Fat depth, muscle depth, fat score and wool growth in Merino dams selected for high or low clean fleece weight and bodyweight
G. Refshauge A B E , S. Hatcher A C , G. N. Hinch A D , D. L. Hopkins A B and S. Nielsen CA Australian Sheep Industry Cooperative Research Centre, Armidale, NSW 2350, Australia.
B Industry and Investment NSW (Primary Industries), Centre for Sheep Meat Development, Cowra, NSW 2794, Australia.
C Industry and Investment NSW (Primary Industries), Orange Agricultural Institute, Orange, NSW 2350, Australia.
D University of New England, School of Environmental and Rural Science, Armidale, NSW 2351, Australia.
E Corresponding author. Email: gordon.refshauge@industry.nsw.gov.au
Animal Production Science 50(6) 479-484 https://doi.org/10.1071/AN09210
Submitted: 16 December 2009 Accepted: 3 May 2010 Published: 11 June 2010
Abstract
Concerns exist that selection for increased clean fleece weight (CFW) is expected to reduce body fatness. Such an effect is likely to impact on reproduction; however, all previous studies have examined non-reproductive yearlings or hoggets. The present study, using adult reproductive dams examined the impact of phenotype [based on high or low phenotypic CFW and bodyweight (BWT) performance], stocking rate (high or low) and litter size on body composition and wool traits. High CFW dams were heavier (P < 0.01) with lower fat depth (P < 0.01) and muscle depth (P < 0.05). The high CFW twin-weaning dams had a lower fat score from lamb marking to pre-joining (P < 0.05), but tended to replete fat reserves faster (P < 0.1) between weaning and pre-joining. At these times of repletion these animals grew longer wool staples (P < 0.05). High BWT ewes had reduced staple length (P < 0.01), and when adjusted for maternal liveweight also reduced fat depth (P < 0.001) and muscle depth (P < 0.05). We conclude that the CFW phenotype impacts on fat reserves but that management of dams in groups according to their CFW performance is not warranted.
Acknowledgements
This work was funded by Sheep CRC 1 and has been supported by the farm staff of the Cowra Agricultural Research and Advisory Station. The technical support provided by Kevin Thornberry is gratefully acknowledged.
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