Ref Code: CAT22

Category

Teaching - not applicable

Research - 5

Objective

To describe fermentative and digestive processes of ingested feeds so that, ultimately, more appropriate dietary formulations can be made to maximise rumen efficiency.

Alternatives to animal use

There are various laboratory devices (eg Rusitec) that can be used to mimic rumen function. Intestinal digestion can be mimicked in vitro but these systems have the disadvantage of not faithfully mimicking inflow and outflow dynamics and do not have the ability for ion flux across membranes to represent a transepithelial passage of ions. These alternatives are not very practical due to these technical limitations and also on the grounds of cost.

Details of procedure

Rumen fistulation is easily accomplished in standing cattle by firstly sedating the animal (eg with Rompun®) or ensuring that the animal has had prior conditioning for standing in races in a bailhead. Following preparation of a site in the lumbar fossa area of the left side for surgery, the site is anaesthetised by local blocking of the lumbar nerves that issue from the 12th and 13th thoracic vertebrae and the first and second lumbar vertebrae. An incision is then made through the hide and careful dissection made to separate muscle layers and reveal the peritoneum. The peritoneum is cut and secured, revealing the rumen which is secured and sutured to the peritoneum, muscles and hide and then punctured. A rubber cannula is then placed into the fistula and secured.

Drugs, chemicals, or biological agents

Rompun® or a similar sedative, nerve block agents such as lignocaine, penicillin, non-steroidal anti-inflammatory agents.

Impact of procedure on the wellbeing of animal(s)

In general, rumen fistulation has only a minor effect and such animals can mature to normal live weights of 650kg.

Reuse and repeated use

Repeated sampling is not a problem, assuming that aeration of the rumen and contents is minimised by properly securing the fistula.

Care of animal(s) during/after procedure

Animals require post-operative attention for the first seven days and any non-dissolvable suture material and detritus removed. Animals should be observed daily from then on to ensure any cannula loss or fluid leakages are rectified as soon as possible. Check the area around the cannula on a daily basis and clean as necessary.

Pain relief measures

It is essential to have adequate anaesthetic block during surgery. In general, no further apparent pain affects the animal’s ability to graze or to ruminate, and consequently, in most cases, no relief measures are necessary.

Qualifications, experience or training necessary to perform this procedure

For complex re-entrant cannulae, experienced surgeons are required, generally with a veterinary background but any Technical or Scientific Officers that are familiar with surgical methods and aseptic technique are capable of the simpler fistulations and cannulations.