1. Advanced gastric atrophy and hypo- or Achlorhydrias cause very low levels of pepsinogen I in contrast to pepsinogen II, which remains elevated in serum

2. Advanced gastric atrophy and hypo- or Achlorhydrias cause very low levels of pepsinogen I in contrast to pepsinogen II, which remains elevated in serum (Samloff, 1982; Samloff et al., 1982)

3. The effects of dietary urea supplementation and of a 10-week trickle infection regime, simulating chronic exposure to Haemonchus contortus, on the zymogenic population of the Abomasa of Hampshire Down lambs was examined.At necropsy a variety of parameters including plasma pepsinogen concentrations, the wet weights of Abomasal fundic mucosal pieces and the amounts of pepsinogen contained in