Biology of fibre growth and possible genetic and non-genetic means of influencing fibre growth in sheep and goats—a review

Sumner, R. M. W.; Bigham, M. L.

doi:10.1016/0301-6226(93)90235-a

Cited by 38 publications

(20 citation statements)

References 78 publications

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“…The values for heritabilities and phenotypic and genetic correlations obtained here are within the ranges reported for the major Australasian breeds (Sumner & Bigham 1993). Within New Zealand, Blair et al (1985) reported realised heritabilities for YGFW in the Massey flocks of 0.10-0.17, whereas obtained a value of 0.36 ± 0.04 (recursive method), and the CO flock paternal half-sib estimate given in Table 1 was 0.35 ± 0.08.…”

Section: Parameter Estimatessupporting

confidence: 54%

Single trait selection for yearling fleece weight or liveweight in Romney sheep—correlated responses in liveweight, fleece traits, and ewe reproduction

Morris

Johnson

Sumner

et al. 1996

New Zealand Journal of Agricultural Research

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An experiment was carried out to study direct and indirect responses to selection in Romney sheep. There were two selection lines, one selected for greasy fleece weight (GFW) and the other for liveweight (LW), maintained alongside a control line (CO). Data from lambs born in 1967-90 were analysed to quantify the correlated responses to selection. By 1990, there had been an average of nine generations of selection with an average generation interval of 2.7 years. The correlated responses analysed included yearling and ewe greasy and clean fleece weights, washing yield, yearling and ewe fleece quality traits (staple length, mean fibre diameter, fibre diameter variation, loose wool bulk, Commission Internationale de l'Eclairange (CIE) Y value (brightness) and CIE Y-Z value (yellowness)), birth weight, weaning weight, yearling liveweight, ewe pre-mating weight, and ewe reproductive rate (fertility, litter size, weaning percentage, and lamb survival). Correlated responses were estimated as the deviation of selection lines from the CO line, and genetic correlations were obtained by restricted maximum likelihood techniques. Direct responses measured in the GFW and LW yearlings were 1.7 and 1.2% per year, respectively. Correlated annual responses were 0.7% in yearling liveweight in the GFW line and 0.2% in yearling fleece weight in the LW line. Corresponding annual changes in ewe performance were 1.5% in greasy fleece weight and 0.5% in pre-mating weight in the GFW line, and 0.0 and 1.2% respectively in the LW line. Mean fibre diameter increased in yearlings and ewes of the GFW line, but did not change in the LW line. There were small but significant increases in staple length in both lines. Loose wool bulk among GFW yearlings was reduced by 0.12% per year but did not change significantly in ewes. Yearlings and ewes of the LW line both showed an increase in bulk (0.15 and 0.43%, respectively). Relative to the CO flock, CIE Y-Z among yearlings increased significantly by 1.35% per annum and 0.25% per annum in the GFW and LW flocks respectively. Among ewes it increased in the GFW line whereas the opposite occurred in the LW line. There was no significant change in percentage ewes lambing as a result of GFW or LW selection. Litter size increased and lamb survival to weaning decreased significantly, but there was a net increase per year in lambs weaned per ewe lambing (0.27% per year for the GFW line and 0.48% per year for the LW line). A95024

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Section: Parameter Estimatessupporting

confidence: 54%

Single trait selection for yearling fleece weight or liveweight in Romney sheep—correlated responses in liveweight, fleece traits, and ewe reproduction

Morris

Johnson

Sumner

et al. 1996

New Zealand Journal of Agricultural Research

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“…Similar observations were reported in sheep, Angora goats and cashmere goats and alpaca (Sumner and Bigham, 1993;Taddeo et al, 1998;Renieri et al, 2007). In Angora rabbit, selection for increased total fleece weight was efficient (Rafat et al, 2007a) and resulted in an increase of fibre length without apparent contribution from fibre diameter.…”

Section: Fibre Growth Patternsupporting

confidence: 85%

“…'Double-coated' (DC) species such as Angora rabbit, cashmere goat and primitive sheep have a coarse outer coat derived from primary hair follicles, and a fine inner coat produced by secondary hair follicles. 'Single-coated' (SC) species such as Angora goat and modern woolled sheep in which all fibres produced by both primary and secondary follicles are essentially similar in their -E-mail: Daniel.allain@toulouse.inra.fr physical characteristics (Sumner and Bigham, 1993). This distinction can be extended to South American camelids.…”

Section: Introductionmentioning

confidence: 99%

Genetics of fibre production and fleece characteristics in small ruminants, Angora rabbit and South American camelids

Allain

Renieri

2010

Animal

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This paper reviews genetics of fibre production and fleece characteristics in small ruminants, Angora rabbit and South American camelids with a special distinction between single-coated (SC) and double-coated (DC) species. Considering the biology of fibre production, there are variations in coat composition and structure, fibre growth pattern and fibre structure and quality between these two main kinds of fibre-producing animals. In SC species, all fibres are nearly similar in dimensions and are produced from individual follicles that have a very long period, essentially permanent, of active growth without a synchronous phase of rest between follicles. In contrast, in DC species the fleece comprises a coarse outer coat and a fine inner coat with variations of coat composition and structure, and fibre growth pattern according to the season with a well-defined duration of fibre growth. Genetic basis of hair growth pattern, coat composition and fibre structure are different between species. In small ruminants, these coat characters are additive and because of several genes whereas in rabbit, several autosomal recessive genes determine fibre growth, coat composition and structure. In alpaca, the fleece type (Suri or Huacaya) is determined by a single dominant gene. This paper also reviews genetic parameters of fibre production traits in Angora goat, Angora rabbit and alpaca in which many aspects of the genetic basis of fibre production are analogous. There are many traits controlling both fibre quality and fibre quantity, and most of these traits tend to be moderately to strongly inherited so that a rapid genetic progress in any traits is possible and indeed has been achieved. However, there are differences in breeding programmes. In DC Angora rabbit, selection for one single trait, the easy measurable total fleece weight has general beneficial effects on fleece quality. However, because of antagonistic relations between qualitative and quantitative traits in SC species, achieving this goal requires a multi-trait selection index approach. Gene mapping studies have recently identified several putative quantitative trait loci and major genes affecting fibre and fleece characteristics in sheep, goat and rabbit are reviewed. The whole genome sequence of sheep and rabbit will be available in the near future and the use of high-density single nucleotide polymorphism chip will allow fine mapping and dissection of the genetic basis of many production traits including fibre production and fleece characteristics. The application of these techniques will thus contribute to improving the efficiency, profitability and sustainability of small ruminant and rabbit fibre production.

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“…This response is exactly what would be expected if the mechanism for the relationship between MFD and FFLwt is that changes in skin surface area and the concomitant change in skin follicle density determines the diameter of fibres (Fraser and Short, 1960;Maddocks and Jackson, 1988;Hynd, 1994). Such an allometric response to animal size has also been observed in Angora goats producing mohair (McGregor et al, 2012) but was not identified in reviews linking wool MFD with liveweight of sheep (Sumner and Bigham, 1993;Adams and Cronjé, 2003).…”

Section: Discussionmentioning

confidence: 91%

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

McGregor

Butler²

2016

animal

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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 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 coefficient, sheep, scaling, wool, skin follicles ImplicationsResponses in mean fibre diameter (MFD) of Merino wool to changes in fleece-free liveweight (FFLwt) were in accord with the primary response of MFD being proportional to the changes in the skin surface area arising from changes in animal size. However, this response can change with individual sheep and nutritional environment. Comparisons of MFD between sheep are more likely to have a biological basis when standardised to a common FFLwt than when standardised to a common age. Wool quality (MFD and staple strength) will be optimised in management systems that maintain constant FFLwt of adult sheep within and between years...

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Biology of fibre growth and possible genetic and non-genetic means of influencing fibre growth in sheep and goats—a review

Cited by 38 publications

References 78 publications

Single trait selection for yearling fleece weight or liveweight in Romney sheep—correlated responses in liveweight, fleece traits, and ewe reproduction

Single trait selection for yearling fleece weight or liveweight in Romney sheep—correlated responses in liveweight, fleece traits, and ewe reproduction

Genetics of fibre production and fleece characteristics in small ruminants, Angora rabbit and South American camelids

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

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