402 Gi'oirth and Dcrelopment of Breeds and Crosses of Pigs 



Till' variations in rate of growth in different breeds have yet to be 

 analysed in terms of the components of the body ; the various systems 

 of the body reach thoir maximum rate of growth at different stages and 

 thus breed variations in the rate of growth may be explained. 



The figures given above for rate of growth may be criticized however 

 because they show the rate from birth to that particular age ; thus they 

 give the total result of growth to tlie particular age and not the rate at 

 which growth is proceeding at the time. The rate of growth between 

 certain ages has been calculated in another way — by subtraisting the 

 weight at x months from the weight at // months and the age at x months 

 from the age at // months and from this finding the rate of growth per 

 week. This has been done for four breeds and the results are sjiown in 

 Fig. 2 and in Table Vlll. From these it will be seen that, as before, the 

 rate of growth falls between 3 and 5 months but attains its maximum 

 (of approximately 1"2 lbs. per week) between 5 and 7 months and then 

 falls again until between '.) and 11 months it is only about 3 lbs. per week. 



Data collected from various authorities for the growth in live weight 

 of the pig are given in the following table : 



Groiolh in lbs. per week gain. 



Months old ... 1 2 3 4 5 G 7 



Biicklcy(32) ... 

 HarpciMiS) 



0.stertag iintl Ziintz(35) 2-8 — — — — — — — — — — — 



The economy of gain in live weight however cannot altogether be 

 measured by the rate of increase per week. J 1 enry and Morrison (36) found 

 from data collected from the U.S. Experimental Stations that pigs of 

 78 lbs. (corresponding to 3 months old) put on 100 lbs. live weight from 

 400 lbs. food whereas pigs of 320 lbs. (corresponding to 9 months old) 

 put on 100 lbs. live weight from .535 lbs. food; the composition of this 

 gain in live weight as shown in Table Vlll however is very different. 



Morgan (37) has pointed out that man is larger than the rabbit because 

 he grows for a longer period but the daily increases in weight are nearly 

 the same. On the other hand, rabbits attain a larger size than guinea- 

 pigs because they grow faster and not for a longer time. Meek (38) too 

 has shown that although a donkey and a Large White pig attain much 

 the same ultimate weight there is a great difference in the form of their 

 growth curve. When one couipares the rate of growth of sheep (Murray (39)) 

 with pigs it will be seen that the maximum rate of daily increase in 



