Testing selection indices for sustainable hill sheep production – lamb growth and carcass traits
- 1 August 2006
- journal article
- Published by Cambridge University Press (CUP) in Animal Science
- Vol. 82 (4), 445-453
- https://doi.org/10.1079/asc200663
Abstract
Two selection indexes, one intended for lamb producers and finishers and one for store lamb producers, were derived using genetic parameters for carcass and maternal characteristics from Conington et al. (2001) and economic values from Conington et al. (2004). This paper summarizes responses to selection for lamb traits only, after 5 years of selection (1998 to 2003) on two farms using these selection indexes. The index for lamb producers and finishers, evaluated on farm 1, with a flock size of 680 ewes, includes economic weightings for maternal traits as well as carcass weight, fat and conformation grades, whereas the index for store lamb producers, evaluated on farm 2, with a flock size of 580 ewes, only includes economic values for maternal traits and lamb growth to weaning. Three selection lines of Scottish Blackface sheep per farm were created with the first lambs born to each line in 1999. These lines were selection (S), control (C) and industry (I); they were of equal size on each farm. Five top- and five average-performing ram lambs were selected each year for the S and C lines respectively using a multi-trait best linear unbiased prediction (BLUP) implementation of the indexes. The I-line used four mature rams bought from industry, selected on appearance only, i.e. adherence to breed ‘type’. Results showed that 5 years after the implementation of the index, the S line had significantly higher index scores than the C or I lines on both farms. The means (s.d.) for the average index scores in 2003 are 114 (328), 119 (371) and 451 (328) (farm 1), and −8 (146), −11 (130), and 250 (129) (farm 2) for the C, I and S lines, respectively, giving predicted net differences (S-C) of £3·38 (farm 1) and £2·58 (farm 2) per ewe. Phenotypic responses showed significant S v. C differences in weaning weight on both farms. As predicted from previous analyses, no changes in carcass quality traits were seen at farm 1 although S-line carcass weights tended to be heavier than those from the C or I lines. The results show that genetic improvement using multi-trait selection indices has been successful and it is a viable, long-term strategy to improve levels of production for hill sheep in extensive environments.Keywords
This publication has 11 references indexed in Scilit:
- In vivo prediction of internal fat weight in Scottish Blackface lambs, using computer tomographyJournal of Animal Breeding and Genetics, 2006
- Comparison of genetic and nongenetic strategies for control of gastrointestinal nematodes of sheepLivestock Production Science, 2003
- Selection for high or low backfat depth in Coopworth sheep: breeding-ewe traitsAnimal Science, 2001
- Multi-trait selection indexes for sustainable UK hill sheep productionAnimal Science, 2001
- A comparison of growth and carcass traits in Scottish Blackface lambs sired by genetically lean or fat ramsAnimal Science, 1998
- Prospects of breeding small ruminants for resistance to internal parasitesInternational Journal for Parasitology, 1996
- Selection for lean growth in terminal sire sheep to produce leaner crossbred progenyAnimal Science, 1996
- Selection indices for lean meat production in sheepLivestock Production Science, 1989
- National estimates of the body composition of British cattle, sheep and pigs with special reference to trends in fatness. A reviewMeat Science, 1986
- Fleece characteristics of three strains of Scottish Blackface sheepAnimal Science, 1966