Relative efficiency of individual selection and reference sire progeny test schemes for beef production

Abstract

Individual selection on the basis of adjusted yearling weight records (policy 1) was compared with selection of proven sires based on progeny test results ('progeny test selection'). The major assumptions in the comparisons were that herd sizes were 100 recorded cows, and that each herd used four joining groups. It was assumed that 25 herds cooperated in using two reference sires in artificial breeding to link progeny test data from young bulls in natural service, thereby increasing selection intensity without the loss in accuracy normally suffered in a single multi-sired herd. In the progeny test comparisons, preselection of young bulls for progeny testing (policy 2) was also compared with random selection among young bulls for progeny testing (policy 3). This paper contains a limited number of comparisons only, in order to indicate the possible extent of selection pressure with different policies. Comparisons in terms of annual genetic progress ranked the policies in the order 2 (greatest), 1, 3, with policy 2 being better than 3 by 90-110%. The advantage of policy 2 over policy 1 was 26-38%. In all cases, using bulls first as yearlings was preferable to 2 1/4 years in terms of annual genetic gain. With individual selection, keeping bulls for 1 year compared with 2 or 3 years had little effect on annual gain, as the rise in selection intensity balanced the rise in generation interval. Inbreeding change per year was more affected, lower rates resulting from bulls being used for 1 year only. Inbreeding rates were small with progeny test selection as described here, as long as proven sons came from young bulls as well as proven sires. The effect of selection intensity under progeny test selection with preselection becomes diluted to 25% in its contribution to annual genetic change. Thus some degree of assortative mating may be useful, or wider use of proven sires relative to young sires. With preselection the break-even number of cooperating progeny test herds was low (three herds), compared with equal rates of genetic gain from individual selection.

A simulation study of the effect of connectedness on genetic trend

“…To prevent lack of connectedness, Foulley and Clerget Darpoux (1978) and Foulley et al (1983) developed the use of reference sire progeny testing schemes. Application of reference sire systems has been of major importance in the development of selection schemes in sheep and beef cattle (Foulley and M6nissier, 1978;Foulley and Bib6, 1979;Morris et al, 1980;Foulley and Sapa, 1982;Miraei Ashtiani and James, 1991, 1993.…”

A simulation study of the effect of connectedness on genetic trend

“…To prevent lack of connectedness, Foulley and Clerget Darpoux (1978) and Foulley et al (1983) developed the use of reference sire progeny testing schemes. Application of reference sire systems has been of major importance in the development of selection schemes in sheep and beef cattle (Foulley and M6nissier, 1978;Foulley and Bib6, 1979;Morris et al, 1980;Foulley and Sapa, 1982;Miraei Ashtiani and James, 1991, 1993.…”

Multiple Ovulation and Embryo Manipulation in the Improvement of Beef Cattle: Relative Theoretical Rates of Genetic Change

“…The family index contains information on an individual and its sibs, paternal half-sibs for the conventional systems and full and paternal half-sibs for MOET systems. Progeny testing selection schemes were based on a sequential culling program as outlined by Morris et al (1980). Young males initially were selected based on family indices of performance records (selection type II), their progeny were tested and progeny-tested males were selected and used for mating.…”

“…With type III selection, allowance must be made for the sequential selection applied to males. The genetic merit of selected females (Gf) is if x riG x h x t~, but the genetic merit of males selected on the progeny test (Gm) can be estimated (Morris et al, 1980) as:…”