• Home
  •  >
  • Animal Science
  •  >
  • Volume 51
  •  >
  • Issue 02
  •  >
  • Expected consequences of the segregation of a major gene in a sheep population in relation to observations on the ovulation rate of a flock of Cambridge sheep

Animal Production

Table of Contents - 1990 - Volume 51, Issue 02  

Research Article

Expected consequences of the segregation of a major gene in a sheep population in relation to observations on the ovulation rate of a flock of Cambridge sheep

J. B. Owena1, C. J. Whitakera2, R. F. E. Axforda1 and I. Ap Dewia1

a1 School of Agricultural and Forest Sciences, University of Wales, Bangor LL57 2UW

a2 Centre for Applied Statistics, University of Wales, Bangor LL57 2UW

Abstract

A simple model was derived relating the phenotypic effect (g) of a major gene to observed values of the population mean and variance for a trait, at specified values of the major gene frequency and at specified basal values of the population mean and variance (in the absence of the major gene). This model was applied to a total of 549 observed values of ovulation rate in ewes of the Cambridge breed at Bangor under a range of assumptions. The mean values of ovulation rate were 2·44 for 243 ewes of 1 year of age and 37·54 for 306 ewes of 2 and 3 years of age with a coefficient of variation for both age sets of 0·50.

The results indicate a minimum value for g, in this data set, of 1·07 for 1 year old and 1·72 for 2 and 3 year old ewes. The results are also consistent with a frequency value in the region of 0·3 to 0·4, with the absence of dominance and with a reasonable concordance with Hardy-Weinburg equilibrium. The results also indicate that the value of g varies according to the background phenotype since it is lower for younger as compared with older ewes.

(Received September 13 1989)

(Accepted February 12 1990)

Keywords