Talked to my vet today and he agrees with
@Silver. She got down for whatever reason and beat the daylights outta herself, trying to get up. Also explains the rectal prolapse.
And the calf? Pneumonia. Currently have one 4 days old I'm treating. Born during yet another one of our epic recent rains. Gave her Inforce 3 & a First Defense bolus when she was a few hours old, tagged her the next day. Wasn't initially concerned yesterday when her mama had her bedded down by herself because this is her 2nd calf, they usually "hide" them a day or so. But by the afternoon, mama was acting anxious. Calf looked fine, nursing and poo looked good but I was on high alert. Temp 102.4 so gave her 4.5cc Resflor Gold. Temp up to 103.8 this morning so hit her with .5cc Draxxin & Banamine Transdermal. She's still nursing like a champ, even tried to kick me while I was taking her temp. And mama brought her in with the herd later today, so cautiously optimistic the meds are kicking in.
Vet assured me the pervious calf wouldn't starve to death on 2 teats, especially at only 3 days old. So, was I complacent, not considering pneumonia because I gave him the Inforce 3 right off the bat and he looked/seemed fine? Probably. Tough lesson to learn. I had 100% success last year, including 3 sets of twins, a calf with a naval infection, one whose mama had mastitis (and subsequently had to supplement) and another pneumonia tsunami after weaning - in spite of 3 rounds of respiratory.
Just when I think I've got it figured out . . . .