394 Growth and Development of Breeds and Crosses of Pigs 



Results. 



The results obtained are considered in sections below under various 

 headings which it was considered might have an eSect on growth and 

 development — breed, age, early maturity, cross-breeding, selection, 

 individual variation and correlation. In general, the results obtained 

 from the Live Classes for actual gross weight have been considered first 

 followed by the proportional development and weights of the various 

 organs as obtained from the Carcase Classes. 



Breed. No satisfactory explanation has yet been offered why one 

 animal or breed should produce meat more economically than another. 

 Armsby and Fries (18) have shown that it does not depend on differences 

 in digestive power; their experiments indicated that the well-bred animal 

 had a lower maintenance requirement than a scrub, due to the hitter's 

 more nervous disposition and greater restlessness. 



Feeding tests for the economy of gain in different breeds of pigs made 

 at the Ontario College of Agriculture (if») have failed to show any uniform 

 difference between breeds as so much depended on the strain used. 

 Carlyle{20), however, who compared Berkshires with Razorbacks or semi- 

 wild swine found that the latter required more feed per unit gained. 

 Similar results were obtained by Diffloth(2i) when comparing Suffolk pigs 

 with those of a fJerman breed. 



It is rather in the utilization than in the absorption of food that breeds 

 differ; variations in utilization will be seen below. Little or nothing is 

 known as to whether the underlying physiological differences in the 

 metabolism of different breeds are due to variation in heat loss by the 

 skin as shown by Wood and ]Iill(22) or to differences in the glycogenic 

 coefficient of the blood controlled by the glands of internal secretion. 

 Liihring(23) states that it is possible to distinguish between the different 

 breeds of pigs by the protein differentiation method. 



Table I shows the average ages and weights of the different breeds of 

 pigs as compiled from the records of the Live Classes. The following 

 Table II shows these weights translated into lbs. per week gained since 

 birth. The weight at birth has been neglected owing to the absence of 

 data for the dift'orent British breeds. Carmichael and Rice(2i) found that 

 the average birt h weights of breeds in America ranged from 2-25 lbs. for 

 Duroc- Jerseys to 2-6 f lbs. for Berkshires but it was considerably affected 

 by other factors such as litter size, sex, age of sow, etc. Meek (25) states 

 that the birth weight varies from 1'.5 lbs. to 4-5 lbs. and Henr\M26) that 

 the variation is from 1-3 lbs. to 3-1 lbs. 



