262 



THE BREEDING OF ANIMALS 



RELATION OF WEIGHT OF DAM TO BIRTH WEIGHT OF 

 LAMB 



250. Birth weight of lambs. The author, 1 investi- 

 gating the birth weight of lambs from grade Merino ewes 

 bred successfully to Shropshire, Hampshire and Merino 

 rams, found that the size of lambs at birth is primarily 

 determined by the nutrition of the foetus while carried 

 in the uterus of the mother. The nutrition of the foetus 

 will of course be determined entirely by the physiological 

 condition of the mother during gestation. This is shown 

 in one test in which the birth weight of twenty-nine lambs 

 sired by two heavy rams averaging 237 pounds in weight 

 was 8.16 pounds. The average weight of two other 

 rams of the same breeds was 142J pounds. The two 

 lighter rams sired twenty-five lambs from the same ewes, 

 or ewes of the same type. The average birth weight of 

 these lambs was 8.75 pounds. The weight of the sires 

 in this case seemed to have little influence on the weight 

 of lambs at birth. In attempting to discover the real 

 factors determining the growth of the foetus as measured 

 by the weight of lambs at birth, it was found that the 



1 F. B. Mumford, "Some Facts Influencing the Weight of 

 Lambs at Birth," Bulletin 53, Missouri Experiment Station. 



