Sheep Bedding Research Articles

FEATURES OF POLYURETHANE MATRIX REMODELING IN SHEEP MODEL EXPERIMENTS

HighlightsThe article describes the features of remodeling of polyurethane matrices during long-term implantation into the vascular bed of sheep. The results indicate high biocompatibility of polyurethane and resistance to bioresorption. The obtained data are significant for the development of medical products for cardiovascular surgery, in particular, biodegradable vascular prostheses. AbstractAim. To evaluate the features of polyurethane remodeling in a long-term experiment on a large animal model.Methods. Matrices made of 12% polyurethane solution in chloroform were manufactured by electrospinning at the Nanon-01A nanofiber electrospinning system (MIC, Japan). Matrix samples in the form of patches were implanted into the carotid arteries of sheep (n = 3) for a period of 6 months. The patency of vessels with implanted matrices was assessed after 2, 4 and 6 months using a portable hand-carried color Doppler - M7 Premium Ultrasound Machine (Mindray, China). The structure of the matrix surface before and after implantation was studied using an S-3400N scanning electron microscope (Hitachi, Japan). Histological examination of the explanted samples was carried out using an AXIO Imager A1 microscope (Carl Zeiss, Oberkochen, Germany) with previous staining of matrix sections with hematoxylin-eosin, Van Gieson and alizarin red C. Data processing was performed using the Statistica 6.0 software.Results. After 2, 4 and 6 months of implantation of polyurethane matrices into the carotid artery of sheep, complete patency of the carotid arteries was revealed. Macroscopically, after 6 months of implantation, the matrix completely resembled the carotid artery wall due to the full consolidation of the matrix with the artery wall and remodeling. Layers of newly formed vascular tissue – neointima and neoadventitia – were formed on the basis of the matrix. Histological examination revealed the structural integrity of the matrix without signs of inflammation and calcification both in the matrix structure and adjacent tissues.Conclusion. The biological inertia of polyurethane matrices with signs of remodeling was noted, which indicates a high biocompatibility of the material. Resistance to bioresorption and the ability to keep the frame of the product for a long time allows us to consider polyurethane as a suitable material for the formation of anti-aneurysmal protection of biodegradable vascular prostheses.

Evaluation of farm yard manure (sheep bedding) on the soil fertility, leaf mineral composition, and growth performance of oil palm seedlings

This study was conducted to evaluate the growth performance and leaf mineral composition of oil palm seedlings as influenced by the application of sheep manure. Partially decomposed farmyard manure from sheep was mixed with soil and filled into polybags (28 cm x 35 cm lay flat) in proportions as treatments: (25% soil: 75% FYM); (50% soil: 50% FYM); (75% soil: 25% FYM); and (100% soil + NPK 15:15:15) as control. The treatments were laid out in Randomized Complete Block Design (RCBD) with four (4) replications. Assessment was made for morphological growth (plant height, leaf number, and butt circumference), physiological growth (crown and root biomass) and leaf nutrients status analysed for N, P, K, Ca and Mg. There was no significant (p ≤ 0.05) difference observed in growth parameters. It was however observed that treatments with a higher amount of manure (25% soil: 75% FYM) showed significantly (p ≤ 0.05) higher biomass production than the control. The leaf nutrients analysis for N, P, K, Ca and Mg indicated lower concentration than their respective optimum levels. This study revealed that oil palm seedlings can grow well on soil amended with farmyard manure from sheep and that higher percentage of 25% soil: 75% FYM seem more promising. The FYM application will help boost the vegetative growth of oil palm seedling thus reducing inorganic fertilizer application in the nursery.

Estimated Reduction in Solids During Sheep Bedding Composting as a Function of the Composition of the Organic Fractions

ABSTRACTThe different organic matter fractions of residues significantly impact the degradability of organic material in composting windrows. Based on that, this study aimed to find out the organic matter fractions that most impact the breakdown rate during composting, besides proposing models to estimate the solids reductions in sheep bedding composting windrows. To that end, 24 sheep beddings from different locations and varied composition were composted so as to ensure the representativeness of the sample. The models found for reduction in total (TS) and volatile (VS) solids as a function of compostable organic matter (COM) and organic matter resistant to composting (OMRC) were not significant. Lignin had correlation coefficients of −0.6, −0.89, and −0.84 in relation to temperature, TS reduction, and VS reduction, respectively. The hemicellulose:lignin ratio was the parameter most correlated with temperature (0.69), TS reduction (0.91), VS reduction (0.92), and nitrogen (0.5), which led to more significant predictive models. It can be concluded that the hemicellulose:lignin ratio is the parameter that most impacts the breakdown of organic matter and nitrogen losses in sheep bedding composting windrows.

Addition of cattle manure to sheep bedding allows vermicomposting process and improves vermicompost quality

Animal waste is usually a good substrate for vermicomposting. However, numerous animal husbandry systems use bedding that consists primarily of lignocellulosic substrates, which hinders earthworm and microorganism’s development and thus, the entire bioconversion process. One possible solution is to mix the used bedding with other waste materials that are more amenable to earthworm ingestion and can provide better conditions for earthworm population growth. Here, we have aimed to examine the effectiveness of such procedure by mixing rice-husk-based sheep bedding with cattle manure in different proportions (0%, 25%, 50%, 75% and 100%). We have carried out vermicomposting experiments in benchtop vermireactors inoculated with 0.88kg of dry matter (sheep bedding+cattle manure). Data used in the Principal Component Analysis were the multiple vermicomposting variables (i.e., EC; pH; HA/FA and C/N ratios; P, K, cellulose, and hemicellulose content). The effect of the treatment on earthworm count was analyzed with ANOVA. We have observed that the addition of at least 25% of cattle manure to sheep bedding allows vermicomposting process but it is necessary 148days to obtain a stabilized vermicompost. However, increasing the proportion of cattle manure to sheep bedding, the vermicomposting time decreases proportionally to 94days. We concluded that vermicomposting can be considered a bioprocess to stabilize rice husk after being used as sheep bedding.

The anaerobic co-digestion of sheep bedding and ⩾50% cattle manure increases biogas production and improves biofertilizer quality

Sheep manure pellets are peculiarly shaped as small ‘capsules’ of limited permeability and thus are difficult to degrade. Fragmentation of manure pellets into a homogeneous mass is important for decomposition by microorganisms, and occurs naturally by physical shearing due to animal trampling, when sheep bedding is used. However, the high lignocellulose content of sheep bedding may limit decomposition of sheep manure. Here, we evaluated if co-digestion of sheep bedding with cattle manure would improve the yield and quality of the useful products of anaerobic digestion of sheep bedding—biogas and biofertilizer—by providing a source of nutrients and readily available carbon. Mixtures of sheep bedding and cattle manure in varying proportions (0%, 25%, 50%, 75%, or 100% cattle manure) were added to 6-L digesters, used in a batch system, and analyzed by uni and multivariate statistical tools. PC1, which explained 64.96% of data variability, can be referred to as ‘organic fraction/productivity’, because higher rates of organic fraction consumption (COD, cellulose and hemicellulose contents) led to higher digester productivity (biogas production, nutrient concentration, and sample stability changes). Therefore, productivity and organic fraction variables were most influenced by manure mixtures with higher (⩾50%) or lower (⩽25%) ratios of cattle manure, respectively. Increasing the amount of cattle manure up to 50% enhanced the biogas potential production from 142Lkg−1TS (0% of cattle manure) to 165, 171, 160Lbiogaskg−1TS for the mixtures containing 100%, 75% and 50% of cattle manure, respectively. Our results show that the addition of ⩾50% cattle manure to the mixture increases biogas production and improves the quality of the final biofertilizer.

Improving the nutrient content of sheep bedding compost by adding cattle manure

Abstract Sheep bedding has favorable characteristics for composting, such as providing readily assimilable carbon and facilitating aeration, which are essential for the growth of composting microorganisms. However, when composted alone, it may have disadvantages related to the time of composting and to the fertilizer value of the compost produced, due to its high lignocellulosic content. To investigate whether cattle manure could improve composting of sheep bedding as well as the agronomic quality of the compost produced, we mixed cattle manure with sheep bedding in varying proportions (0–100%) and evaluated several parameters of the composting process and of the final compost, such as changes in temperature, macronutrients, and carbon content before and after the composting process. The addition of ≥50% cattle manure to the mixture increased composting efficiency, resulting in a more stable compost with higher nutrient content. The high content of rice husk in sheep bedding limited the addition of higher proportions of this component to the composting mixture. We identified an efficient way to improve the quality of compost generated during waste management of sheep manure and bedding.

Sheep Bedding in the Centennial Mountains of Montana and Idaho: Effects on Vegetation

ABSTRACT. In summer, bands of sheep are grazed in western North American mountains. At night the sheep are concentrated into bedding areas. In the study area, each bedding area is only utilized by sheep for one night a year for 2 out of 3 years. Vegetation in the bedding areas was compared to vegetation outside these areas. Both perennial forb cover and total perennial cover were greater outside (48% and 61%, respectively) than inside (29% and 36%, respectively) the bedding areas. Annual forb cover one year after sheep grazing was greater inside (17%) bedding areas than outside (5%). Immediately after sheep bedding, total forb cover was greater outside the bedding areas. Forb and grass biomass were greater outside the bedding areas compared to inside. Total vegetation biomass outside (240 g · m-2) the bedding areas was more than double the amount inside (86 g · m-2) immediately after bedding. In the year after bedding, vegetation biomass inside the bedding areas increased, but was still less than outside....

IMPACT OF SHEEP BEDDING ON SOIL NUTRIENT DYNAMICS IN THE CENTENNIAL MOUNTAINS OF MONTANA AND IDAHO

Sheep and lamb production is an important industry in Idaho, with summer sheep grazing in the mountains a common practice. Sheep are concentrated in bedding areas at night leading to concentrated grazing and manure and urine accumulation in these areas. To address the effects of bedding on soil nutrient status, we monitored 16 bedding areas in the Centennial Mountains, with a general survey performed in 2004 followed by more intense monitoring of six sites from 2005 to 2006. In 2004, soils were analyzed for total carbon (C) and nitrogen (N), organic C, total P, Olsen P, water-soluble phosphorus (WSP), soluble nitrate, and soluble ammonium. Over the period 2005-2006, soils were analyzed for soluble nutrients including Olsen P, WSP, soluble nitrate, and soluble ammonium. The 16 sites evaluated in 2004 had significantly greater total N, C, and organic C concentrations in the nonbedded areas, whereas Olsen P, WSP, and ammonium concentrations were greater in the bedding areas. When six sites were monitored over time, there was no significant effect of bedding on soluble P concentrations over time or between bedding and control areas, whereas there was a significant effect of time on soluble N concentrations but no significant differences between bedding and control areas. Although these results are preliminary, it seems as if sheep bedding can alter the nutrient content of soils increasing some measures of soil nutrients, while decreasing others, which ultimately can affect the productivity and plant species diversity in these areas.

Effects of undernutrition in early pregnancy on systemic small artery function in late-gestation fetal sheep

Objective: The aim of this study was to investigate functional development of small arteries from the skeletal circulation of fetal sheep and to determine whether maternal undernutrition affects responses to vasoconstrictive and vasodilatory agonists in arteries from the late-gestation fetus. Study Design: We investigated vasoconstrictive and vasodilatory responses of isolated small (approximately 300 μm) arteries from the femoral vascular bed of fetal sheep and from late-gestation pregnant ewes. Ewes were fed either 100% of the nutritional requirement throughout pregnancy (control group) or a restricted diet of 85% or 50% of the nutritional requirement for the first 70 days of pregnancy. For the remainder of pregnancy all ewes were fed the complete diet. Results: Among control group animals vasoconstriction in response to norepinephrine was well developed in fetuses at 0.6 and 0.9 gestation with respect to that in the ewes. When expressed as a percentage of the response to 125-mmol/L potassium (to correct for differences in vessel size and muscle mass), maximum constriction in response to norepinephrine was greater in fetal vessels from 0.9 gestation than in either those at 0.6 gestation or those of the ewes. Endothelium-dependent vasorelaxation responses to acetylcholine and bradykinin were also well developed in fetuses at 0.6 and 0.9 gestation and were similar to those in the ewes. In fetuses at 0.9 gestation the 50% nutritional restriction of the ewe led to blunted endothelium-dependent vasodilatation in response to acetylcholine and blunted endothelium-independent vasodilatation in response to sodium nitroprusside. Responses in the fetuses at 0.9 gestation in which the ewes were fed a restricted diet of 85% were normal. Conclusion: This study shows that from midgestation onward small arteries from the skeletal circulation of the fetal sheep have the functional capacity to respond to norepinephrine and endothelium-dependent vasodilators (eg, acetylcholine and bradykinin). The blunted responses to acetylcholine and sodium nitroprusside in the fetuses at 0.9 gestation among the group of dietarily restricted ewes (restricted diet of 50% group) were indicative of impaired vascular smooth muscle sensitivity to nitric oxide. This defect may contribute to the development of hypertension in later life. (Am J Obstet Gynecol 2000;183:1301-7.)

Effect of inhibitors of nitric oxide release and action on vascular tone in isolated lungs of pig, sheep, dog and man.

1. The actions of inhibitors of the release or action of nitric oxide (NO) on pulmonary vascular resistance (PVR) were investigated in lungs isolated from pig, sheep, dog and man. 2. In pig, sheep and human lungs perfused with Krebs-dextran solution, both N omega-nitro-L-arginine methyl ester (L-NAME; 10(-5) M) and Methylene Blue (10(-4) M) increased basal PVR. This increase was reversed by sodium nitroprusside (10(-5) M). In pig lungs N omega-monomethyl-L-arginine (10(-4) M) increased PVR by 154%. This increase was partially reversed by L-arginine (10(-3) M). L-NAME had no effect in dog lungs. 3. Pulmonary artery pressure-flow (PPA/Q) relationships were studied over a wide range of flows. In pigs, sheep and human lungs perfused with Krebs-dextran solution, L-NAME increased the PPA/Q slope. This increase was reversed by sodium nitroprusside. In dog lungs L-NAME had no effect. 4. In blood-perfused lungs, the respective responses to L-NAME were similar to those observed with saline. Acute hypoxia in pig and dog lungs increased intercept pressure. Addition of L-NAME during hypoxia increased the PPA/Q slope in both species. 5. In the human, there was no difference in the absolute increase of PVR or PPA/Q slope elicited by L-NAME between hypertensive and control lungs. 6. We conclude that NO is continuously released in the pulmonary vascular bed of pig, sheep and humans under normoxic conditions. In dog lungs inhibition of NO synthesis increases PVR only under hypoxic conditions. In human lungs with pulmonary hypertension, NO is still released under basal conditions.

Regional Variation of Postjunctional α- Adrenoceptor Responses in the Developing Renal Vascular Bed of Sheep

Postjunctional alpha 1- and alpha 2-adrenoceptor vasoconstrictor responses were evaluated in isolated segments of main renal artery, segmental renal artery, and renal vein from fetal (130-138 d of gestation; term 145 d), newborn (3-15 d age), and nonpregnant adult sheep. Vascular rings were mounted at their optimal resting tension and responses to phenylephrine (alpha 1-adrenoceptor agonist) and guanabenz and UK14304 (both alpha 2-adrenoceptor agonists) were determined. Optimal resting tension increases with development in the main renal artery, segmental renal artery, and renal vein of sheep. Arterial vessels develop more isometric tension to alpha 1-adrenoceptor stimulation than to alpha 2-adrenoceptor stimulation, whereas venous segments develop similar isometric tension to alpha 1- and alpha 2-adrenoceptor stimulation. The segmental renal artery develops more isometric tension to alpha 2-adrenoceptor stimulation than the main renal artery. No large developmental differences exist among vessels in the sensitivity (concentration required for half maximal response, ED50) to alpha-adrenoceptor stimulation except for the renal vein with alpha 2-adrenoceptor stimulation. Maximum isometric tension corrected for vessel cross-sectional area decreases with age for all vessels with both alpha 1- and alpha 2-adrenoceptor stimulation. These findings may reflect developmental differences in receptor number and affinity or differences in vascular smooth muscle function. In addition, these data suggest that whereas both alpha 1- and alpha 2-adrenoceptors mediate vasoconstriction in the renal circulation, they may do so at different sites.

Effects of epinephrine on the renal vascular bed of fetal, newborn, and adult sheep.

The renal hemodynamic response to renal artery infusions of epinephrine were compared in conscious and chronically instrumented fetal (125-139 days gestation; term 145 days), newborn (5-13 days postnatal), and nonpregnant adult sheep. Epinephrine produced similar dose related decreases in renal blood flow velocity in all three groups. The mean estimated concentration of epinephrine in renal blood producing a 50% decrease in renal blood flow velocity, ED50, was 0.008 microgram/ml. Epinephrine infusions during renal alpha-adrenoceptor blockade with phentolamine produced increases in renal blood flow velocity that were of greater magnitude in fetal compared to newborn and adult sheep. The maximal increase in renal blood flow velocity observed were 57 +/- 11%, 22 +/- 3%, and 18 +/- 3% in fetal, newborn, and adult sheep, respectively (p less than 0.001). This vasodilation produced by epinephrine during alpha-adrenoceptor blockade was completely inhibited by ICI 118,551, a beta 2-adrenoceptor antagonist. Inhibition of renal vascular beta-adrenoceptors with propranolol in fetal sheep did not enhance alpha-adrenoceptor-mediated renal vasoconstriction with epinephrine infusions. Results of the present study demonstrate similar renal vasoconstrictor responses to renal artery infusion of epinephrine in fetal, newborn, and adult sheep. In contrast, the renal vasodilator responses observed with epinephrine infusions during renal alpha-adrenoceptor blockade were greater in fetal compared to newborn and adult sheep. However, epinephrine-mediated renal vasoconstriction was not enhanced by blockade of beta-adrenoceptors in fetal sheep.

Ontogeny of alpha-adrenoceptor responses in renal vascular bed of sheep.

The renal hemodynamic response to renal arterial infusions of guanabenz (alpha 2-adrenoceptor agonist) and phenylephrine (alpha 1-adrenoceptor agonist) were compared in conscious and chronically instrumented fetal (132-140 days gestation; term 145 days), newborn (6-15 days postnatal), and nonpregnant adult sheep. Phenylephrine produced similar dose-related decreases in renal blood flow velocity in all three groups at low concentrations (less than 1.8 X 10(-7) M) of drug in renal blood, whereas at the highest concentration adults demonstrated the most vasoconstriction and newborns the least (P less than 0.05 ANOVA). Responses to phenylephrine infusion during renal alpha 1-adrenoceptor blockade with prazosin were completely inhibited. Guanabenz produced greater renal vasoconstriction in adult sheep (P less than 0.05 ANOVA) at all concentrations (0.6 X 10(-6) to 8 X 10(-6) M) when compared with fetal and newborn sheep. Guanabenz-mediated vasoconstriction was not affected by alpha 1-adrenoceptor blockade with prazosin but was completely inhibited by the addition of an alpha 2-adrenoceptor antagonist idazoxan. Results of the present study demonstrate that renal vasoconstriction is mediated by both alpha 1- and alpha 2-adrenoceptors in fetal, newborn, and adult sheep. Moreover, these results suggest that renal alpha 1- and alpha 2-adrenoceptor-mediated vasoconstrictor responses mature at different rates.

Effects of dopamine in the renal vascular bed of fetal, newborn, and adult sheep.

The renal hemodynamic response to renal arterial dopamine infusions was compared in unanesthetized fetal (129-137 days gestation, full term 145 days), newborn, and adult sheep. Mean arterial blood pressure and heart rate remained unchanged during intrarenal dopamine infusions. Dopamine produced dose-related decreases in mean renal blood flow velocity in all three groups. When compared with adult sheep fetal sheep were slightly more sensitive to the vasoconstrictive effects of dopamine ED50 (mean effective dose ratio: fetus/ED50 adult = 0.368 +/- 0.047, P less than 0.05). Increases in mean renal blood flow velocity were not seen at any dose given (1-16 micrograms/kg body wt in fetuses, 2-32 micrograms/kg body wt in newborns and adults) until dopamine was infused during alpha- and beta-adrenoceptor blockade. The largest mean increase in renal flow velocity was 13 +/- 3, 16 +/- 3, and 17 +/- 4% in fetal, newborn, and adult sheep, respectively. cis-Flupentixol inhibited the vasodilation. This study demonstrates the presence of renal vasodilation following renal arterial dopamine infusions in fetal, newborn, and adult sheep when renal alpha- and beta-adrenoceptors are blocked. Vasodilator responses are similar in all three groups, and increases in renal blood flow velocity are small compared with that of other experimental models.

Extrahepatic Metabolism and Distribution of Aspirin in Vascular Beds of Sheep

The dispositions of aspirin, its metabolite, salicylic acid, and its subsequent metabolite, salicyluric acid, were studied in eight anesthetized sheep infused with aspirin (61 and 485 μg-min−1.kg−1) for 75min. Plasma samples were withdrawn from the portal vein, hepatic vein, pulmonary artery, left ventricle, left femoral vein, and left femoral artery. Significant extraction of aspirin occurred across the liver and hind leg, with mean availabilities of 0.75, 0.98, and 0.82 observed across the liver, lung, and hind leg, respectively. The extraction of aspirin was not affected by coadministration of sodium salicylate (30–1200mg equiv salicylic acid). This extraction reflected hydrolysis of aspirin to salicylic acid; the metabolism of aspirin in the hind leg, lung, and liver being confirmed with tissue homogenate studies. The metabolism of aspirin in the extrahepatic tissues is significant in relation to the proposed selective presystemic acetylation of platelet cyclooxygenase by aspirin and the use of low-dose aspirin for thrombotic indications.

CORONARY AND PERIPHERAL VASCULAR RESISTANCE IN THE ANAESTHETIZED DIABETIC SHEEP

To determine whether vascular resistance was altered in diabetes, the vascular resistance in both the peripheral arterial bed and the circumflex coronary artery was compared in six normal and five diabetic adult sheep, under pentobarbitone anaesthesia. Diabetes induced by alloxan significantly increased blood glucose (15.6 mmol/l, s.e.m. = 2.8, vs 5.5 mmol/l, s.e.m. = 0.6; P greater than 0.001) compared with controls. Systolic blood pressure was lower in diabetics (92 mmHg, s.e.m. = 12, vs 123 mmHg, s.e.m. = 5; P less than 0.025) as was diastolic blood pressure (73 mmHg, s.e.m. = 15, vs 104 mmHg, s.e.m. = 4; P greater than 0.05). Basal peripheral resistance was lower in diabetics than controls (36.0 mmHg.min/l, s.e.m. = 7.9, vs 42.3 mmHg.min/l, s.e.m. = 2.8), but not significantly so. Methoxamine markedly increased peripheral vascular resistance in both groups, but did not change coronary vascular resistance, due to autoregulation. The dose-response curves of peripheral or coronary arteries to methoxamine showed no significant difference between diabetic and control sheep. Dose-response curves for isoprenaline and noradrenaline infusion suggested there may be altered beta-receptor sensitivity in diabetes. In conclusion, there are marked differences in the vascular beds of diabetic and normal sheep under basal conditions. In contrast to previous studies, alpha-adrenoceptors are not different in diabetics, but further studies in unanaesthetized animals are indicated, as beta-receptor sensitivity may be altered in diabetes.

The effects of nifedipine on the systemic and coronary vascular beds of the sheep: a potential method for induction of ischaemia.

Nifedipine has been reported to aggravate symptoms of ischaemic heart disease in some patients. To investigate the possible reasons for this, vascular resistance changes in the systemic and coronary beds of sheep were compared with and without coronary artery stenoses. In six anaesthetized sheep, the dose-response curve comparing vascular resistance to nifedipine dose showed greater sensitivity than that reported for either dogs or humans. The coronary vascular bed was more reactive than the systemic vascular bed but this difference did not reach a level of statistical significance. With fixed non-elastic proximal coronary artery stenoses, the relationship of both coronary flow and coronary resistance to a standard dose of nifedipine (5 micrograms/kg) was indirectly related to the degree of stenosis. With stenosis reducing flow at rest by 50% or more, nifedipine usually produced a reduction in coronary flow in the stenosed artery and associated ST elevation, consistent with severe ischaemia in the distribution of the coronary. This effect is related to the reduction in perfusion pressure.

Blood flow measurement during exercise in sheep using Doppler ultrasonic method.

Continuous recording of blood flow to the coronary, renal and hindlimb vascular beds of sheep has been carried out using flow probes implanted around the major vessels supplying these regions. Blood flow has been recorded at rest, with the sheep running at speeds of 1–16 kmh−1 on a treadmill, and during the recovery period. A Doppler flowmeter has been developed to facilitate compatibility with existing equipment, to enable reliable reproduction of the unit and to keep costs to a minimum. To minimize interference accompanying the violent movements of exercise great care must be taken with the electrical connections and flow probes require streamlining to facilitate implantation. Blood flow to both hindlimb and coronary vascular beds increased during exercise while that to the renal vascular bed did not change. Thus continuous recording with the Doppler ultrasonic flowmeter can be utilised during all phases of exercise, unlike other methods such as the use of radioactive microspheres which provides only point estimations and has limited application for repeated measurement.

Experimental Transmission of Protostrongylus stilesi to Bighorn-Mouflon Sheep Hybrids

The life cycle of the lungworm, Protostrongylus stilesi Dikmans, 1931, was completed by experimental transmission of infective-stage larvae in the terrestrial snail, Vallonia pulchella, to bighorn X mouflon hybrid (Ovis canadensis canadensis X 0. musimon) sheep. Infection attempts were successful in 3 of 4 cases. Proof of infection was substantiated through identification of male and female adult P. stilesi from lung tissue of the animals. The activity of infective-stage P. stilesi in these hybrid sheep is strongly indicative that similar results do occur in the bighorn sheep. Other variations of the life cycle, i.e., prenatal transmission, may also exist in bighorn sheep. However, the present research has shown that bighorn sheep-terrestrial mollusc-bighorn sheep is no doubt an actual mode of transmission of P. stilesi. To that extent, the life cycle is now known. The life cycle of Protostrongylus stilesi in bighorn sheep (Ovis canadensis) is incompletely known. The adult nematode lives in the lung parenchyma of the definitive host. The eggs are laid in the lung, hatch into firststage larvae, and eventually make their way into the intestinal tract, leaving the body of the host with the feces. The first-stage larva must leave the sheep feces and enter an intermediate host where it develops to the infective stage. This stage must then enter the definitive host. This part of the cycle has been the subject of intensive experimentation (Pillmore, 1955, 1959 a-c, 1961; Post and Winter, 1957; Post, 1958). All species of Protostrongylus with known life cycles require terrestrial molluscs as intermediate hosts. Therefore, studies on the life cycle of P. stilesi have been focused on finding a terrestrial mollusc which will transfer the infection back to the definitive host. Past research has shown several species of molluscs, including Vallonia pulchella, will accept firststage larvae of P. stilesi. Metamorphosis from first to third stage has been observed on several occasions (Honess, 1955; Pillmore, 1955, 1956; Post and Winter, 1957; Post, 1958). Attempts to complete the life cycle of the worm have met with inconclusive results or failure beReceived for publication 13 July 1971. * This research was financed by Rachelwood Wildlife Research Preserve, New Florence, Pennsylvania (Publication No. 11) and administered through the Department of Fishery and Wildlife Biology, Colorado State University, Fort Collins, Colorado. cause lungworm-free bighorn sheep have not been available for experimentation and domestic sheep appeared to be resistant. The purpose of the present research was to complete the life cycle of P. stilesi by transmission of the infective larvae from the intermediate host to the definitive host. Vallonia pulchella was used as the experimental intermediate host. Definitive hosts were mouflonbighorn sheep hybrids (Ovis musimon X O. canadensis canadensis). MATERIALS AND METHODS First-stage larvae of P. stilesi were obtained from the feces of wild-ranging bighorn sheep in Rocky Mountain National Park, Colorado. Fecal droppings were collected in bighorn sheep bedding areas and air-dried for maximum preservation of larva . A Baermann apparatus was used to separate Ist-stage lungworm larvae from fecal samples. Land snails of the species V. pulchella were obtained from Laramie, Wyoming (Post and Winter, 1957). These snails were collected from a greenhouse-eliminating the possibility of prior exposure to P. stilesi. Hybrid sheep from crosses of bighorn and mouflon were provided by Rachelwood Wildlife Research Preserve, New Florence, Pennsylvania. Two animals were 4 bighorn and 3/ mouflon. The other 2 animals were 1/2 bighorn and 1/2 mouflon. These animals harbored infections of Muellerius sp. and Pneumostrongylus sp. These natural infections were determined by means of preliminary fecal sampling. The sheep were treated with Tramisol (American Cyanamid Co., Princeton, New Jersey) for removal of the Muellerius infection. The animals were considered free of this lungworm when larval lungworm production dropped to zero and remained there through 6 weeks of daily fecal sampling. Pneumostrongylus first-stage larvae remaining in fecal samples were