In ruminants protection against environmental pathogens in the early post-natal period is largely dependent on passively-acquired immunity from maternal colostrum since evidence suggests placental transfer of antibody does not occur. Our overall aim is to develop antibody based treatments for protection of neonatal animals. In this study we have re-examined aspects of maternal antibody transfer to offspring especially in the light of recent evidence that feeding specific antibodies to neonatal rats decreases subsequent immune responses to the corresponding antigen. In experiment 1, pregnant ewes immunised with model antigen (human growth hormone) were terminated at 135 days gestation and blood samples collected from the ewe and fetus. Analysis of fetal plasma by antibody dilution/tracer binding assay procedures produced no evidence of antibody transfer to the fetal circulation via the placenta. In a further study the kinetics of specific antibodies were examined in lambs from immunised ewes. One group of lambs was permitted to suckle from the ewe for the duration of the trial (40 days) whereas the other group was permitted initial sucklings only, separated from the ewe 24 hours post partum and then fed a milk substitute. Analysis of specific antibodies titres revealed a very similar trend in both the amount of antibody transferred to lamb plasma and its persistence with the half-life for both groups calculated at approx. 13 days In the second experiment lambs from ewes immunised during pregnancy against E.coli and fed specific antibodies via maternal colostrum as neonates were compared to a matched control group of lambs derived from non-immunised ewes for subsequent immune responses against the same antigen. Peak antibody titres as analysed by ELISA were lower in lambs from immunised ewes than in control group lambs (mean titre (-log 10) 5.29
Proceedings of the New Zealand Society of Animal Production, Volume 55, , 174-175, 1995
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