scholarly journals Mitotic Activity in Wool Follicle Bulbs

1961 ◽  
Vol 14 (4) ◽  
pp. 659 ◽  
Author(s):  
PG Schinckel
Keyword(s):  
Mitotic Activity ◽  
Fibre Diameter ◽  
Volume Rate ◽  
Fibre Growth ◽  
Wool Follicle

The quantitatIve significance of mitosis in wool follicle bulbs in relation to the rate of fibre growth was investigated in 10 major fleece phenotypes (fine .Merino, medium Merino mosaic, strong Merino, Merino lustre mutant, Corriedale carpet-wool, Corriedale mosaic, Southdown, and Border Leicester). Mitotic activity in the follicle bulbs was estimated with the aid of colchicine and the volume rate of fibre growth was inferred from fibre diameter.

Effect of DL-methionine supplementation on fleece growth by Australian cashmere goats

1987 ◽  
Vol 109 (1) ◽  
pp. 197-199 ◽  
Author(s):  
A. J. Ash ◽  
B. W. Norton
Keyword(s):  
Fibre Diameter ◽  
Maximum Length ◽  
Early Winter ◽  
Wool Growth ◽  
Mean Diameter ◽  
Fibre Growth ◽  
Cashmere Goats ◽  
Methionine Supplementation ◽  
Almost Continuous

Australian feral goats have recently been found to produce commercially viable quantities of the luxury fibre cashmere (Smith, Clarke & Turner, 1973). Cashmere is the fine down produced by secondary follicles as an undercoat during winter. Fibre diameter ranges from 8 to 24 μm with a mean diameter of 16 μm. Unlike modern breeds of sheep such as the Merino which exhibit almost continuous wool growth, cashmere growth is distinctly seasonal with fibre growth commencing in summer (long daylength) and reaching a maximum length in early winter (short daylength) (McDonald, 1985). The cashmere is cast in spring with growth recommencing again in summer.

Response to selection in Australian Merino sheep. VII. Phenotypic and genetic parameters for some wool follicle characteristics and their correlation with wool and body traits

1975 ◽  
Vol 26 (5) ◽  
pp. 937 ◽  
Author(s):  
N Jackson ◽  
T Nay ◽  
HN Turner ◽  
Turner H Newton
Keyword(s):  
Control Systems ◽  
Genetic Control ◽  
Genetic Parameters ◽  
Unit Area ◽  
Fibre Diameter ◽  
Environmental Correlations ◽  
Merino Sheep ◽  
Wool Follicle ◽  
Australian Merino

Four numerical characteristics-follicle depth, follicle curvature, number of follicles per unit area of skin, and ratio of number of secondary to number of primary follicles-describing the size, shape, and arrangement of wool follicles have been measured in Peppin Merino sheep at 4-5 months (weaning), 15-16 months (two-tooth shearing) and at later ages ranging from 2 1/2 to 7 1/2 years. Estimates of their repeatability, heritability and phenotypic, genetic, and environmental correlations with 10 wool and body characteristics are reported. All four follicle characteristics were found to be highly inherited and sufficiently correlated with wool characteristics to be of interest to both the wool biologist and the sheep breeder. Fixed environmental effects influenced the expression of some follicle characteristics, while others, notably follicle curvature at any age, were unaffected, and therefore potentially more useful as practical selection aids. Groups of sheep selected for clean wool weight with control of (i) fibre diameter and wrinkle score, and (li) crimp frequency and wrinkle score, exhibited changes in the four follicle characteristics, which agreed with what the genetic correlation estimates would predict. The role of follicle characteristics in the biology of genetic control of wool growth is portrayed by fitting causal models invoking follicle characteristics as intermediates between the gene and the wool character. The analysis separates three independent genetic control systems, the identity of which corresponds closely to factors postulated in previous theoretical studies.

Lifetime changes in wool production of Merino sheep following differential feeding in fetal and early life

2006 ◽  
Vol 57 (8) ◽  
pp. 867 ◽  
Author(s):  
R. W. Kelly ◽  
J. C. Greeff ◽  
I. Macleod
Keyword(s):  
Detrimental Effect ◽  
Fibre Diameter ◽  
Feed Restriction ◽  
Gestation Length ◽  
Merino Sheep ◽  
Wool Production ◽  
Free Weight ◽  
Wool Follicle ◽  
Pregnant Ewe

In commercial Merino farming, a major determinant of profitability is quantity and quality of wool production. We tested the hypothesis that the level of feed restriction commonly encountered by autumn/early winter lambing Merino ewes in southern Australia was sufficient to have a detrimental effect on their progeny’s lifetime wool production. Two periods of feed restriction of the dams were tested, viz. from day 50 to 140 of gestation (Expt 1), and from day 50 of pregnancy to weaning at 12 weeks of age (Expt 2). In order to reduce the numbers of experimental animals required, identical twin lambs were produced by cloning embryos. There was a total of 35 and 22 pairs of clones in Expts 1 and 2 that were recorded to 6.4 and 4.4 years of age, respectively. In Expt 1 it was estimated (i.e. conceptus-free weight) that the submaintenance (Sub-M) ewes lost 18 kg in weight compared with 9 kg by the Control (C) ewes over the period of differential feeding. In Expt 2 the Sub-M ewes lost 10 kg during pregnancy and 10 kg during lactation, compared with a loss of 3 kg and a gain of 4 kg over the same period in the C ewes. Gestation length was 1.3 days shorter (P < 0.01) in the Sub-M than C ewes in Expt 1. Birthweights of the Sub-M lambs were 0.5 kg lighter than the C lambs in Expts 1 (P < 0.01) and 2 (P < 0.05). At 12 weeks of age, liveweights of the lambs in the Sub-M and C treatments were 24.2 and 25.9 kg in Expt 1 (P < 0.01) and 14.0 and 25.0 kg in Expt 2 (P < 0.001). Corresponding liveweights at 4 months of age were 30.9 and 32.5 kg (P < 0.01) and 19.9 and 29.7 kg (P < 0.001), the Sub-M animals producing less clean wool (0.1 and 0.4 kg, P < 0.01 and < 0.001, Expts 1 and 2, respectively), that was finer in Expt 2 (2.7 μm, P < 0.001) than their C counterparts. Throughout the rest of the study the Sub-M animals in Expt 2 (but not Expt 1) were on average 3.2 kg lighter (P ranging from < 0.05 to < 0.001) than C animals. In both experiments the ratio of secondary to primary wool-producing follicles was lower (1.1–2.6 units, P < 0.001) in the Sub-M than C animals. These differences led to (P < 0.05) lower significantly adult clean wool production of 0.17 kg (Expt 1) and 0.24 kg (Expt 2) per annum. There was no significant interaction between nutritional treatment and age of the animal for clean wool production. Within experiments there were no significant differences between nutritional treatments in any of the wool quality measurements. However, when fibre diameter data for both experiments were combined for 3.4 and 4.4 years of age, the Sub-M animals were significantly broader (0.3 μm, P < 0.01) when compared with the C animals. We conclude that Sub-M feeding of the pregnant ewe will permanently affect liveweight, the wool follicle population, and wool production and quality, in Merino sheep. Extension of the period of under feeding into lactation (Expt 2) appears to increase the amplitude of the differences in young animals, which is largely overcome by the time the animal reaches 2.4 years of age.

Effects of methylthiouracil treatment on the growth and moult of cashmere fibre in goats

1996 ◽  
Vol 62 (3) ◽  
pp. 513-520 ◽  
Author(s):  
S. M. Rhind ◽  
S. R. McMillen
Keyword(s):  
Fibre Diameter ◽  
Live Weight ◽  
Term Treatment ◽  
Hair Follicles ◽  
Long Term Treatment ◽  
Fibre Growth ◽  
The Mean ◽  
Secondary Fibre

AbstractThe effect of long-term treatment of goats with methylthiouracil on the timing, amount and quality of secondary fibre (cashmere) growth and timing of cashmere moult in goats was investigated. From early June, groups of 10 Icelandic × Scottish feral goats were dosed orally each day, for a 15-month period, with 5 mg methylthiouracil per kg live weight in 30 ml water (treated; T) or with water only (control; C). Treatment with methylthiouracil resulted in a significant reduction (P < 0·05) in the proportion of active secondary hair follicles present during March. This was associated with a delayed onset of moult of cashmere in T compared with C goats at both the head (11 March v. 23 February; s.e. 3·33 days; P< 0·05) and mid side (27 March v. 26 February; s.e. 3·58 days; P < 0·001). There was no effect on the time of onset (C, 19 July; T, 19 July; s.e. 5·84 days) or cessation of cashmere fibre growth (C, 9 December; T, 8 December; s.e. 1·69 days) or the mean growth rate (C, 0·473 mm/day; T, 0·451 mm/day; s.e. 0·025) and fibre diameter (C, 16·9 μm; T, 15·4 jim; s.e. 0·266). Wlien present in the fleece, the mean weight and proportion of cashmere was higher in C than in T goats (P < 0·05). It is concluded that methylthiouracil treatment altered secondary follicle activity and the time of onset of the moult of cashmere and that these changes may be a result of reduced triiodothyronine production from thyroxine and associated secondary changes in profiles of insulin and IGF-1.

Seasonal variation in fibre diameter and length in wool of grazing Merino sheep with low or high staple strength

1999 ◽  
Vol 39 (5) ◽  
pp. 507 ◽  
Author(s):  
A. C. Schlink ◽  
G. Mata ◽  
J. M. Lea ◽  
A. J. M. Ritchie
Keyword(s):  
Fibre Diameter ◽  
Fibre Length ◽  
Subterranean Clover ◽  
Experimental Period ◽  
Strength Group ◽  
Pooled Data ◽  
Length Growth ◽  
Fibre Growth ◽  
Staple Strength ◽  
Highly Correlated

The associations between fibre growth characteristics and wool staple strength were investigated in groups (n = 10) of Merino wethers with either low or high staple strength. Sheep grazed together on pastures based on subterranean clover and annual rye grass for about 13 months. The sheep were weighed and injected intradermally with [35 S]-cysteine at about 14-day intervals. Mid-side patches were harvested and dye bands placed in the wool at about 28-day intervals. Patch clean wool growth, pasture digestible dry matter/ha and pasture crude protein/ha had similar seasonal amplitudes of production (287, 286 and 267% of respective minimum). These were significantly higher than the seasonal amplitude in liveweight (24.5%). The seasonal amplitude in fibre diameter was significantly greater than that for rate of fibre elongation (71.4 and 41.4% respectively). This seasonality in fibre length and diameter resulted in statistically significant seasonal fluctuations in the ratio of fibre length growth to fibre diameter. Fortnightly variability in fibre diameter was not significantly related to variability in fibre length growth rate between sheep for individual time periods. However, for the pooled data over the experimental period a statistically significant relationship (R2 = 0.13, P<0.01) was improved with the addition of parameters for sampling time and staple strength group. Staple strengths for the low and high staple strength groups were 25.6 and 32.8 N/ktex respectively (P = 0.057). There were no significant differences between the staple strength groups in seasonal change in liveweight, wool production or fibre parameters measured in this study but the low staple strength group had longer fibres. Staple strength was most highly correlated with mid-side fibre diameter coefficient of variation (R2 = 0.50) followed by seasonal amplitude in liveweight.

scholarly journals Effects of Internally Administered N-[5-( 4-Aminophenoxy)Pentyl]Phthalimide on Wool Follicles and Skin of Sheep

1980 ◽  
Vol 33 (2) ◽  
pp. 183 ◽  
Author(s):  
RE Chapman ◽  
RDG Rigby
Keyword(s):  
Body Weight ◽  
Cell Division ◽  
Mitotic Activity ◽  
Sebaceous Gland ◽  
Skin Surface ◽  
Skin Thickness ◽  
Sebaceous Glands ◽  
Wool Follicle ◽  
Dark Staining ◽  
Dermal Papillae

When N-[5-(4-aminophenoxy)pentyl]phthalimide was administered to sheep in sufficient quantities to permit manual removal of the fleece (400 mg/kg body weight orally, or 75 mg/kg body weight intravenously during a period of 48 h), cell division ceased in the wool follicle bulbs within 1 day. Dark-staining bodies (autophagic vacuoles) developed concomitantly in the cytoplasm of the bulb cells. The nuclei of cells in the keratogenous zones of the fibres became pycnotic 2 days after dosing and subsequent keratinization of these portions of the fibres was impaired. All the follicles retrogressed prior to day 7 after dosing, and the root ends which formed on the fibres moved towards the skin surface, reaching the level of the sebaceous glands by day 7. At this time mitotic activity recommenced around the dermal papillae in about 50% of the follicles. A small number of tips of new fibres emerged from the skin surface of some of the depilated sheep by day 14. The root ends on the fibres in the fleeces harvested at days 7-15 were fragmented with various degrees of taper. By 21 days, most follicles were growing emergent fibres. Thickening of the epidermis, increase in sebaceous gland size and decrease in skin thickness occurred in some of the depilated sheep.

Transient treatment of pregnant Merino ewes with modulators of cortisol biosynthesis coinciding with primary wool follicle initiation alters lifetime wool growth

2013 ◽  
Vol 53 (10) ◽  
pp. 1101 ◽  
Author(s):  
M. L. McDowall ◽  
N. S. Watson-Haigh ◽  
N. M. Edwards ◽  
H. N. Kadarmideen ◽  
G. S. Nattrass ◽  
...  
Keyword(s):  
Transforming Growth Factor ◽  
Fibre Diameter ◽  
Fibre Length ◽  
Gene Families ◽  
Transforming Growth Factor Β ◽  
In Utero ◽  
Skin Development ◽  
Merino Sheep ◽  
Wool Follicle ◽  
Critical Phases

The economically important characteristics of the adult fleece of Merino sheep, such as increases in clean fleece weight, fibre length, fibre diameter and crimp characteristics are determined during critical phases of fetal development of the skin and its appendages. Genetics plays a major role in the development of traits, but the maternal uterine environment could also influence development. Treatment of pregnant ewes with cortisol and its analogues has previously been shown to produce changes in wool follicle morphology. The aim of this study was to determine the effect of transient manipulation of maternal cortisol status during critical phases of wool follicle initiation and development in utero. From Days 55–65 post-conception, singleton-bearing Merino ewes were treated with metyrapone (cortisol inhibitor) or betamethasone (cortisol analogue). Lambs exposed to metyrapone in utero were born with hairier birthcoats than the control or betamethasone treatment groups (P < 0.05), displayed a 10% increase in staple length and a reduction in crimp frequency for the first three shearings (P < 0.05). Co-expression network analysis of microarray data revealed up-regulation of members of the transforming growth factor-β and chemokine receptor superfamilies, gene families known to influence hair and skin development. These experiments demonstrate that presumptive transient manipulation of maternal cortisol status coinciding with the initiation of fetal wool follicle development results in long-term alteration in fleece characteristics, namely fibre length and fibre crimp frequency. These results indicate it is possible to alter the lifetime wool production of Merino sheep with therapeutics targeted to gene expression during key windows of development in utero.

Mimosine, administered orally, and two related compounds of chemical defleecing agents for sheep

1978 ◽  
Vol 29 (5) ◽  
pp. 1065 ◽  
Author(s):  
PJ Reis ◽  
DA Tunks ◽  
AM Downes
Keyword(s):  
Oral Dose ◽  
Single Oral Dose ◽  
Intravenous Infusion ◽  
Fibre Diameter ◽  
Daily Ration ◽  
Before And After ◽  
Fibre Growth ◽  
High Concentrations ◽  
Oral Doses ◽  
Related Compounds

Oral doses of mimosine (ranging from 400 to 800 mg/kg body weight) were given to 71 sheep, either as two successive daily doses (10 sheep) or as a single dose (61 sheep). The effectiveness of these treatments for defleecing was assessed and in some sheep measurements were made of the concentration of mimosine in plasma after dosing, and of the rate of wool growth before and after dosing. In addition, the effectiveness as defleecing agents of two related compounds (an analogue of mimosine, 'isomimosine', and a metabolite, 3,4-dihydroxypyridine (DHP)) was assessed. Two successive daily doses of mimosine (300 mg/kg/day) allowed all sheep to be defleeced. With sheep consuming a daily ration of 600 g, a single oral dose of mimosine (400 mg/kg) was sufficient to allow defleecing of most sheep; when the daily ration was 1200 g, a dose of 600 mg/kg was required to allow defleecing of most sheep. The effectiveness of oral doses for defleecing could be explained by the absorption of mimosine over a period in excess of 24 hr. Concentrations of mimosine in plasma were usually above 100 µmoles/l 24 hr after an effective dose. Failure to achieve complete cessation of fibre growth occurred occasionally, irrespective of dose level, and two sheep died after dosing. Fasting prior to dosing appeared to obviate the effects of previous high nutrition, but increased the risk of toxic effects. Fasting resulted in exceptionally high concentrations of mimosine in plasma (200–300 µmoles/l) 1 and 2 days after dosing. Both fibre diameter and mass of wool grown were increased in the early regrowth after dosing with mimosine. 'Isomimosine' had a similar potency to mimosine for stopping fibre growth in sheep, whether given as an intravenous infusion or as a single oral dose. DHP, given as an intravenous infusion, was ineffective as a defleecing agent.

Is there a specific weakness in staple strength around the break of season?

1999 ◽  
Vol 39 (4) ◽  
pp. 401 ◽  
Author(s):  
N. R. Adams ◽  
D. G. Masters ◽  
A. C. Schlink ◽  
G. Mata ◽  
T. O'Dea
Keyword(s):  
Fibre Diameter ◽  
Rainfall Event ◽  
Rain Event ◽  
Rumen Microorganisms ◽  
Ruminal Microorganisms ◽  
Feed Deprivation ◽  
Gradual Group ◽  
Wool Follicle ◽  
Staple Strength ◽  
Group 2

In a Mediterranean climate the weak point of the staple normally occurs at the break of season in autumn, but it is not clear whether the staple simply breaks at the minimum fibre diameter or whether there is a specific weakness at this time. Three hypotheses were tested to determine if specific environmental effects on staple strength could be detected under field conditions. First, environmental stresses associated with rainfall and low temperature, resulting in a sudden disruption of warm summer–autumn conditions and lack of feed, may cause follicle shutdown. Second, the sudden decline in feed available following the rain event and the response of sheep to chase the green pick rather than eat the available dry feed may reduce the flow of nutrients to wool. Third, the slow adaptation by rumen microorganisms to changes in the diet from dry to green pasture may result in a further reduction of nutrients available to the wool follicle. We compared a group of sheep managed to minimise nutrient intake fluctuations at the break of season with a group grazing under normal farm practice and tested the hypothesis that a specific lowering of staple strength is associated with the break of season. On 2 April (3 days after the first rains of the season), 120, 18-month-old Merino wethers were allocated to 2 groups, paddock and yard. The paddock group comprised sheep following normal farm practice. The yard group was confined to yards and fed to maintain liveweight, to determine whether the break in the staple was associated with the rainfall event or with the subsequent changes in feed intake. These animals were left off feed for 4 days beginning 24 April. Within each group, 2 separate treatments were imposed. The paddock group was split, and half were moved into covered pens inside a shearing shed on 15 May, a few days before a second major rainfall event, to examine directly stresses associated with rainfall. The sheep from the yard group were kept as a single mob until 3 June, when they were split into 2 groups, sudden and gradual, in relation to their release onto green pasture, to examine the effect of adaptation time to green feed on the flow of nutrients to wool and staple strength. The sudden group was released onto green pasture, while the gradual group was given access to the pasture for increasing periods over the next week. The point of break was delayed by moving sheep into yards after the initial rainfall, suggesting that the rain event per se was not the direct cause of the break in the staple in this experiment. Furthermore, protecting the paddock sheep against the second major rainfall event by shedding half of them did not affect staple strength. The point of break in the staple in the yard group occurred after an accidental 4-day feed deprivation period. This indicates that even short periods of liveweight loss from feed deprivation due to poor or inattentive management when sheep are in low nutritional condition at this time of the year may precipitate the point of break. The rate of release onto green feed after yarding did not significantly affect staple strength and we conclude this was not an important factor. We conclude that neither stress associated with rainfall nor adaptation of ruminal microorganisms to the change in feed weakened the wool.

scholarly journals Evidence of a unique developmental mechanism specifying both wool follicle density and fibre size in sheep selected for single skin and fleece characters

1989 ◽  
Vol 53 (1) ◽  
pp. 57-62 ◽  
Author(s):  
G. P. M. Moore ◽  
N. Jackson ◽  
J. Lax
Keyword(s):  
Fibre Diameter ◽  
Statistical Association ◽  
Merino Sheep ◽  
Developmental Mechanism ◽  
Negative Linear Correlation ◽  
Foetal Life ◽  
Wool Follicle ◽  
Fleece Weight ◽  
The Relationship ◽  
Staple Length

SummarySkin and fleece traits have been characterized in four lines of Merino sheep selected for high- and low-fibre diameter (D±) and staple length (L±) from a medium-woolled flock. Over a period of 20 years, each line responded in the desired direction, producing fleeces composed of thick or thin fibres and long or short wool staples. However, variations in the amounts of wool grown that might be expected from these procedures were compensated by changes in unselected characters. Thus a predicted difference in fleece weights between high and low staple length lines was reduced by an increase in fibre crimp frequency in L− sheep. Similarly, changes induced in fibre diameter in the D lines resulted in small effects on fleece weight in comparison to the large (and inverse) effects on follicle numbers. Towards the end of the selection regime, mean follicle density in D− sheep was twice that of D+ sheep. This intriguing response within the follicle population was examined further: an analysis of the relationship between follicle density and fibre diameter amongst the four lines revealed a highly significant, negative linear correlation. The implication of this statistical association is that the numbers of follicles initiated in skin during foetal life had a direct bearing on the sizes of wool fibres eventually produced. It was concluded that both features must be under the control of a single developmental mechanism. Since the expression of each of the characters is separated in time, the mechanism must be activated during the earlier event, i.e. at or before the phase of follicle initiation.

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