Comparison of pulmonary defense mechanisms in Rocky Mountain bighorn (Ovis canadensis canadensis) and domestic sheep

Alveolar macrophages were obtained from Rocky Mountain bighorn sheep (Ovis canadensis canadensis) and domestic sheep for the purpose of comparing pulmonary host defense mechanisms in the two species. Specific variables studied included (1) characterization of the cell types present in the lung, (2) alveolar macrophage phagocytic and bactericidal functions, (3) measurement of protein levels in lavage fluid, and (4) measurement of cortisol levels in lavage fluid. While phagocytic cell populations were similar between bighorn and domestic sheep, a significantly higher percentage of lymphocytes were present in bighorns than domestics (20% in bighorn versus 6% in domestic sheep). Significant differences were not observed in the phagocytic or bactericidal functions of macrophages between the two species. Significant differences were not observed in either lavage fluid protein levels or in cortisol levels.     

Genomic association with pathogen carriage in bighorn sheep (Ovis canadensis)

Genetic composition can influence host susceptibility to, and transmission of, pathogens, with potential population‐level consequences. In bighorn sheep (Ovis canadensis), pneumonia epidemics caused by Mycoplasma ovipneumoniae have been associated with severe population declines and limited recovery across North America. Adult survivors either clear the infection or act as carriers that continually shed M. ovipneumoniae and expose their susceptible offspring, resulting in high rates of lamb mortality for years following the outbreak event. Here, we investigated the influence of genomic composition on persistent carriage of M. ovipneumoniae in a well‐studied bighorn sheep herd in the Wallowa Mountains of Oregon, USA. Using 10,605 SNPs generated using RADseq technology for 25 female bighorn sheep, we assessed genomic diversity metrics and employed family‐based genome‐wide association methodologies to understand variant association and genetic architecture underlying chronic carriage. We observed no differences among genome‐wide diversity metrics (heterozygosity and allelic richness) between groups. However, we identified two variant loci of interest and seven associated candidate genes, which may influence carriage status. Further, we found that the SNP panel explained ~55% of the phenotypic variance (SNP‐based heritability) for M. ovipneumoniae carriage, though there was considerable uncertainty in these estimates. While small sample sizes limit conclusions drawn here, our study represents one of the first to assess the genomic factors influencing chronic carriage of a pathogen in a wild population and lays a foundation for understanding genomic influence on pathogen persistence in bighorn sheep and other wildlife populations. Future research should incorporate additional individuals as well as distinct herds to further explore the genomic basis of chronic carriage.     

Psoroptic scabies in Rocky Mountain bighorn sheep (Ovis canadensis canadensis) from Wyoming

Thirteen Rocky Mountain bighorn sheep (Ovis canadensis canadensis) with clinical signs of psoroptic scabies were captured in Wyoming. Signs included droopy ears, depilation on the head and neck, and exudate in the ears. Mites were identified as either Psoroptes cervinus or P. equi. Two ewes with scabies at the time of original capture had no clinical signs of mite infection 1 and 2 yr later.     

Seroprevalence of Toxoplasma gondii in Rocky Mountain bighorn sheep (Ovis canadensis)

Serum samples from 697 Rocky Mountain bighorn sheep (Ovis canadensis) from North America were examined for antibodies to Toxoplasma gondii by the modified agglutination test incorporating mercaptoethanol and formalin-fixed tachyzoites. Antibodies to T. gondii were found in 25 of 697 (3.6%) sheep in titers of 1:25 (8 sheep), 1:50 (4 sheep), 1:100 (7 sheep), 1:200 (1 sheep), 1:400 (1 sheep), 1:800 (1 sheep), and 1:1,600 (3 sheep). This is the first record of T. gondii exposure in bighorn sheep.     

Resolving ambiguities in the karyotype of domestic sheep (Ovis aries)

Internally consistent G-, Q- and R-banded karyotypes and idiograms for sheep chromosomes at the 422-band level of resolution are presented. These were derived by sequential Q- to G-staining, and sequential Q- to R-staining of prometaphase spreads prepared from sheep with normal and Robertsonian chromosomes. The fused chromosomes served as stable morphological markers. To minimise confusion due to chromosomal nomenclature, we have listed chromosome-specific (reference) molecular markers that have been mapped byin situ hybridization to sheep chromosomes. The use of molecular markers in conjunction with the sequential Q- to G- and sequential Q- to R-banded karyotypes and iodiograms provided here will elimiate ambiguities in identifying and numbering sheep chromosomes and will facilitate their comparison with cattle chromosomes. Edited by: J.B. Rattner     

Squamous cell carcinoma in a free-ranging bighorn sheep (Ovis canadensis californiana)

An oral squamous cell carcinoma which invaded maxillary bones with metastasis to the right retropharyngeal lymph node was diagnosed in a free-ranging California bighorn sheep (Ovis canadensis californiana) from Washington. Much of the maxillae had been replaced with tumor and reactive tissue, and many teeth were missing or loose. The tumor was predominantly confined to the shape of the maxillary bones and was unusual because it was bilaterally symmetrical.     

Resolving ambiguities in the karyotype of domestic sheep (Ovis aries)

The unambiguous identification of ovine chromsomes has become essential for the mapping of the sheep genome, which predominantly consists of telocentric chromosomes of gradually decreasing size. Nucleolus organizer regions (NORs) and Robertsonian fusions have been used here as the cytological and morphological markers, respectively, to define the banding pattern of eight paris of sheep telocentric chromosomes that have an ambiguous identification status. Five Robertsonian chromosomes involving most of the ambiguous chromosomes as well as normal prometaphase chromosomes were stained sequentially and separately by QFQ, GTG, and Ag-NOR methodologies. The prometaphase banding patterns of the ambiguous chromosomes 4, 6, 8, 9, 21, 24, 25 and 26 are represented schematically. For providing an accurate image of the banding pattern, a system of shading has been employed to show the relative intensity of bands in a given chromosome. The results presented here will facilitate the regional mapping of the sheep genome, extend the information on cytogenetic homology with other bovids, and substantially accelerate the comparative mapping studies in Bovidae.     

Mitochondrial DNA variation of domestic sheep (Ovis aries) in Kenya

The history of domestic sheep (Ovis aries) in Africa remains largely unknown. After being first introduced from the Near East, sheep gradually spread through the African continent with pastoral societies. The eastern part of Africa was important either for the first diffusion of sheep southward or for putative secondary introductions from the Arabian Peninsula or southern Asia. We analysed mitochondrial DNA control region sequences of 91 domestic sheep from Kenya and found a high diversity of matrilines from the widespread haplogroup B, whereas only a single individual from haplogroup A was detected. Our phylogeography analyses of more than 500 available mitochondrial DNA sequences also identified ancestral haplotypes that were probably first introduced in Africa and are now widely distributed. Moreover, we found no evidence of an admixture between East and West African sheep. The presence of shared haplotypes in eastern and ancient southern African sheep suggests the possible southward movement of sheep along the eastern part of Africa. Finally, we found no evidence of an extensive introduction of sheep from southern Asia into Africa via the Indian Ocean trade. The overall findings on the phylogeography of East African domestic sheep set the grounds for understanding the origin and subsequent movements of sheep in Africa. The richness of maternal lineages in Kenyan breeds is of prime importance for future conservation and breeding programmes.     

Bloat in sheep (Ovis aries)

1. Most of the field studies on bloat are conducted with cattle and most of the laboratory experiments seeking to explain the various parameters associated with bloat are done with sheep. 2. Based on grazing behaviour, it would be expected that sheep might bloat more severely than cattle because they selectively choose to eat leaves over stems and chew what they ingest more frequently than cattle. Furthermore, sheep appear to select legumes over grasses because the legumes can be eaten more rapidly. However, because they are selective, sheep eat more slowly than cattle. Despite a higher bloat expectation, bloating in sheep is reported to be less of a problem than in cattle. 3. Although frothing of rumen ingesta was described earlier in cattle as the cause of acute legume bloat, experiments with frothy bloat in sheep preceded those in cattle. 4. Anti-frothing agents were used in sheep before cattle to treat acute legume bloat. 5. Experiments devoted to the study of eructation in ruminants were carried out on sheep, then cattle. 6. Convincing evidence that rumen motility does not cease during acute legume bloat was gathered using sheep. 7. Although the transected tracheal technique for the determination of the volume of eructated gas was developed with cattle, the pathway of eructated gas was confirmed with sheep. 8. All the current evidence accumulated from experiments with sheep supports the hypothesis that death due to legume bloat is caused by acute neural, respiratory, and cardiovascular insult resulting from the effect of the distended rumen on thoracic viscera, diaphragm, intercostal muscles, and the abdominal vena cava. 9. Experiments with sheep and cattle being fed scabrous and nonscabrous diets similar in chemical composition show that sheep are more resistant than cattle to the increase in intrarumen pressure, decline in rumen contraction amplitude, and decrease in rumen contraction frequency caused by nonscabrous diets. 10. The sequence of events in the reticulorumen during primary and secondary contractions previously described following visual and palpation experiments with cattle was confirmed by the use of myoelectrodes implanted in the various sacs of the reticulorumen of sheep. 11. Elevated intrarumen pressure is associated with an increase in the frequency of primary (mixing) and secondary (eructation) contractions (more secondaries than primaries).(ABSTRACT TRUNCATED AT 400 WORDS)     

Interspecific transfer of IVM IVF-derived red sheep (Ovis orientalis gmelini ) embryos to domestic sheep (Ovis aries )

Two embryo production methodologies were investigated to generate Red sheep embryos for use in an interspecific embryo transfer program. In Experiment 1, 4 multiparous female Red sheep (Ovis orientalis gmelini ) were implanted with CIDR type G devices for 11 d. Forty-eight hours prior to CIDR removal, a total of 22.5 mg bid of FSH-P was administered over a 3-d period. Laparoscopic embryo collection was performed 5 d post breeding, and embryos were transferred to domestic recipient ewes (Ovis aries and Ovis orientalis musimon ). In Experiment 2, 7 nulliparous female Red sheep were implanted with CIDR devices and injected with 200 IU of PMSG and 25 mg of FSH-P on the 8th day of implant insertion. At 60 to 70 h post PMSG/FSH-P treatment, follicular oocytes were aspirated laparoscopically. The recovered oocytes were matured in M199 (with fetal calf serum, FSH, LH, penicillin and streptomycin) at 39 degrees C in a humidified atmosphere containing 5% CO(2). At 24 h oocytes were fertilized with frozen-thawed semen at a concentration of 1.6 x 10(6) sperm/ml. The ova/embryos were placed in CR2 or BOEC culture medium at 20-22 h post IVF. Following 3 to 4 d in culture, embryos were transferred laparoscopically to the uterine horn of synchronized recipients. In Experiment 1, 4 embryos and 6 UFO were collected from 2 embryo donors, respectively. Two embryos were transferred with the aid of a laparoscope to each of 2 Rambouillet recipients, one of which gave birth to a healthy Red sheep lamb at 158 d of gestation. In Experiment2, a total of 62 oocytes was collected from 7 oocyte donors; 16 developed to the 16- to 32-cell stage and were transferred to 8 recipients. Three of these IVM-IVF embryos were transferred laparoscopically to 2 Mouflon recipients, resulting in no pregnancies. Thirteen IVM-IVF embryos were transferred to 6 Rambouillet recipients. Each of these gave birth to a single healthy Red sheep lamb. Gestation lengths of the 3 IVM-IVF lambs ranged from 152 to 162 d. This research demonstrates that when using compatible species IVM-IVF technology in conjunction with interspecific ET can lead to the production of live offspring and can be used to propagate exotic ovine species.     

Grooming in desert bighorn sheep (Ovis canadensis mexicana) and the ghost of parasites past

Ectoparasites such as ticks have a negative effect on host fitness,whereas parasite-defense grooming is effective in removing ticks.The central control (programmed grooming) model proposes thatanimals engage in preventive tick-defense grooming in responseto an internal timing mechanism, even in the absence of peripheralstimulation from parasites. This model predicts that smalleranimals will groom more frequently than larger ones becauseof the higher cost of parasitism for a small animal (body sizeprinciple). The peripheral stimulation (stimulus driven) modelpredicts no size-related differences in grooming rate in theabsence of tick bite irritation. We observed grooming behaviorin a Chihuahuan desert population of bighorn sheep (Ovis canadensismexicana), where ticks have been absent for perhaps thousandsof years. Although not exposed to ticks, bighorns self groomedby means of oral and scratch grooming, albeit at very low ratescompared to size-matched ungulates in both tick-infested andtick-free environments. Logistic regression and general linearmodels revealed both the probability that grooming was performedduring a 10-min focal sample and the rate of grooming when itoccurred was greater for younger, smaller age/sex categoriesof less body mass. Oral and scratch grooming were negativelyassociated with body mass during both years, with juveniles(X = 15 kg) grooming the most frequently and the oldest males(X = 70–85 kg) grooming the least. Assuming that programmedgrooming evolved in a tick-infested environment, the currentgrooming behavior of this population is a relict of their ancestralenvironment, an adaptation to the "ghost of parasites past."     

Birthdate and survival in bighorn lambs (Ovis canadensis)

The relationship between parturition date and lamb survival was investigated among individually marked bighorn ewes in south-western Alberta, Canada. Lambs were born from 17 May to 21 July. Most births occurred in the first two weeks of the lambing period. Lambs born in May enjoyed greater survival than lambs born in June and July. The viability of lambs born after 10 June was extremely low. Inadequate nutrition is suggested as the cause of greater mortality of lateborn lambs. Ewes that give birth late are at an earlier stage of lactation when forage quality declines and may not produce sufficient milk to ensure lamb survival. Their lambs have access to high-quality forage for a shortened period. The proportion of late lambs appeared to be correlated with ewe density in the winter range.     

Response of vaccinated and unvaccinated bighorn sheep (Ovis canadensis canadensis) to experimental respiratory syncytial virus challenge

Five Rocky Mountain bighorn sheep (Ovis canadensis canadensis), approximately 5 mo old and without detectable antibody titers to respiratory syncytial virus (RSV), were assigned to two groups to study the effects of RSV challenge inoculation in vaccinated (n = 3) and unvaccinated (n = 2) bighorns. The three lambs vaccinated with a modified live bovine RSV vaccine developed a detectable antibody response to the vaccine. Vaccinated and unvaccinated lambs challenged with an ovine isolate of RSV developed increased levels of neutralizing antibody, but clinical signs of disease were not observed. Neutralizing antibody titers to RSV remained higher (2-4-fold) in vaccinated lambs over time when compared to unvaccinated lambs.