Livestock Production Science 67 2001 223–239 www.elsevier.com locate livprodsci
Breeding objectives for beef cattle in Ireland
a , b
c d
e
P.R. Amer , G. Simm , M.G. Keane , M.G. Diskin , B.W. Wickham
a
AgResearch Invermay , Private Bag 50034, Mosgiel, New Zealand
b
Animal Biology Division , SAC, West Mains Road, Edinburgh EH9 3JG, UK
c
Teagasc , Grange Research Centre, Dunsany, Co. Meath, Ireland
d
Teagasc , Athenry Research Centre, Athenry, Co. Galway, Ireland
e
Irish Cattle Breeding Federation Society Ltd ., Bandon, Co. Cork, Ireland
Received 8 October 1999; received in revised form 26 April 2000; accepted 7 May 2000
Abstract
Breeding objectives for beef cattle in Ireland were derived and used to define selection sub-indexes. The intention of the sub-indexes was to simplify selection decisions by commercial bull and semen buyers for situations where all of the resulting
progeny are slaughtered, or when some female progeny are kept as replacement breeding cows. Separate sets of economic values for calving ease and gestation length are proposed for use in separate calving sub-indexes depending on whether dairy
cows or beef cows are to be mated. Proposed economic values for calf quality, growth, calving and reproduction sub-indexes were assumed to be independent of the breed of cow to be mated. It was also recommended that separate total indexes for
dairy cow and beef cow matings be constructed as simple linear functions of the sub-indexes.
2001 Elsevier Science B.V.
All rights reserved.
Keywords : Beef cattle; Selection index; Terminal sire; Reproduction
1. Introduction omic values are needed for each trait in the breeding
objective to ensure that selection emphasis is propor- Clearly defined breeding objectives are vital for
tional to the economic importance of each of these effective genetic improvement of all livestock
traits. Having a clear breeding objective is also an species. Since they were first proposed for animals
important prerequisite to the development of cost by Hazel 1943, multiple-trait selection indexes
effective breeding strategies, and to the identification have become the method of choice for maximising
of a set of traits making up the selection criteria genetic gain in a chosen breeding objective. These
which contribute to accurate prediction of traits indexes simplify comparisons of animals based on
affecting commercial profitability. estimated breeding values for individual traits. Econ-
The organisational structure for beef performance recording, data capture and breeding programmes in
Ireland is in the process of change Keane and
Corresponding author. Tel.: 164-3-4893-809; fax: 164-3-
Diskin, 1996. Some time has elapsed since breeding
4893-739. E-mail address
: amerpagresearch.cri.nz P.R. Amer.
objectives for Irish beef cattle have been evaluated in
0301-6226 01 – see front matter
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224 P
.R. Amer et al. Livestock Production Science 67 2001 223 –239
detail Cunningham, 1974; Barlow, 1982; Barlow breed parent in these herd types are shown in Table
and Cunningham, 1984. Thus, it is timely for a 1. These breeding objective traits are divided into
reassessment of the breeding objective for Irish beef five groups, with some repetition for traits included
cattle. in the reproduction group. This repetition facilitates a
The primary objective of this paper was to outline more simple combination of a reproduction sub-
the approaches taken in the development of a index with sub-indexes for the other groups. Where
breeding objective for Irish beef cattle. The sec- economic values vary across mating terminal sire
ondary objective was to explore the potential mag- versus sire to breed female replacements and pro-
nitude of variation in economic values when calcu- duction beef breed matings to dairy versus beef
lated for some alternative breeds and production cows systems, sub-indexes can be presented to
systems. This largely involved the use of published index users to allow flexibility in selection emphasis
methodology and models, adapted to be relevant to across relevant groups of traits. Sub-indexes are
Irish beef cattle production, although in some in- computed by setting economic values for all breed-
stances, new models and approaches were used, and ing objective traits not in the sub-index of interest to
these are also described here. zero Amer et al., 1998a.
Traits expressed by calves prior to or at weaning are assumed to have both direct and maternal
2. Materials and methods breeding values estimated for them. While economic
