Charleen,
I'm not sure about other gourds. It would depend on the amount of cucurbitacin, the toxic substance found in all members of the squash family, they contain. In the edible squash varieties, that compound is much reduced, but then humans don't eat pounds of the stuff which would increase the amount of toxin consumed.
We'd only been ranching a year when I broke my ankle in 3 places and was laid up for months. I would have gone stir crazy if I hadn't had my computer as a research tool. I found it amazing how much agricultural information is available from legitimate sources, ".gov, .edu, or .org." I used those sources because the information is free and they have nothing to gain as they aren't trying to sell you someting. I learned a lot about grasses, cattle, wildflowers, weeds and toxic plants during that period of time.
Unfortunately, not all livestock react to the same toxic plant material in the same way or I would gladly share my list of links and plants with you. Some plants are universally toxic, but others may harm some livestock and not others. Since my list of links is about toxins and cattle, it wouldn't do you andy good since horses, and Charlie is part horse, are more sensitive and appear to react to a larger number of plants. Luckily, it is easier to find lists of toxic plants that affect horses which you might consider using since I haven't seen any that specifically refer to mules or Charlie's other ancestor, the donkey. Texas A & M sells a book on the most common toxic plants and identifies which livestock is sensitive to it. It even lists the symptoms to look for.
I use the pasture closest to the house as a birthing pasture. That way I can keep an eye on any potential birthing problems. I have a small corral that opens into that pasture. After birthing, mother and calf stay in other small pastures visible from the house until they are a month or two old when we move them to the other pastures. Last fall, we had 25 little ones at once (I'e been trying to synchronize all births down to a 3 month period.) They were soooo cute, playing and running together or in small groups. Then the smaller calves discovered they could get over the ground wire and under the hot wire to get to my garden and away from mom. The older calves figured out how to short out the hot wire to get in. They rampaged through my garden at will and ate just about all I had planted out. I discovered Crinums are not as toxic as listed when they ate all my pink ones. Luckily, my Brugs were already in the greenhouse. With this new fence, they will have to learn to fly, but since the gate can still be left open, I'll have to be careful about what I plant or there will be more trips to the vet.
