Reproductive,behavioral, and endocrine characteristics of the Dall's sheep (Ovis dalli dalli)

Failed interspecific embryo transfer between Dall's sheep (Ovis dalli dalli) and domestic ewes (Ovis aries), and a paucity of physiological data available for the Dall's sheep, provided incentive for developing a reproductive database in Dall's sheep. Urine samples were collected on a regular basis from a captive herd of Dall's sheep during the breeding to lambing interval over a 3 year period. To provide comparative endocrine data during pregnancy, samples also were collected during a single gestation period from five Suffolk ewes. All urine samples were analyzed for pregnanediol-3-glucuronide (PdG) and estrone conjugates (EC). Behavioral observations from Dall's sheep were made each year during the rut and lambing periods to calculate estrous cycle and gestation lengths. Placentas from Dall's sheep (n = 20) and Suffolk ewes (n = 10) were collected, the total number of cotyledons counted, and the length, width, area, and weight of eight cotyledons/horn from each placenta calculated. Endocrine and behavioral results indicated that the Dall's sheep is seasonally polyestrous and monovulatory, with a mean estrous cycle length of 18.2 ± 0.3 days, a mean luteal phase of 11.8 ± 0.5 days, and an average gestation length of 171.6 ± 0.9 days. While hormonal patterns for pregnancy generally were similar between the two species, there was a pronounced difference in the magnitude of hormone concentrations, particularly PdG, and an absence of a marked preparturition EC rise in domestic sheep. Cotyledon numbers, weight, and area were smaller (P < 0.05) in the Dall's sheep, compared to Suffolk ewes. These data suggest that unsuccessful interspecies embryo transfer attempts may have been due to failed fetal/maternal communications resulting from hormonal and/or placental differences. © 1996 Wiley-Liss, Inc.     

Protostrongylid parasites and pneumonia in captive and wild thinhorn sheep (Ovis dalli)

We describe health significance of protostrongylid parasites (Parelaphostrongylus odocoilei and Protostrongylus stilesi) and other respiratory pathogens in more than 50 naturally infected Dall's sheep (Ovis dalli dalli) from the Mackenzie Mountains, Northwest Territories (1998-2002) as well as in three Stone's sheep (O. d. stonei) experimentally infected with P. odocoilei (2000-2002). Histological lesions in the brain and distribution of P. odocoilei in the muscles of experimentally and naturally infected sheep were consistent with a previously hypothesized "central nervous system to muscle" pattern of migration for P. odocoilei. Dimensions of granulomas associated with eggs of P. odocoilei and density of protostrongylid eggs and larvae in the cranial lung correlated with intensity of larvae in feces, and all varied with season of collection. Prevalence of P. stilesi based on the presence of larvae in feces underestimated true prevalence (based on examination of lungs) in wild Dall's sheep collected in summer and fall. Similarly, counts of both types of protostrongylid larvae in feces were unreliable indicators of parasitic infection in wild Dall's sheep with concomitant bacterial pneumonia associated with Arcanobacterium pyogenes, Pasteurella sp., and Mannheimia sp. Diffuse, interstitial pneumonia due to P. odocoilei led to fatal pulmonary hemorrhage and edema after exertion in one experimentally infected Stone's sheep and one naturally infected Dall's sheep. Bacterial and verminous pneumonia associated with pathogens endemic in wild Dall's sheep in the Mackenzie Mountains caused sporadic mortalities. There was no evidence of respiratory viruses or bacterial strains associated with domestic ruminants, from which this population of wild sheep has been historically isolated.     

Survival of bighorn sheep (Ovis canadensis) commingled with domestic sheep (Ovis aries) in the absence of Mycoplasma ovipneumoniae

To test the hypothesis that Mycoplasma ovipneumoniae is an important agent of the bighorn sheep (Ovis canadensis) pneumonia that has previously inevitably followed experimental commingling with domestic sheep (Ovis aries), we commingled M. ovipneumoniae-free domestic and bighorn sheep (n=4 each). One bighorn sheep died with acute pneumonia 90 days after commingling, but the other three remained healthy for >100 days. This unprecedented survival rate is significantly different (P=0.002) from that of previous bighorn-domestic sheep contact studies but similar to (P>0.05) bighorn sheep survival following commingling with other ungulates. The absence of epizootic respiratory disease in this experiment supports the hypothesized role of M. ovipneumoniae as a key pathogen of epizootic pneumonia in bighorn sheep commingled with domestic sheep.     

Cranial asymmetry in a Dall sheep ram (Ovis dalli dalli).

The horns of a 13-yr-old Dall sheep ram (Ovis dalli dalli) from the Sheep Mountain herd in Kluane National Park (Yukon, Canada) had unique characteristics. The right horn was 1,127 mm long, while the left horn was only 861 mm long and compressed and distorted at its base. The reduced growth of the left horn was due to chronic epidermitis and osteomyelitis of the cornual process, which began when the ram was 5 yr of age.     

Population genetic structure of North American thinhorn sheep (Ovis dalli)

The thinhorn sheep (Ovis dalli ssp.) provides a rare example of a North American large mammal that occupies most of its native range and maintains close to ancestral population size. There are currently two recognized subspecies, Dall's sheep (O. d. dalli) and Stone's sheep (O. d. stonei), the validity of which remains uncertain. We investigated the spatial genetic structure of thinhorn sheep populations representing both subspecies by genotyping individuals (n = 919) from across the species range at 12 variable microsatellite loci. We found high levels of genetic diversity within (HE = 0.722) and significant genetic structure among the 24 sampled areas (FST = 0.160). Genetic distance measures and Bayesian clustering analyses revealed the presence of at least eight subpopulations that are delineated by mountain range topology. A strong overall pattern of isolation-by-distance is evident across the sampling range (r = 0.75, P < 0.001) suggesting limited dispersal and extensive philopatry. Partial Mantel tests of this relationship showed mountain range distinctions represent significant barriers to gene flow (P = 0.0001), supporting the Bayesian analyses. Genetic structure was more strongly pronounced in southern Yukon and Alaska than elsewhere. We also show evidence for genetic differences between the two currently recognized thinhorn subspecies.     

Mate Guarding in Male Dall's Porpoises (Phocoenoides dalli)

Mate guarding, whereby a male closely attends and defends a fertile female from extra‐pair matings, is one mating tactic males of many species use to protect their paternity. Although female defense occurs in many species of terrestrial mammal, comparable examples among cetaceans are largely absent, potentially as a result of the wide dispersion and mobility of females and their prey. Here, we investigate whether the close association of individual male Dall's porpoises with individual females during the breeding season is consistent with mate guarding. As mate guarding is predicted to be costly, and in other taxa is often associated with a reduction in foraging efficiency, we also examine whether males trade‐off this activity with time at depth. Males maintained longer associations and closer distances with female partners than with male ones. They also surfaced in greater synchrony with, and more often approached, their female partners than male ones. In contrast to males with male partners, males paired with females engaged in agonistic interactions with other adult males, and infrequently affiliated with extra‐pair individuals. These data suggest males are actively attempting to maintain their associations with females, while also acting to reduce female extra‐pair copulations and increase their own paternity. Guarding males also undertook shorter dives than non‐guarding males, suggesting that they trade‐off time at depth with guarding. Such a trade‐off is likely to involve a reduction in foraging opportunities, due to a decrease in time spent at foraging depth. Mate guarding in this species may be facilitated by the relatively smaller size and decreased mobility of newly calved, estrous females, particularly if females also benefit from guarding.     

Parasites of the Dall's porpoise (Phocoenoides dalli True)

The prevalences of three helminths, Campula oblonga, Halocercus dalli and Crassicauda sp., recovered from Dall's porpoises which were net-entrapped incidentally in the vicinity of the Western Aleutian Islands in the northwest Pacific are reported. Specimens of Campula oblonga were found within the bile ducts of 46% of 127 livers examined. The prevalence of hepatic trematodiasis increased with the age of the host. Pulmonary nodules associated with Halocercus dalli were noted in 71% of the Dall's porpoises. Adult H. dalli were recovered from the main stem bronchi of heavily infected lungs. Younger animals exhibited a relatively higher prevalence. Specimens of Crassicauda sp. were found within the main lactiferous canal of 69% of 29 mammary glands examined. The prevalence was highest in mature porpoises. Possible detrimental effects and the modes of transmission of the three species of parasites are also considered.     

盘羊肺炎支原体感染PCR 检测方法的建立与初步应用

羊支原体性肺炎,是由支原体引起的一类高度接触性传染病,又称羊传染性胸膜肺炎(Infections pleuropneumonia of sheep and goats),临床症状主要表现为高热、咳嗽、消瘦、     

Muskox lungworm (Umingmakstrongylus pallikuukensis) does not establish in experimentally exposed thinhorn sheep (Ovis dalli)

Muskoxen (Ovibos moschlatus moschatus) on the northwestern mainland of Nunavut and Northwest Territories, Canada, are infected with the protostrongylid lungworm, Umingmaksrongylus pallikuuhkensis. The geographic range of this muskox population is expanding to the south and west, and it is anticipated that these animals will eventually become sympatric with Dall's sheep (Ovis dalli dalli) in the Mackenzie and Richardson Mountains. To address the concern of wildlife managers that U. pallikulkensis may infect and adversely affect Dalls sheep, four Dalls/Stone's (Ovis dalli stonei) hybrid lambs and one adult muskox (Ovibos moschatus wardi) were each given 100 third-stage larvae of U. pallikuukensis. All animals were intensively monitored for 9 mo postinfection (PI) using clinical examinations, fecal analyses, hematology, blood chiemistry and medical imaging. No first-stage larvae of U. pallikuinkensis were recovered from the lambs and monitoring revealed nio evidence that the parasite had established in any of these animals. First-stage larvae were found in the feces of the muskox beginning at 94 days PI, and typical parasite cysts were visible in lung radiographs at 188 days PI. This study addresses an important management and wildlife health issue associated with the potential for host-switching of pathogens and indicates that it is improbable that thinhorn sheep are suitable hosts for U. pallikuukensis.     

Development and pathogenesis of Parelaphostrongylus odocoilei (nematoda: protostrongylidae) in experimentally infected thinhorn sheep (Ovis dalli )

Recently, the protostrongylid nematode Parelaphostrongylus odocoilei has been reported in a new host species, thinhorn sheep (Ovis dalli). For the first time, we completed the life cycle of P. odocoilei in three Stone's sheep (O. dalli stonei) and two thinhorn hybrids (O. dalli stonei x O. dalli dalli), each infected with 200 third-stage larvae from slugs (Deroceras laeve). The prepatent period ranged from 68 days to 74 days, and shedding of first-stage larvae (L1) peaked at >10,000 L1 per gram of feces between 90 and 110 days postinfection. A total of 75, 27, and 14 adult P. odocoilei were recovered from skeletal muscles of three Stone's sheep. Starting in the prepatent period, all infected sheep lost weight and developed peripheral eosinophilia. At 2 wk before patency, two thinhorn hybrids developed neurologic signs (hind end ataxia, loss of conscious proprioception, and hyperesthesia) that resolved at patency. Eosinophilic pleocytosis and antibody to Parelaphostrongylus spp. were detected in the cerebrospinal fluid of the affected sheep, suggesting that the migration route of the "muscleworm" P. odocoilei may involve the central nervous system. Twenty days after treatment with ivermectin, neurologic signs recurred and larval shedding ceased in one infected thinhorn hybrid, whereas multiple treatments transiently suppressed but did not eliminate larval shedding in the other. During patency, two Stone's sheep with numerous eggs and larvae of P. odocoilei in the lungs died of respiratory failure following anesthesia or exertion. Parelaphostrongylus odocoilei has widespread geographic distribution, high prevalence, the possibility of causing neurologic and respiratory disease, resistance to treatment, and may constitute a significant emerging disease risk for thinhorn sheep.     

Detecting the signature of selection on immune genes in highly structured populations of wild sheep (Ovis dalli)

The confounding effects of population structure complicate efforts to identify regions of the genome under the influence of selection in natural populations. Here we test for evidence of selection in three genes involved in vertebrate immune function - the major histocompatibility complex (MHC), interferon gamma (IFNG) and natural resistance associated macrophage polymorphism (NRAMP) - in highly structured populations of wild thinhorn sheep (Ovis dalli). We examined patterns of variation at microsatellite loci linked to these gene regions and at the DNA sequence level. Simple Watterson's tests indicated balancing selection at all three gene regions. However, evidence for selection was confounded by population structure, as the Watterson's test statistics from linked markers were not outside of the range of values from unlinked and presumably neutral microsatellites. The translated coding sequences of thinhorn IFNG and NRAMP are fixed and identical to those of domestic sheep (Ovis aries). In contrast, the thinhorn MHC DRB locus shows significant evidence of overdominance through both an excess of nonsynonymous substitution and trans-species polymorphism. The failure to detect balancing selection at microsatellite loci linked to the MHC is likely the result of recombination between the markers and expressed gene regions.     

Horn growth rate and longevity: implications for natural and artificial selection in thinhorn sheep (Ovis dalli)

We used horn measurements from natural and hunted mortalities of male thinhorn sheep Ovis dalli from Yukon Territory, Canada, to examine the relationship between rapid growth early in life and longevity. We found that rapid growth was associated with reduced longevity for sheep aged 5 years and older for both the hunted and natural mortality data sets. The negative relationship between growth rate and longevity in hunted sheep can at least partially be explained by morphologically biased hunting regulations. The same trend was evident from natural mortalities from populations that were not hunted or underwent very limited hunting, suggesting a naturally imposed mortality cost directly or indirectly associated with rapid growth. Age and growth rate were both positively associated with horn size at death for both data sets, however of the two growth rate appeared to be a better predictor. Large horn size can be achieved both by individuals that grow horns rapidly and by those that have greater longevity, and the trade-off between growth rate and longevity could limit horn size evolution in this species. The similarity in the relationship between growth rate and longevity for hunted and natural mortalities suggests that horn growth rate should not respond to artificial selection. Our study highlights the need for the existence and study of protected populations to properly assess the impacts of selective harvesting.     

Eimeria dalli sp. n. (Protozoa: Eimeriidae) from Dall Sheep Ovis dalli

Eimeria dalli sp. n. is described from fecal samples collected from Dall sheep, Ovis dalli, from the Kenai Peninsula, Alaska. The oocysts are spherical or subspherical with mean dimensions of 43.7 × 37.4 μm. The outer oocyst wall is rough and irregular. No micropyle, micropylar cap or residuum was observed. Sporocysts were elongate ovoid with mean dimensions of 19.0 × 10.7 μm. Stieda bodies were not discernible.     

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)