The Egypt Centre has 25 coffin clamps found at Armant. Here is one, EC2082.
Cows would have been placed on a board. Metal clamps like the one above would have been placed around them and then linen bandages tied across the body and to the clamps would have ensured that the cow stayed in place. There is a papyrus called the Apis papyrus, which describes the rituals for the mummification of the Apis bull. It seems that similar rites were also carried out on the Buchis and the mother of the Buchis. The Papyrus states that 22 coffin clamps should be used. Most of the burials of the Buchis and the mother of the Buchis used between 21 and 23 clamps.
We also have a stela found at Armant which shows Commodus offering to the mother of a Buchis bull.