Free Access
Genet. Sel. Evol.
Volume 36, Number 5, September-October 2004
Page(s) 509 - 526
Genet. Sel. Evol. 36 (2004) 509-526
DOI: 10.1051/gse:2004014

Reduction of inbreeding in commercial females by rotational mating with several sire lines

Takeshi Hondaa, Tetsuro Nomurab and Fumio Mukaic

a  Graduate School of Science and Technology, Kobe University, Kobe, Japan
b  Faculty of Engineering, Kyoto Sangyo University, Kyoto, Japan
c  Faculty of Agriculture, Kobe University, Kobe, Japan

(Received 17 November 2003; accepted 27 April 2004)

Abstract - A mating system to reduce the inbreeding of commercial females in the lower level was examined theoretically, assuming a hierarchical breed structure, in which favorable genes are accumulated in the upper level by artificial selection and the achieved genetic progress is transferred to the lower level through migration of males. The mating system examined was rotational mating with several closed sire lines in the upper level. Using the group coancestry theory, we derived recurrence equations for the inbreeding coefficient of the commercial females. The asymptotic inbreeding coefficient was also derived. Numerical computations showed that the critical factor for determining the inbreeding is the number of sire lines, and that the size of each sire line has a marginal effect. If four or five sire lines were available, rotational mating was found to be quite an effective system to reduce the short- and long-term inbreeding of the commercial females, irrespective of the effective size of each sire line. Oscillation of the inbreeding coefficient under rotational mating with initially related sire lines could be minimized by avoiding the consecutive use of highly related lines. Extensions and perspectives of the system are discussed in relation to practical application.

Key words: inbreeding / coancestry / rotational mating / commercial females

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© INRA, EDP Sciences 2004