Some observations on the gastrointestinal tract of the plains zebra in Kenya

 (writing in progress)
 
While doing research in the slaughterhouse on Wildlife Ranching and Research, in November 1987, June 1988, and Jan. 1989, I made the following notes from carcases of the plains zebra (Equus quagga boehmi), shot on the ranch and butchered for sale.

Most of this ranch was recently incorporated into Nairobi National Park (https://www.youtube.com/watch?v=6OKP13w4Tds).

I dissected and measured the gut of the plains zebra, among other spp. of ungulates.
 
For background information, see https://practicalhorsemanmag.com/health-archive/architecture-of-the-equine-digestive-system-11756/ and http://www.gaitedhorses.net/Articles/Colic.html and https://www.horsehage.co.uk/nutrition/horse-digestive-system/ and https://veteriankey.com/gastrointestinal-physiology/ and https://ohioline.osu.edu/factsheet/1022 and https://www.extension.iastate.edu/equine/blog/dr-peggy-m-auwerda/digestive-anatomy-and-physiology-horse#:~:text=The%20horse%27s%20gastrointestinal%20tract%20consists,and%20rectum%20(figure%201).&text=Anatomical%20features%20of%20the%20mouth,teeth%2C%20tongue%20and%20salivary%20glands and https://hygain.com.au/blogs/library/how-many-stomachs-does-a-horse-have

The stomach is strikingly small with a thick wall. The contents are more finely ground up than expected for a monogastric (non-ruminant) ungulate. The smell of the stomach contents is ‘herby’ and fragrant. This is a fresh smell, not a digested smell.

In one specimen, their texture is about the same as the faeces of the zebra; the stomach contents are caked, not fluid. In another specimen, shot during the rainy season and probably grazing fresh, short pasture, the stomach contents are fine and green - as rich-looking as the normal rumen contents of the coexisting Thomson’s gazelle (Eudorcas thomsonii).

There is a surprisingly large number of botfly larvae alive in the stomach (observed on several occasions, not just once). See https://entnemdept.ufl.edu/creatures/livestock/horse_bot_fly.them. These act as endoparasites, attached to the stomach wall.

The small intestine is as long as expected, but softer (thicker-walled) than expected. The first half of the small intestine is more or less empty, its contents being a yellowish mucusy liquid like thick congealed soup. The second half of the small intestine has fine-textured plant contents (liquid). Towards the end of the small intestine the intestinal wall is surprisingly thick and muscular, so that its contents squirted out on pressure, as if from a garden hose.

The caecum is extremely large, with the shape of a fat caterpillar. Its contents smell just like the insides of the rumen of a giraffe (Giraffa tippelskirchi). I see a few large nematodes inside the caecum.

The caecum and large intestine are folded back on themselves intricately, the connecting membranes making this part of the intestines hard to tease out in dissection. The large intestine, beyond the jumble of caecum and proximal colon, is surprisingly short, and sacculated so that faecal pellets form immediately on the exit of the gut contents from the proximal colon.

The pellets are at first soft, becoming progressively harder and drier towards the end of the colon. Here, the single row of faecal pellets is piled up inside the rectum. I.e. the single row of pellets is converted to an accumulation several deep. The rectum is thus not just a terminus for the faecal pellets, but a ‘dam’ for them.
 
(writing in progress)

Posted on 12 de julho de 2022, 11:52 PM by milewski