Goats keep the weeds eaten and they like to climb, so will spend lots of time on concrete rubble. Lots of Mexicans like goats, they eat goats, and the animals are more common than in the US. This is a good thing about Mexicans.
Slaughtering goats is done with a knife cutting the throat. Then they would be hung on trees to butcher.
The Romans used blood as a concrete additive. It is an air entraining agent, making the concrete lighter and freeze resistant.
Back in the day a soul was needed under the cornerstone, the first stone laid, of a new building. Animals were most often substituted for people, or written notes of people's names. One's shadow must not fall on a foundation excavation unless involved in the work.
Here is a patent for blood as a concrete additive:
http://www.freepatentsonline.com/4203674.html
Good work archiving those videos.