NUTRITION AND FERTILITY 371 



rather be ascribed to the absence of the necessary external 

 stimuli without which the generative organs of animals are 

 incapable of discharging their functions. This view may also 

 help to explain why some animals {e.g. insects) make their 

 appearance in great numbers in one year and are comparatively 

 scarce in another. 



In those animals which, as a general rule, breed readily in 

 a state of domestication or confinement, it is probable that 

 nutrition plays the most important part in regulating the 

 capacity to produce offspring. That an insufficient or markedly 

 abnormal diet must affect this power is almost self-obvious. It 

 is also clear that the effects of excessive nutriment are likewise 

 prejudicial to the proper discharge of the reproductive functions. 

 No better example could be given of the way in which over- 

 feeding results in a condition of sterility than that afforded by 

 the barren Shire mares which have been a noticeable feature at 

 recent agricultural shows. Breeders of cows and sheep have 

 learnt from long experience and at great cost the disastrous 

 consequences of an over-nourishing diet upon the fertility of 

 their stock. It would seem, however, that owing to the desire 

 to excel in the showyard breeders of draught horses are falling 

 continually into the old error. In the classes provided for 

 barren Shire mares there are invariably to be found some of 

 the finest specimens of the breed, so that those animals which 

 appear best calculated to produce a superior class of foals are 

 useless for stock-breeding purposes. Little or nothing is 

 certainly known regarding the way in which excessive feeding 

 checks the tendency to conceive, but this result may probably 

 be ascribed to fatty degeneration in the organs of reproduction. 



It is a somewhat remarkable fact that, although numerous 

 experiments have been undertaken to determine the effects of 

 different methods of treatment upon wool, meat, or milk 

 production, no systematic attempt had been made until quite 

 recently to deal with the factors which influence fertility in 

 livestock. A few years ago, however, the Royal Agricultural 

 Society instituted an inquiry into the causes of barrenness and 

 abortion among different breeds of sheep in the south of England. 

 The investigation was conducted by Mr. Heape, whose report 

 was subsequently published in the Journal of the Society.^ 



I Heape, " Abortion, Barrenness, and Fertility in Sheep," Jour. Royal Agric. 

 Soc. vol. X. 1899. 



