Tunicamycin reduces wool growth by slowing the mitotic activity of wool follicles

1997 ◽  
Vol 48 (3) ◽  
pp. 331 ◽  
Author(s):  
S. C. Davies ◽  
I. H. Williams ◽  
C. L. White ◽  
J. E. Hocking Edwards
Keyword(s):  
Direct Effect ◽  
Vascular System ◽  
Fibre Diameter ◽  
Fibre Length ◽  
Annual Ryegrass ◽  
Wool Growth ◽  
Wool Follicle ◽  
Low Levels ◽  
A Minor ◽  
Annual Ryegrass Toxicity

Reductions in wool growth have previously been observed in ewes exposed to low levels of corynetoxins, the causal agents of annual ryegrass toxicity. In this experiment, tunicamycin, a commercially available and closely related toxin, was infused into an isolated area of skin on the abdominal flank. Eleven sheep were continuously infused for 5 days with saline on one side and a total dose of either 35 or 350 µg tunicamycin/kg affected skin on the other side. Both fibre length (P < 0·05) and fibre diameter (P < 0·01) were reduced by tunicamycin treatment. Cell division in the wool follicle bulb was also reduced by tunicamycin (P < 0·005), indicating that the toxin is able to have a direct effect on the follicles and their ability to produce wool. The permeability of the vascular system increased in the skin tissue treated with tunicamycin, but only at the highest toxin dose (P < 0·05); therefore, poor nutrient supply to the follicle may be a minor contributor to reduced wool growth. The direct effect of tunicamycin on the wool follicle explains why wool growth is reduced by low levels of corynetoxins independently of, and prior to, effects on the whole animal.

The influence of selection and plane of nutrition on the components of fleece weight in Merino sheep

1958 ◽  
Vol 9 (6) ◽  
pp. 802 ◽  
Author(s):  
RB Dun
Keyword(s):  
Fibre Diameter ◽  
Fibre Length ◽  
Small Contribution ◽  
Cross Sectional ◽  
Single Character ◽  
The Mean ◽  
Low Levels ◽  
The Difference ◽  
Fleece Weight ◽  
High Level

The components of clean fleece weight were examined in five experimental flocks of medium-wool Peppin Merinos. Four single-character selection groups – clean fleece weight plus, clean fleece weight minus, crimps per inch plus, and crimps per inch minus – were examined by measuring fleece production in 18-month-old ewe progeny. Measurements were also made on progeny from the "nucleus" flock, which was selected for clean fleece weight with subsidiary selection for crimps per inch and against fold score. Data were collected in 1952 and 1954. The 1954 figures were obtained from a nutrition experiment in which sheep mere grown from weaning to 18 months on a high and on a low plane of nutrition. The mean measurements of the components of clean fleece weight (W) were compared between flocks using the "percentage deviation" technique. Four comparisons were made: (1) Nucleus/Fleece minus; (2) Fleece plus/Fleece minus; (3) Crimps minus/Crimps plus; (4) high nutritional plane/low nutritional plane. In comparisons (1) , (2), and (3), difference in weight of wool per unit area of skin (w) accounted for nearly all the difference in W. Body weight (S) made a small contribution while difference in fold score (R) was negligible. Fibre density (N) accounted for +86 per cent., and fibre cross-sectional area (A) for –28 per cent., of the difference in W in comparison (1). In comparison (2) the figures were N +47 per cent., A +21 per cent., while the figures for comparison (3) were N –26 per cent., A +121 per cent. The increase in fleece weight was invariably accompanied by a decrease in crimps per inch. In all three comparisons primary density (P) was the major cause of change in N. Fibre length (L) made a uniform contribution of approximately +15 per cent. in the three comparisons.The relative importance of the components of fleece weight was similar at both high and low levels of nutrition.The effect of a high level of nutrition was to produce large increases in A, L, and S. The increase in S was compensated by an equal decrease in P. The increase in fibre diameter was not associated with any change in crimps per inch.

Sublethal exposure to corynetoxins affects production of grazing sheep

1996 ◽  
Vol 36 (6) ◽  
pp. 649 ◽  
Author(s):  
SC Davies ◽  
CL White ◽  
IH Williams ◽  
JG Allen ◽  
KP Croker
Keyword(s):  
Birth Weight ◽  
Liver Damage ◽  
Fibre Diameter ◽  
Clinical Signs ◽  
Wool Fibre ◽  
Embryo Survival ◽  
Weaning Weight ◽  
Wool Growth ◽  
Low Levels ◽  
Production Losses

This paper reports the production losses resulting from treating sheep with sublethal doses of corynetoxins, the causal agent of annual ryegrass toxicity. Merino ewes were given 3 levels of corynetoxins twice weekly for 11 weeks from 26 days before the start of joining to day 51 of pregnancy, giving a cumulative dose of 0 , 0.4 or 0.8 mg/kg liveweight. The effect on ovulation, pregnancy, lamb birth weight, lamb survival and weaning weight were measured along with the liveweight and wool growth of the ewes. Corynetoxin treatment depressed (P<0.005) the activity of uridine diphospho-N-acetylglucosamine: dolichol-phosphate N-acetylglucosamine-1-phosphate transferase and liver damage was detected in ewes on the high toxin treatment (P<0.05). Ewe liveweight was unaffected by treatment but wool growth and wool fibre diameter were reduced by 10 and 7%, respectively (P<0.05). Corynetoxin treatment appeared to increase ovulation (P<0.05) and, as there was no effect on conception and embryo survival, this resulted in a 30-35% increase in the number of lambs weaned. Lamb birth weight and survival were not affected by treatment but weaning weight of the low toxin group was depressed (P<0.05). While reproduction was not adversely affected, the sheep in this trial were exposed to extremely low levels of corynetoxins which did not accumulate to levels capable of causing detectable liver damage until 23 days after joining. Even at these levels of intake, well below those required to show clinical signs (3-5 mg/kg liveweight), wool growth was reduced, suggesting that sheep grazed on mildly toxic pasture experience wool production losses in the absence of signs of the clinical disease.

The use of thyroxine to reduce average fibre diameter in fleece wool when feed intake is increased

2001 ◽  
Vol 41 (5) ◽  
pp. 611 ◽  
Author(s):  
G. J. Lee ◽  
K. J. Thornberry ◽  
A. J. Williams
Keyword(s):  
Saline Solution ◽  
Daily Intake ◽  
Fibre Diameter ◽  
Fibre Length ◽  
Treatment Groups ◽  
Average Fibre Diameter ◽  
Wool Growth ◽  
Average Fibre ◽  
Ad Libitum ◽  
The Difference

An experiment was conducted to determine whether thyroxine injections would control the increases in fibre diameter when the wool growth of Merino wethers is stimulated by an increased supply of feed. Fifty-seven sheep were allocated to 1 of 5 levels of daily intake, ranging from 0.75 maintenance to ad libitum, and injected every third day with 3 mg of L-thyroxine or a saline solution (control). Sheep treated with thyroxine had elevated plasma tri-iodothyronine (T3) levels, which were highest in sheep fed the least (P<0.01). Ad libitum intakes of sheep treated with thyroxine tended to be higher than that of control sheep, particularly in the fifth to seventh weeks of the experiment, and liveweight gain over the initial 4 weeks was significantly (P<0.001) less. Wool growth was increased by thyroxine treatment, although the difference was small in the second half of the experiment at the highest intake levels. Fibre diameter of sheep treated with thyroxine was greater at low intakes, although the difference diminished as intake increased. Fibre length in the second half of the experiment was positively related to intake, but there were no effects of thyroxine. Although the relationships of fibre diameter and length with wool growth did not differ between the treatment groups, length accounted for more of the variation in wool growth in the second half of the experiment in treated wethers than in control wethers (0.376 v. 0.182 of the variation, respectively). Thyroxine did not appreciably reduce the extent of the increase in fibre diameter associated with an increase in the availability and intake of feed.

scholarly journals A comparative study of herbage intake, ingestive behaviour and diet selection, and effects of condensed tannins upon body and wool growth in lambs grazing Yorkshire fog (Holcus lanatus) and annual ryegrass (Lolium multiflorum) dominant swards

2001 ◽  
Vol 136 (2) ◽  
pp. 241-251 ◽  
Author(s):  
F. MONTOSSI ◽  
J. HODGSON ◽  
S. T. MORRIS ◽  
D. F. RISSO ◽  
I. L. GORDON
Keyword(s):  
Condensed Tannins ◽  
Lolium Multiflorum ◽  
Fibre Diameter ◽  
Diet Selection ◽  
Carcass Weight ◽  
Annual Ryegrass ◽  
Holcus Lanatus ◽  
Wool Growth ◽  
Herbage Intake ◽  
Grazing Behaviour

An experiment was carried out from August to early November 1994 to examine differences in diet selection, herbage intake, grazing behaviour and animal performance between weaned lambs rotationally grazing swards of annual ryegrass (Lolium multiflorum)/white clover (Trifolium repens) and Yorkshire fog (Holcus lanatus)/T. repens with or without Lotus corniculatus. There were four replicate groups of six lambs per treatment. The effects of condensed tannins (CT) on lamb production were assessed by twice-daily oral administration of 10g polyethylene glycol (PEG; molecular weight 4000) to half the lambs on each sward. The Lotus content of all swards was very low, and results are presented here for main sward comparisons meaned over lotus treatments. Overall mean estimates of pre-grazing herbage mass and sward surface height for the annual ryegrass and Yorkshire fog swards respectively, were 5820 v. 4360±190 kgDM/ha (P<0·001) and 29 v. 21±0·6cm (P<0·001). The coefficient of organic matter digestibility (OMD) of the diet selected and herbage intake were higher on Yorkshire fog than on annual ryegrass (0·78 v. 0·74 ± 0·080g/kg; P<0·05, and 1070 v. 860±57g OM per lamb per day, P<0·05 respectively), reflecting the higher content in the diet of grass green leaf (980 v. 930g/kg±14g/kg, P<0·05) and the lower content of dead material (80 v. 110±15g/kg, P<0·08). Lambs grazing on Yorkshire fog swards had higher clean wool growth rate (1470 v. 1280±30mg/cm per day, P<0·01) and greater fibre diameter (31 v. 29±0·2μ, P<0·001), greater liveweight gain (152 v. 108±5·5g/day, P<0·001), final weight (42 v. 38±0·5kg, P<0·001), carcass weight gain (89 v. 69±2·5g/day, P<0·001), carcass weight (19 v. 17±0·3kg, P<0·001) and soft tissue thickness (GR value 11 v. 8±0·5mm, P<0·01), and lower faecal egg counts (FEC; square root transferred values 9·2 v. 11·0±0·4 eggs/g fresh faeces, P<0·01) than lambs grazing annual ryegrass swards. Similar dietary concentrations of condensed tannins (CT) between Yorkshire fog and annual ryegrass swards (4·2 v. 3·7 DM±0·2g/kg, P<0·08) increased clean wool growth (1440 v. 1310±32 mg/cm per day, P<0·05), fibre diameter (30·7 v. 29·5±0·21μ, P<0·01) and liveweight gain (141 v. 120±4·3g per lamb per day, P<0·01), although differences in carcass weight (17·9 v. 18·2±0·3kg) and FEC transformed values (9·6 v. 11·0±0·6 eggs/g fresh faeces) were not significant. The effects of CT on animal performance were greater in Yorkshire fog swards. CT had no significant effects on diet selection, herbage intake and grazing behaviour patterns.

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.

Follicular determinants of the length and diameter of wool fibres. 2. Comparison of sheep differing in thyroid hormone status

1994 ◽  
Vol 45 (6) ◽  
pp. 1149 ◽  
Author(s):  
PI Hynd
Keyword(s):  
Thyroid Hormone ◽  
Fibre Diameter ◽  
Fibre Length ◽  
Fibre Volume ◽  
Concomitant Change ◽  
Wool Growth ◽  
Root Sheath ◽  
Inner Root Sheath ◽  
Hormone Status ◽  
Dividing Cells

The thyroid hormone status of Corriedale sheep was manipulated in order to produce a change in the rate of fibre elongation (L) with no concomitant change in the diameter (D) of the fibres, to allow the follicular factors responsible for fibre L to be determined. Thyroidectomy resulted in a 60% decrease in wool growth per unit area of skin and a 40% decrease in the rate of fibre volume output, due largely to a decline in fibre L from 412 ,8m/day to 277 8m/day ( P < 0.0001) while fibre D was unchanged (23.9 8m v. 21.9 pm, P > 0-05). Elevation of plasma thyroxine levels to 250% of Control values had no significant effect on fibre L and D, but patch wool growth was increased ( P < 0.05). A high proportion (22.9%) of the follicles in the hypothyroid sheep was inactive in comparison to the low levels of inactivity in the control (1.2%) and hyperthyroid animals (0.1%). The rate of division of follicle bulb cells was depressed by hypothyroidism and increased by hyperthyroidism (P < 0.0001), but there was no effect of thyroid status on the size of the cortical cells released from the wool fibres. Hypothyroid sheep had slightly smaller follicle bulbs and dermal papillae than the control and hyperthyroid animals. The proportion of dividing cells entering the fibre cortex (estimated from cortical cell volume, rate of fibre volume growth and rate of cell division) was depressed by thyroidectomy suggesting that relatively more dividing cells entered the inner root sheath in the follicles of hypothyroid sheep. This is supported by the lower production ratio (ratio of area of fibre to area of fibre-plus-inner root sheath) of the hypothyroid sheep. It is concluded that the rate of fibre elongation is depressed in hypothyroid sheep as a result of both a reduction in the rate of division of cells in the follicle bulb and fewer of these dividing cells entering the fibre cortex. This mechanism allows rapid changes in the rate of fibre elongation to occur with little change in the size of the follicle bulb, and may account for a number of scenarios in which fibre length changes rapidly with no concomitant change in fibre diameter. Fibre diameter, on the other hand, appears to be closely related to the dimensions of the follicle bulb, and by association, to the rate of bulb cell production. Selection of sheep with small follicle bulbs and at the same time, high production ratios, may be means of increasing fibre length whilst maintaining low fibre diameter.

Effect of light and temperature on wool growth

1978 ◽  
Vol 90 (2) ◽  
pp. 329-334 ◽  
Author(s):  
A. A. Elsherbiny ◽  
H. A. Eloksh ◽  
A. S. Elsheikh ◽  
M. H. Khalil
Keyword(s):  
Seasonal Changes ◽  
Seasonal Pattern ◽  
Fibre Diameter ◽  
Fibre Length ◽  
Atmospheric Temperature ◽  
Wool Fibre ◽  
Wool Growth ◽  
Dim Light ◽  
Normal Light ◽  
Winter Time

SummaryWool samples were collected from 39 rams representing five breed groups of sheep: Merino (M), Ossimi (0), and the crosses between them, viz. ¾ Ossimi–¾ Merino (¾ O), ½ Ossimi–½ Merino (½ O) and ½ Ossimi–¾ Merino (¼ O) maintained at Sakha Experiment Station, Kafrelsheikh, Egypt, with the objectives of detecting the effect of the seasonal changes in normal light rhythm and temperature on wool fibre length and diameter. Animals were divided into two light treatments groups, the first consisting of four animals from each breed kept under continuous dim light conditions throughout the year and the second of three animals from Ossimi and four from each breed group kept inside an open pen free to sunlight and shade zones under daylight rhythm throughout the year. It was found that fibre length as well as fibre diameter in normal light exceeded that in dim light except in winter time. Breed groups showed different responses to the absence of light especially the Ossimi and the ¾ O whose fibre lengths were most affected. The breed groups had larger fibre diameters in normal light than in dim light except Merino and ¼ O. Seasonal changes in temperature had a highly significant effect on fibre length but not on fibre diameter. Higher temperature coincided with lower increases in fibre length. Season to season variation in wool growth seemed to suggest that the number of light hours per day and atmospheric temperature counteracted each other resulting in a non-significant seasonal pattern.

Cell proliferation in the wool follicles of fleeceweight selected and control Romney rams

1993 ◽  
Vol 44 (2) ◽  
pp. 239 ◽  
Author(s):  
KE Kelly ◽  
PM Haris ◽  
MJ Birtles ◽  
DW Dellow ◽  
AJ Hall
Keyword(s):  
Cell Proliferation ◽  
Fibre Diameter ◽  
Fibre Length ◽  
Cell Movement ◽  
The Other ◽  
Three Dimensions ◽  
Circumflex Artery ◽  
Low Levels ◽  
And Control ◽  
Infusion Period

Two year old Romney rams from the Massey University fleeceweight-selected (FW) and control (C) lines, five from each line, were given arterial catheters into a branch of the deep circumflex artery on each side of the sheep, to permit local infusion into patches of skin on each lateral abdominal flank. One side of each sheep was infused with saline to give a direct FW v. C comparison, while the other side was infused with low levels of either growth hormone, thyroxine, prolactin or insulin for 4 days. At the end of the infusion period, biopsy samples were taken from each flank for measurement of follicle activity, particularly bulb cell proliferation using intracutaneous injections of 5-bromo-2'-deoxyuridine (BrDU). After a period of recovery, the saline and treated sides were reversed and another series of infusions were performed and biopsies undertaken. Wool from the FW sheep had greater fibre length growth rate and fibre diameter than the C wool (P < 0.05). This was associated with larger follicle bulbs (P < 0.05) and greater numbers of BrDU labelled cells (P < 0.05) in the bulbs of the FW skin. In a restricted number of samples from two sheep, where BrDU was successfully given as repeated intracutaneous injections into the same site (one at 72 h and one at 6 h prior to biopsy), 55-60% of the numbers of BrDU cells in a section of bulb appeared in a section of the shaft of the same follicle. When converted to three dimensions, the efficiency of labelled bulb cell movement into the shaft was 30-40%. Hormonal infusions showed few significant effects with the restricted numbers of animals in each treatment. Thyroxine reduced the size of follicle bulbs (P <0.05) and the numbers of labelled bulb cells in skin from the infused area.

Effects of shearing time and time of lambing on wool growth and processing characteristics

1984 ◽  
Vol 24 (126) ◽  
pp. 337 ◽  
Author(s):  
GW Arnold ◽  
AJ Charlick ◽  
JR Eley
Keyword(s):  
Growth Rate ◽  
Seasonal Pattern ◽  
Fibre Diameter ◽  
Fibre Length ◽  
Lower Percentage ◽  
Dominant Factor ◽  
Lower Yield ◽  
Merino Sheep ◽  
Wool Growth ◽  
Fleece Weight

Wool growth rate, seasonal pattern of fibre diameter, clean fleece weight, quality and the processing characteristics of wool were measured on medium-wool Merino sheep shorn in March (autumn) or October (spring) coupled with March or June lambing. These four management systems were compared under two nutritional regimes in the medium rainfall area of Western Australia. The sheep grazed annual pastures only, or had lupin grain and stubble during summer in addition to the pasture. The study ran for two shearing periods. Time of shearing was the dominant factor. Sheep shorn in March produced 14% more clean wool and fewer tender fleeces than sheep shorn in October. The autumn wool had a lower yield, higher fibre diameter and when processed had a higher card loss, lower percentage noil and lower top and noil yield. However, mean fibre length in the top was substantially higher and the variation in fibre length lower. Vegetable matter was higher in autumn shorn wools. There were some interacting effects of lambing time and type of feed regime. Sheep fed lupins had lower yielding wool but this effect was more pronounced in June lambings and was reflected in differences in top and noil yield. From measurements of wool growth rate, it was found that the extra wool was produced in autumn after shearing, due possibly to stimulated appetite that cannot occur after spring shearing because the sheep are too fat.

THE INFLUENCE OF NUTRITIONAL AND CLIMATIC FACTORS ON WOOL GROWTH AND QUALITY: II. LABORATORY METHODS USED IN THE MEASUREMENT OF WOOL CHARACTERS

1938 ◽  
Vol 16d (6) ◽  
pp. 166-173
Author(s):  
P. Larose ◽  
A. S. Tweedie
Keyword(s):  
Climatic Factors ◽  
Fibre Diameter ◽  
Fibre Length ◽  
National Research Council ◽  
Laboratory Methods ◽  
University Of Alberta ◽  
Wool Growth ◽  
The University ◽  
Wool Wax

The methods described were employed in the laboratories of the National Research Council for the examination of wool samples sent from the University of Alberta. The samples (as mentioned in Part I) were from sheep used to investigate the effect of various environmental factors on wool growth and quality.The determination of crimp, staple length, fibre length, tensile strength, elongation, fibre diameter, moisture content, wool wax, suint, dirt, and yield of clean wool is described. The methods for the measurement of fibre diameter and for the determination of wool wax, suint, dirt, and clean wool involved new technique and some novel features; they are, therefore, described more fully than the others.

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