Section 14 — Animal Genetics and Breeding 



7. Respiratory metabolism in irradiated eggs 

 during 12- 18th days of the incubation period 

 was more intensive than in the control eggs. 

 The difference in O2 consumption and CO2 

 output in favour of treated eggs varied in dif- 

 ferent trials from 5 to 40 per cent depending on 

 initial quality of the eggs and consequently de- 

 pending on the effect of irradiation. 



8. The postnatal growth, development and 

 viability of the chickens hatched from treated 

 eggs were the same as in the control group. 



9. The egg productivity of over 4000 pullets 

 hatched from treated eggs and maintained at the 

 range or in the cages exceeded the control by 

 10 per cent. 



10. The quantity, quality and fertilizing ca- 

 pacity of the sperm of the experimental cockerels 

 (developed from treated eggs) were the same as 

 the sperm of the control cockerels. 



11. The preliminary observations show that 

 the progeny of the 1st and 2nd generations from 

 hens hatched from the irradiated eggs didn't 

 reveal any abnormalities. 



14.31. Selection on X-ray Induced Variation in 

 Chickens. Hans Abplanalp, Dorothy C. 

 Lowry and Everett R. Dempster (Davis, 

 U.S.A.). 



weight, at a weeks of age. The coefficient 0.4 is 

 approximately the mean value of k, the growth 

 rate of y relative to x (coefficient of heterauxe- 

 sis) between 2 and 10 weeks. Two further lines, 

 B (big) and S (small), have been selected up and 

 down for *io. After 4 generations of selection 

 H and L differ by 0.067 in i\o (= 17 per cent 

 difference in shank length at the same body 

 weight), the realized heritability being 0.57. 

 After 3 generations B and S differ by 0.143 

 (=39 per cent) in .no; r.h. = 0.47. Two esti- 

 mates of the genetic correlation between ;'io 

 and X10 (- 0.32 from the correlated response in 

 H-L; + 0.26 from B-S) differ significantly. 



Genetic variation in iw arises by (at least) 

 two distinct developmental pathways; by chan- 

 ges in post-natal k, and by embryonic changes 

 without change in post-natal k. The former 

 pathway accounts for only 20 per cent of the 

 H-L difference. Measurements of adult skeletons 

 show far-reaching and anatomically complex 

 differences in shape between H and L. There 

 are anatomical and developmental similarities 

 between H-L and ectomorphy-mesomorphy in 

 humans. Possible interrelations between different 

 anatomical and developmental kinds of varia- 

 tion will be discussed. 



Full publication in Genet. Res.4, No. 2, 1963. 



Populations of SCWL chickens were given 

 8000 r X-ray irradiation administered to the 

 semen of males during seven generations. The 

 populations used for this study derived from a 

 flock which had been under selection for high 

 egg number over 18 years. While irradiated 

 populations were prepared without artificial se- 

 lection, a control of equal size was reproduced 

 under similarly relaxed selection, and the orig- 

 inal line continued under artificial selection 

 for egg number. Following the irradiation phase, 

 all lines were subjected in replicate to four 

 generations of artificial selection for egg number. 

 Response to selection for egg number and cor- 

 related response in egg size and viability are 

 discussed. 



14.32. Quantitative Developmental Genetics of 

 Body Shape and Size in Domestic Fowl. A. G. 



Cock (Edinburgh, Great Britain). 



From a population of mixed breed origin, 

 two lines, H (high) and L (low), have been se- 

 lected in opposite directions for an index of 

 relative shank length, /'10 = vio - OAxw, where 

 y a = logio shank length, and Xa, = logio body 



14.33. Response to Selection for Body Size at Two 

 Ages in the Fowl. E. S. Merritt and S. B. 

 Slen (Ottawa and Lethbridge, Canada). 



In broiler or meat-type chickens rapid early 

 growth is highly important for efficiency of pro- 

 duction. Large adult size, on the other hand, 

 results in increased maintenance and feed re- 

 quirements of breeding stock. A study was under- 

 taken to determine whether a selection response 

 for increased broiler weight could be achieved 

 simultaneously with a decrease in adult weight. 



Three lines were drawn from a random-bred 

 control strain (Ottawa Meat Control). One was 

 selected for increased weight at 63 days of age, 

 one for increased weight at 147 days of age, 

 and the other for an increase in 63-day weight 

 but a decrease in 147-day weight. A sample of 

 the random-bred control population, bred inde- 

 pendently of these lines, was reared with each 

 generation of the selected lines. 



Heritability estimates for 63- and 147-day 

 weights calculated on the control or base popu- 

 lation were approximately 0.55 with a genetic 

 correlation estimate of 0.75 between them. After 



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