Okay, I FINALLY properly identified what it is that's growing in yard that my pigs like so much. It's called Bidens pilosa, commonly called spanish needles or beggarticks.
Here is a page on them:
https://plants.usda.gov/cgi_bin/topics.cgi?earl=plant_profile.cgi&symbol=BIPI
And another showing it's food and medicinal uses:
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Apparently it's a medicinal plant in China, and a common vegetable in Africa, and an invasive weed in the US.
Nutritional Analysis from:
https://www.ibiblio.org/pfaf/cgi-bin/arr_html?Bidens+pilosa&PRINT
Edible Uses
Leaves; Tea.
Leaves - raw or cooked[177]. A resinous flavour[173]. Added to salads or steamed and added to soups and stews, they can also be dried for later use[183]. A nutritional analysis is available[218].
Young shoot tips are used to make a tea[177].
Composition
Seed (Fresh weight) In grammes per 100g weight of food:
Protein: 17.5 Fat: 17.1
Leaves (Dry weight) In grammes per 100g weight of food:
Water: 0 Calories: 295 Protein: 24.5 Fat: 4 Carbohydrate: 56.4 Fibre: 12.1 Ash: 15.1
In milligrammes per 100g weight of food:
Calcium: 1721 Phosphorus: 273 Sodium: 11 Potassium: 267 VitaminA: 12
More cut/pastes:
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Beggar ticks or Spanish needles (Bidens pilosa)
This is an annual herb that is a common garden weed throughout much of the world's tropical and sub-tropical zones. Leaves of this plant are sometimes eaten raw when very young, but more often steamed. They are dried for later use in parts of Africa and in the Philippines. In Zimbabwe they are lightly boiled with a little peanut butter mixed in afterwards.
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"Although the fat content of leaves is generally low, some exceptions are Bidens pilosa (22.5%) "
This is a link to a poster for a Zulu nutritional program showing it's vitamin C another other content:
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Anyway, guess it's safe, the pigs LOVE it. It's not only cheap, it's totally free and it looks like it might also be very good for them.
Any comment? Did I miss anything?
Fawn