Nutrition and metabolism of the geriatric dog

Sixteen 10-12-year-old and eight 1-year-old dogs were studied over a two year period to determine comparative differences in physiological response to 4 diets varying in protein content and percentages of energy contributed by protein. The ability of old dogs to utilize nutrients as supplied by these foods was not significantly different from that of young adult dogs. Except for indices of mitogenic stimulation and serum urea nitrogen (SUN) other physiological parameters studied were not affected by the diet fed. Regardless of diet, old dogs had significantly higher serum levels of cholesterol, phosphorus and alkaline phosphatase and had lower indices of mitogenic stimulation than did young dogs.     

Pharmacokinetics of orally administered tramadol in Muscovy ducks (Cairina moschata domestica)

This study documents the pharmacokinetics of oral tramadol in Muscovy ducks. Six ducks received a single 30 mg/kg dose of tramadol, orally by stomach tube, with blood collection prior to and up to 24 hr after tramadol administration. Plasma tramadol, and metabolites O‐desmethyltramadol (M1), and N,O‐didesmethyltramadol (M5) concentrations were determined by high‐pressure liquid chromatography (HPLC) with fluorescence (FL) detection. Pharmacokinetic parameters were calculated using a one‐compartment model with first‐order input. No adverse effects were noted after oral administration. All ducks achieved plasma concentrations of tramadol above 0.10 μg/ml and maintained those concentrations for at least 12 hr. Elimination half‐life was 3.95 hr for tramadol in ducks, which is similar to other avian species. All ducks in this study produced the M1 metabolite and maintained plasma concentrations above 0.1 μg/ml for at least 24 hr.     

US Sheep Industry and the Public Grazing Fee

Since the mid-1940s US sheep inventory has experienced dramatic declines, which has weakened the sheep industry significantly, making it increasingly important to analyze potential policy implications that could affect US sheep inventories in the future. Public grazing lands are often used in sheep production, especially within the western United States. The public grazing fee is, therefore, a cost within the production of sheep. A US sheep model applying capital stock inventory accounting methodology is developed to model both the supply and demand within the joint sheep and wool industries. The model is used to create a baseline projection for the next several years. Various public grazing fee policies are created to demonstrate the effects of the policies on the levels of sheep inventory and sheep and wool production within the country. Results indicate removing the public grazing fee (set at $0/animal unit month) may slow the rate of decline but would not be effective at reversing the declining trend. This suggests reducing the public grazing fee is not a viable policy option to help bring stability to the sheep and wool industries. However, projections indicate raising the grazing fee would have a substantial adverse effect on the industries. Consideration should be given to these results as grazing fee policy is adjusted moving forward.     

Grain-dependent functional responses in habitat selection

Context

Spatial scale is an important consideration for understanding how animals select habitat, and multi-scalar designs in resource selection studies have become increasingly common. Despite this, examination of functional responses in habitat selection at multiple scales is rare. The perceptual range of an animal changes as a function of vegetation association, suggesting that use, selection and functional responses may all be habitat- and scale-dependent.

Objectives

Our objective was to determine how varying grain size affects our interpretation of functional response in habitat selection and to elucidate scalar and landscape effects on habitat selection.

Methods

We quantified the functional response of GPS-collared, female white-tailed deer (Odocoileus virginianus, n = 18) in Riding Mountain National Park, Canada, to different habitat types. Functional responses were quantified at multiple spatial scales by regressing proportion of habitat used against proportion of habitat available at different buffer radii (ranging from 75–1000 m radius) surrounding used (telemetry) locations and available points within the individual’s seasonal home range. We examined how functional responses changed as a function of grain by plotting grain size against the slope of the functional response.

Results

We detected functional responses in most habitat types. As expected, functional responses tended to converge towards 1 (use proportional to availability) at large buffer sizes; however, the relationship between scale and functional response was typically non-linear and depended on habitat type.

Conclusions

We conclude that a multi-scalar approach to modelling animal functional responses in habitat selection is important for understanding patterns in animal behaviour and resource use.

     

Repurposing Ionophores as novel antimicrobial agents for the treatment of bovine mastitis caused by Gram‐positive pathogens

Increasing reports of multidrug‐resistant bacterial infections in animals has created a need for novel antimicrobial agents that do not promote cross‐resistance to critically important antimicrobial classes used in human medicine. In response to the recent emergence of antimicrobial resistance in several bovine mastitis pathogens, in vitro antimicrobial susceptibility was determined for four polyether ionophores (lasalocid, monensin, narasin and salinomycin) against Staphylococcus spp. and Streptococcus spp. isolated from clinical cases. In addition, erythrocyte haemolysis and WST ‐1 cell proliferation assays were used to assess in vitro mammalian cell cytotoxicity and biofilm susceptibility testing was performed using the minimum biofilm eradication concentration (MBEC ?) biofilm assay. Lasalocid, monensin, narasin and salinomycin exhibited bacteriostatic antimicrobial activity against all pathogens tested, including methicillin‐resistant staphylococci, with MIC ₉₀ values <16 μg/ml. Narasin and monensin displayed the least toxicity against mammalian cell lines and all compounds significantly reduced viable cell numbers in a Staphylococcus aureus biofilm. Based on in vitro characterization, all four ionophores offer potentially novel treatments against bovine mastitis but in vivo studies will be essential to determine whether acceptable safety and efficacy is present following intramammary administration.