Seasonal and Diurnal Changes in Starch Content and Sugar Profiles of Bermudagrass in the Piedmont Region of the United States

Seasonal and diurnal patterns of sugar accumulation in bermudagrass (Cynodon dactylon) pastures were monitored to evaluate risk factors for pasture-associated laminitis of ponies and horses. Bermudagrass was collected from four plots in the morning and afternoon on a weekly basis, from mid-July until late August. Tissue was air-dried to simulate hay, or frozen to retain the sugar profiles of fresh pasture. Samples were analyzed colorimetrically for total water-soluble and ethanol-soluble carbohydrates, and electrochemically for starch. In addition, sugars were separated and quantified by high-performance liquid chromatography coupled to pulsed amperometric detection. The dominant sugars in extracts were glucose, fructose, and sucrose. Some minor peaks, corresponding to tri- and tetrasaccharides, were also detected in some extracts. Starch increased over time in fresh and dried tissue, and concentrations varied diurnally in fresh, but not in dried tissue (P = .021). Sucrose in dried tissue decreased and then increased, with higher concentrations than in fresh tissue on all sampling dates (P = .024). Glucose and fructose exhibited diurnal variation on one and two dates, respectively (P = .034 and .0028, respectively). These results reveal trends in carbohydrate concentrations and profiles that may help to evaluate the likelihood of equine laminitis outbreaks on bermudagrass.     

Pharmacokinetics and Effects of Alkalization During Oral and Intravenous Administration of Naproxen in Horses

The use of suitable therapeutic protocols is particularly important when extra-label drugs are used or when physiological parameters are modified, as in the case of the administration of alkaline substances to racehorses. The pharmacokinetics of naproxen (NAP), after both intravenous (iv) and oral administration of 10 mg/kg body weight (BW), was investigated in horses under normal metabolic conditions and in horses whose conditions were modified by the iv administration of 250 mg/kg BW of sodium bicarbonate (NaHCO₃). The hypothesis that blood and consequent urinary alkalization could modify NAP pharmacokinetics was evaluated. Drug quantification was performed on serum and urine using High Performance Liquid Chromatography (HPLC) with ultraviolet-visible detection. Results were also integrated with cycloxygenase (COX)-inhibition published data to suggest an appropriate schedule for NAP dosage in horses. After iv administration, NAP was rapidly distributed (t_1/2α: 0.71 ± 0.43 iv NaHCO₃ and 0.55 ± 0.62 hours No NaHCO₃), whereas its elimination was quite slow (t_1/2β: 6.74 ± 0.41 hours), particularly in iv NaHCO₃ animals (t_1/2β: 8.95 ± 1.37 hours). After oral treatments, NAP was more rapidly absorbed and elimination was slower in iv NaHCO₃ animals (t_1/2λ_z: 17.50 ± 6.66 vs. 7.17 ± 0.91 hours). The oral bioavailability of NAP was approximately 87% and 77% in No NaHCO₃ and iv NaHCO₃, respectively. Urinary excretion of the drug as a parent compound was low. The alkalization procedure did not anticipate the elimination of the acidic drug as expected, but it also influenced the absorption of the drug that was administered orally. The dosage scheme of 10 mg/kg BW iv or orally seems to be appropriate to produce an anti-inflammatory effect for 12 to 24 hours.