Pharmacokinetics of a long-acting formulation of oxytetracycline in freshwater crocodiles (Crocodylus siamensis) after intramuscular administration at three different dosages

To date, the necessary pharmacokinetic information has been limited to establish suitable therapeutic plans for freshwater crocodiles. Therefore, this study was conducted to evaluate the pharmacokinetic profile of the oxytetracycline long-acting formulation (OTC-LA) in the freshwater crocodile, Crocodylus siamensis, following a single intramuscular (i.m.) administration at three different dosages of 5, 10 and 20 mg/kg body weight (b.w.). Blood samples were collected at assigned times up to 216 h after i.m. administration at the three different dosages. The plasma concentrations of OTC were measured using a validated liquid chromatography tandem-mass spectrometry (LC-MS/MS) method. The Cmax (± SD) values of OTC were 2.15 ± 0.51 µg/mL, 7.68 ± 1.08 µg/mL and 17.08 ± 2.09 µg/mL at doses of 5, 10 and 20 mg/kg b.w., respectively. The elimination half-life values were 33.59 ± 2.51 h, 38.42 ± 5.47 h and 38.04 ± 1.98 h at dosages of 5, 10 and 20 mg/kg b.w., respectively. Based on the pharmacokinetic data, the pharmacokinetic/pharmacodynamic (PK/PD) index, the susceptibility break-point and plasma protein binding, a dosage once every two weeks of 10 mg/kg b.w. OTC intramuscularly might be suitable for initiating the treatment of susceptible bacterial infections in freshwater crocodiles. However, further PK/PD studies are warranted to confirm whether the dose rates used in this study can produce longer-term antimicrobial success for diseases caused by susceptible bacteria in freshwater crocodiles

Importance of body-water circulation for body-heat dissipation in hot-humid climates: a distinctive body-water circulation in swamp buffaloes

Thermo-regulation in swamp buffaloes has been investigated as an adaptive system to hot-humid climates, and several distinctive physiological responses were noted. When rectal temperature increased in hot conditions, blood volume, blood flow to the skin surface and skin temperature markedly increased in buffaloes relatively to cattle. On the other hand, the correlation between blood volume and plasma concentration of arginine vasopressin (AVP) was compared between buffaloes and cattle under dehydration. Although plasma AVP in cattle increased immediately for reducing urine volume against a decrease in blood volume as well as the response observed in most animal species, the increase in plasma AVP was delayed in buffaloes, even after a large decrease in blood volume. In buffaloes, a marked increase in blood volume facilitated the dissipation of excess heat from the skin surface during wallowing. In addition, the change in plasma AVP observed in buffaloes was consistent with that of other animals living in habitats with the high availability of water. These results suggest that the thermo-regulatory system in buffaloes accelerates body-water circulation internally and externally. This system may be adaptive for heat dissipation in hot-humid climates, where an abundance of water is common

Effects of evaporative cooling on reproductive performance and milk production of dairy cows in hot wet conditions

Fourteen animals of second and third lactationof Thai Friesian crossbred cows (87.5% Friesian × 12.5%Bos indicus) located at Sakol Nakhon Research andBreeding Centre, Department of Livestock Development,Ministry of Agriculture and Cooperatives, were dividedrandomly into two groups of seven each to evaluate theeffects of evaporative cooling on reproductive and physiologicaltraits under hot, humid conditions. Resultsindicated that installation of evaporating cooling in theopen shed gave a further improvement in ameliorating heatstress in dairy cows in hot-wet environments by utilisingthe low humidity conditions that naturally occur during theday. The cows housed in an evaporatively cooled environmenthad both a rectal temperature and respiration rate(39.09⁰C, 61.39 breaths/min, respectively) significantlylower than that of the non-cooled cows (41.21⁰C;86.87 breaths/min). The former group also had highermilk yield and more efficient reproductive performance(pregnancy rate and reduced days open) than the lattergroup. It is suggested that the non-evaporatively cooledcows did not gain benefit from the naturally lower heatstress during night time