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Coarser wool is not a necessary consequence of sheep aging: allometric relationship between fibre diameter and fleece-free liveweight of Saxon Merino sheep

Published online by Cambridge University Press:  26 May 2016

B. A. McGregor  and
K. L. Butler
B. A. McGregor*
Affiliation:
Institute for Frontier Materials, Deakin University, Geelong, VIC 3220, Australia
K. L. Butler
Affiliation:
Biometrics Group, Agricultural Research, Department of Economic Development Jobs Transport and Resources, Hamilton, VIC 3030, Australia
*
†E-mail: bruce.mcgregor@deakin.edu.au
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Abstract

The mean fibre diameter (MFD) of wool is the primary determinant of price, processing performance and textile quality. This study determines the primary influences on MFD as Saxon Merino sheep age, by allometrically relating MFD to fleece-free liveweight (FFLwt). In total, 79 sheep were grazed in combinations of three stocking rates and two grazing systems (GS: sheep only; mixed with Angora goats) and studied over 3 years. Measurements were made over 14 consecutive periods (Segments), including segments of FFLwt gain or FFLwt loss. Using shearing and liveweight records and dye-bands on wool, the FFLwt and average daily gain (ADG) of each sheep were determined for each segment. The mean and range in key measurements were as follows: FFLwt, 40.1 (23.1 to 64.1) kg; MFD, 18.8 (12.7 to 25.8) μm. A random coefficient restricted maximum likelihood (REML) regression mixed model was developed to relate the logarithm of MFD to the logarithm of FFLwt and other effects. The model can be written in the form of ${\rm MFD}\,{\equals}\,\rkappa \left( {{\rm GS,}\,{\rm A}{\rm ,}\,{\rm Segment}{\rm .Plot,}\,{\rm Segment,}\,{\rm ADG}} \right){\times}{\rm FFLwt}^{{\left( {\ralpha \left( {{\rm GS}} \right){\plus}\rbeta \left(\rm A \right){\plus}\rgamma \left( {{\rm Segment}{\rm .Plot}} \right)} \right)}} $ , where $\ralpha \left( {{\rm GS}} \right)\,{\equals}\,\;\left\{ {\matrix{\!\! {0.32\left( {{\rm SE}\,{\equals}\,{\rm 0}{\rm .038}} \right)\,{\rm when}\,{\rm sheep}\,{\rm are}\,{\rm grazed}\,{\rm alone}} \hfill \cr \!\!\!\!{0.49\left( {{\rm SE}\,{\equals}\,{\rm 0}{\rm .049}} \right)\,{\rm when}\,{\rm sheep}\,{\rm are}\,{\rm mixed}\,{\rm with}\,{\rm goats}} \hfill \cr } } \right.$ β(A) is a random animal effect, γ(Segment.Plot) a random effect associated with Segment.plot combinations, and κ a constant that depends on GS, random animal effects, random Segment.plot combination effects, Segment and ADG. Thus, MFD was allometrically related to the cube root of FFLwt over seasons and years for sheep, but to the square root of FFLwt for sheep grazed with goats. The result for sheep grazed alone accords with a primary response being that the allocation of nutrients towards the cross-sectional growth of wool follicles is proportional to the changes in the skin surface area arising from changes in the size of the sheep. The proportionality constant varied systematically with ADG, and in sheep only grazing, was about 5 when sheep lost 100 g/day and about 6 when sheep gained 100 g/day. The proportionality constant did not systematically change with chronological age. The variation in the allometric coefficient between individual sheep indicates that some sheep were more sensitive to changes in FFLwt than other sheep. Key practical implications include the following: (a) the reporting of systematic increases in MFD with age is likely to be a consequence of allowing sheep to increase in size during shearing intervals as they age; (b) comparisons of MFD between sheep are more likely to have a biological basis when standardised to a common FFLwt and not just to a common age; (c) wool quality (MFD, staple strength) are most likely to be optimised in management systems that maintain constant FFLwt of adult sheep within and between years.

Keywords

allometric coefficientsheepscalingwoolskin follicles
Type
Research Article
Information
animal , Volume 10 , Issue 12 , December 2016 , pp. 2051 - 2060
Copyright
© The Animal Consortium 2016 

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References

Adams, NR and Cronjé, PB 2003. A review of the biology linking fibre diameter with fleece weight, liveweight, and reproduction in Merino sheep. Australian Journal of Agricultural Research 54, 1–10.CrossRefGoogle Scholar
Alexander, G and Williams, OB (eds) 1973. The pastoral industries of Australia. Sydney University Press, Sydney, Australia.Google Scholar
Allden, WG 1979. Feed intake, diet composition and wool growth. In Physiological and environmental limitations to wool growth (ed. JL Black and PJ Reis), pp. 61–78. University of New England Publishing Unit, Armidale, Australia.Google Scholar
Black, JL and Reis, PJ (eds) 1979. Physiological and environmental limitations to wool growth. University of New England Publishing, Armidale, Australia.Google Scholar
Black, JL, Robards, GE and Thomas, R 1973. Effects of protein and energy intakes on the wool growth of Merino wethers. Australian Journal of Agricultural Research 24, 399–412.CrossRefGoogle Scholar
Burns, M 1954. Observations on the development of the fleece and follicle population in Suffolk sheep. Journal of Agricultural Science Cambridge 44, 86–99.Google Scholar
Chapman, RE and Wheeler, JL 1963. Dyebanding: a technique for fleece growth studies. Australian Journal of Science 26, 53–54.Google Scholar
Collins, JD and Chaikin, M 1968. Structural and non-structural effects in the observed stress–strain curves on wet wool fibres. Journal of the Textile Institute 59, 379–400.CrossRefGoogle Scholar
Cronjé, PB and Smuts, M 1994. Nutrient partitioning in Merino rams with different wool growth rates. Animal Production 59, 55–60.Google Scholar
Di, J, Zhang, Y, Tian, K-C, Lazate, , Liu, J-F, Xu, X-M, Zhang, Y-J and Zhang, T-H 2011. Estimation of (co)variance components and genetic parameters for growth and wool traits of Chinese superfine Merino sheep with the use of a multi-trait animal model. Livestock Science 138, 278–288.CrossRefGoogle Scholar
Fozi, MA, van der Werf, JHJ and Swan, AA 2012. Modelling genetic covariance structure across ages of mean fibre diameter in sheep using multivariate and random regression analysis. Animal Production Science 52, 1019–1026.CrossRefGoogle Scholar
Fraser, AS and Short, BF 1960. The biology of the fleece. Animal research laboratories technical paper no. 3. CSIRO, Melbourne, Australia.Google Scholar
Hannah, MC 2012. SEDLSI. In GenStat Reference Manual (Release 15), Part 3 Procedures (ed. RW Payne), pp. 927–929. VSN International, Hemel Hempstead, UK.Google Scholar
Hill, JA, Ponzoni, RW and James, JW 1999. Micron blowout: heritability and genetic correlations with fibre diameter and secondary follicle diameter. Australian Journal of Agricultural Research 50, 1375–1380.CrossRefGoogle Scholar
Hunter, L 1980. The effects of wool fibre properties on processing performance and yarn and fabric properties. Proceedings of 6th International Wool Textile Research Conference, Pretoria, vol. 2, pp. 133–188.Google Scholar
Hynd, PI 1994. Follicular determinants of the length and diameter of wool fibres. 1. Comparison of sheep differing in fibre length/diameter ratio at two different levels of nutrition. Australian Journal of Agricultural Research 45, 1137–1147.Google Scholar
International Wool Textile Organisation 2005. IWTO-47 measurement of the mean and distribution of fibre diameter of wool using an optical fibre diameter analyser (OFDA). International Wool Textile Organisation, Ilkley, UK.Google Scholar
Liu, SM, Mata, G, O’Donoghue, H and Masters, DG 1998. The influence of live weight, live-weight change and diet on protein synthesis in the skin and skeletal muscle in young Merino sheep. British Journal of Nutrition 79, 267–274.Google Scholar
Maddocks, IG and Jackson, N 1988. Structural studies of sheep, cattle and goat skin. CSIRO, Blacktown, Australia.Google Scholar
Martin, SJ, Atkins, KD, Semple, SJ, Sladek, MA, Thackeray, RH, Staines, JM, Casey, AE, Graham, RP and Russell, AJ 2010. Merino bloodlines: the comparisons 1999-2010. Primefact 930. Department of Industry & Investment NSW, Sydney, Australia.Google Scholar
McGregor, BA 2010a. The influence of stocking rate and mixed grazing of Angora goats and Merino sheep on animal and pasture production in southern Australia. 1. Botanical composition, sward characteristics and availability of components of annual temperature pastures. Animal Production Science 50, 138–148.Google Scholar
McGregor, BA 2010b. Influence of stocking rate and mixed grazing of Angora goats and Merino sheep on animal and pasture production in southern Australia. 2. Liveweight, body condition score, carcass yield and mortality. Animal Production Science 50, 149–157.Google Scholar
McGregor, BA 2010c. The influence of stocking rate and mixed grazing of Angora goats and Merino sheep on animal and pasture production in southern Australia. 3. Mohair and wool production and quality. Animal Production Science 50, 168–176.CrossRefGoogle Scholar
McGregor, BA, Butler, KL and Ferguson, MB 2012. The allometric relationship between mean fibre diameter of mohair and the fleece-free liveweight of Angora goats over their lifetime. Animal Production Science 52, 35–43.Google Scholar
McGregor, BA, Naebe, M, Wang, H, Tester, D and Rowe, J 2015. Relationships between wearer assessment and the instrumental measurement of the handle and prickle of wool knitted fabrics. Textile Research Journal 85, 1140–1152.CrossRefGoogle Scholar
McGregor, BA, Presidente, PJA and Campbell, NJ 2014. The influence of stocking rate and mixed grazing of Angora goats and Merino sheep on animal and pasture production in southern Australia. 4. Gastrointestinal parasitism. Animal Production Science 54, 587–597.Google Scholar
Newton Turner, H and Young, SSY 1969. Quantitative genetics in sheep breeding. Macmillan Company of Australia, Melbourne, Australia.Google Scholar
Payne, RW (ed.) 2014. The guide to GenStat®; release 17. Part 2: statistics. VSN International, Hertfordshire, UK.Google Scholar
Schmidt-Nielsen, K 1984. Scaling: why is animal size so important?. Cambridge University Press, Cambridge, UK.CrossRefGoogle Scholar
Snyman, MA, Olivier, JJ and Olivier, WJ 1996. Variance components and genetic parameters for body weight and fleece traits of Merino sheep in an arid environment. South African Journal of Animal Science 26, 11–14.Google Scholar
Standing Committee on Agriculture (SCA) 1990. Feeding standards for Australian livestock: ruminants. Standing Committee on Agriculture, CSIRO, East Melbourne, Australia.Google Scholar
Steel, JW, Symons, LEA and Jones, WO 1980. Effects of level of larval intake on the productivity and physiological and metabolic responses of lambs infected with Trichostrongylus colubriformis . Australian Journal of Agricultural Research 31, 821–838.Google Scholar
Sumner, RMW and Bigham, ML 1993. Biology of fibre growth and possible genetic and non-genetic means of influencing fibre growth in sheep and goats – a review. Livestock Production Science 33, 1–29.Google Scholar
Valera, M, Arrebola, F, Juarez, M and Molina, A 2009. Genetic improvement of wool production in Spanish Merino sheep: genetic parameters and simulation of selection strategies. Animal Production Science 49, 43–47.Google Scholar
White, DH and McConchie, BJ 1976. Effect of stocking rate on fleece measurements and their relationships in Merino sheep. Australian Journal of Agricultural Research 27, 163–174.CrossRefGoogle Scholar