330 



CELLS, TISSUES, AND ORGANISMS 



Lbs 

 I60 



ISO 



LAMBS 



Aja Daya 



Figure 9. Growth curves of lambs on various schedules of nutrition. (Verges, 

 1939.) 



By differential planes ( levels ) of nutrition at different periods of 

 the animal's life, the proportions and composition of its body at any 

 given body weight can be changed (Figure 9). Palsson and Verges 

 ( 1952 ) showed that when lambs were fed on a high plane of nutrition 

 throughout, all parts of the body were equally served, so that in a 30- 

 pound carcass a high proportion of fat and muscle to bone was ob- 

 tained ( Figure 10 ) . On a low plane of nutrition throughout, carcasses 

 of this weight, owing to the priority of the early-maturing bone, had a 

 low proportion of fat and muscle as compared to bone. When the 

 nutrition was high in early life, a large-framed animal was produced, 

 but if this was followed by underfeeding, bone continued to grow at 

 the expense of muscle and fat. When nutrition was low in early life, 

 a stunting of bone growth took place, and when such an animal was 

 afterward put on a high plane, fat and muscle grew more rapidly than 

 bone, so that a high proportion of these tissues to bone was produced. 



Differences in the shape of bones also can be produced by changes 

 in the plane of nutrition. The reason for this is that growth in length 

 possesses an early-maturing pattern, whereas growth in thickness pos- 

 sesses a late-maturing pattern. On a low plane of nutrition, therefore, 

 length growth continues while thickness growth is slowed down con- 

 siderably; thus thin bones are produced (Figure 11). This is just 



