Reduction in wool follicles prior to birth in Merino sheep

1999 ◽  
Vol 11 (5) ◽  
pp. 229 ◽  
Author(s):  
J. E. Hocking Edwards
Keyword(s):  
Primary Follicle ◽  
Merino Sheep ◽  
Secondary Follicle

This study was undertaken to identify whether all secondary follicles that are initiated are present at birth in the Merino fetus, and if not, when does net initiation of secondary follicles cease. Skin was sampled from fetal lambs at 36, 26 and 16 days before the estimated date of parturition and from lambs at birth and 2, 4, 6, 8 and 13 weeks after birth. The ratio of secondary to primary follicles (S/P) reached a maximum 16 days before birth and was significantly lower at birth (P<0.002) and at all postnatal ages (P<0.05). There was no difference between S/P at birth and S/P at later ages. Postnatal primary follicle density, secondary follicle density and the percentage of fibre-producing follicles followed similar patterns to those reported by others. This is the first conclusive demonstration that secondary follicle initiation is completed several weeks prior to birth and that there are less secondary follicles at birth than at 134 days of gestation.

Perinatal wool follicle attrition coincides with elevated perinatal circulating cortisol concentration in Merino sheep

2007 ◽  
Vol 58 (7) ◽  
pp. 748 ◽  
Author(s):  
A. C. Toland Thompson ◽  
M. L. Hebart ◽  
N. M. Penno ◽  
P. I. Hynd
Keyword(s):  
Surface Area ◽  
Plasma Cortisol ◽  
Post Partum ◽  
Skin Surface ◽  
Cortisol Concentration ◽  
Primary Follicle ◽  
Merino Sheep ◽  
Secondary Follicle ◽  
Plasma Cortisol Concentration ◽  
Wool Follicle

The development of the follicle population in Merino sheep skin was studied from 30 days pre-partum to 112 days post-partum in single- and twin-born Merino lambs. The total number of primary follicles estimated from primary follicle density and skin surface area did not change over this period, while secondary follicle number increased to Day 28 post-partum in singles and Day 56 post-partum in twins. Twins had 14% fewer total follicles than singletons (P < 0.001), largely reflecting a bodyweight (hence estimated skin surface area) difference of 10%, with little difference in total follicle density (P > 0.05). Immediately post-partum there was a 36% decrease (P < 0.0001) in the secondary to primary follicle ratio (S/P) of the twin lambs, while a small non-significant decrease (7%; P > 0.05) occurred in the single lambs. This attrition coincided with a surge in plasma cortisol concentration that commenced ~12 days before birth and persisted for 6–12 days post-partum. The surge in plasma cortisol concentration occurred in both single and twin lambs, commencing on Day 138 of gestation; however, the peak cortisol concentration and the period over which cortisol remained elevated was greater in twin lambs than in singletons (P < 0.001). This study confirms a previous finding of a perinatal reduction in S/P ratio in Merino sheep. The reduction was greater in twin lambs than in singletons but the follicles of twins recovered rapidly so that there was little difference in final S/P ratio between birth types after Day 30 post-partum. The postnatal follicle reduction followed the perinatal surge in plasma cortisol concentration and appeared to reflect the magnitude of the cortisol surge in that twins, which displayed a higher peak cortisol concentration, had a greater reduction in active follicles than singletons.

Relationships between skin follicle characteristics and fibre properties of Suri and Huacaya alpacas and Peppin Merino sheep

2012 ◽  
Vol 52 (7) ◽  
pp. 442 ◽  
Author(s):  
M. B. Ferguson ◽  
B. A. McGregor ◽  
R. Behrendt
Keyword(s):  
Negative Correlation ◽  
Fibre Diameter ◽  
Variable Number ◽  
Primary Follicle ◽  
Merino Sheep ◽  
Secondary Follicle ◽  
The Mean ◽  
Fibre Traits ◽  
Fibre Characteristics ◽  
Skin Samples

We aimed to quantify the number, type and arrangement of skin follicles in Huacaya and Suri alpaca skin and correlate their follicle characteristics with fibre traits of harvested fibre and compared these relationships with those of Merino sheep. Fibre and skin samples were collected from the mid-side of 12 Huacaya alpacas, 24 Suri alpacas and 10 Merino sheep. The mean fibre diameter (MFD ± s.e.) of the Huacaya and Suri were: 35.5 ± 0.9 and 28.3 ± 1.0 μm, respectively. The follicle groups found for alpacas were very different from the normal trio of primary follicles found in sheep and goats. The follicle group of the alpacas consisted of a single primary follicle surrounded by a variable number of secondary follicles. The mean ± s.e. primary follicle density was 3.1 ± 0.3 and 2.7 ± 0.1 follicles/mm2 for Huacaya and Suri, respectively. The mean ± s.e. secondary follicle density (SFD) was 13.7 ± 1.2 and 17.5 ± 0.6 follicles/mm2 for Huacaya and Suri, respectively. The mean ± s.e. ratio of secondary to primary follicles (S/P ratio) was 5.1 ± 0.5 for the Huacaya and 7.3 ± 0.2 for the Suri alpacas. The sheep had higher S/P ratios and SFD, lower MFD and produced significantly heavier fleeces. The key correlations found between traits in alpacas include a negative correlation between SFD and MFD (r = –0.71, P = 0.001) and a negative correlation between S/P ratio and MFD (r = –0.44, P = 0.003) and a positive correlation between S/P ratio and total follicle density (r = 0.38, P = 0.010). The study revealed that important relationships exist between alpaca skin follicle characteristics and fibre characteristics. It was the number of secondary follicles in a group that imparts density and a corresponding reduced MFD.

Wool follicle development in the New Zealand Romney and N type sheep. II. Follicle population density during foetal development

1958 ◽  
Vol 9 (1) ◽  
pp. 138 ◽  
Author(s):  
SK Stephenson
Keyword(s):  
New Zealand ◽  
Population Density ◽  
Subsequent Development ◽  
The Body ◽  
Limiting Factor ◽  
Follicle Development ◽  
Primary Follicle ◽  
Foetal Development ◽  
Secondary Follicle ◽  
The Face

Quantitative aspects of follicle initiation and development have been studied in a series of N-type and New Zealand Romney foetuses. Density of the follicle population and ratios of secondary to primary follicles were examined on 13 positions of the body which covered the main wool-bearing areas, the face and head, and the limbs. Primary follicle development is initiated first on the head and limbs and throughout subsequent development these regions are most advanced. Primary follicle density reaches a maximum between 75 and 90 days of foetal age, after which it decreases as a result of skin growth. Secondary follicle initiation is more rapid on the wool-bearing areas of the body, and higher ratios of secondary to primary follicles are recorded from these regions. No real differences have been found between N-type and New Zealand Romney foetuses in population density of the different follicle types at any age or in the number of secondary follicles developed per primary follicle. The growth of larger primary fibres and follicles in N-type foetuses is not accompanied by, and does not result from, a lower density of primary follicles. There does not appear to be any marked relation between the decreasing density of primary follicles after 90 days of foetal age and the initiation of secondary follicle anlagen. This fact, and the absence of any differences in the number of secondary anlagen formed per primary follicle in N-types, suggest that crowding in N-types is not a limiting factor in the formation of secondary follicle anlagen.

scholarly journals Red LED light promotes hair follicle development to improve fibre quality in Su line Angora rabbit

2019 ◽  
Author(s):  
Feng Qin ◽  
Jing Wang ◽  
Le Shao ◽  
Xiaoqing Pan ◽  
Jie Yang ◽  
...  
Keyword(s):  
Hair Follicle ◽  
Fibre Diameter ◽  
Follicle Development ◽  
Fibre Quality ◽  
Primary Follicle ◽  
Led Light ◽  
Secondary Follicle ◽  
Red Led ◽  
Wool Yield ◽  
Hair Follicle Development

Abstract Background: Light has crucial roles in animal physiological activities. This study aimed to investigate the effects of different colours of light-emitting diodes (LEDs) on rabbit fibre quality and hair follicle development. 50 three-month-old Su line Angora rabbits were randomly assigned to five groups. Treatment groups were exposed to same intensities of red, green and blue LED light under 16 h light:8 h dark photoperiod regimes. Control groups were exposed to white light and black. The trial spanned 73 days. Results: Results showed that LED colours exerted different effects on wool yield, fibre quality, hormones and hair follicle development. The wool yield of red group was higher than that of white, green and black groups (P<0.05). The shoulder fibre length of red group was higher than that of white and green groups (P<0.05). The coarse fibre diameter of white group was lower than that of green and black groups (P<0.05). The fibre diameter of red group was the lowest and was lower by 13.9% than that of control group (P>0.05). The coarse fibre ratio of green group was higher (13.31%) than that of red group (3.81%, P<0.05). The follicle groups of white, green and black groups consisted of 1 primary follicle associated with 3 or 4 secondary follicle groups and those of blue group consisted of 1 primary follicle associated with 5–10 secondary follicle groups. The follicle of red group consisted of numerous secondary follicles and a few primary follicles. In same magnification, the numbers of follicle groups of white, red, green, blue and black groups were 14.0, 16.5, 10.0, 11.67 and 11.0, respectively. The numbers of follicle groups of red and green groups significantly differed (P<0.05). Serum melatonin (MT) of red group was highest than that of white and green groups (P<0.01), higher than that of black group (P<0.05), serumTriiodothyronine (T 3 ) of red group was higher than that of white and black groups (P<0.05). Conclusions: Thus, the data reveal that red LED light can improve fibre quality, this may be due to red LED light which can enhance the secretion of melatonin to promote hair follicle development .

Genetic studies of South Australian Merino sheep. 4. Genetic, phenotypic and environmental correlations between various wool and body traits

1982 ◽  
Vol 33 (2) ◽  
pp. 363 ◽  
Author(s):  
IP Gregory
Keyword(s):  
Great Increase ◽  
Fibre Diameter ◽  
Skin Thickness ◽  
Primary Follicle ◽  
Genetic Studies ◽  
Environmental Correlations ◽  
Merino Sheep ◽  
Selection For ◽  
Fleece Weight ◽  
Australian Merino

Genetic, phenotypic and environmental correlations were estimated between 23 quantitative and qualitative wool and body traits of South Australian Merino sheep. Clean fleece weight was significantly correlated genetically with greasy fleece weight (0.62), yield (0.47), staple length (0.41), crimps per inch (-0.34), secondary/primary follicle ratio (0.37) and skin thickness (0.39). No significant half-sib genetic correlation was found between clean fleece weight and fibre diameter and the dam-offspring correlation was quite low, although significant (0.16, P < 0.05). This indicates that selection for clean fleece weight should not lead to any great increase in fibre diameter. Skin thickness is discussed as a possible early indicator of clean fleece weight.

Fleece characteristics and the wool follicle population of the Merilin, a Uruguayan sheep breed

1981 ◽  
Vol 32 (3) ◽  
pp. 251-256 ◽  
Author(s):  
W. H. J. Clarke ◽  
J. B. Donnelly ◽  
A. Lombardini ◽  
R. González
Keyword(s):  
Body Weight ◽  
Sheep Breed ◽  
Limited Data ◽  
Firm Conclusion ◽  
Primary Follicle ◽  
Secondary Follicle ◽  
Wool Follicle ◽  
Fleece Weight ◽  
Staple Length

ABSTRACTTotal follicle density, primary follicle density, secondary follicle density, secondary/primary ratio and incidence of medullated fibres were studied in skin specimens from 78 2-year-old Merilin rams representing nine parent studs in Uruguay. The limited data available suggest that the studs sampled may fall into various groups, although separation into distinct groups is not equally well defined for all variables measured. Consequently, a firm conclusion about the Merilin awaits further information on fleece weight, staple length and body weight.

The post-natal development of the skin follicle population of a strain of Merino sheep.

1955 ◽  
Vol 6 (1) ◽  
pp. 68 ◽  
Author(s):  
PG Schinckel
Keyword(s):  
Normal Skin ◽  
Primary Follicle ◽  
Progressive Decline ◽  
Skin Expansion ◽  
Rate Of Development ◽  
Merino Sheep ◽  
Sigmoid Curve ◽  
Australian Merino

Observations are reported on the development of the follicle population during post-natal life in three groups of sheep from a strain of Australian Merino. The primary follicle number is complete by birth, and changes in density thereafter merely reflect the normal skin expansion accompanying growth. This constancy with time of the primary follicle number validates the use of the ratio of secondary to primary follicles (S/P) as a measure of the development of the secondary follicles. The S/P ratio followed a sigmoid curve characterized by a small increase in the ratio during the first week, a large increase in the second, and a progressive decline in the rate of development of secondary follicles thereafter.

Selection for high and low ratio and high and low primary density in Merino sheep

1978 ◽  
Vol 29 (5) ◽  
pp. 1077 ◽  
Author(s):  
JM Rendel ◽  
T Nay
Keyword(s):  
Point Of View ◽  
Primary Follicle ◽  
Merino Sheep ◽  
Selection For ◽  
Fleece Weight

The result of selecting sheep up and down for secondary to primary follicle ratio (S/P) and up and down for the number of primary follicles to the square millimetre is examined from the point of view of Fraser's theory of competition between follicles. The possibility of finding other characters in which variation will cause variation in fleece weight has also been investigated. It is concluded that selection which increased the S/P ratio and primary density did not increase fleece weight; follicle depth is possibly one skin character which, when changed, causes changes in fleece weight but this requires confirmation.

Genetic studies of South Australian Merino sheep. 3. Heritabilities of various wool and body traits

1982 ◽  
Vol 33 (2) ◽  
pp. 355 ◽  
Author(s):  
IP Gregory
Keyword(s):  
Body Weight ◽  
Fibre Diameter ◽  
Skin Thickness ◽  
Production Traits ◽  
Primary Follicle ◽  
Merino Sheep ◽  
Main Production ◽  
Fleece Weight ◽  
Australian Merino ◽  
Staple Length

Heritabilities have been estimated for a large number of quantitative and qualitative wool and body traits recorded on two flocks of South Australian Merino sheep over a 12-year period. Data were unadjusted for fixed environmental effects and so the estimates are applicable to the heterogeneous populations found in most practical situations. Dam-offspring heritabilities of quantitative traits ranged from 0.15 for primary follicle number to 0.63 for body weight. Greasy and clean fleece weights, percentage clean yield, staple length, crimps per inch, fibre diameter, secondary and total follicle number, skin thickness, coefficient of variation of fibre diameter and secondary/primary follicle ratio had moderate to high heritabilities. Dam-offspring heritabilities of qualitative traits ranged from 0.12 for weather damage of the fleece to 0.75 for birthcoat. Total folds, face cover and hocks had high heritabilities, and wool character, type of staple formation and wool quality had moderate heritabilities. The main production traits (body weight, greasy fleece weight, yield, clean fleece weight, staple length, fibre diameter and total follicle number) were corrected for variation due to type of birth and age of dam and their heritabilities re-estimated. No change occurred in the half-sib heritabilities; dam-offspring heritabilities increased by an average of 0.05.

The effects of exogenous melatonin and prolactin on wool follicle development in ovine foetal skin grafts

1993 ◽  
Vol 44 (5) ◽  
pp. 993 ◽  
Author(s):  
CE McCloghry ◽  
DE Hollis ◽  
A Foldes ◽  
AJ Rintoul ◽  
P Baker ◽  
...  
Keyword(s):  
Nude Mice ◽  
Follicle Development ◽  
Skin Grafts ◽  
Epidermal Thickness ◽  
Exogenous Melatonin ◽  
Merino Sheep ◽  
Secondary Follicle ◽  
Wool Follicle

The fleece of the Merino sheep is composed predominantly of wool fibres grown from secondary wool follicles. This study investigates the effects of melatonin and prolactin on the development of secondarv follicles in grafted ovine foetal skin. Skin from day 85 ovine foetuses was grafted onto nude mice, developed for 40 days and then excised. Mice received either 30 8g prolactin ip mouse-1 day-1 (P), one melatonin implant (Regulin�) sc mouse -1 (M), commencing at grafting or no further treatment (C). Wool follicle density and development were assessed in grafted skin and compared with day 125 control foetal skin. Cuticle structure of graft fibres was also examined and compared with those of day 125 foetuses. Total follicle density and the rate of follicle initiation were reduced in the grafts compared with control foetal skin. Total follicle density did not vary significantly between treatments, but the number of derived secondary follicles was greater in grafts from mice receiving prolactin (group P). Follicles in grafted skin were larger, produced medullated fibres, and were not grouped, in comparison with follicles in the control foetal skin. Epidermal thickness was greater in grafts than in control foetal skin. The cuticle structure of graft fibres from all groups was similar to the control wool fibres. These findings indicate that prolactin, but not melatonin, may be involved in the regulation of derived secondary follicle development.

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