air for the five months' period, with monthly average max- 

 imums as high as 63 i)er cent. The i^en average for the five months 

 v.as 81 per cent, with average monthly maximums of 84 per cent. 



The measure of moisture in ]">en litter and similar litter without 

 hens showed that for the five months' jieriod an average of 45.3 ])er 



