Development of black pigmented skin spots and pigmented wool fibres in a Merino flock—causes, field observations, and wool measurement
M. R. FleetSouth Australian Research and Development Institute, Livestock Systems Alliance, Turretfield Research Centre, Rosedale, SA 5350, Australia. Email: fleet.malcolm@saugov.sa.gov.au
Australian Journal of Agricultural Research 57(7) 751-760 https://doi.org/10.1071/AR05032
Submitted: 31 January 2005 Accepted: 1 February 2006 Published: 14 July 2006
Abstract
The development of black-grey pigmented skin spots and pigmented wool fibres on adult Merino sheep over a 3-year period was assessed. Effects of long-term grazing of oestrogenic pasture and multiple shearing were studied. The number of affected sheep and number of pigmented spots on affected sheep increased with age, with the greatest increase at 8.5 years age. Grazing of oestrogenic pastures had no effect but twice yearly shearing increased the development of pigmented spots after 2 years of treatment. Measurements on fleeces and top from sheep with no apparent pigmented spots showed that this wool was generally free of pigmented fibres. In contrast, wool from affected individuals generally had high concentrations of pigmented wool fibres, with substantial pigmented lengths (means 20–40 mm) and intensely darkened, which related to the field records of black-grey pigmented skin spots. The amounts of dark pigmented fibres found in the processed top from affected fleeces ranged between 262 and 1293/kg. Based on these findings, sheep age is an important factor for inclusion in decision systems alerting wool buyers to the risk of hidden dark fibres. However, if adequate inspection of sheep during shearing is practical to isolate fleeces from sheep with black-grey pigmented skin spots in the fleece areas, then the risk level applied could be lowered or removed for the wool from the unaffected sheep.
Additional keywords: pigmented spots, old Merino sheep.
Acknowledgments
I thank Peter Flavel, David Little, and farm staff for the management and access to sheep at Parndana Research Centre. Several other staff assisted in the collection of field records. Debra Partington (BiometricsSA) undertook a preliminary analysis of data from the field inspections of sheep. Janice Altman undertook the dark fibre inspections of staple wool, and Annette Mackie and Tahera Pourbeik inspected the samples of wool top. I thank Roger Foulds and his team at CSIRO Division of Textile Physics (Ryde, NSW) for organising the processing of fleeces to top and measuring transmittance on the extracted pigmented fibres. Funding from Australian wool producers assisted the wool measurements.
Fleet MR
(1996) Pigmentation types — understanding the heritability and importance. Wool Technology and Sheep Breeding 44, 264–280.
Fleet MR
(1999) Random spot and relationship with other pigmentation in Merinos. Association for the Advancement of Animal Breeding and Genetics 13, 290–293.
Fleet MR
(2002) Pigment prevention in sheep: Complex or simple? Wool Technology and Sheep Breeding 50, 410–416.
Fleet MR, Forrest JW
(1984) The occurrence of spots of pigmented skin and pigmented wool fibres in adult Merino sheep. Wool Technology and Sheep Breeding 32, 83–90.
Fleet MR,
Forrest JW,
Walker SK, Rogers GE
(2004) Foetal development of melanocyte populations in Merino wool-bearing skin. Wool Technology and Sheep Breeding 52, 101–123.
Fleet MR,
Foulds RA,
Pourbeik T,
McInnes CB,
Smith DH, Burbidge A
(1995) Pigmentation relationships among young Merino sheep and their tops. Australian Journal of Experimental Agriculture 35, 343–351.
| Crossref | GoogleScholarGoogle Scholar |
Fleet MR,
Mahar TJ, Turk JA
(2002) Merino crossbreeding and objectionable sheep fibres: the problem and potential solution. Wool Technology and Sheep Breeding 50, 650–656.
Fleet MR, Smith DH
(1990) Pigmented fibres in white-skirted fleece wool of piebald Merino sheep. Australian Journal of Agricultural Research 41, 155–166.
| Crossref | GoogleScholarGoogle Scholar |
Fleet MR,
Vage DI,
Klungland H,
Olsen RT,
Nattrass GS, Bennie MJ
(2005) Observations on white spotting in a Damara × Merino family. Association for the Advancement of Animal Breeding and Genetics 16, 192–195.
Forrest JW, Fleet MR
(1985) Lack of tanning in white Merino sheep following exposure to ultraviolet light. Australian Veterinary Journal 62, 244–246.
| PubMed |
Forrest JW, Fleet MR
(1986) Pigmented spots in the wool-bearing skin of white Merino sheep induced by ultraviolet light. Australian Journal of Biological Sciences 39, 125–136.
| PubMed |
Forrest JW,
Fleet MR, Rogers GE
(1985) Characterisation of melanocytes in wool-bearing skin of Merino sheep. Australian Journal of Biological Sciences 38, 245–257.
| PubMed |
Franceschi S,
Baron AE, La Vecchia C
(1990) The influence of female hormones on malignant melanoma. Tumori 76, 439–449.
| PubMed |
Kelley RB, Shaw HEB
(1942) Note on the occurrence and inheritance of pigmented wool. Journal of the Council for Scientific and Industrial Research 15, 1–3.
Kijas JMH,
Moller M,
Plastow G, Andersson L
(2001) A frameshift mutation in MC1R and a high frequency of somatic reversions cause black spotting in pigs. Genetics 158, 779–785.
| PubMed |
McLeod SD,
Ranson M, Mason RS
(1994) Effects of estrogens on human melanocytes in vitro. The Journal of Steroid Biochemistry and Molecular Biology 49, 9–14.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Moule GR
(1961) The fertility of sheep grazing oestrogenic pastures. Australian Veterinary Journal 37, 109–114.
Rouzaud F,
Kadekaroo AL,
Abdel-Malek ZA, Hearing VJ
(2005) MC1R and the response of melanocytes to ultraviolet radiation. Mutation Research 571, 133–152.
| PubMed |
Schmutz JL
(2003) Physiological skin changes during pregnancy. Presse Medicale 32, 1806–1808.
Snell RS, Bischitz PG
(1960) The effect of large doses of oestrogen and oestrogen and progesterone on melanin pigmentation. Journal of Investigative Dermatology 35, 73–82.
| PubMed |
Thornton MJ
(2005) Oestrogen functions in skin and skin appendages. Expert Opinion on Therapeutic Targets 9, 617–629.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Våge DI,
Fleet MR,
Ponz R,
Olsen RT,
Monteagudo LV,
Tejedor MT,
Arruga MV,
Gagliardi R,
Postiglioni A,
Nattrass GS, Klungland H
(2003) Mapping and characterisation of the dominant black colour locus in sheep. Pigment Cell Research 16, 693–697.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Våge DI,
Klungland H,
Lu D, Cone RD
(1999) Molecular and pharmacological characterization of dominant black coat colour in sheep. Mammalian Genome 10, 39–43.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Zaun H
(1983) Pregnancy and ovulation inhibitors as risk factors in malignant melanoma. Hautartz 34, 593–595.
