404 Growth uml Development of Breed h and Crosses of Pigs 



in form of the growth curves of the pig and the donkey and these differ- 

 ences are an exaggeration of what early maturity means in animals. In 

 the guinea-pig Read (ii ) found that during uterine development cycles of 

 growth took place and the same thing occurs in inan when growth is 

 accelerated about the age of puberty (Robertson (42)). These facts indicate 

 that it is impossible, in more than a very general sort of way, to construct 

 growth formulae to fit the curve of growth of any animal. 



Carcase. Pluck. Intestines 

 84 6-3 22 Or 



82 58 200i^ 



80 5-3 180 



78 4-8 160 



76 4-3 140 



74 



3-8 120 



3 5 7 9 11 



months 



Fig. 3. Proportions of parts — pigs (4 breeds). Per cent, of live weight. 



The proportional development of the carcase, pluck and alimentary 

 canal, etc. at the different ages is shown by the average of four breeds 

 at the end of Table VII and is also given in diagrammatic form in Fig. 3. 

 The carcase percentage shows a steady rise from 74-5 per cent, at 

 3 months old to 83 per cent, at 1 1 months old ; the greatest rate of rise 

 occurs between 5 and 7 months and afterwards slows down somewhat. 

 With this rise in carcase percentage the proportions of pluck and 

 alimentary canal etc. fall rapidly between 3 and 7 months and after- 

 wards more slowly; the alimentary canal etc. ("unaccounted for") on 

 the whole falling more than the pluck, which is to be expected since the 

 latter includes the caul fat. Semmler(43) found in pigs that the lungs of 

 young animals are relatively larger than those of old pigs of the same 

 breed. 



The actual rate of growth of the carcase, pluck and alimentary canal 

 in lbs. per week is shown in Fig. 2 and also in Table VIII. From this 



