肉用绵羊与湖羊杂交产羔性能的研究

湖羊是分布于我国江苏、浙江两省太湖周边地区的高繁殖力绵羊品种 ,以耐高温、高湿、性成熟早、四季发情、多胎、高产著称。我们曾对湖羊产区吴县东山镇、西山镇两地进行过湖羊繁殖性能的调查和繁殖率选育研究 ,湖羊的平均产羔率为2 3 2 2 0 % ,东山湖羊资源保护区产羔率为 2 5 2 8% ,其中经选育保种的 14 8头高繁殖力基础母羊 ,产羔率高达 3 2 0 60 %。湖羊羔皮是我国传统的出口商品 ,在国际市场上享有软宝石美称。然而 ,随着社会的发展和人们消费习惯的变化 ,羔皮从 2 0世纪 90年代后逐渐失去了国际市场 ,而羊肉市场潜力看好。为适应市…     

Factors affecting dystocia and offspring vigour in different sheep genotypes

Birth difficulty and poor lamb vigour are significant causes of perinatal lamb mortality. In this study we investigated whether sheep breeds differing in appearance, muscularity and selection history also had differences in dystocia and lamb vigour, and considered some of the factors that may contribute to the variation in these traits. Data were collected at birth from a total of 3252 lambs of two terminal sire breeds selected for lean growth (Suffolk [S], n = 500 and Texel [T], n = 1207), from a Hill breed (Scottish Blackface [B], n = 610), which has been mainly selected for hardiness, and a crossbred (Mule × T [M], n = 935) representing a maternal line. For each lamb the degree of assistance at delivery, lamb presentation, amount of assistance to achieve successful sucking, sex, litter size and birth weight were recorded. T lambs required the most, and B and M lambs the least assistance at birth, S lambs were intermediate (% lambs assisted: T = 55.7, S = 30.7, B = 22.7, M = 24.9, P < 0.001). T and S lambs were equally likely to be malpresented at birth (29% of births) and more likely to be malpresented than B or M lambs (20%; P < 0.001). In T and S breeds lambs requiring veterinary assistance at delivery were mainly heavy and singleton lambs, whereas in B and M breeds these were exclusively low birth weight lambs in multiple litters. Although heavier lambs needed greater birth assistance, T lambs were lighter than S and M lambs, but heavier than B lambs (birth weight (kg): S = 4.66, M = 4.56, T = 4.32, B = 3.67, P < 0.001). S lambs were more likely to require assistance with sucking than other breeds, and T lambs also required more assistance than B or M lambs (% lambs assisted to suck: S = 56.0, T = 31.6, M = 19.8, B = 18.4, P < 0.001). Heavier lambs were more likely to suck unaided than lighter lambs (P < 0.001). The data suggest that the two terminal sire breeds, selected narrowly for greater productivity (muscle growth and conformation), are more likely to experience birth difficulty and poorer lamb vigour than the breed selected for hardiness, or the cross breed. Whether these effects arise as a consequence of genetic selection (e.g. for specific lamb conformation), or as a result of management practices to achieve selection goals (e.g. increased intervention at lambing) is unknown. Specific actions to improve birth difficulty and lamb vigour, such as including these traits in the selection index, would be beneficial in improving the welfare of ewes and lambs of the terminal sire breeds.     

Antibody response in sheep experimentally infected with different small ruminant lentivirus genotypes

Two groups of sheep were experimentally infected by intratracheal route with two small ruminant lentivirus (SRLV) isolates belonging to different genotypes (It-561 genotype A3 and It-Pi1 genotype B2). Seroconversion was evaluated using recombinant homologous and heterologous matrix protein/capsid antigen fusion protein. Results clearly indicate that seroconversion against homologous antigen was detected well in advance as regards heterologous antigen in both groups, although the advantage of using homologous antigen was less evident in detecting seroconversion against the caprine arthritis encephalitis virus (CAEV)-like strain, compared with the maedi-visna virus (MVV)-like infection. Commercially available ELISAs detect CAEV-like seroconversion earlier than MVV-like infection suggesting a closer relationship between CAEV-like isolate and the antigen used in the latter ELISA tests. Seven recombinant subunits developed from matrix protein and capsid antigen of strain K1514 (prototype A1) were used to better define the antibody response in sheep infected with It-561 isolate. Two animals clearly reacted against type specific epitopes in the early stage of infection. This study highlights the relative insensitivity of gag encoded cross-reacting epitopes during the early stage of infection and suggests the development of novel diagnostic tests based on both genotype specific antigens.     

Mapping PrPSc propagation in experimental and natural scrapie in sheep with different PrP genotypes

Twenty-one orally inoculated and seven naturally infected sheep with scrapie were examined for PrP(Sc) in peripheral tissues and in the central nervous system (CNS), using immunohistochemistry. In the inoculated group, VRQ (valine at codon 136, arginine at codon 154 and glutamine at codon 171)/VRQ sheep generally had a greater accumulation of the pathologic form of prion protein (PrP(Sc)) in peripheral tissues, as compared with VRQ/ARQ (alanine at codon 136, arginine at codon 154, and glutamine at codon 171) animals at corresponding time points after inoculation. PrP(Sc) was not detected in the ileal Peyer's patch, the spleen, the superficial cervical lymph node, and peripheral nervous tissues of several inoculated VRQ/ARQ animals. All inoculated VRQ/VRQ sheep, but only one of eight inoculated VRQ/ARQ animals, were PrP(Sc)-positive in the CNS. Thus, the propagation of PrP(Sc) seemed slower and more limited in VRQ/ARQ animals. Tissue and cellular localization of PrP(Sc) suggested that PrP(Sc) was disseminated through three different routes. PrP(Sc)-positive cells in lymph node sinuses and in lymphatics indicated spreading by lymph. The sequential appearance of PrP(Sc) in the peripheral nervous system and the CNS, with satellite cells as early targets, suggested the periaxonal transportation of PrP(Sc) through supportive cells. Focal areas of vascular amyloid-like PrP(Sc) in the brain of five sheep, suggested the hematogenous dissemination of PrP(Sc). There was a poor correlation between the amount of PrP(Sc) in the CNS and clinical signs. One subclinically affected sheep showed widespread PrP(Sc) accumulation in the CNS, whereas three sheep had early clinical signs without detectable PrP(Sc) in the CNS. A VV(136) (homozygous for valine at codon 136) sheep inoculated with ARQ/ARR (alanine at codon 136, arginine at codon 154, and arginine at codon 171) tissue succumbed to disease, demonstrating successful heterologous transmission. Less susceptible sheep receiving VRQ/VRQ or ARQ/ARR material were PrP(Sc)-negative by immunohistochemistry, enzyme-linked immunosorbent assay, and western blot.     

Frequent lambing of sheep flocks in Spain: productivity and management consequences

The first part of this paper reviews the Spanish literature dealing with the possibility of increased lambing frequency in Spanish flocks. Seasonal anoestrus occurs in all the Spanish breeds considered, although even in the most unfavourable month some sexual activity is observed, such as in Aragonesa flocks, where it reaches up to 80% in some years. The percentage of cyclical ewes in spring is favourably influenced by good feeding levels and by the introduction of males previously removed from the flock for a few months.In the second part we deal with the results obtained in several commercial farms in Aragon differing in mating management. No hormone treatments are used in these farms. In the farms where orderly and short matings are practised more lambings (1.39 vs. 1.29) and more lambs/ewe/year (1.76 vs. 1.40) are obtained than in those with continuous or nearly continuous mating periods. They can also choose the most favourable dates to obtain their lambs with regard to sale prices and ewe supplementary feed costs. In these conditions, Romanov × Aragonesa ewes give 40% more lambs/ewe than Aragonesa ewes without decreasing the number of lambings per year.     

不同MBL基因型绵羊感染绵羊肺炎支原体后的免疫相关因子表达规律分析

将32只2月龄中国美利奴羊人工感染绵羊肺炎支原体(MP),分别在攻毒前1 d(-1 d)、攻毒后1 d、7 d、14 d和21 d收集新鲜抗凝血,提取总RNA后应用Real-time PCR的方法定量检测细胞因子IL-2、IL-4、IFN-γ、TNF-α,补体C1、C3和甘露糖结合凝集素(MBL)。结果表明,不同MBL基因型绵羊攻毒感染后血清MBL浓度呈下降趋势,其中MBL浓度较高的C型和D型绵羊,其促炎因子IL-2、IFN-γ浓度较高,抗炎因子IL-4在攻毒后1d呈升高趋势,此后开始下降;MBL浓度较低的A型和B型绵羊,攻毒后其TNF-α浓度升高显著,随炎症的舒缓,逐渐降低;补体C1和C3在攻毒后表现出不同的变化,证实MP感染后,激活补体途径,可能与MBL的浓度变化有关。     

Molecular detection of Chlamydophila abortus in post-abortion sheep at oestrus and subsequent lambing

Enzootic abortion of ewes (EAE), resulting from infection with the bacterium Chlamydophila abortus (C. abortus), is a major cause of lamb loss in Europe. The purpose of this study was to assess the potential impact of the shedding of organisms in post-abortion ewes at oestrus and subsequent lambing on the epidemiology of EAE. Using a newly developed C. abortus specific real-time PCR assay, few chlamydial genomes could be detected in vaginal swabs taken from post-abortion ewes at oestrus. At subsequent parturition, all ewes lambed normally with no macroscopic or microbiological evidence of infection. Real-time PCR analysis of placental samples identified very few or no chlamydial genomes, which contrasted significantly with samples taken at the time of abortion, where an average of 2.7x10(7) chlamydial genomes per microgram of total tissue DNA was detected. Few genomes could also be detected from vaginal and cervical tissue samples and lymph nodes taken post-mortem. The results, although not discounting the possibility of a chronic low level persistent infection in post-abortion ewes, suggest that the low levels of chlamydial DNA detected during the periovulation period and at lambing do not significantly impact on the epidemiology of EAE. In terms of flock management, the products of abortion should be considered the major and principal source of infection for transmission to na?ve ewes.     

The peri-parturient rise in sheep. Faecal worm egg counts in normal and late lambing ewes

The trichostrongylid and strongylid egg output in a group of ewes lambing in March, the middle of the usual lambing time in the Netherlands, was compared with counts in groups of older ewes and yearling ewes lambing in May-June and with counts in a group of barren ewes. The groups lambing in March showed only a rise related to parturition date as normally seen in the Netherlands. A few of the late lambing ewes showed a slight rise in spring, but all of them showed a peri-parturient rise related to parturition date. In the late lambing ewes and in the barren ewes egg counts due to reinfection were seen in summer. It is concluded that under the present circumstances a true spring rise, the calendar phenomenon, occurs very irregularly, while a peri-parturient rise related to the parturition date is a common phenomenon. The occurence of high egg counts in summer, excluding consideration on the barren ewes, in the late lambing ewes only, suggests that changing the traditional husbandry system may influence the epidemiological pattern of the trichostrongylid infections.     

呼伦贝尔短尾羊产前补饲精喂对家畜个体特征及生产效益的影响

在内蒙古草原牧区,冬季对绵羊补饲精喂的研究具有重要的意义。为研究产羔前对母畜舍饲精料后,呼伦贝尔短尾羊体重、体尺及经济效益的变化,本研究选取60对待产的呼伦贝尔短尾母绵羊作为试验对象,在母畜产羔前一个月,试验组母畜舍饲精料,对照组仅补饲干草,分析100日龄内家畜体重、体尺及经济效益变化。利用方差及偏最小二乘回归法,分析产前补饲对家畜个体、生产效益的影响及影响家畜体重的主要体尺权重,结果显示,100 d时间段内,母畜体重呈先减少后增加的趋势;仔畜出生后一个月左右的时间段,试验组仔畜的胸围、胸宽、体高、胸深、体长和体斜长显著高于对照组(P<0.05)。影响呼伦贝尔短尾羊体重的主要体尺指标为:胸围、胸宽、体高和胸深,影响权重达到50%以上。补饲使得仔畜的成活率、出售价格显著高于未进行补饲的对照组(P<0.05)。通过补饲母畜不仅可以影响仔畜体重和体尺指标,而且对提高仔畜成活率和经济效益具有重要的作用,这为今后后备母羊的选育、家畜的精准淘汰提供了理论基础。     

Cortisol in pregnancy toxaemia of sheep

Of 31 pregnant ewes with clinical signs of pregnancy toxaemia, 24 had hypoglycaemia and hyperketonaemia at the time that a single blood sample was obtained. Twenty-five of these had a plasma cortisol concentration in excess of 10 ng/ml and six had a value below this. All the seven animals which did not show both hypoglycaemia and hyperketonaemia had a plasma cortisol concentration in excess of 10 ng/ml. Taking all the sheep together, 80% had a high plasma cortisol concentration. This could be the consequence of increased adrenal output or reduced excretion by the liver.     

Coxiella burnetii shedding and environmental contamination at lambing in two highly naturally-infected dairy sheep flocks after vaccination

Abortion due to Coxiella burnetii was confirmed in the 2007/08 season in two naturally-infected dairy sheep flocks. Proportion of C. burnetii shedders and bacterial loads in vaginal mucus were high among aborted or lambed ewes, as was within-flock seroprevalence. Before the next reproductive season (2008/09) 75% of ewes and 50% of replacement lambs were vaccinated (Coxevac, CEVA Santé Animale) keeping the remaining as untreated controls. Compared with the previous year results when abortion outbreak started, a great reduction in the percentage of abortions, in the number of shedders and in the bacterial burden excreted by the ewes was found in both flocks. However, seroconversion in non-vaccinated yearlings from both flocks and the presence of C. burnetii DNA in bioaerosols taken at sheep premises at lambing indicated that infection was still active. No differences were observed between vaccinated and control groups in terms of proportion of C. burnetii shedders. These results suggest that optimal results of vaccination in heavily infected flocks may not be obtained in a short-term period.     

Coxiella burnetii shedding and environmental contamination at lambing in two highly naturally-infected dairy sheep flocks after vaccination

Abortion due to Coxiella burnetii was confirmed in the 2007/08 season in two naturally-infected dairy sheep flocks. Proportion of C. burnetii shedders and bacterial loads in vaginal mucus were high among aborted or lambed ewes, as was within-flock seroprevalence. Before the next reproductive season (2008/09) 75% of ewes and 50% of replacement lambs were vaccinated (Coxevac, CEVA Santé Animale) keeping the remaining as untreated controls. Compared with the previous year results when abortion outbreak started, a great reduction in the percentage of abortions, in the number of shedders and in the bacterial burden excreted by the ewes was found in both flocks. However, seroconversion in non-vaccinated yearlings from both flocks and the presence of C. burnetii DNA in bioaerosols taken at sheep premises at lambing indicated that infection was still active. No differences were observed between vaccinated and control groups in terms of proportion of C. burnetii shedders. These results suggest that optimal results of vaccination in heavily infected flocks may not be obtained in a short-term period.     

PrP genotypes of rare breeds of sheep in Great Britain

In total 31,669 blood samples were collected from 1187 flocks of 27 rare breeds of sheep in the UK, and their genotype profiles at the prion protein locus were determined. The frequencies of the five alleles varied widely among the breeds and some had only two of the alleles and others had all five; the average was three. The average allele frequencies across all 27 breeds were 49.7 per cent for ARR, 4.4 per cent for AHQ, 2.7 per cent for ARH, 37.4 per cent for ARQ and 5.8 per cent for VRQ. The highest frequencies for each allele were 90.7 per cent for ARR in the Leicester Longwool, 24.7 per cent for AHQ in the Hebridean, 68.7 per cent for ARH in the Manx Loghtan, 98.7 per cent for ARQ in the North Ronaldsay and 28.4 per cent for VRQ in the Boreray. All 27 breeds had the ARR allele, 21 had AHQ, 11 had ARH, 26 had ARQ and 20 had VRQ.     

Small ruminant lentivirus genetic subgroups associate with sheep TMEM154 genotypes

Small ruminant lentiviruses (SRLVs) are prevalent in North American sheep and a major cause of production losses for the U.S. sheep industry. Sheep susceptibility to SRLV infection is influenced by genetic variation within the ovine transmembrane 154 gene (TMEM154). Animals with either of two distinct TMEM154 haplotypes that both encode glutamate at position 35 of the protein (E35) are at greater risk of SRLV infection than those homozygous with a lysine (K35) haplotype. Prior to this study, it was unknown if TMEM154 associations with infection are influenced by SRLV genetic subgroups. Accordingly, our goals were to characterize SRLVs naturally infecting sheep from a diverse U.S. Midwestern flock and test them for associations with TMEM154 E35K genotypes. Two regions of the SRLV genome were targeted for proviral amplification, cloning, sequence analysis, and association testing with TMEM154 E35K genotypes: gag and the transmembrane region of env. Independent analyses of gag and env sequences showed that they clustered in two subgroups (1 and 2), they were distinct from SRLV subtypes originating from Europe, and that subgroup 1 associated with hemizygous and homozygous TMEM154 K35 genotypes and subgroup 2 with hemi- and homozygous E35 genotypes (gag p < 0.001, env p = 0.01). These results indicate that SRLVs in the U.S. have adapted to infect sheep with specific TMEM154 E35K genotypes. Consequently, both host and SRLV genotypes affect the relative risk of SRLV infection in sheep.     

青海绵羊与不同品种肉羊杂交筛选试验

在常规放牧条件下,用陶赛特羊(D)、渡德代羊(B)、特克塞尔羊(T)等肉羊为父本,小尾寒羊(X)、青海当地绵羊--山谷型藏羊(Q)为母本,分4个杂交组合进行筛选试验.结果表明:DX、BX组的初生、1月龄、3月龄、6月龄、8月龄平均体重极显著地高于同龄当地羔羊(P＜0.01);DQ、TQ组的初生、1月龄、3月龄、6月龄、8月龄平均体重显著高于同龄当地羔羊(P＜0.05);杂种羊的体长、胸围等体尺也有较大提高;DX、BX、DQ组8月龄杂种羊胴体重极显著高于同龄当地羔羊(P＜0.01);TQ组8月龄杂种羊胴体重显著高于同龄当地羔羊(P＜0.05);杂种羔的屠宰率也高于同龄当地羔羊,且肉质与当地羊相同,体形均趋向父本,肌肉丰满,适应性强.因而,DX、BX、DQ、TQ组合都优于对照组,但DX、DQ组合最优.即利用无角陶赛特羊不论改良当地绵羊,还是引进的小尾寒羊,效果最佳.