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)     

Blood biochemistry values of sheep (Ovis aries ligeriensis)

1. Analysis of biochemical parameters were carried out on material pooled from 30 female sheep (Ovis aries ligeriensis). 2. The values determined were for the common metabolites and enzymes utilized for specific studies in general metabolism (urea, glucose, cholesterol, lipids, bilirubin, uric acid, creatinine, alkaline phosphatase, GOT, GPT, LDH, LAP, CGT, CK and amylase). 3. Results of these studies were compared with values from normal human adults. 4. The differences obtained in human and sheep ranges can be explained by the different physiology of the two species. 5. This study gives values for the sheep as an experimental animal in biomedical research.     

Sister chromatid exchange in chromosomes of sheep (Ovis aries)

Blood lymphocyte cultures from 32 Comisana and Laticauda sheep breeds (15 males and 17 females) raised in Southern Italy were studied using sister chromatid exchange (SCE) test. Of the 932 cells studied, the SCE-mean value was 7.20 +/- 2.5 per cell for both breeds. Indeed, the SCE mean values were 7.12 +/- 2.45 and 7.28 +/- 2.55 in Comisana and Laticauda breeds, respectively, and the differences were not significant. No statistical differences were noticed between male and female cells (7.25 +/- 2.39 and 7.16 +/- 2.60, respectively). The SCE frequency distribution did not follow a Poisson distribution. The number of SCE were significantly higher than expected in chromosomes 1, 2 and 3 (p < 0.001) and significantly lower than expected in the X and remaining chromosomes (p < 0.001) on the basis of relative chromosome lengths.     

Physiological and genetic characteristics of black-boned sheep (Ovis aries)

Here we report for the first time the discovery of sheep that have black bones and black muscles. The spectral pattern of pigment extracted from tissues of these black-boned sheep is similar to that of black-boned Chinese silky fowl. Additionally, black-boned sheep have significantly higher plasma colour, tyrosinase activity and kidney function than normal sheep. Synonymous nucleotide substitutions in the tyrosinase (TYR) and melanocortin 1 receptor (MC1R) genes were detected in black-boned sheep when compared with the corresponding sequences in normal sheep. In addition, a missense mutation (215T>C) in exon 2 of tyrosinase-related protein 1 (TYRP1) was detected in black-boned sheep, and this resulted in a putative valine-to-alanine substitution at codon 68 (Val68Ala).     

A novel maternal lineage revealed in sheep (Ovis aries)

It is generally believed that domestic sheep have two maternal lineages (haplotypes A and B), based on mitochondrial DNA analysis. In the present study, we provide evidence that a novel maternal lineage (haplotype C) is exhibited in Chinese native sheep. To verify this finding, 231 samples were collected from six Chinese local breeds, which cover the vast geographical region of sheep inhabitation in China. For comparison, 50 samples were collected from two Western breeds collected in China. Mitochondrial DNA was screened by PCR single-strand conformational polymorphism (SSCP), leading to the identification of novel band patterns in ND2 and ND4 genes in the Chinese breeds. Interestingly, mutations at the two loci were in strong linkage disequilibrium. Direct sequencing of the DNA fragments revealed a non-synonymous substitution in ND2. Furthermore, two synonymous mutations were identified by comparisons of the novel type (haplotype C) and the established types (haplotypes A and B). The entire mitochondrial control region for 55 samples was then sequenced to construct a phylogenetic tree and median joining network. Both the tree and network demonstrated a topology of three groups, which is in consistent with the SSCP analysis. Unlike Western breeds, Chinese breeds are composed mainly of haplotypes A and B, but with a small fraction of haplotype C. According to Fu's test and mismatch distribution, haplotype C has not been subject to a recent population expansion. Based on these results, we propose a novel origin for Chinese sheep.     

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.     

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.     

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     

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.     

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.     

The primary-secondary rumen contraction and gas expulsion in sheep (Ovis aries)

1. Sheep rumens were insufflated with nitrogen to 5, 10, 15 and 20 cm HOH pressure and sustained at each pressure for 5 min. 2. Measurements included rumen motility, reticulorumen myoelectrical activity, eructation frequency and volume, and changes in tracheal pressure. 3. Associated with elevated intrarumen pressure was a previously unreported type of rumen contraction on which gas expulsion occurred, the primary-secondary contraction. 4. Gas expulsion volume was similar on primary-secondary and secondary contractions. 5. The maximum rumen contraction rate per min was 4-5 for secondaries and 1-2 for primary-secondaries. 6. Irrespective of the sustained initial pressure, resting intrarumen pressure was reached within 5 min.     

Mechanics of locomotion of dogs (Canis familiaris) and sheep (Ovis aries)

Records have been made of the forces exerted on the ground by dogs and a sheep, in walking, trotting, cantering and slow galloping. Film has been taken simultaneously. The difference between walking and trotting was much less marked for the sheep than for the dogs.
Step length and stride length increase as speed increases. They are expressed as functions of the Froude number.
The vertical component of the force exerted by a foot on the ground shows two main maxima in walking, except in the case of the fore feet of sheep. In this case and in other gaits there is only one main maximum. The vertical movements of the fore and hind quarters which occurred in examples of each gait have been calculated from the force records.
The force exerted by a foot on the ground changes direction in the course of a step so as to remain more or less in line with a point fixed relative to the animal, but dorsal to its back.
The force records show impact disturbances in the first 003 sec of contact of each foot with the ground.
The point of application of the force on the sole of a foot tends to move posteriorly as the force increases.
The results are discussed in relation to a theoretical account of the mechanics of locomotion on legs.     

Elevated intra-rumen pressure and secondary rumen contractions in sheep (Ovis aries)

1. Sheep rumens were insufflated with nitrogen to 5, 10, 15, and 20 cm water pressure and sustained at each pressure for 10 min. 2. Measurements included rumen motility, reticulorumen myoelectric activity, eructation frequency and volume, changes in tracheal pressure and rumen contraction amplitude. 3. As intra-rumen pressure increased, contractions designated as special secondary contractions appeared. 4. At a pressure of approximately 15 cm water, most of the special secondary contractions became regular secondaries; therefore, the special secondaries were called pro-secondary contractions. 5. Increased intra-rumen pressure was associated with respiratory distress. The recovery phase following, rumen insufflation was accompanied by hyperpnea.     

Ecology and behaviour of domestic sheep (Ovis aries): a review

Behaviour of sheep is complex and poorly understood. It is only within the past 20 years that a concerted effort has been made to elucidate those aspects of behaviour which have most relevance to sheep raising under open-range conditions. The present report attempts to summarize and review published work on the behaviour and ecology of sheep. The whole question of the significance of behaviour and the extent to which it is possible to shape it is a field which is open for study. This paper is an attempt to summarize the work on sheep behaviour and on those aspects of physiology which impinge. Consideration is given to the evolution of Bovids, scope of domestication and world distribution of sheep since these aspects have a major influence on the sheep with which we deal today. Animal requirements for food, water, shelter, protection from predators, and control of disease and parasites have been largely met by man and the forces for selection which operated among the progenitors of domestic sheep have been largely negated. Despite this, genetic selection still goes on. Behavioural adaptation to a wide variety of environmental and nutritional regimes is a common feature among free-ranging sheep. Reproductive success, a matter of considerable commercial concern is often poor. Lamb survival is of critical importance. Factors involved in neonatal mortality are reviewed in detail. Finally, the now extensive literature on sheep behaviour, physiology and management is collated in a bibliography with over 150 literature citations.     

NADPH-dependent inhibition of lipid peroxidation in rat liver microsomes.

Microsomal NADPH-driven electron transport is known to initiate lipid peroxidation by activating oxygen in the presence of iron. This pro-oxidant effect can mask an antioxidant function of NADPH-driven electron transport in microsomes via vitamin E recycling from its phenoxyl radicals formed in the course of peroxidation. To test this hypothesis we studied the effects of NADPH on the endogenous vitamin E content and lipid peroxidation induced in liver microsomes by an oxidation system independent of iron: an azo-initiator of peroxyl radicals, 2,2'-azobis (2,4-dimethylvaleronitrile), (AMVN), in the presence of an iron chelator deferoxamine. We found that under conditions NADPH: (i) inhibited lipid peroxidation; (ii) this inhibitory effect was less pronounced in microsomes from vitamin E-deficient rats than in microsomes from normal rats; (iii) protected vitamin E from oxidative destruction; (iv) reduced chromanoxyl radicals of vitamin E homologue with a 6-carbon side-chain, chromanol-alpha-C-6. Thus NADPH-driven electron transport may function both to initiate and/or inhibit lipid peroxidation in microsomes depending on the availability of transition metal catalysts.