Section 14 — Animal Genetics and Bre edmg 



14.56. Current Progress in Three Selection Experi- 

 ments with Hill Sheep. A. F. Purser (Edinburgh, 

 Great Britain). 



Three separate two-way selection experiments 

 started by the Animal Breeding Research 

 Organization in 1953-54 with hill sheep are 

 described briefly. In one experiment, selection 

 for cannon bone length at eight weeks of age 

 has resulted in marked changes in cannon bone 

 length at all ages from birth onwards. Other 

 skeletal and body weight changes have also 

 occurred. In the second experiment selection for 

 the average degree of fibre medullation in the 

 lamb fleece has altered adult fleece type and the 

 timing of the waves of shedding of kemp 

 fibres. The third experiment involves selection for 

 two extremes of birthcoat type. Correlated 

 changes have occurred in birth weight, lamb 

 mortality and in adult fleece grade and fleece 

 weight, with the intermediate birthcoat type 

 being generally better than either extreme type. 

 The heritabilities of all three characters are 45-55 

 per cent and response to selection in each line 

 has been approximately as predicted. However, 

 evidence of a decline in genetic variance in 

 each of the selected characters will be presented. 



14.57. The Effect of Two Associated Biochemical 

 Polymorphisms on Red Cell and Production 

 Traits in Sheep. J. H. Watson, A. G. H. Khat- 

 tab and R. F. E. Axford (Bangor, Great 

 Britain). 



Two genetic loci governing haemoglobin type 

 and erythrocyte potassium concentration, show 

 evidence of association in the College flock of 

 Welsh Mountain sheep. In 1777 sheep departure 

 from randomness of association stems from an 

 excess of haemoglobin B homozygotes among 

 high potassium animals. This inbalance extends 

 to the three remaining phenotypes containing the 



haemoglobin B gene but not to haemoglobin A 

 homozygotes. 



Differences in potassium concentration be- 

 tween the three haemoglobin types are accounted 

 for by their packed cell volumes. At both high 

 and low potassium levels haemoglobin A 

 homozygotes have higher blood potassium 

 concentration and packed cell volume than 

 haemoglobin B homozygotes. AB heterozygotes 

 are close to mid-parent values. Red cells con- 

 taining haemoglobin A, although more numerous 

 than those containing haemoglobin B, are also 

 more fragile. 



Differences in production records of these 

 sheep are small, rarely significant, but consistent. 

 Low potassium types are marginally superior to 

 high potassium types in all liveweight measure- 

 ments and first fleece weight. Haemoglobin A 

 homozygotes are marginally better than BB 

 homozygotes, with AB heterozygotes inter- 

 mediate. 



14.58. Some Genetic Studies on the Buffaloes in the 

 U.A.R. A. A. Asker, L. H. Bedeir, A. A. El- 

 Itriby and I. A. Ahmed (Cairo, Egypt). 



Records collected on two herds of buffaloes 

 maintained by the Ministry of Agriculture were 

 analysed to study the inheritance of some dairy 

 traits and to investigate the interrelationships 

 between these characters. More than 400 

 buffaloes having 1614 records were included in 

 this report. The repeatability of 305 day milk 

 yield, total milk yield, maximum weekly pro- 

 duction, intensity, persistency and lactation 

 period were 0.40, 0.41, 0.34, 0.39, 0.18 and 0.27 

 respectively. The corresponding heritability 

 estimates were, 0.26, 0.27, 0.43, 0.38, 0.33 and 

 0.27 respectively. The phenatypic as well as the 

 genetic correlations between characters studied 

 were high which indicate that most of these 

 characters are affected by the same sets of genes. 



270 



