Bovine Nitrate Sampling

By Dr. Jen Lehr & Dr. Deon Van Der Merwe

Recently, KSVDL has received a large number of bovine samples that were unsuitable for nitrate testing. In the past, submission of the entire globe had been recommended. However, the longer the fluid stays within the eye the more likely hemolysis will occur. This is enhanced by the rigors the sample undergoes while being shipped to the laboratory.

KSDVL recommends that samples for nitrate testing be collected in the field, and that the entire globe not be submitted.

Aqueous humor (ocular fluid) is an excellent sample to collect in suspected cases of nitrate toxicosis. Nitrate levels in ocular fluid are relatively stable postmortem.

Samples of ocular fluid are easily collected at necropsy with a sterile needle and syringe.

Sampling procedure:

1. Begin by ensuring the surface of the eye is free from mud and other debris. A 16-18 gauge 1-inch needle and 3-12 cc syringe is used, depending of the size of the animal.
2. Enter the anterior chamber through the cornea.
3. Gently aspirate 1-2cc of ocular fluid.
4. After collection, the fluid should be placed in a sterile red-top tube.
5. The sample should be shipped on an ice pack. Following these procedures should ensure a suitable sample is obtained for nitrate testing.