512 FEEDING FARM ANIMALS 



breeding; viz., that like produces like. It is omy reasonable 

 to suppose that the average size of the progeny at birth^ 

 would be larger from the Clyde mare than from the mare 

 standard bred; that from the Shorthorn cow, larger 

 than progeny from the Jersey; that from the Lincoln, 

 larger than progeny from the Southdown, and that from 

 the large Yorkshire, larger than progeny from the 

 small Yorkshire. And so it is on the average in these 

 respective instances. 



It could not be otherwise than that the food given 

 to the dam during pregnancy exercised a determining in- 

 fluence on the size of the progeny at birth, since foetal de- 

 velopment is a direct result of the constituents contained in 

 the food. An excess of carbohydrates is adverse to develop- 

 ment and an excess of protein is liable to result in impaired 

 vitality. 



Performance in the pregnant dam influences size 

 through the diversion of the energies of the system. Nor- 

 mal and ordinary exercise of those energies is favorable 

 to foetal development, through the healthy influence ex- 

 erted by use in the various functions of the system. For 

 instance, regular breeding not excessive in frequency, will 

 produce more desirable progeny as a rule than fitful breed- 

 ing. But should the energies of the system be over-taxed 

 during pregnancy, as when the cow is carried through a 

 high pressure milking test, or the pregnant mare is over- 

 worked, or the pregnant ewe is put into high show condi- 

 tion, the influence is adverse to both size and vigor in 

 the progeny. 



That the number produced at a birth influences size 

 at birth is sustained by the evidences of observation and 

 experience. Although the results are not constant, and in 

 the nature of things cannot be, the average weight of single 

 lambs at birth, is greater than that of twin lambs in the 

 same flock. This also is true of the average weight of 

 pigs in large litters as compared with those of small litters. 



