Matching herbicide application rates with the environmental conditions and growth stages of nodding thistle (Carduus nutans) and hairy buttercup (Ranunculus sardous) in pastures

Glasshouse experiments were conducted to evaluate whether herbicide application rates could be reliably reduced without compromising the efficacy of the herbicide. The seedling, and vegetative and preflowering plants of nodding thistle ( Carduus nutans ) and hairy buttercup ( Ranunculus sardous ) were treated with different rates of glyphosate or a mixture of picloram and triclopyr. Half of the plants were well-watered at all times while the other half was moisture-stressed for 1 week before the herbicide treatments were applied. Hairy buttercup was more susceptible to glyphosate than nodding thistle, while both were equally susceptible to the picloram/triclopyr mixture. Moisture stress significantly reduced the efficacy of both herbicide treatments, regardless of the plant development stage or the herbicide rate applied.     

RESOLUTION OF LESIONS ON STIR IMAGES IS ASSOCIATED WITH IMPROVED LAMENESS STATUS IN HORSES

Magnetic resonance (MR) imaging is important in diagnosing musculoskeletal injuries in horses. However, there is still much to learn regarding the significance of lesions identified in equine MR images. Of particular importance is the clinical significance of signal change as a function of pulse sequence. We hypothesized that a resolution of tendon, ligament, and bone marrow lesions on short‐tau inversion recovery (STIR) images would be associated with a return to soundness, and that a persistence of tendon and ligament lesions on only T1‐weighted (T1w) gradient recalled echo (GRE) images would not be associated with persistent lameness. The medical records and MR images of 27 horses that had a hyperintense lesion in initial STIR MR images followed by a subsequent follow‐up MR imaging examination were reviewed. Horses whose tendon or ligament lesions had resolved on STIR images at the time of the recheck examination were significantly more likely to be sound than horses whose lesions persisted on STIR images (P=0.039). This association did not exist in horses with bone marrow lesions (P=1.00). Horses whose tendon or ligament lesions persisted only on T1w GRE images were no more likely to be sound than horses whose lesion persisted on at least one other sequence type (P=0.26). However, the low number of horses included in this analysis may have precluded identification of a significant difference in lameness status. Tendon or ligament lesions visualized on STIR images may represent active lesions that may contribute to lameness in the horse.     

Congenital diabetes insipidus in a kitten

Congenital diabetes insipidus in an 8-week-old, female longhair kitten is described. The mean urine specific gravity was 1–006; this remained unchanged after water deprivation but rose following intramuscular injection of vasopressin tannate. Pathological examination suggested pituitary malformation as the cause of the condition.     

Distribution of kanamycin in ocular tissues of calves

The ocular distribution of kanamycin following intramuscular, bulbar subconjunctival injection, or after constant rate intravenous infusion to calves was studied. Steady-state plasma concentrations of kanamycin were achieved in either normal calves, or in those experimentally infected with Moraxella bovis, and the concentrations of kanamycin in the serum, aqueous humor, vitreous body, tears, and the ocular tissues were measured. Kanamycin was not detected in the retina, lens, vitreous body, or the aqueous humor of any eyes, but the concentration of drug in the tears, conjunctiva, cornea and the orbital lacrimal gland of these calves ranged between 18 and 21% of that in serum. At steady-state plasma levels, the kanamycin concentrations in tears from eyes with keratoconjunctivitis and from normal eyes were similar. A study using lyophilized, powdered, ocular tissues in vitro showed that kanamycin was highly bound to the bovine retina and iris, and could be eluted using 0.2 N NaOH. The binding of kanamycin to other ocular tissues, including cornea, conjunctiva and lens, was significantly less. The concentration of kanamycin in the serum and the tears of calves was also measured after intramuscular or bulbar subconjunctival injection. After intramuscular administration of kanamycin (10 mg/kg of body-weight), the mean serum concentration was maximal at 1 h (32 micrograms/ml) and remained greater than or equal to 1.0 microgram/ml for 8 h. The mean tear concentration was maximal (3.1 micrograms/ml) at 30 min, and remained greater than or equal to 1.5 micrograms/ml for only 2.5 h. Following bulbar subjunctival administration of kanamycin (100 mg, single subconjunctival dose), the mean tear concentration was 1127 micrograms/ml at 30 min, less than or equal to 4.1 micrograms/ml at 4 h, and thereafter was less than or equal to 1.0 microgram/ml. It was concluded that kanamycin has limited distribution to the ocular tissues following parenteral administration. Binding of the drug to the ocular pigments may be responsible for its limited intraocular penetration.