Comparison of manual assessments of ewe fat reserves for on-farm use
C. G. Shands A , B. McLeod A , M. L. Lollback B , G. Duddy C , S. Hatcher D F and W. J. O’Halloran EA NSW Department of Primary Industries, Glen Innes Research and Advisory Station, Glen Innes, NSW 2370, Australia.
B NSW Department of Primary Industries, Tamworth Agricultural Institute, 4 Marsden Park Road, Calala, NSW 2340, Australia.
C NSW Department of Primary Industries, Yanco Agricultural Institute, Private Mail Bag, Yanco, NSW 2703, Australia.
D NSW Department of Primary Industries, Orange Agricultural Institute, Forest Road, Orange, NSW 2340, Australia.
E NSW Department of Primary Industries, Building C2, University of New England Armidale, NSW 2351, Australia.
F Corresponding author. Email: sue.hatcher@dpi.nsw.gov.au
Animal Production Science 49(7) 630-636 https://doi.org/10.1071/AN09031
Submitted: 27 February 2009 Accepted: 1 April 2009 Published: 11 June 2009
Abstract
The two systems currently used in Australia for assessing the body reserves of live sheep (fat and condition scoring) were evaluated for their ability to quantify the range of scores within a mob and their ability to discriminate between sheep of varying fatness. Three ewe genotypes (fine Merino, medium Merino and first-cross Border Leicester × Merino) were independently assessed by four assessors experienced in each system (i.e. eight assessors). Twenty-four hours after assessment the ewes were slaughtered in a commercial abattoir and hot carcass measures of tissue depth at the GR site (thickness of tissue over the 12th rib, 110 mm from the midline) taken to allow correlation with the assessed live scores. There was at least three times more phenotypic variation in fat score assessment compared with condition score as the fat score assessors used a wider range of scores. Despite this the average repeatability of fat scoring (0.73–0.85) was greater than condition scoring (0.64–0.84) particularly within the fine Merino genotype. Although there was a strong linear relationship between assessments of fat and condition scoring, the regression coefficients comparing the two scoring systems indicated a greater discrimination among animals on fat score across all three genotypes. Furthermore the fat scores had a significantly higher correlation with GR tissue depth measured on the carcass than condition scores. These data indicate that both systems will similarly assess the average body fat reserves of a mob or animals; however, fat scoring achieves greater discrimination when the goal is to identify individuals that are lower or higher than the mob average.
Acknowledgements
Funding for this project was provided by Meat and Livestock Australia. The participation of the FS (Brent McLeod, Chris Shands, Michael Lollback and Geoff Duddy all from NSW DPI) and CS (Ian Rose and Tom Plaisted DAFWA, Darren Gordon DPI Vic. and Katrina Copping SARDI) assessors is gratefully acknowledged as was the input of Dr Chris Oldham (DAFWA) in experimental design and assistance during the experimentation. Dr Kevin Atkins provided helpful advice and discussion regarding the statistical analysis of the data and its interpretation.
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