Comparative pharmacokinetics of metronidazole in camels, sheep and goats

The pharmacokinetics of metronidazole was determined after a single intramuscular (i.m.) dose of 30 mg.kg(-1)-body weight in five camels, sheep and goats. Marked differences were found between the three species in some of the kinetic parameters. For example, the elimination half-lives t(1/2); (h) in camels, sheep and goats were 10.0, 6.21 and 5.87, respectively. The drug maximum concentrations in plasma, C-max (mg.ml(-1)), were 28.3, 54.6 and 54.4 in camels, sheep and goats, respectively. The time to reach C-max, t(max) (h), were 5, 4 and 2 in camels, sheep and goats, respectively. The mean residence times (MRT; h) in camels, sheep and goats were 16.7, 10.8 and 8.64, respectively. In the light of the present kinetic data and known microbial sensitivities of metronidazole, we recommend an i.m. dose of 15 mg.kg(-1) in camels and 10 mg.kg(-1) in sheep and boats. every 12 h.

Nitrate-nitrate toxicity in cattle and sheep grazing Dactyloctenium radulans (button grass) in stockyards

Hungry cattle and sheep introduced to stockyards containing a dominant or pure growth of Dactyloctenium radulans (button grass) suffered acute nitrate-nitrite toxicity in four incidents in inland Queensland between 1993 and 2001. Deaths ranged from 16 to 44%. Methaemoglobinaemia was noted at necropsies in all incidents. An aqueous humour sample from one dead steer contained 75 mg nitrate/L and from one dead sheep contained 100 mg nitrate and 50 mg nitrite/L (normal = ca 5 mg nitrate/L). Both lush and dry button grass were toxic. The nitrate content of button grass from within the stockyards ranged from 4.0 to 12.9% as potassium nitrate equivalent in dry matter and from outside the stockyards ranged from

Of sheep and rain: large-scale population dynamics of the red kangaroo

1. We analysed time-series data from populations of red kangaroos (Macropus rufus, Desmarest) inhabiting four areas in the pastoral zone of South Australia. We formulated a set of a priori models to disentangle the relative effects of the covariates: rainfall, harvesting, intraspecific competition, and domestic herbivores, on kangaroo population-growth rate. 2. The statistical framework allowed for spatial variation in the growth-rate parameters, response to covariates, and environmental variability, as well as spatially correlated error terms due to shared environment. 3. The most parsimonious model included all covariates but no area-specific parameter values, suggesting that kangaroo densities respond in the same way to the covariates across the areas. 4. The temporal dynamics were spatially correlated, even after taking into account the potentially synchronizing effect of rainfall, harvesting and domestic herbivores. 5. Counter-intuitively, we found a positive rather than negative effect of domestic herbivore density on the population-growth rate of kangaroos. We hypothesize that this effect is caused by sheep and cattle acting as a surrogate for resource availability beyond rainfall. 6. Even though our system is well studied, we must conclude that approximating resources by surrogates such as rainfall is more difficult than previously thought. This is an important message for studies of consumer-resource systems and highlights the need to be explicit about population processes when analysing population patterns.

Transmission dynamics of the Echinococcus granulosus sheep-dog strain (G1 genotype) in camels in Tunisia

Cystic echinococcosis, caused by Echinococcus grantilosus, is highly endemic in North Africa and the Middle East. This paper examines the abundance and prevalence of infection of E. granulosus in camels in Tunisia. No cysts were found in 103 camels from Kebili, whilst 19 of 188 camels from Benguerden (10.1%) were infected. Of the cysts found 95% were considered fertile with the presence of protoscolices and 80% of protoscolices were considered viable by their ability to exclude aqueous eosin. Molecular techniques were used on cyst material from camels and this demonstrated that the study animals were infected with the G1 sheep strain of E. granulosus. Observed data were fitted to a mathematical model by maximum likelihood techniques to define the parameters and their confidence limits and the negative binomial distribution was used to define the error variance in the observed data. The infection pressure to camels was somewhat lower in comparison to sheep reported in an earlier study. However, because camels are much longer-lived animals, the results of the model fit suggested that older camels have a relatively high prevalence rate, reaching a most likely value of 32% at age 15 years. This could represent an important source of transmission to dogs and hence indirectly to man of this zonotic strain. In common with similar studies on other species, there was no evidence of parasite-induced immunity in camels. (C) 2004 Elsevier B.V. All rights reserved.

The effects of intra-amniotic injection of periodontopathic lipopolysaccharides in sheep

Objective: Periodontal disease may cause several complications of pregnancy, including fetal death. The purpose of this study was to investigate in sheep the effects of the intra-amniotic injection of lipopolysaccharide from 3 periodontopathic organisms and to compare these effects with those resulting from similar injection of Escherichia coli lipopolysaccharide. The outcomes that were studied included the rates of fetal death and the features of inflammation and lung maturation in survivors. Study design: At 118 days of pregnancy, ewes that were bearing single fetuses were allocated at random to receive intra-amniotic injections of saline solution (n = 13 fetuses), or lipopolysaccharide from Porphyromonas gingivalis (in doses from 0.1 to 10 tug [n = 22 fetuses]), Actinobacillus actinomycetemcomitans (10 mg [n = 6 fetuses]; 1 mg [n = 6 fetuses]), Fusobacterium nucleation (10 mg [n = 6 fetuses]) or Escherichia coli (10 mg [n = 14 fetuses]; 1 mg [n = 7 fetuses]). Surviving fetuses were delivered abdominally at 125 days of gestation (term, 150 days). Results: When compared with Escherichia coli lipopolysaccharide at similar dosages, periodontopathic lipopolysaccharides had high rates of fetal lethality. Only 6 of 22 fetuses that were exposed to intra-amniotic Porphyromonas gingivalis lipopolysaccharide survived doses of 0.1 to 10 mg, and only 3 of 6 fetuses survived 10-mg Actinobacillus actinomycetemcomitans lipopolysaccharide. Escherichia coli lipopolysaccharide did not cause fetal loss when given at doses of 10 mg (n = 14 fetuses) or l mg (n = 7 fetuses). Fetuses that survived exposure to these lipopolysaccharides showed features of inflammation in amniotic fluid and cord blood at birth and enhanced lung maturation. Conclusion: Lipopolysaccharides from these 3 periodontopathic organisms have much higher rates of fetal lethality than Escherichia coli lipopolysaccharide but can cause similar intrauterine inflammatory responses and improvements in lung volumes in survivors. Sources of inflammation that are distant from the uterus may underlie a proportion of unexplained stillbirth and other complications of pregnancy. (c) 2005 Mosby, Inc. All rights reserved.

Effect of smoke inhalation on viscoelastic properties and ventilation distribution in sheep

Smoke inhalation injuries are the leading cause of mortality from burn injury. Airway obstruction due to mucus plugging and bronchoconstriction can cause severe ventilation inhomogeneity and worsen hypoxia. Studies describing changes of viscoelastic characteristics of the lung after smoke inhalation are missing. We present results of a new smoke inhalation device in sheep and describe pathophysiological changes after smoke exposure. Fifteen female Merino ewes were anesthetized and intubated. Baseline data using electrical impedance tomography and multiple-breath inert-gas washout were obtained by measuring ventilation distribution, functional residual capacity, lung clearance index, dynamic compliance, and stress index. Ten sheep were exposed to standardized cotton smoke insufflations and five sheep to sham smoke insufflations. Measured carboxyhemoglobin before inhalation was 3.87 +/- 0.28% and 5 min after smoke was 61.5 +/- 2.1%, range 50-69.4% ( P < 0.001). Two hours after smoke functional residual capacity decreased from 1,773 +/- 226 to 1,006 +/- 129 ml and lung clearance index increased from 10.4 +/- 0.4 to 14.2 +/- 0.9. Dynamic compliance decreased from 56.6 +/- 5.5 to 32.8 +/- 3.2 ml/ cmH(2)O. Stress index increased from 0.994 +/- 0.009 to 1.081 +/- 0.011 ( P < 0.01) ( all means +/- SE, P < 0.05). Electrical impedance tomography showed a shift of ventilation from the dependent to the independent lung after smoke exposure. No significant change was seen in the sham group. Smoke inhalation caused immediate onset in pulmonary dysfunction and significant ventilation inhomogeneity. The smoke inhalation device as presented may be useful for interventional studies.

Differential regulation of suppressor of cytokine signaling-3 in the liver and adipose tissue of the sheep fetus in late gestation

Differential regulation of suppressor of cytokine signaling-3 in the liver and adipose tissue of the sheep fetus in late gestation. Am J Physiol Regul Integr Comp Physiol 290: R1044 - R1051, 2006. First published November 10, 2005; doi: 10.1152/ajpregu. 00573.2005. - It is unknown whether the JAK/STAT/suppressor of cytokine signaling-3 (SOCS-3) intracellular signaling pathway plays a role in tissue growth and metabolism during fetal life. We investigated whether there is a differential profile of SOCS-3 expression in the liver and perirenal adipose tissue during the period of increased fetal growth in late gestation and the impact of fetal growth restriction on SOCS-3 expression in the fetal liver. We also determined whether basal SOCS-3 expression in the fetal liver and perirenal adipose tissue is regulated by endogenous fetal prolactin (PRL). SOCS-3 mRNA abundance was higher in the liver than in the pancreas, spleen, and kidney of the sheep fetus during late gestation. In the liver, SOCS-3 mRNA expression was increased (P < 0.05) between 125 (n < 4) and 145 days (n < 7) gestation and lower (P < 0.05) in growth-restricted compared with normally grown fetal sheep in late gestation. The relative expression of SOCS-3 mRNA in the fetal liver was directly related to the mean plasma PRL concentrations during a 48-h infusion of either a dopaminergic agonist, bromocriptine (n < 7), or saline (n < 5), such that SOCS-3 mRNA expression was lower when plasma PRL concentrations decreased below similar to 20 ng/ml [y = 0.99 - (2.47/x) + (4.96/x(2)); r(2) = 0.91, P < 0.0001, n < 12]. No relationship was shown between the abundance of phospho-STAT5 in the fetal liver and circulating PRL. SOCS-3 expression in perirenal adipose tissue decreased (P < 0001) between 90 - 91 (n < 6) and 140 - 145 days (n < 9) gestation and was not related to endogenous PRL concentrations. Thus SOCS-3 is differentially expressed and regulated in key fetal tissues and may play an important and tissue-specific role in the regulation of cellular proliferation and differentiation before birth.

Effect of nutrition level and diets on creatinine excretion by sheep

In this experiment, creatinine (C) excretion by sheep was measured when they were fed different diets at different levels of intake. Creatinine excretion was not affected by the level of feed intake or the addition of salt to lucerne-based diets. However, differences between individual animals were significant. Creatinine excretion was significantly affected by diets, which were formulated by combining different amounts of lucerne chaff, oaten chaff and sorghum. It was also found that there were significant diurnal changes in the ratios of purine derivatives to creatinine (PD:C) in 3 hourly urine samples when the animals were fed either once or twice daily, but the average value for the PD:C ratio of any two urine samples taken 12 h apart was close to the daily mean. The results of this experiment suggest that if separate determination of the creatinine excretion by individual animals is made and the average value of the ratio of PD:C in two spot urine samples taken 12 h apart is used to predict PD excretion by spot urine sampling, microbial nitrogen flow can be estimated more accurately than when a fixed value of creatinine excretion is used for all animals and only a single urine sample is taken. (c) 2005 Elsevier B.V. All rights reserved.

Prolactin and the expression of suppressor of cytokine signaling-3 in the sheep adrenal gland before birth

Prolactin and the expression of suppressor of cytokine signaling-3 in the sheep adrenal gland before birth. Am J Physiol Regul Integr Comp Physiol 291: R1399-R1405, 2006. First published June 29, 2006; doi: 10.1152/ajpregu.00252.2006.-The fetal pituitary-adrenal axis plays a key role in the fetal response to intrauterine stress and in the timing of parturition. The fetal sheep adrenal gland is relatively refractory to stimulation in midgestation (90-120 days) before the prepartum activation, which occurs around 135 days gestation (term = 147 +/- 3 days). The mechanisms underlying the switch from adrenal quiescence to activation are unclear. Therefore, we have investigated the expression of suppressor of cytokine signaling-3 (SOCS-3), a putative inhibitor of tissue growth in the fetal sheep adrenal between 50 and 145 days gestation and in the adrenal of the growth-restricted fetal sheep in late gestation. SOCS-3 is activated by a range of cytokines, including prolactin (PRL), and we have, therefore, determined whether PRL administered in vivo or in vitro stimulates SOCS-3 mRNA expression in the fetal adrenal in late gestation. There was a decrease (P < 0.005) in SOCS-3 expression in the fetal adrenal between 54 and 133 days and between 141 and 144 days gestation. Infusion of the dopaminergic agonist, bromocriptine, which suppressed fetal PRL concentrations but did not decrease adrenal SOCS-3 mRNA expression. PRL administration, however, significantly increased adrenal SOCS-3 mRNA expression (P < 0.05). Similarly, there was an increase (P < 0.05) in SOCS-3 mRNA expression in adrenocortical cells in vitro after exposure to PRL (50 ng/ml). Placental and fetal growth restriction had no effect on SOCS-3 expression in the adrenal during late gestation. In summary, the decrease in the expression of the inhibitor SOCS-3 after 133 days gestation may be permissive for a subsequent increase in fetal adrenal growth before birth. We conclude that factors other than PRL act to maintain adrenal SOCS-3 mRNA expression before 133 days gestation but that acute elevations of PRL can act to upregulate adrenal SOCS-3 expression in the sheep fetus during late gestation.

The critical dietary potassium concentration for induction of mineral disorders in non-lactating Welsh Mountain sheep

Diets with more than 30 g K/kg DM have previously been associated with hypomagnesaemia in grazing cattle, and to test whether such diets lead to mineral disorders in sheep, the absorption of Mg and other elements was investigated using experimental diets to which KC I had been added to provide 27, 29, 32 or 34 g K/kg DM. The apparent absorption, balance and apparent retention of Mg, and to a lesser extent Ca, were reduced for sheep offered the diets with 32 or 34 g K/kg DM. The absorption and retention of K, Na, P, Zn, Pb and Cd was not affected by treatment. The blood intracellular Ca concentration was reduced by the diets with 29, 32 or 34 g K/kg DM, compared to the diet with 27 g K/kg DM, but the concentration of other elements was unaffected. Blood plasma Ca concentration was increased at the highest level of K inclusion, providing evidence of mild hyperkalaemia and the involvement of Ca homeostatic mechanisms. It is concluded that Mg absorption by sheep will be impaired if the diet contains more than 30 g K/kg DM, equivalent to an intake of approximately 13 g K/d, but that a high K diet may be beneficial before parturition to accustom the sheep to Ca mobilization before lactation. (c) 2005 Elsevier B.V. All rights reserved.

Dermal deposition of diazinon on workers using various sheep ectoparasiticide application systems

This study measured the dermal deposition levels of diazinon on workers who apply the ectoparasiticide to sheep using one of five different application systems, namely, portable plunge dipping, fixed plunge dipping, shower dipping, hand jetting, and automatic jetting races. The highest level of dermal exposure occurred while hand jetting and a comparable level occurred in automatic jetting races. The next highest level of dermal exposure was while using the portable and the fixed plunge dipping systems. The shower dipping system appeared to expose workers to the least deposition of diazinon. The variability between the different methods was statistically significant, and the contrast between the three applications using dipping and the two using jetting was highly statistically significant. The variability between testing sessions was too great to allow the methods to be ranked as accurately as the authors would prefer. However, the differences between the methods were large enough to be of practical importance to OHS risk management. (author abstract)