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1.
The sampling distribution of Bovicola ovis (Schrank) on sheep was examined in two flocks, one with a light and one with a heavy infestation of lice. The derived distributions were used to calculate the sensitivity of detecting lice on individual sheep and in flocks by fleece parting regimes that varied in number of parts per animal and number of sheep per flock, different scenarios of flock sizes, proportion infested and louse density were examined. Lice were aggregated among fleece partings in the heavily infested flock and described by a negative binomial distribution with k values between 0.3 and 1.92. The distribution was indistinguishable from Poisson in the lightly infested flock. The assumed distribution had little effect on sensitivity, except when only one fleece part per animal was examined. On individual sheep where louse density was 0.5 per 10 cm part or greater, there were only marginal gains from inspecting more than 10 parts per animal. Increasing the number of sheep inspected always increased sensitivity more than increasing number of parts per sheep by an equivalent amount. This advantage was greatest in situations where a low proportion of sheep in the flock were infested with a high density of lice, and less where a low proportion of sheep were infested with a low density of lice, or a high proportion of sheep were infested with a high density of lice.  相似文献   

2.
Pruritic behaviour and deranged fleece are often used as indicators of sheep louse infestation but the exact relationship between infestation and the observation of signs of pruritis was unclear. Two studies were conducted to examine this association. In the first, 24 castrate Merino sheep were randomly assigned to six pens in groups of four and the sheep in three pens infested with 10 lice each on the right mid-side. Louse numbers were counted, fleece derangement scored and pruritic behaviour assessed periodically on each sheep until 38 weeks after infestation. In the second study a single moderately infested sheep was paddocked for 15 weeks with 32 uninfested sheep and louse numbers and fleece derangement monitored for 41 weeks. In the pen studies, differences between infested and non-infested sheep in fleece derangement and pruritic behaviour first became significant (p<0.05) at 8 and 14 weeks, respectively and at louse densities of 0.06 and 0.27 per 10 cm wool part. Some sheep showed definite signs of deranged fleece as early as 5 weeks after initial infestation. In the paddock studies, it took 37 weeks until lice were detected on all sheep in the flock. The correlation between louse numbers and fleece derangement score first became significant (r=0.44 and p<0.05) at 9 weeks after introduction of the lousy sheep, reached a maximum of r=0.79 (p<0.001) at 22 weeks when 84% of sheep had lice detected and the mean louse density was 0.29 per part, and then declined to r=0.12 (n.s.) at 41 weeks when all sheep were infested and the mean louse density was 3.04 per part. It is concluded that fleece derangement is a powerful early indicator of the presence of lice and that sheep may exhibit signs of pruritis well before lice can be readily found by direct inspection. Fleece derangement may be useful as a basis for establishing economic thresholds for the application of long wool treatments in developing louse infestations but appears to be a poor indicator of louse numbers once the infestation is advanced.  相似文献   

3.
The in vivo pediculicidal effectiveness of 1% and 2% formulations of tea tree (Melaleuca alternifolia) oil (TTO) against sheep chewing lice (Bovicola ovis) was tested in two pen studies. Immersion dipping of sheep shorn two weeks before treatment in both 1% and 2% formulations reduced lice to non detectable levels. No lice were found on any of the treated sheep despite careful inspection of at least 40 fleece partings per animal at 2, 6, 12 and 20 weeks after treatment. In the untreated sheep louse numbers increased from a mean (±SE) of 2.4 (±0.7) per 10cm fleece part at 2 weeks to 12.3 (±4.2) per part at 20 weeks. Treatment of sheep with 6 months wool by jetting (high pressure spraying into the fleece) reduced louse numbers by 94% in comparison to controls at two weeks after treatment with both 1% and 2% TTO formulations. At 6 and 12 weeks after treatment reductions were 94% and 91% respectively with the 1% formulation and 78% and 84% respectively with the 2% formulation. TTO treatment also appeared to reduce wool damage in infested sheep. Laboratory studies indicated that tea tree oil 'stripped' from solution with a progressive reduction in concentration as well as volume as more wool was dipped, indicating that reinforcement of active ingredient would be required to maintain effectiveness when large numbers of sheep are treated. The results of these studies suggest significant potential for the development of ovine lousicides incorporating TTO.  相似文献   

4.
The spatial distribution of chewing lice (Bovicola ovis) on their hosts was examined in Polypay and Columbia ewes initially artificially infested on the midside or the neck. Densities of lice were determined at 69 body sites in eight body regions at approximately monthly intervals for 2 years. In the second year, half of the ewes were mated and lice were counted at 26 body sites on the resulting lambs. Polypay ewes had higher densities of lice than Columbias at most inspections but there was little effect of infestation point or mating on either numbers or the distribution of lice. During periods of high louse numbers densities were generally greatest on the sides or the back. Densities on the head were also high at times and peaked later than overall louse densities. Shearing markedly reduced density but increased the proportion of lice found on the neck, belly and lowleg sites. The distribution of lice on the lambs was similar to that on the ewes except that fewer lice were found on the head. Comparisons of lice per part with the numbers of lice extracted from clipped patches indicated that a sheep with wool bearing area of 1 m2 and a mean count of one louse per 10 cm fleece parting carried approximately 2000 lice. At most times of the year inspections for sheep lice should be concentrated on the sides and back, but in recently shorn sheep greater attention should be paid to the lower neck and ventral regions. Implications of the observed distributions of lice for the efficacy of chemical treatments are discussed.  相似文献   

5.
An experiment was designed to evaluate the effects of five sire breeds (Dorset, Finnsheep, Romanov, Texel, and Montadale), two dam breeds (Composite III [CIII] and northwestern whiteface [WF]), and three shearing seasons (December, February, and April, corresponding to August, October, and December breeding seasons) and their interactions on wool and other characteristics of F1 ewes. Fleeces were collected and characterized from six 2-yr-old F1 ewes representing each of the 90 sire breed x dam breed x shearing season x year (three) subclasses. Characteristics measured objectively were grease and clean fleece weights, clean yield, mean fiber diameter and SD, and mean staple length and SD. Visual assessments of fleece color were also made. Data collected on the F1 ewes were analyzed using a mixed model analysis of variance procedure. The model included fixed effects of year of birth, sire breed, dam breed, shearing season, six two-way interactions, and the three-way interaction of sire breed x dam breed x shearing season. The random effect of individual sire within year of birth x sire breed was also fitted. Texel- and Montadale-sired ewes produced more clean wool (P < 0.05) (approximately 0.24 kg) than Dorset-, Finnsheep-, and Romanov-sired ewes. Texel-sired ewes produced the coarsest wool (28.7 microm) (P < 0.05), whereas Romanov-sired ewes produced the finest (24.9 microm) and longest (9.12 cm) fleeces (P < 0.05). Ewes from WF dams produced more and finer wool (0.15 kg and 2.7 microm) than ewes from CIII dams (P < 0.001). Ewes shorn in December produced more, coarser, and longer wool (P < 0.05) than those shorn in February and April. This trend in wool production is opposite to that in conception rate (reported previously). Romanov-sired ewes produced the lowest percentage of white fleeces (62.6%), whereas Dorset-sired ewes produced the most (P < 0.001) white fleeces (96.3%). Estimates of heritability were calculated for grease and clean fleece weights (0.36), percentage of clean yield (0.31), average fiber diameter and SD (0.86 and 0.42, respectively), and average staple length and SD (0.49 and 0.00, respectively). Although necessary for a thorough evaluation of these 10 types of crossbred ewes, it is estimated that wool income would only constitute a small portion (1 to 5%) of overall income from sheep of this type.  相似文献   

6.
Summary The relative efficacy of 6 shower dip chemicals most frequently used for the treatment of sheep lice (Bovicola ovis) in Western Australia was examined. Groups of 20 sheep infested with lice were treated with products containing either alphamethrin, cyhalothrin, diazinon or diazinon plus piperonyl butoxide and rotenone, formulated as emulsifiable concentrates, and with products containing either coumaphos or magnesium fluorosilicate, formulated as wettable powders. All treatments were applied through a shower dip (Sunbeam model SSD). Inspections for lice were conducted until 9 months after dipping. No lice were found on sheep treated with the 4 emulsifiable concentrate products. In contrast, treatment with the wettable powders, which contained either coumaphos or magnesium fluorosilicate as the active ingredient, did not eradicate the lice infestations. The degree to which the fleece was wetted was assessed 20 minutes after dipping and showed that the wettable powder dips penetrated the fleece less than the emulsifiable concentrate dips. Less fluid was retained by wool staples in an in-vitro test when dip wash was made with the wettable powders. It was concluded that the degree of wetting attained at dipping was an important factor in achieving eradication of sheep lice.  相似文献   

7.
SUMMARY Benign footrot was studied in 1 1/2-years-old Merinos on 2 farms in central Victoria from September 1987 to August 1990, Inclusive. Treatment groups of 100 sheep grazed together with the remaining untreated sheep. Inspections were carried out every 3 weeks during the spring transmission period until the number of lesions greater than score 2 dropped below 3%. At each inspection, each sheep was weighed and lesion scores for each foot and digit were recorded, the treated group of sheep was treated by standing in 20% (w/v) zinc sulphate-sodium lauryl sulphate for 1 hour, and bacteriological samples were randomly collected from 5 sheep with and 5 without lesions. Dichelobacter nodosus organisms were obtained from sheep in both groups.
Laboratory tests indicated benign organisms in flock A and low virulence, intermediate organisms in flock B. During the first 2 years, the number and severity of lesions were greater in flock A than in flock B. However, in the third year, with an early 'autumn break', there was a rapid and severe outbreak of footrot in flock B; 98% of the flock had lesions at the first inspection in July 1989. Flock A had a less dramatic increase in lesions of footrot. Both treated and untreated groups in flock B recovered rapidly between the third and fourth inspections. A later increase in lesions for both flocks coincided with damage caused by barley grass seeds. During this period there was a significant difference (P / 0.001) in body weight between the treated and untreated sheep on farm B. An extra 0.2 kg of skirted fleece was obtained from treated sheep when shorn in 1990, compared with the untreated group (P = 0.04). Treated sheep had fewer tender fleeces, 11% compared with 25%. Wool from the untreated group was 0.5 micron finer but the value was 1.79 a head (7%) less than that from the treated group.  相似文献   

8.
OBJECTIVE: To investigate the roles of shade, fleece length and wool type in the protection of sheep from Hypericum perforatum poisoning. ANIMALS: Adult Merino ewes of superfine, fine and medium wool type. DESIGN: Seventy sheep were divided into seven equal groups. During late spring and summer a series of successive, replicate experiments was conducted, each using one group and lasting 5 days. The sheep carried 14 to 24 weeks wool growth. In each experiment the treatments tested were Hypericum +, sunlight + (n = 7); Hypericum +, sun - (n = 1); Hypericum -, sun + (n = 1); Hypericum -, sun - (n = 1). Next, 24 sheep in two equal groups were used in experiments of similar design to the above. Each group consisted of nine recently (1 to 3 weeks previously) shorn and three wool covered (25 to 26 weeks growth) sheep. The treatments tested were Hypericum +, sunlight +, fleece - (n = 9); Hypericum +, sun -, fleece + (n = 1); Hypericum -, sun +, fleece + (n = 1); Hypericum -, sun -, fleece + (n = 1). PROCEDURES: Finely milled Hypericum was administered by gavage to provide 3 mg hypericin / kg body weight. Sheep were sheltered from direct sunlight or were exposed for 5 h per day for 4 successive post-treatment days. Rectal temperatures were measured immediately before and at the end of each sunlight exposure session. Rectal temperature above 40 degrees C was considered indicative of hypericin poisoning. RESULTS: After Hypericum treatment hypericin poisoning was displayed by 26.5% of woolled sheep that were exposed to sunlight, but by none of those that were fully shaded. In similarly treated but recently shorn sheep 94% displayed hypericin poisoning when exposed to sunlight. In the wool covered group the percentages of poisoned animals based on wool type were: superfine 14%, fine 28.5%, medium 33.3%. In the recently shorn group the percentage for all three approached 100%. CONCLUSIONS: A majority of Merinos with at least 14 weeks wool growth will not be poisoned by a single oral dose of 3 mg hypericin /kg, but because hypericin persists in the blood circulation for several days this safe dose will be lowered by continuous daily ingestion. Sheep with access to substantial areas of shade could safely ingest much greater amounts of hypericin. Wool removal greatly increases the risk of poisoning. Superfine Merinos with a wool cover should be able to ingest more hypericin than comparable, medium wool types, without any increased risk of poisoning. The ability of ruminant livestock to safely ingest Hypericum is probably determined more by the amount of skin protection they have against incident sunlight than by differences in hypericin metabolism and excretion capacity.  相似文献   

9.
中国绵山羊养殖历史悠久,品种资源丰富,在国民经济中起重要作用。羊毛按纤维类型可分为同质毛和异质毛,同质毛的特点是被毛由同一类型的羊毛纤维组成,其特点是羊毛的纤维直径、长度、卷曲等外表特征基本相同,异质毛的特点是被毛中兼有绒毛、有髓毛、无卷曲和少卷毛等不同类型的羊毛纤维,其化学、物理性能均不相同。毛囊是控制哺乳动物被毛生长的重要器官,是唯一具有周期性发育并可终生再生的器官,控制着被毛发生发育与自然脱落。毛囊依据其形成时间和结构可分为初级毛囊(primary follicles)和次级毛囊(secondary follicles),初级毛囊生长髓质发达的粗毛,次级毛囊产生无髓毛的绒毛。有髓毛较粗长且弯曲少,多用于加工粗纺织品、毛毯、地毯、毡制品;无髓毛直径一般不超40 μm,弯曲多,是毛纺工业的优质原料。毛囊的发育受到不同信号通路和基因的影响,如Wnt信号通路、骨形态发生蛋白质(BMP)信号通路、成纤维细胞生长因子(FGF)信号通路、音猬因子(SHH)信号通路、Notch信号通路等以及角蛋白家族基因、BMPs家族基因、同源异型盒基因(Hox)等。作者对国内外对绵山羊胎儿期皮肤毛囊发育及调控机制进行综述,以期为提高以绵山羊被毛产量及改善被毛品质为主要育种目标的选育提供参考。  相似文献   

10.
Two synthetic pyrethroid (cypermethrin) based pour-on insecticide formulations, with high cis/trans isomer ratios (80:20) but differing in their respective active ingredient concentrations and solvent component(s), were applied to sheep infested with the biting-louse, Bovicola ovis. All treated sheep were penned with louse-infested sheep 9,12 and 15 weeks after the insecticide was applied. The 2% cypermethrin formulation achieved a higher level of control than the 1.25% cypermethrin formulation at each challenge interval when applied 12 weeks after shearing. The 2% cypermethrin formulation provided 97-100% control of lice from 4 to 16 weeks after application on sheep shorn 6 or 12 weeks prior to treatment. The 1.25% cypermethrin formulation provided 85% control of lice 4 weeks after application on sheep shorn 12 weeks prior to treatment, the level of control increasing to a maximum of 100% by week 9, and declining thereafter. The 2% cypermethrin formulation may provide a better level of control in long-woolled sheep than 1.25% cypermethrin, by compensating for the diluent effect of lipid.  相似文献   

11.
The eradication of lice from Merino sheep with wool up to 65 mm long was achieved by spraying insecticide onto the tip of wool over the sides and back. The insecticides used were cyhalothrin and diazinon in small volumes and at high concentration. When infested sheep were sprayed with 100 ml of cyhalothrin 1,500 ppm or diazinon 36,000 ppm, no live lice were seen 23 days after treatment. When treated sheep were challenged with live lice 100 days after treatment an infestation did not establish. Cyhalothrin at a lower concentration of 1,000 ppm gave excellent control but at 500 ppm only fair control was obtained. Diazinon at 24,000 ppm gave probable eradication and at 12,000 ppm excellent control. If a practical method of applying the insecticide to the tip of wool can be developed, then this technique should provide an effective means of eradicating lice in sheep with long wool. This would greatly assist the sheep industry in controlling and eradicating sheep lice.  相似文献   

12.
Objective To compare the wettability and efficacy of diazinon dip wash made with and without the addition of zinc sulphate.
Design Field experiments using a shower and a plunge dip complemented by in-vitro wettability experiments.
Procedure A flock of infested sheep was divided into groups and treated in a shower dip with clear or cloudy dam water plus up to 1.5% zinc sulphate. Another infested line of sheep was treated using a plunge dip with nil or 1% zinc sulphate. In both experiments, wetting was assessed after dipping and louse counts were conducted for 9 months after treatment. Five in-vitro experiments compared the wettability of dip wash containing diazinon with up to 1.5% zinc sulphate added.
Results In the shower dipping experiment, live lice were found at 1 month after dipping in the cloudy water groups with 0.75%, 1.0% and 1.5% zinc sulphate and at 2 months in the 0.75% zinc sulphate group. No lice were found at subsequent inspections or at any time in the groups that were plunge dipped. Zinc sulphate decreased the amount of dip wash retained by wool staples in all in-vitro experiments (P < 0.05).
Conclusion Zinc sulphate should be considered as a risk factor that could cause failure to eradicate a lice infestation. The risk can be overcome by ensuring that all sheep are saturated at dipping and that the dip wash, and any holding tanks, are agitated throughout the dipping event.  相似文献   

13.
Two synthetic pyrethroid (cypermethrin) based “pour-on” insecticide formulations, with high cis/trans isomer ratios (80:20) but differing in their respective active ingredient concentrations and solvent component(s), were applied to sheep infested with the biting-louse, Bovicola ovis. All treated sheep were penned with louse-infested sheep 9, 12 and 15 weeks after the insecticide was applied. The 2% cypermethrin formulation achieved a higher level of control than the 1.25% cypermethrin formulation at each challenge interval when applied 12 weeks after shearing. The 2% cypermethrin formulation provided 97-100% control of lice from 4 to 16 weeks after application on sheep shorn 6 or 12 weeks prior to treatment. The 1.25% cypermethrin formulation provided 85% control of lice 4 weeks after application on sheep shorn 12 weeks prior to treatment, the level of control increasing to a maximum of 100% by week 9, and declining thereafter. The 2% cypermethrin formulation may provide a better level of control in long-woolled sheep than 1.25% cypermethrin, by compensating for the diluent effect of lipid.  相似文献   

14.
Ninety mature Targhee ewes were randomly allocated to nine lots. Lots were randomly assigned to three fleece preparation treatments: 1) nonskirted (control); 2) bellies removed, in which bellies and topknots were removed on the shearing floor; and 3) skirted, in which bellies and topknots were removed and remaining fleece was thrown on a table and lightly skirted. Bellies and topknots composed about 6 to 7% of the fleece weight. An additional 6.6% was removed when fleeces were skirted. Top fiber diameters were not affected (P greater than .10) by skirting. Although not significant (P greater than .10), percentage yield, vegetable content, percentage of noilage, top fiber length, and yellowness indexes tended to be most desirable for skirted lots and least desirable for unskirted lots. Lots with bellies removed were intermediate. Removal of bellies reduced vegetable contamination by 8.4%, with an additional reduction of about .5% by further skirting. Skirting reduced the number of fibers less than 25.4 mm (P less than .10) by 42%. Minimal colored fiber contamination of top was observed. One colored fiber per 15 g of top was detected in two lots of the treatment with bellies removed. All other lots contained no colored fibers. All wools evaluated were well below industry limits set for use in high-quality white or pastel fabrics. All skirted lots of wool evaluated in this study had improved processing characteristics for all processing traits evaluated.  相似文献   

15.
These studies were conducted to investigate the possible role of certain aspects of the on-host ecology and off-host survival of the sheep scab mite, Psoroptes ovis, in the dissemination of infestation. All developmental stages of the mite occurred in the fleece both proximally or distal to the skin of infested Merino and Dorper sheep. A larger proportion of mites was present in the fleece of Dorper sheep distal to the skin in the late afternoon and early morning than at other times during the day. Immature and adult mites readily transferred to tufts of wool or hair placed on infested sheep of both breeds. No mites could be found on wool or hair rubbed off onto tree trunks or branches or other structures in enclosures housing heavily infested sheep, nor could any mites be collected from the soil of these enclosures, whereas more than 80% of mites artificially seeded onto soil samples were recovered. The longest mean off-host survival times for larvae, nymphs, and male and ovigerous female mites were recorded at 10 degrees C, and were 9.25 days (RH = 90%), 15 days (RH = 33% and 75%), 10.5 days (RH = 75% and 90%) and 11.25 days (RH = 90%) respectively. Under natural climatic conditions ovigerous females in glass vials containing Merino wool survived for 17 days compared to 15 days for females in vials without wool; this difference was, however, not significant. The mean off-host pre-hatch period for eggs varied between 5.9 days (T = 25 degrees C and RH = 33%) and 22.1 days (T = 10 degrees C and RH = 75%), while the longest time individual eggs took to hatch at the latter temperature and RH was 31 days.  相似文献   

16.
Polymer matrix ear tags containing 13.7% w/w tetrachlorvinphos or 8.5% w/w cypermethrin were applied to Merino wethers infested with lice and carrying two months wool. The cypermethrin tags reduced louse numbers by a maximum of 89% in comparison to controls at 16 weeks after treatment and by 85% at the conclusion of the experiment 38 weeks after application. Lice were not eradicated from any sheep. The number of lice counted on sheep treated with tetrachlorvinphos-impregnated tags was not significantly different from controls.  相似文献   

17.
Transmission of sheep lice is thought to occur mainly by sheep to sheep contact although the possibility of other sources of infestation is often suggested. This study investigated the period of survival of Bovicola ovis after removal from sheep under varying conditions and assessed the likelihood of new infestations arising from contaminated facilities, wool caught on fences and shearers' footwear.In laboratory studies with lice held away from sheep at 4, 20, 25 and 36.5 degrees C, adults and nymphs survived longest at 25 degrees C (LT90 of 11.7 and 24.1 days for adults and large nymphs, respectively). Nymphs survived longer than adults and lice provided with raw wool survived longer than lice provided with wool that had been degreased. Nymphal lice survived for up to 29 days on unscoured wool at 36.5 degrees C, but the LT50 was less than 9 days in most experiments. In shearing sheds in winter and early spring lice survived for up to 14 and 16 days, respectively. These periods of survival are considerably longer than previously indicated for B. ovis. Most lice dropped out of wool staples attached to a fence within 1 h and only two of a total of 225 lice were still present after 24 h, suggesting that sheep are unlikely to become infested from wool caught on fences. Adult and nymphal lice readily transferred to shearers' moccasins and survived there for up to 10 days, indicating that transmission of lice on the footwear of shearers or other sheep handlers may be a cause of new infestations. Microwaving each moccasin for 5 min killed all lice and may provide a simple method of reducing the likelihood of transmission of B. ovis between properties.  相似文献   

18.
The effect of regular selenium supplementation on the body weight, wool production and mortality of young Merino sheep was investigated. Groups of Se-treated and control sheep involving from 260–500 on each of 15 farms were observed from six weeks to 19 months of age. Ten mg Se as sodium hydrogen selenite was administered orally to the treated sheep at two-monthly intervals. Treated and control sheep grazed together throughout the trial period. Statistically significant responses to selenium were recorded in body weight gains on four farms, in decreased mortality on five farms and as an increase in fleece weight on eight farms. The response in fleece weight varied from 2.9-7.6% and could not be explained as a result of increased body weight. The increase in fleece weight was not due to an increase of grease in the wool but appeared to be due to an increase in fibre diameter and to a lesser extent an increase in staple length. A statistically significant decrease in the incidence of tender fleeces as a result of selenium supplementation was also recorded. All farms on which responses to selenium were obtained were in areas with average annual rainfall more than 20 inches. On two farms selenium caused statistically significant depressions in the parameters measured. Both farms were in areas with less than 20 inches average annual rainfall.  相似文献   

19.
The juvenile live weights, yearling fleece weight and wool characteristics of 2987 Romney progeny of 114 sires born over 9 breeding seasons in a fleece-weight-selected and a random control line were analysed. The high fleece weight-selected flock performance was higher (P < 0.001) for weaning weight and spring weight (6.9 and 8.4%), higher (P < 0.001) for greasy and clean fleece weight (23.8 and 24.3%), and also higher (P < 0.001) for FD by 1 μm, staple length by 6 mm, and wool yellowness by 0.3 unit than random control yearling sheep. Heritability estimates for weaning and spring live weight, greasy fleece weight, clean fleece weight, yield, fibre diameter, staple length, staple strength, loose wool bulk, brightness and yellowness were 0.15, 0.51, 0.35, 0.36, 0.40, 0.57, 0.41, 0.24, 0.46, 0.12 and 0.14 respectively. The heritability estimates are within the range of the long wool sheep breeds studied previously. The high selection differential achieved in the initial screening commercial flocks however facilitated to approach a selection response peak in a shorter selection duration and thus resulted in a non-significant genetic gain in greasy fleece weight when averaged over the 9 years of selection.  相似文献   

20.
SUMMARY: A comparative study of various fleece properties known to influence fleece-rot susceptibility was made in a merino flock consisting of sheep which were found to be either resistant or susceptible to fleece-rot and body strike following heavy rains. The fleece properties measured were fibre diameter, fibre diameter variation, wax content, suint content, wax to suint ratio, suint pH, insoluble nitrogen content, wool colour and wettability. Fibre diameter variation, due mainly to the presence of coarse, secondary fibres in the staple, was the only fleece property which differed significantly (p < 0.001) between resistant and susceptible animals. The coefficient of variation of fibre diameter was lowered from a mean value of 22.7 ± 0.3% in susceptible sheep to 20.0 ± 0.3% in resistant sheep. A causal relationship between high fibre diameter variation and fleece-rot susceptibility is suggested. Sheep with irregular fibre size may retain free moisture in the fleece for longer, and thereby become more susceptible to fleece-rot than sheep with uniform fibre diameter, other predisposing factors being equal.  相似文献   

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