GROWTH IN SIZE AND BODY PROPORTIONS IN FARM ANIMALS 



331 



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Figure 10. The effects of different feeding levels on relative proportions of 

 fat, muscle, and bone developed in a 30-pound lamb carcass. (Verges, 1939.) 



what occurs in unimproved breeds, which have thin bones compared 

 with the relatively thick bones of improved meat breeds (Hammond, 

 1932). 



Similarly, because male cattle and sheep develop to a greater ex- 

 tent than the females, the bones are longer and thicker in the male than 

 in the female. Low-plane nutrition reduces these differences (Palsson 

 and Verges, 1952). Male characters such as the thickness of bone and 

 the masculinity of the head and neck are caused by testicular hormones, 

 and when the animals are reared on a low plane of nutrition these 

 characters approach those of the female ( Fredericksen, 1929 ) . \Miile 

 some of this effect may be due to a lower honnone output, most of it 

 is due to the fact that such characters are late developing and so have 

 a low priority of nutrition. 



Such interactions between hormones and nutrition are seen also in 

 those organs that have several life cycles during the life of the animal 



