94 THE BREEDING OF ANIMALS 



year-old ewes an increase of 174 per cent, and four- to 

 six-year-old ewes an increase of 178 per cent. After 

 the age of six years, there was a distinct falling off in the 

 percentage of increase. 



The foregoing table (page 93) is reprinted entire from 

 the Wisconsin bulletin and is interesting as showing the 

 distribution of twin and triplet births among the different 

 ages and the sex of lambs. 



93. Influence of age of ram on fertility of ewes. 

 The number of young at a birth is generally believed 

 to be determined by the number of ova which are ripened 

 by the female during any one period of heat. The vigor 

 or age of the male used is not generally regarded as hav- 

 ing any influence in determining the number born at 

 one time. The Wisconsin Station l found that during 

 a period of six years, the flock of ewes served by a year- 

 ling ram produced 150 per cent of lambs. The same 

 flock during a similar period of six years was served for 

 three of these years by two- and three-year-old rams. 

 The average percentage of lambs born from the older 

 rams was 180 per cent. The author in discussing these 

 results remarks : " These data are quite at a variance 

 with the opinion commonly held by sheepmen, generally 

 to the effect that a well grown, vigorous yearling ram 

 is at his best as a sire. It is also contrary to the belief 

 held by many that the vigor of the sire has no apparent 

 influence on the percentage of increase." 



94. The effect of the age of poultry parents on the 

 offspring. The general conclusion that fully mature 

 animals are more fertile seems to be substantiated by 

 the poultry-breeding experiment conducted by Atwood. 2 



1 Wisconsin Experiment Station, Bulletin 95. 



2 Atwood, West Virginia Experiment Station, Bulletin No. 124. 



