Wool Staple Strength Research Articles

The effect of annual shearing time on wool production by a spring-lambing Merino flock in south-eastern Australia

Time of shearing affects many aspects of wool production and sheep health but no study has examined these factors concurrently in a spring-lambing, self-replacing Merino flock in southern Australia. A 5-year field experiment compared wool production in spring-lambing Merino ewes and their progeny shorn at different times and managed under commercial conditions in south-eastern Australia. Groups of 200 adult ewes were shorn in December, March or May, and their progeny were shorn in December or October, March or June, or May or July, respectively. There was no consistent association between time of shearing and the staple strength of wool (P = 0.73). December-shorn ewes produced significantly lighter and finer fleeces (average 19.1 μm, 3.0 kg clean weight) than did March-shorn ewes (19.4 μm, 3.1 kg). Fleeces from ewes shorn in May were of similar weight to those from March-shorn ewes (3.1 kg), but they were of significantly broader diameter (19.7 μm). In young sheep, desirable changes in some wool characteristics for each shearing group were offset by undesirable changes in others. On the basis of median historical (1991–2006) wool prices, shearing ewes in March and their progeny first in June produced the greatest total value of wool over a sheep’s lifetime ($161/head). The wool values per head for other shearing times were as follows: March (weaners)–March (ewes): $158; October–December: $157; December–December: $153; July–May: $151; and May–May: $148. Thus, December and March shearing were appropriate alternatives for maximising wool value produced from a self-replacing Merino flock in south-eastern Australia, whereas May was a less preferable shearing time because it always produced wool of lesser value.

Differences in survival and neonatal metabolism in lambs from flocks selected for or against staple strength

In the field, we found that lamb mortality was lower (P < 0.01) in a flock selected for wool staple strength (SS+) than in a flock selected against staple strength (SS–), or a random-bred control flock (R); mortality rates calculated from 4200 records were 17.0, 22.8, and 24.1%, respectively. The proportion of twins was similar in all flocks, but birth weights differed (P < 0.01), being 4.40, 4.25, and 4.14 kg, respectively. Biochemical profiles were measured in lambs from 20 ewes from each flock around the time of birth in an animal-house study, to define potential causes of the genetic difference in survival. In the intensive study, birth weight was similar for all groups; however, gestation length was slightly shorter in the SS+ lambs (P < 0.05 for SS+ v. R). All lambs had low plasma concentrations of the essential amino acids and glucose at birth, compared with after suckling. Plasma concentrations of glucose, non-esterified fatty acids (NEFA), and blood urea nitrogen (BUN) at birth differed between lambs from the flocks with the greatest difference in mortality (i.e. SS+ v. R); that is, SS+ lambs had higher concentrations of glucose (1.84 v. 1.23 mm; P < 0.01) and NEFA (1.52 v. 1.08 mm; P < 0.05), and lower concentrations of BUN (7.7 v. 9.7 mm; P < 0.01) at birth, and for the next 9 h. The semimembranosus and semitendinosus muscle of the SS+ lambs also had lower concentrations of ATP (7.4 v. 5.0 μmol/g, respectively) compared with lambs from the other flocks, immediately post-partum. Muscle phosphocreatinine was also slightly lower in the SS+ lambs. No differences between the genotypes were observed in reserves of glycogen, carcass fat, brown adipose tissue, or in neonatal thyroid hormones. In summary, sheep selected for high wool staple strength had lower lamb mortality than the other 2 flocks. This was accompanied by metabolic differences at birth that can be associated with greater metabolic maturity, rather than greater energy reserves.

Summer-autumn rainfall effects on wool staple strength and position of break. II. Rainfall simulations, with or without wind, on sheep on days of different ambient temperatures

Previous small-scale field work failed to show any influence on staple strength from various different rainfall simulations, other than those where sheep grazed germinating green pasture following rainfall. The present study was designed to incorporate variables such as ambient temperature and the influence of wind into rainfall simulations onto Merino sheep. Different treatments did not show any effect on staple strength despite sheep being subjected to simulated rainfall events on warm and cool days, with or without additional wind. This lack of effect on wool quality was despite significant treatment effects on sheep rectal and skin temperatures.

Metabolic hormones and tissue concentrations of mRNA for IGF-I in lines of sheep that differ in their protein synthesis response to feed intake.

The rate of protein synthesis in the skin and muscle of sheep that have been genetically selected for high wool staple strength (SS) is less dependent on the level of dietary intake than that of low SS sheep. This study examined potential hormonal mediators of this difference in responsiveness. Sheep from SS+ and SS- genotypes were fed at 0.4, 1.1 or 1.8 times maintenance. Circulating concentrations of metabolic hormones and tissue concentrations of the mRNA for IGF-I were measured and compared with rates of protein synthesis measured previously. Plasma concentrations of GH, insulin, cortisol, thyroxine and IGF-I responded similarly to dietary intake in both genotypes, but SS+ sheep had higher plasma concentrations of IGF-I at all levels of nutrition (P<0.05). There were no interactions between diet and genotype. The concentration of mRNA for IGF-I was higher in the liver of SS+ sheep (P<0.05), and tended to increase (P=0.06) with nutrient intake, but there were no significant effects of genotype or nutrition in skin, muscle or gut. Concentrations of mRNA for IGF-I were not related to the rate of protein synthesis in any tissue examined. It was concluded that IGF-I did not drive the rate of protein synthesis directly, but it may mediate the responsiveness of protein synthesis rate, or protein degradation rate, to nutrient supply.

The timing of nutritional restriction during reproduction influences staple strength

The staple strength of wool from Merino ewes (liveweight 41 kg; condition score 1.5) was assessed in response to a short-term nutritional restriction at different stages of pregnancy and lactation. Single- and twin-bearing ewes were fed to maintain maternal liveweight (control) or restricted to lose 2 kg in maternal liveweight between Days 85 and 98, 113 and 126, or 141 and 154 of pregnancy, or Days 169 and 182 in early lactation. Unmated control ewes were fed to maintenance, and a group of unmated ewes was restricted between the equivalent of Days 141 and 154 of pregnancy. All groups were maintained in group-feeding pens from Day 8 of pregnancy to 4 weeks after weaning of lambs. The ewes were fed lucerne hay. Control ewes fed to maintain liveweight produced sound wool (unmated 52.7, or single-rearing 46.0, and twin-rearing 43.0 N/ktex). Nutritional restriction only reduced the staple strength of wool produced by unmated ewes by 2.2 N/ktex (P &gt; 0.05), but reduced that of reproducing ewes by 0–26.8 N/ktex. The decline in staple strength of reproducing ewes increased as the time of restriction during pregnancy advanced. Restriction during lactation did not significantly (P &gt; 0.05) influence staple strength. The effect of restriction appeared to be mediated via changes in diameter along fibres. The results indicate that there is variation in the sensitivity of staple strength to short-term nutritional restriction, with both pregnancy status and the stage of pregnancy at which the restriction is imposed influencing the impact on staple strength.

Summer-autumn rainfall effects on wool staple strength and position of break. I. Small-scale field simulations of rainfall onto sheep grazing dry pasture in February and April

Despite a great deal of anecdotal evidence linking summer–autumn rainfall events to the position of break (POB) of wool from sheep grazed in a Mediterranean environment, there are no published experiments directly investigating this relationship. This trial examined the effects on staple strength (SS) and POB of simulated rainfall onto sheep grazing dry pasture residues during February and April. The simulated rainfall events had few significant effects on the wool quality parameters of the sheep in this trial. The natural rainfall associated with the ‘break’ of the season had a much greater influence on SS and POB. A significant effect on POB was noted in the wool from sheep that had been exposed to simulated rainfall and then grazed germinating green pasture for approximately 15–20 days. The effect on POB could be an effect of the green feed alone or a combination of the green feed and simulated rainfall. When grazing wetted dry pasture, sheep appeared to alter their grazing behaviour and showed more apparent ‘selectivity’. Overall grazing times did not appear to be affected and sheep in several treatment groups were observed to graze whilst their rainfall simulations were in progress. Wetting of dry pasture also appeared to increase the ‘toughness’ of the plant material available.

Wool and liveweight responses to nutrition by Merino sheep genetically selected for high or low staple strength

The biological mechanisms underlying differences in wool staple strength were examined in 2 groups of Merino sheep that have been genetically selected for high or low staple strength, while holding fibre diameter constant. The sheep were fed below maintenance for 87 days, and then re-fed ad libitum for 63 days with a diet containing either 9% or 23% crude protein, in a cross-over design, after which they returned to the paddock until shearing. The fleeces of the 2 groups differed in staple strength (25·2 v.17·5 N/ktex, P &lt; 0·001) but were similar in mean fibre diameter and clean fleece weight. However, the pattern of wool growth was different. When fed below maintenance, sheep from the sound group grew more wool than sheep from the tender group (P &lt; 0·05), but lost more liveweight (P &lt; 0·01). During re-feeding, the sound sheep grew less wool than the tender sheep (P &lt; 0·05), but gained more liveweight. The mean fibre diameter at the point of break was similar in both groups. Immediately after re-feeding, the fibre diameter increased more rapidly in the tender group than in the sound (P &lt; 0·001), but a similar difference was observed between the high and low protein diets, with no effect on staple strength. The sound sheep had a lower standard deviation of fibre diameter than the tender sheep (P &lt; 0·001), both in the whole fleece and in 3-weekly midside patches. The data indicated that the variability of fibre diameter between fibres made a larger contribution than the variability along fibres to the difference between the groups in overall variability of fibre diameter. The sheep were then grazed together at pasture for a second year and again differed in staple strength. In addition, the sound sheep grew less wool on green spring pastures and had a lower clean fleece weight (P &lt; 0·05). The differences in wool growth rates between sheep from the sound and tender lines depended more on whether pasture was green than on the amount of pasture available. We conclude that the difference in staple strength between the sound and tender groups was most closely associated with the variability between fibres in diameter, and was also affected by a difference in variation in diameter along the fibres. Staple strength was not affected by the amount of wool at the point of break, or by the rate of change in fibre diameter after feeding. The sheep in the sound group grew less wool than those in the tender group when on good nutrition.

Mineral supplementation and wool production of young Merino sheep on the south coast of Western Australia

Wool-free liveweight change (LWC), wool growth rate, annual wool production, and wool characteristics of young Merino wethers fed supplements of lupins with gypsum or a multi-element mineral lick were examined in 12 experiments at 5 farms between 1989 and 1992. The source of sheep varied between experiments; age was 4.5-6.5 months and liveweight 28-37 kg at the beginning of supplementation. Sheep were fed lupins, lupins coated with gypsum (15-20 g/kg lupins), or lupins along with access to the mineral lick (offered at 140 g/sheep.week). The amount of lupins offered in all treatments within any experiment was the same. Supplementary feeding varied between experiments from 150 to 240 days. The sheep grazed annual pastures at stocking rates of 8-1 6.7ha. Average lick intake was 12-18 g/sheep. day. During supplementary feeding, there was considerable variation in LWC (-80 to +110 g/day) and clean wool growth rates (3.8-15.1 g/day) within and between experiments. However, there was no significant positive effect of gypsum or mineral lick supplementation on LWC or clean wool growth rates during or after supplementary feeding in any experiment. There were positive (P&lt;0.01) relationships between LWC and clean wool growth rates during supplementation. Also, for some spring-shorn sheep types, staple strength of wool was linearly related (P&lt;0.01) to LWC in the period before the position of break in the wool staple. Annual wool production, average fibre diameter, and staple strength of midside wool were not significantly increased by supplements of gypsum or mineral lick in any experiment.

Improving production from September-born Merino lambs with a lupin grain supplement and phomopsis-resistant lupin stubbles

As a means of providing nutrition on dry pasture in the wheatbelt of Western Australia, supplements of lupin grain were fed to late-born Merino lambs and their dams before weaning onto lupin stubble. Each ewe-lamb pair consumed an average 19.5 kg lupin grain over the 46 days before weaning. This produced an extra 3.6 kg (P&lt;0.01) liveweight gain by these lambs compared with their unsupplemented cohorts at weaning. The growth of the weaned lambs grazing phomopsis-resistant lupin stubbles was primarily influenced by the amount of residual lupin grain available to each sheep and liver injury caused by ingestion of phomopsins. In the first 69 days of stubble grazing, sheep stocked at 10ha gained 7.3 kg while those stocked at 20ka gained 2.1 kg (P&lt;0.001). In the first 13 months of life, lambs supplemented with lupin grain before weaning grew more (P&lt;0.05) clean wool by 0.17 kg than the unsupplemented lambs. However, the value of this extra wool would not have covered the cost of the lupin grain eaten. Wool staples produced by sheep grazed at 10/ha on lupin stubble were stronger (P&lt;0.001) than those produced by sheep grazed at 20ha (24.4 v. 17.7 N/ktex). The position of greatest weakness in the staple coincided with weight loss prior to removal from the stubble. Singleton lambs born in September and weaned onto a phomopsis-resistant lupin stubble reached liveweights consistent with survival over the summer and good productivity in their first year of life. The effects of lupinosis and reductions in wool staple strength may have been avoided by monitoring liveweight change and taking the sheep off the stubbles when they were near peak liveweight.

Lactic acidosis and its effect on wool tensile strength

An experiment was conducted to test the effect of the feed additive virginiamycin (VM) on lactic acidosis and wool tensile strength in sheep given wheat. The ground wheat grain was given in a slurry by stomach tube in increasing amounts each day up to a maximum of 1 kg per dose or until rumen pH dropped below 5.20. Sixty mature Merino wethers were all fed wheat chaff ad libitum and given the following treatments: 10 control sheep were only fed the basal diet; 10 were given intra-ruminal doses of VM; 20 sheep were given wheat grain intra-ruminally; and 20 sheep were given wheat grain containing VM. Virginiarnycin was given at a rate equivalent to 80 mg/day. All animals were fed chaff for 83 days prior to and for 120 days following the wheat and VM treatments. Rumen pH and L-lactic acid concentration were measured in all 60 sheep from the day that wheat was first given until 3 days after the last wheat drench. Lactic acidosis, defined by a rumen pH of less than 5.2 and rumen lactic acid concentration of greater than 20 mmol/L, significantly decreased staple strength of wool in sheep given the wheat drenches. Inclusion of VM with the wheat grain significantly increased (P &lt; 0.05) the tensile strength of the wool compared with the effect of wheat on its own. Reduction in wool strength was more closely correlated with a reduction in feed intake in the days following the lactic acidosis than with either rumen pH or the concentration of rumen lactic acid.

A multi element supplement for grazing sheep. I. Intake, mineral status and production responses

The safety and effectiveness of a loose mineral lick containing all known essential elements was investigated in an experiment in which 96 Merino weaner wethers grazed subterranean clover/grass pastures during summer and autumn. The treatments were no supplement or mineral mix ad libitum; there were four plots of 12 sheep per treatment. The mean intake was 29 � 1 g/head per day of the mix and those offered the minerals had blood concentrations of P, S, Se and vitamin BIZ in the normal range. Unsupplemented Control sheep had blood concentrations of P, S and Se in the deficient range for all or part of the experimental period. There was an estimated 1.6-fold range in mineral intake between sheep, and none refused the mix. Concentrations of Cu, Cd and F in tissues and bone of sheep offered the mineral mix were within accepted safety margins. The mineral lick increased live weights by 4.5 kg during summer (P &lt; 0 - 05), increased clean fleece weight by 240 g (9%), (P &lt; 0.01), and increased wool staple strength by 15 N/kt (40%), (P &lt; 0.01). The pasture concentrations of most macro elements decreased between November and March, respective concentrations being (g/kg DM): K, 17- 7 and 1.9; Na, 4-0 and 0.31; S, 1.6 and 0.9; N, 12.9 and 10; P, 1-95 and 1-08; Ca, 7-86 and 9-75; Mg, 2.29 and 1-38. Changes in trace element concentrations were small, the respective values being (mg/kg): Cu, 9.7 and 10-3; Mn, 47 and 67; Fe, 56 and 323; Zn, 20 and 20; Mo, 0-2 and 0.35; and Se, 0.015 and 0.032. The loose mineral lick was a safe and effective means of supplying macro and trace elements to grazing sheep during summer.

Effect of daily infection withOstertagia circumcinctalarvae on food intake, milk production and wool growth in sheep

SUMMARYForty pregnant sheep were allocated to four groups and maintained indoors in individual pens on a pelleted diet. During the last 6 weeks of pregnancy and the first 6 weeks of lactation groups were infected daily with 4000 larvae ofOstertagia circumcinctaor remained as controls in a cross-over design. Thus groups were either not infected (CC), infected only during pregnancy (IC), during lactation (CI) or during both pregnancy and lactation (II). Food was offered on the basis of body weight at the beginning of pregnancy and lactation. Food intake, body-weight change, faecal egg counts, plasma pepsinogen and milk production were measured weekly, wool growth and fibre diameter during 21-day periods and tensile strength of wool over the whole experimental period.Eggs were seen in faeces of only three sheep infected during pregnancy, but in all sheep infected during lactation; maximum mean values were 467 ± 144 and 222 ± 58 eggs/g fresh faeces in CI and II sheep, respectively. Pepsinogen concentrations rose after 1 week of infection during pregnancy and lactation; peak values were 868 + 57 and 1104 ± 146 m-u/l, respectively.Infection reduced food intake by 16% during lactation but had no effect during pregnancy. There were significant interactions between pregnancy and lactational treatments on intake during lactation. Infection during lactation increased bodyweight loss; mean values were 57, 40, 114 and 78 g/day for groups CC, IC, CI and II respectively. Milk production was decreased during weeks 4–6 of lactation, mean values being 1·59 and 1·32 kg/day in control and infected groups, respectively.Infection reduced wool growth and wool fibre diameter by 20 and 7%, respectively, during the final 3 weeks of infection during lactation. The staple strength of wool grown during the experiment was reduced by 14, 45 and 23% in IC, CI and II groups, respectively. Infection moved the point of greatest wool tenderness from parturition in control sheep to a time during the period of infection, particularly when infection occurred during lactation.

Staple strength

Abstract There is a marked decrease in the staple strength of wool offered for sale at both Christchurch and Dunedin as the selling season progresses. The staple strength of wool sold in the pre-Christmas sales is twice that of wool sold after Christmas. This decrease, which is more marked in the Crossbred than in the fine wools, may be assessed by hand testing staples for soundness, and can thus be measured by the wool trade without the need of any special testing equipment. During the present investigations, as the selling season progressed, the break level rose to 40 per cent; the proportion of staples which could be hand broken reached about 75 per cent, while the amount of cotted wool rose to about 20 per cent. Over a period of 5 seasons, the unsound poor style wool sold at the last sale brought a higher price than the sound better syle wool in the first sale. To obtain sound good style wool, sheep should be shorn either before lambing time or as soon as practicable after lambing.