Pharmacokinetics of gentamicin in the calf: developmental changes

The purpose of this study was to determine the pharmacokinetic values for gentamicin in neonatal calves and to compare these values with those in adult cattle (cows). Gentamicin (4 mg/kg of body weight) was administered IV to 7 Holstein bull calves on days 1 (between 12 and 24 hours of age), 5, 10, and 15 after birth, and was administered once IV to 7 Holstein cows. Serum was collected from each animal before administration and at 22 different time intervals from 2 to 400 minutes after injection. Sera were analyzed for gentamicin concentrations. Decay of serum gentamicin concentrations was best described by a 2-compartment pharmacokinetic model. Elimination half-life (t1/2 (beta)) of gentamicin decreased from day 1 (149 minutes) to day 5 (119 minutes), but did not change between days 5 and 15 (111 minutes). Compared with the t1/2(beta) in 1- and 15-day-old calves, the t 1/2 (beta) in cows was shorter (76 minutes). In the calves, apparent volume of distribution (based on total area under the disposition curve) did not change between 1 (393 ml/kg) and 5 (413 ml/kg) days of age, decreased on day 10 (341 ml/kg) and cows day 15 (334 ml/kg), and was markedly smaller than that in cows (140 ml/kg). Total body clearance of gentamicin in cows (1.29 ml/min X kg) was lower than that seen in calves on day 1 (1.92 ml/min X kg) and on day 15 (2.10 ml/min X kg). The decrease in apparent volume of distribution of gentamicin was mirrored by a large decrease in the extracellular fluid volume, as measured by inulin space.(ABSTRACT TRUNCATED AT 250 WORDS)     

An update on Reproductive Technologies with Potential Short-Term Application in Pig Production

Over the past decade, there has been an increase in the development and/or in the improvement of emerging reproductive technologies in pigs. Among emerging reproductive technologies with potential short-term application in pig production are: artificial insemination with low number of spermatozoa, cryopreservation of spermatozoa and embryos, sperm sexing, and non-surgical embryo transfer. The following review will give emphasis to recent advancements in these reproductive technologies that are starting to show possibilities of serious applications under field conditions.     

Terbutaline pharmacokinetics in cows: preliminary data

The objective of this study was to determine the serum pharmacokinetics of terbutaline in healthy cows. In the initial experiment, terbutaline was administered once as an intravenous (i.v.) bolus to 6 near-term pregnant beef cows within 24 h after parturition at a low but therapeutically relevant dose, 5 microg/kg. A 2nd experiment was conducted in the same cows with a higher dose, 0.5 mg/kg, but an otherwise similar experimental design. The serum concentration of terbutaline was determined by means of high-performance liquid chromatography with fluorescence detection in both experiments. After i.v. administration of 0.5 mg/kg, the mean peak serum concentration, residence time, and half-life were 708.22 (standard deviation 509.6) ng/mL, 6.75 (3.6) min, and 6.93 (2.4) min, respectively. The results indicate that terbutaline is rapidly eliminated from the bloodstream after i.v. administration in cattle, falling below the assay's limit of detection 30 min after administration.     

Pilot study investigating the ability of an herbal composite to alleviate clinical signs of respiratory dysfunction in horses with recurrent airway obstruction

Recurrent airway obstruction (RAO), known previously as chronic obstructive pulmonary disease (COPD), is a debilitating respiratory condition that significantly contributes to lost training days and illness in racehorses. Herbs are becoming increasingly popular for the prophylaxis or treatment of the clinical signs of RAO despite a paucity of research on efficacy and safety. We evaluated the ability of an herbal composite containing garlic, white horehound, boneset, aniseed, fennel, licorice, thyme, and hyssop to reduce the clinical signs of RAO, hypothesizing that the product would safely reduce signs and would improve the inflammatory cell profile within the lungs. The composite was fed to 6 horses with symptomatic RAO for 21 d in a crossover manner. Ventigraphs were used to record respiratory rate and intrapleural pressure; the proportion of inflammatory cells in fluid aspirated from the trachea was determined. Blood biochemical and hematologic screening was conducted to identify possible adverse effects. Treatment with the composite did not result in statistically significant changes in any of the parameters evaluated. A trend to a decrease in respiratory rate (P = 0.1) and an increase in the proportion of macrophages (P = 0.1) was observed in the horses receiving the herbal composite compared with placebo. These data indicate a potential for the herbal composite to safely reduce the elevated respiratory rate in horses with RAO. Future research with a greater number of horses is warranted to further characterize the effect of this product on horses with RAO.     

Retained Functional Integrity of Bull Spermatozoa after Double Freezing and Thawing Using PureSperm® Density Gradient Centrifugation

The main aim of this study was to compare the motility and functional integrity of bull spermatozoa after single and double freezing and thawing. The viability and morphological integrity of spermatozoa selected by PureSperm density gradient centrifugation after cryopreservation of bovine semen in two commercial extenders (Experiment 1) and the function of bull spermatozoa before and after a second freezing and thawing assisted by PureSperm selection (Experiment 2) were examined. On average, 35.8 +/- 12.1% of sperm loaded onto the PureSperm density gradient were recovered after centrifugation. In Experiment 1, post-thaw motility and acrosome integrity were higher for spermatozoa frozen in Tris-egg yolk extender than in AndroMed, whether the assessments were made immediately after thawing [80.4 +/- 12.7 vs 47.6 +/- 19.0% motile and 78.8 +/- 8.3 vs 50.1 +/- 19.5% normal apical ridge (NAR), p < 0.05] or after preparation on the gradient (83.3 +/- 8.6 vs 69.4 +/- 15.9% motile and 89.5 +/- 7.2 vs 69.1 +/- 11.4% NAR, p < 0.05). For semen frozen in Tris-egg yolk extender, selection on the PureSperm gradient did not influence total motility but significantly improved the proportion of acrosome-intact spermatozoa. After the gradient, both the total motility and percentage of normal acrosomes increased for spermatozoa frozen in AndroMed (Minitüb Tiefenbach, Germany). In Experiment 2, there was no difference in sperm motility after the first and second freeze-thawing (82.9 +/- 12.7 vs 68.8 +/- 18.7%). However, the proportion of acrosome-intact spermatozoa was significantly improved by selection through the PureSperm gradient, whether measured by phase contrast microscopy (78.9 +/- 9.7 vs 90.4 +/- 4.0% NAR, p < 0.05) or flow cytometry (53.4 +/- 11.7 vs 76.3 +/- 6.0% viable acrosome-intact spermatozoa, p < 0.001). The improvement in the percentage of spermatozoa with normal acrosomes was maintained after resuspension in the cooling extender and cooling to 4 degrees C (88.2 +/- 6.2) and after re-freezing and thawing (83.6 +/- 6.56% NAR). However, flow cytometric assessment of the sperm membranes revealed a decline in the percentage of viable spermatozoa with intact membranes after the second freezing and thawing compared with after gradient centrifugation (76.3 +/- 6.0% vs 46.6 +/- 6.6%, p < 0.001) to levels equivalent to those obtained after the first round of freeze-thawing (53.4 +/- 11.7% viable acrosome-intact spermatozoa). Sperm movement characteristics assessed by computer-assisted analysis were unaffected in the population selected on the PureSperm gradients but declined after cooling of the selected and extended spermatozoa to 4 degrees C. There was no further change in these kinematic measurements after the cooled spermatozoa had undergone the second round of freeze-thawing. These results demonstrate that bull semen can be frozen and thawed, followed by a second freeze-thawing cycle of a population of spermatozoa selected by PureSperm, with retained motility and functional integrity. This points to the possibility of using double frozen spermatozoa in bovine artificial insemination programmes and to the potential benefits of PureSperm density gradient centrifugation for the application of cryopreserved bull spermatozoa to other biotechnological procedures such as flow cytometric sex sorting followed by re-freezing and thawing.     

Simulating fire frequency and urban growth in southern California coastal shrublands,USA

Fire is an important natural disturbance in the Mediterranean-climate coastal shrublands of southern California. However, anthropogenic ignitions have increased fire frequency to the point that it threatens the persistence of some shrub species and favors the expansion of exotic annual grasses. Because human settlement is a primary driver of increased ignitions, we integrated a landscape model of disturbance and succession (LANDIS) with an urban growth model (UGM) to simulate the combined effects of urban development and high fire frequency on the distribution of coastal shrublands. We tested whether urban development would contribute to an expansion of the wildland-urban interface (WUI) and/or change in average fire return intervals and compared the relative impacts of direct habitat loss and altered fire regimes on functional vegetation types. We also evaluated two methods of integrating the simulation models. The development pattern predicted by the UGM was predominantly aggregated, which minimized the expansion of the WUI and increase in fire frequency, suggesting that fire risk may be higher at intermediate levels of urbanization due to the spatial arrangement of ignition sources and fuel. The comparison of model coupling methods illustrated how cumulative effects of repeated fires may occur gradually as urban development expands across the landscape. Coastal sage scrub species and resprouting chaparral were more susceptible to direct habitat loss, but increased fire frequency was more of a concern to obligate seeder species that germinate from a persistent seed bank. Simulating different scenarios of fire frequency and urban growth within one modeling framework can help managers locate areas of highest risk and determine which vegetation types are most vulnerable to direct habitat loss, altered fire regimes, or both.