Group 1: unchallenged recipients and development of scrapie in offspring.

CD = caesarean derivation and hand rearing, NB = natural birth, reared by recipient ewe.*(scr) – embryo donor later developed natural scrapie**Where two progeny indicated per recipient, these developed in utero together and born as “twins”. Deaths are from scrapie (Death scrapie) or other causes (Death other) and given in days of age (d).