Can an increased intake of metabolizable protein affect the periparturientrelaxation in immunity against Teladorsagia circumcincta in sheep?

Within the overall hypothesis that the periparturient relaxation of immunit y (PPRI) to gastrointestinal parasites has a nutritional basis, we studied whether an increased intake of metabolizable protein (MP) could affect the expression of immunity to Teladorsagia (Ostertagia) circumcincta of twin-be aring and -rearing Greyface ewes. Two sets of iso-energetic diets were form ulated to provide either 85% (L-) or 130% (H-) of the MP requirements durin g the last 6 weeks of pregnancy (-P) and the first 6 weeks of lactation (-L ). Thirty ewes were allocated to LP or HP. Six ewes of each group were slau ghtered after lambing (S-0); the remaining 24 ewes of each group were alloc ated to either LL or HL, thus creating four treatment combinations during l actation (LP/LL, LP/HL, HP/LL and HP/HL; n=12). Six ewes of each treatment combination were slaughtered at Week 3 (S-3) or at Week 6 (S-6) in lactatio n. The HP ewes were heavier at lambing, produced heavier lambs, had lower faec al egg counts (FECs), a lower concentration of plasma pepsinogen, a higher concentration of plasma albumin during late pregnancy and more abomasal glo bule leukocytes (GLs) but similar worm burdens at S-0 compared to the LP ew es. The LP/HL and HP/HL ewes had a higher calculated milk production than t he LP/LL and HP/LL ewes. FECs increased for each treatment combination duri ng the first 3 weeks of lactation. This increase concurred with fewer aboma sal GLs at S-3 compared to S-0. The LP/HL and HP/HL ewes had a higher propo rtion of immature worms and more abomasal GLs than the LP/LL and HP/LL ewes at S-6. The FECs continued to increase during the second 3 weeks of lactat ion for the LP/LL ewes only, which concurred with an elevated plasma pepsin ogen concentration and an absence of abomasal GLs at S-6. The plasma pepsin ogen concentration decreased rapidly for the LP/HL ewes during lactation. W e conclude that an increased intake of MP could enhance the expression of i mmunity to T. circumcincta of twin-bearing and -rearing Greyface ewes. (C) 2000 Elsevier Science B.V. All rights reserved.