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1.
Pelibuey and Suffolk sheep were compared as to their capacity to regulate body temperature under environmental hyperthermia by measuring their differences in cellular response to heat stress (HS). In a first experiment, seven Pelibuey and seven Suffolk ewes were kept in a climatic chamber for 6 h daily during 10 days (temperatures within the 18 to 39.5 °C range). As chamber temperature rose, sheep rectal temperature increased in both groups, but to a lesser extent in Pelibuey (0.3 °C) than in Suffolk sheep (0.7 °C) (P?<?0.05). In a second experiment, cellular viability was assessed using cultured blood mononuclear cells from 15 Pelibuey and 15 Suffolk sheep. They were incubated at 37 °C for 24 h (control) or 43 °C for 6 h followed by 18 h at 37 °C (HS). In a third experiment, another blood mononuclear cells culture from eight Pelibuey and eight Suffolk sheep was kept at 37 °C for 15 h; these were subsequently cultured for 6 h at 37 °C (controls) or 43 °C (HS). Next, HSP-70 concentration was determined. HS reduced the percentage of viable cells to a greater extent in Suffolk [37 °C (73.7 %) vs. 43 °C (61.9 %); P?<?0.05] than in Pelibuey sheep [37 °C (74.9 %) vs. 43 °C (66.7 %); P?>?0.05]. HS significantly increased HSP-70 average concentrations for both breeds at 43 °C. A significant effect was observed for the breed by temperature interaction (P?<?0.05) caused by a greater difference between Pelibuey and Suffolk at 43 °C (2.85 vs. 0.53 ng/mL, respectively; P?<?0.05) than at 37 °C (0.05 vs. 0.03 ng/mL, respectively; P?>?0.05). In conclusion, Pelibuey sheep show more effective body temperature regulation under conditions of environmental hyperthermia. Also, cell viability after HS was higher in Pelibuey than in Suffolk, an effect that could be mediated by an HSP-70-related mechanism.  相似文献   

2.
We assessed whether rolling damage by grazing horses could be reduced by constructing areas assigned for rolling. A group of horses were enclosed in a paddock with and without rolling areas made of dry soil, sand, and straw. Their behavior was recorded for 1 week in the paddock without any treatment (control paddock). Then the horses were moved to another paddock with the rolling areas (rolling paddock). After a 3-week familiarization period, horses were observed for 1 week. In the rolling paddock, the frequency and time spent rolling were significantly greater in rolling areas than in nonrolling areas. Horses significantly preferred the soil rolling area than sand and straw (P < .05). Although rolling was considered the most relevant body care behavioral element, the effects of the substrate in rolling areas on other body care behavioral activities, such as mutual and self-grooming, also were investigated. The frequency and duration of mutual grooming and the duration of self-grooming decreased significantly in the rolling paddock compared with the control paddock (P < .05). Hence, offering a rolling area encourages horses to roll in these areas and keeps the pasture in good condition; therefore, grazing time can be increased, with less reliance on supplementary feed.  相似文献   

3.
Scrapie is one of several transmissible spongiform encephalopathies of livestock. Disease susceptibility is linked to polymorphisms in the normal prion protein gene that encodes the mammalian prion precursor. Codon 171 of this gene is a major determinant of scrapie susceptibility. Selection for arginine (R) at codon 171 is encouraged by the USDA to decrease the incidence of scrapie. Objectives of this study were to determine the frequency of R allele variants at codon 171 in a sample of sheep from five breeds (Columbia, Hampshire, Rambouillet, Suffolk, and Targhee) and western white-faced commercial ewes and to determine whether the R allele is associated with ewe and lamb production traits. Genotyping was performed on 532 ewes and 901 lambs from the University of Wyoming flock, in addition to 820 rams from 52 sheep producers from Wyoming and surrounding areas, using a DNA mismatch assay that discriminated the R allele from others at codon 171. Genotyping was performed by DNA sequencing on 127 rams representing all breeds, except Hampshire from the USDA Sheep Experiment Station at Dubois, ID. The 171R allele was found in all five breeds and in the commercial western white-faced ewes. Genotype frequencies varied (P < 0.001) by breed in ewe and ram populations. Influence of R-allele frequency on ewe lambing records and individual lamb records was analyzed for Columbia (62, 161, 121), Hampshire (89, 193, 162), Rambouillet (87, 179, 133), Suffolk (67, 178, 161), and commercial sheep (227, 463, 324) for numbers of ewes, total number of ewe production records, and individual lamb records, respectively. Suffolk ewes without the R allele (non-R/non-R) gave birth to more (P or= 0.08) by ewe genotype. Lamb birth and weaning weights were not influenced (P >or= 0.12) by lamb genotype in any of the breeds or in the commercial flock. In this population, ultimate lamb production was only influenced by genotype at codon 171 in the Suffolk flock.  相似文献   

4.
A mixed breed flock of lambs, consisting of Suffolks, Hampshires, Columbias and Finnish breeds, were vaccinated with binary ethylenimine inactivated bluetongue virus (BTV) serotypes 11, 17 and a mixture of 11 and 17 in aluminum hydroxide. Agar gel precipitin antibodies were used as an indicator of immunity. Sero-conversion of Hampshires and Suffolk lambs was poor at 43% as compared to 84% in the Columbia and Finn lambs. These results indicate a breed difference in immunological response to inactivated BTV vaccine.  相似文献   

5.
Effects of sex and strain of bird on factors influencing welfare in chickens were investigated in 288 21-week-old Potchefstroom Koekoek (PK), Ovambo (OV), and Naked Neck (NN) chickens. The birds were allocated to 4 paddocks of Chloris gayana and a house subdivided into 4 pens. There were 12 males per strain and 12 females per strain in each paddock. Similarly, 12 males per strain and the same number of females were placed in each pen in the house. Twelve birds, 4 each of NN, OV, and PK, were randomly selected per paddock and per pen, and tonic immobility (TI) was determined. Ambient temperature and humidity were recorded and fitted into a PROC MIXED model as random effects, with strain and sex as main effects. On the last d of the trial, blood samples were collected from 9 (3 of each strain) randomly selected birds per paddock, via brachial venepuncture, using 5 mL syringes and 22 gauge needles. At slaughter, the liver and spleen were recovered and weighed immediately. Organ weights were expressed relative to body weight (BW) of each bird. Sex of bird influenced (P < 0.05) BW, spleen, and relative liver weights and heterophil to lymphocyte (H/L) ratio. Strain did not influence (P > 0.05) TI but affected (P < 0.05) all other parameters. Rearing system (P < 0.05) influenced all parameters. Strain × sex interactions were significant (P < 0.05) on all organ weights. Males appeared more stressed than females. The free-range system could minimize stress in birds though mechanisms should be devised to prevent attacks by predators. Perhaps future research could be designed to study similar parameters over a longer observation period using younger slow-growing chickens.  相似文献   

6.
There have been no reports of natural scrapie in Irish Blackface Mountain (BM) sheep which account for approximately 16% of the Irish national sheep flock. The aim of this study was to determine if Irish BM sheep had unusual clinical and/or pathological features of scrapie which would account for failure to diagnose the disease in this breed. BM (n=7), Texel (n=3) and Suffolk sheep (n=1) of scrapie-susceptible PrP genotypes (ARQ/ARQ and VRQ/ARQ) were orally challenged with scrapie-infected brain inoculum. The incubation period, clinical signs, pathology and distribution of disease specific prion protein (PrP(d)) in scrapie-affected BM sheep were similar to scrapie in the Texel and Suffolk sheep. It was concluded that there was no evidence to suggest that scrapie in BM sheep differs clinicopathologically from scrapie in other breeds of sheep.  相似文献   

7.

The reproductive efficiency of sheep herds depends to a great extent on the ram. Male reproductive evaluation allows to select for the best and eliminate those with reproductive problems. The objective was to evaluate the effect of breed and age group on the reproductive behavior of hair sheep rams in the tropics of Mexico. Pelibuey (n?=?42), Blackbelly (n?=?30), Dorper (n?=?44), and Katahdin (n?=?30) rams of two age groups: young (n?=?74, 1–1.5 years old) and adult (n?=?72, 2–4 years old) were evaluated. Serving capacity (10-min duration) and breeding soundness evaluation (BSE) tests were carried out in each ram. In the first test, rams were classified as suitable and unsuitable, and in the BSE test, they were classified as satisfactory, questionable, or unsatisfactory. The response variables were analyzed using chi-square test or analyses of variance (ANOVA). ANOVA included the fixed effects of breed, age group, and their interaction. In the serving capacity test, 79.5% of the rams were considered suitable, with no breed differences (P?>?0.05). Adult rams (90.3%) had the highest proportion of suitable rams (P?<?0.05). In the BSE test, 80.2% of the rams were satisfactory; only breed being significant (P?<?0.05). Pelibuey breed had the highest proportion of satisfactory rams (91.4%). Breed × age interaction was no significant for any trait. After serving capacity and BSE tests, a high proportion of rams was found not suitable for reproduction (36.3%), which is expected to cause low fertility in the flock.

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8.
本研究旨在阐明低温环境对杜泊羊和萨福克羊生产性能的影响,并进一步探究其影响机制,为内蒙古地区杜泊羊和萨福克羊引种改良、杂交利用提供数据参考。试验选取12月龄体重相近、健康无病的杜泊羊和萨福克羊各20只(公母各半)进行研究,蒙古羊20只(公母各半)作为对照,测定3种羊的生理、血清生化指标及免疫性能并做对比研究。结果显示:杜泊羊和萨福克羊体温、呼吸频率及心率全天均无显著差异(P>0.05);与蒙古羊相比,杜泊羊和萨福克羊全天心率较低(P<0.05),且杜泊羊上午的体温显著低于蒙古羊(P<0.05),全天的呼吸频率显著高于蒙古羊(P<0.05)。杜泊羊和萨福克羊血清中谷丙转氨酶(ALT)、超氧化物歧化酶(SOD)活性及三碘甲腺原氨酸(T3)和甲状腺素(T4)水平与蒙古羊无显著差异(P>0.05),谷草转氨酶(AST)和碱性磷酸酶(AKP)活性显著高于蒙古羊(P<0.05);萨福克羊的乳酸脱氢酶(LDH)活性显著高于杜泊羊和蒙古羊(P<0.05)。与蒙古羊相比,杜泊羊和萨福克羊血清白介素2(IL-2)、白介素4(IL-4)、免疫球蛋白A(IgA)、免疫球蛋白M(IgM)及免疫球蛋白G(IgG)含量均无显著差异(P>0.05),但杜泊羊血清中IL-2的浓度显著高于萨福克羊(P<0.05)。综上所述,在内蒙古冬季低温环境下,杜泊羊和萨福克羊全天心率显著低于蒙古羊,血清中ALT和AKP活性显著高于蒙古羊;杜泊羊血清中LDH活性显著低于萨福克羊,IL-2的含量显著高于萨福克羊。除AST活性超出正常范围,杜泊羊和萨福克羊其余血清生化指标均在正常范围内。说明在内蒙古低温环境下,杜泊羊和萨福克羊可以维持正常的生理状态,并较好地适应内蒙古地区的环境气候。  相似文献   

9.
A postal census of vaginal prolapse in sheep flocks in the Borders region of Scotland yielded 540 replies from 963 owners (56 per cent). There were 262,250 ewes in 976 flocks and 2573 vaginal prolapses were reported. Analysis of the data revealed that 390 (40 per cent) of the flocks had no vaginal prolapses and in 237 (24.3 per cent) the reported prevalence was between 0.1 per cent and 1.0 per cent. Only 63 (6.5 per cent) of flocks had a greater than 5 per cent prevalence of vaginal prolapses. The greatest number of prolapses occurred in an upland flock of greyface ewes mated with Suffolk tups with 50 cases among 700 ewes (7.1 per cent) and the highest prevalence was in an upland Scottish blackface flock of ewes bred with Suffolk tups with 15.2 per cent (35 cases among 230 ewes). There were marked breed differences; very few hill breeds were affected and most cases occurred in greyface ewes mated with Suffolk tups.  相似文献   

10.
Heel contraction is an undesired but common condition in domestic horses. Some authors indicate shoeing as a risk factor. There is a correlation between shoeing and a restriction of heel expansion, but the clinical significance is unknown. This study aimed to evaluate the influence of shoeing and other risk factors, such as age, access to paddock, and breed, on heel contraction. This study included 114 horses, 55 of which were barefoot their whole life and 59 had been shod consistently for at least the previous year. The width and length of the frog were measured. Linear mixed-effects models were performed for the width:length ratio, where the fixed effects were age, sex, breed, pasture or paddock time, shoeing and its duration, and limb. The random effects included the horse and the yard. Although heel contraction occurs more often in shod horses compared with barefoot horses, the difference between the two conditions was not statistically significant, when other factors were considered. The most important factors that impacted contraction were individual horse features and breed (P < .001). The effect of age and a yard was noticed (P < 0,5). The sex, paddock time, and the shoeing and its duration were found not to have statistical significance. The study concluded that heel contraction is multifactorial problem, mainly caused by breed and unknown features correlated with individual. It was not confirmed that horseshoeing causes heel contraction. Because of significant difference in incidence of contraction between yards, there is a need to further investigation of environmental factors causing this hoof distortion.  相似文献   

11.
Granulocytic Ehrlichia infection in sheep is common in Norway in areas with Ixodes ricinus. In this study, 2 sheep flocks that had been grazing on I. ricinus infested pastures the previous season, were blood sampled after being housed indoors for nearly 6 months during wintertime. Thirty animals from each flock were examined for granulocytic Ehrlichia infection in the peripheral blood by blood inoculation studies, stained blood smear evaluation, polymerase chain reaction (PCR) analysis and serology (IFA-antibodies). The animals were sampled twice within a three-week period, the first time before and the second time after lambing. Two sheep in one flock were found Ehrlichia positive by both blood smear evaluation and PCR before lambing, and 3 sheep were found positive after lambing; 2 by blood smear examination and 3 by PCR. In the other flock, no sheep was found infected before lambing, but 2 ewes were found positive after lambing by both blood smear evaluation and PCR. In the first flock, 87% of the animals were found seropositive before lambing, and the mean antibody titre (log10 +/- SD) to E. equi was 2.45 +/- 0.401. In the second flock, 40% were found seropositive before lambing, and the mean antibody titre was 1.93 +/- 0.260. Seroprevalence and mean antibody titre in these 2 flocks were significantly different (p < 0.001). The present study indicates that sheep may be a reservoir host for granulocytic Ehrlichia infection from one grazing season to the next under natural conditions in Norway.  相似文献   

12.
This study evaluated the efficacy of prescribed fire applied within landscape-scale rotational grazing treatments to reduce mesquite (Prosopis glandulosa Torr.) encroachment and restore herbaceous productivity and cover. One-herd, multiple-paddock rotational grazing was used to accumulate herbaceous fine fuel for fires via prefire deferment and to provide periodic postfire deferment for grass recovery. Treatments were an unburned continuous-grazed control, a four-paddock-1 herd system with fire (4:1F), and an eight-paddock-1 herd system with fire (8:1F), with two replicates per treatment (1 294–2 130 ha per replicate). The management plan was to burn 25% of each system (one paddock in the 4:1F; two paddocks in the 8:1F treatments) and defer grazing during all or portions of the 9 mo (May to January) prior to burning. Deferral was “internalized” by grazing on the remaining 75% of each treatment without reducing stocking rate determined for the entire system. Mesquite cover increased on clay-loam soils from 22% to 40% in unburned paddocks over 7 yr (1995–2001). This increase, coupled with extended drought, reduced fine fuel amounts for fire and limited the number and intensity of fires that were applied. It was possible to burn one paddock in the 8:1F treatment (12.5% of total area), but not in the 4:1F treatment (25% of total area) during drought. Fires reduced mesquite and cactus (Opuntia spp.) cover by 25–79% and 24–56%, respectively, but cover of these species increased to prefire levels within 6 yr. All fires reduced (P ≤ 0.05) total herbaceous biomass for 1 yr postfire. The 8:1F treatment increased (P ≤ 0.05) grass biomass on loamy-bottom soils and reduced (P ≤ 0.05) bare ground on clay-loam and loamy-bottom soils in unburned paddocks compared to the unburned continuously grazed control. The 8:1F treatment, through internalized grazing deferment, facilitated the application of fire to reduce woody cover during extended drought without degrading the herbaceous understory.  相似文献   

13.
Lifetime production of first-generation 1/4 and 1/2 Finnsheep crossbred ewes from Rambouillet (R), Targhee (T) and Columbia (C) dams was compared with that from randomly selected purebred R, T and C ewes. All 1,190 ewes, representing nine breed groups, were managed under range conditions and mated annually to Suffolk rams. Lifetime production was evaluated as the total lamb and total wool production per ewe from the time each entered the breeding flock at 7 mo of age through the period each remained in the flock (potentially seven producing years). Culling was for debilitating unsoundness only. The study was designed to determine the average lifetime production per breed group as affected by natural ewe attrition. Orphan-reared lambs were not included in lamb production nor were foster lambs, except those actually born in and reared by the groups. Differences among pooled breed groups (1/4 Finns, 1/2 Finns and purebreds) were not significant for average final age in the flock (5.1, 5.1 and 4.9 yr, respectively), but differences were significant (P less than .01) for lifetime lamb and wool production. Average lifetime fleece weights of 1/4 and 1/2 Finn ewes were only 95 and 82% as high, respectively, as those of purebreds. However, 1/4 and 1/2 Finn ewes had 34 and 46%, respectively, higher numbers of lambs weaned (at 130 d) and 30 and 38% higher total weight of lamb weaned than purebreds.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

14.
The aim of this study was to determine the prevalence of pestivirus antibodies in sheep and goats in India. A total of 2803 serum samples collected between 2004 and 2008 from 1777 sheep in 92 flocks and 1026 goats in 63 flocks belonging to 13 states were tested by competition ELISA for detection of pestivirus antibodies. In sheep, the true prevalence rate was 23.4% (95% confidence interval: 22.9%–27.0%) and in goats it was 16.9% (95% CI: 16.4%–21.3%). The flock level seroprevalence was 66.3% for sheep and 54.0% for goats. Geographical variation in individual and flock prevalence was highly significant. A significant association (p?<?0.05) was found between sheep and goat flocks having cattle contact and the flock level seroprevalence. The seroprevalence was lower in 6 months–1 year age group compared to the 1–2 year and >2 year age groups in both sheep and goats. Cross neutralization studies on 61 seropositive sheep and 34 seropositive goat samples representing all positive flocks, exhibited > four fold higher titre to bovine viral diarrhoea virus type 1 (BVDV-1) in 41 sheep and 23 goat samples and to BVDV-2 in one sheep and goat each. This study for the first time showed serological evidence of wide spread BVDV infections in Indian sheep and goats, with BVDV-1 predominating and BVDV-2 occasionally besides highlighting the potential risk of infection to other species, which needs to be considered whenever BVD control measures are initiated.  相似文献   

15.
This study evaluates the effect of the number and sex of contemporary siblings on male-like play behavior of Suffolk lambs (Ovis aries). Fourteen males and 14 females, all single born, plus 26 ram lambs born co-twin to another male (n = 14) or female (n = 12) as well as 26 ewe lambs born co-twin to another male (n = 12) or female (n = 14) were observed daily for 7 weeks from 1 week of age. Two observers sitting outside a sand-bedded pen (10 × 5 m) recorded received and performed behavior (butts, nudging, attempts to mount, and mounts) by the lambs in the pen from 08:00 to 09:00 and 16:00 to 17:00 hours. Animals were in the pen only during the observation periods; the rest of the day they remained with their mothers in individual pens. Male-like play behavior patterns were displayed by both male and female lambs. Males were more active (P < 0.05) than females. Butting was the most frequent activity and performed mostly by ram lambs, recipients were generally males, and most resulted in reciprocal simultaneous encounters (sparring). Single males performed most of the nudging activity, which was the least frequent of the observed behaviors. Males with twin brothers mounted significantly (P < 0.05) more than males with twin sisters, and females with twin sisters performed the lowest amount of gutting and nudging. Lower (P < 0.05) levels of activity were found during the first 2 weeks. Overall, it was concluded that male lambs performed and received more male-like play behaviors than female lambs and the influence of sex of contemporary sibling was restricted to some behaviors: butting and nudging in females and mounting in males.  相似文献   

16.
Milk production and lamb growth were characterized in 118 multiparous, 3- to 7-yr-old Rambouillet, Columbia, Polypay, and Suffolk ewes under spring sage range and high mountain meadow grazing from 28 to 98 d postpartum. Daily milk yield as measured by the lamb suckling weight differential technique did not differ (P greater than .05) among breeds, although milk production of Suffolk ewes tended to be higher than that of the other three breeds. Within the Rambouillet, Columbia, and Polypay breeds, total estimated yield of ewes with twins was 13 to 17% higher than that of ewes with singles, whereas in the Suffolk breed, suckling twins increased total milk yield 61% over that of ewes with singles. Twin lambs induced a larger differential in dam milk production in late lactation (70 to 98 d) than in earlier lactation (28 to 70 d). Number of lambs did not influence milk protein, Ca, or P content (P greater than .05). Fat levels in colostrum and 4-d milk were elevated 14 and 20%, respectively, in ewes suckling twins compared with ewes suckling singles. Under range conditions, Suffolk ewes suckling single or twin lambs lost more BW (12 and 21% of 4-d postpartum body weight, respectively) than Rambouillet (4 and 7%), Columbia (5 and 8%), or Polypay (8 and 8%) ewes. Correlation coefficients of milk production and lamb growth rate were positive and significant (P less than .05) up to 56 d of age. Growth rate was less closely associated with milk production for twin than for single lambs.  相似文献   

17.
在紫花苜蓿混播草地放牧利用过程中,由于家畜行为对分区位置和放牧阶段的适应机制尚不清晰,制约了混播草地的科学利用和高效转化。本文研究了苜蓿混播草地分区位置和放牧阶段对绵羊活动距离和活动时间的影响。结果表明：放牧分区位置距离饮水点和休息区的距离每增加100 m,绵羊的活动距离增加2.42 km·d-1,活动时间增加46.74 min·d-1。不同放牧阶段草地质量差异明显,绵羊的活动距离和活动时间随着放牧阶段,即进入放牧分区后的天数增加而显著增加。绵羊通过改变活动距离和活动时间适应放牧分区位置和放牧阶段草地质量的变化,增加活动速率来适应草地质量的降低。苜蓿混播草地集约化放牧育肥时,饮水点和休息区距离放牧分区最远端的距离不宜超过198 m,每个分区放牧时间不宜超过4 d。研究结果可为苜蓿混播草地肉羊高效放牧育肥提供技术支撑。  相似文献   

18.
Abstract

Factors influencing rate of barren ewes, number of lambs born per pregnant ewe, and autumn live weight of the lambs were studied in 627 Norwegian sheep flocks based on herd level data from the Norwegian Sheep Recording System and a mailed questionnaire to the sheep farmers. The following factors were significantly associated (P<0.05) with rate of barren ewes: breed, herd average lambing date, type of production/age of farmer, routines for treatments for parasites, and housing type. Number of lambs born per pregnant ewe was significantly associated with rate of barren ewes, herd average lambing date, breed, percentage grass silage of total roughage, and no separation of gimmers during the housing period. Corrected autumn live weight of the lambs was significantly associated with breed, flock size, lambs born per pregnant ewe, no separation of gimmers during the housing period, and type of summer pasture.  相似文献   

19.
Chopped switchgrass (SG) and chopped bermudagrass (BG) were evaluated as alternatives to pine shavings (PS) for broiler litter over 3 flocks. Twenty-four pens were filled with the 3 litter types. Live performance parameters included mortality, BW, BW gain, feed consumption, and feed conversion. Mortality was not different for litter type or flock. All other live variables were different (P < 0.0001) for flock. Mean foot pad scores (FPS) were only different (P < 0.0001) for flock. Litter performance variables included litter and cake moisture content (MC), pH, litter ammonia concentration, and cake nutrient values [nitrogen, phosphorus, and potassium (N–P–K)]. Litter and cake MC differed by litter type and flock (P < 0.0001). Litter MC was 1% lower for SG than BG or PS. Cake depth observations were similar for litter type. Litter pH differed by flock (P = 0.008) while cake pH differed for both litter type (P = 0.05) and flock (P < 0.0001). Beginning and ending litter ammonia concentration were different for flock (P < 0.0001). Potassium was different for both litter type (P = 0.04) and flock (P < 0.0001) while nitrogen and phosphorus differed only by flock (P < 0.0001). Chopped SG and BG performed as well as PS as a litter material over 3 grow-out cycles. Based on the results of this study, chopped grass materials appear to be a viable alternative to PS for broiler bedding.  相似文献   

20.
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   

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