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An immunoglobulin-fortified milk replacer and a subcutaneous (SC) injectable solution of immunoglobulins (Ig) were examined as methods of achieving passive immunity in neonatal calves. Bovine Ig, from abattoir blood, were purified by polyphosphate fractionation and ion-exchange chromatography. In experiment 1, carried out at Agriculture Canada Research Station, Agassiz, 37 colostrum-deprived Holstein-Friesian bull calves were allotted to one of four treatments. Col/WM calves were fed colostrum on day 1 and whole milk, days 2 - 42. MR-Nolg calves (control) were fed milk replacer with no Ig, days 1-42. MR-Hi/Lo calves were fed milk replacer with Ig at 50 mg/ml on day 1, and at 10 mg/ml, days 2 -21. MR-Hi/No calves were fed milk replacer with Ig at 50 mg/ml, day 1,'and with no Ig, days 2 - 21. From days 2 2 - 42, MR-Hi/Lo and MR-Hi/No treatment calves received milk replacer with no Ig. In experiment 2, carried out at the University Research Farm at Oyster River, 24 colostrum-deprived Holstein-Friesian bull calves were allotted to one of three treatments. The first two treatments were the same as for experiment 1, Col/WM and MR-Nolg fed for days 1-21. MR-Lo Inj calves were fed milk replacer with Ig at 10 mg/ml, days 1-21, and were also given a SC injection of Ig solution within the first 6 hours of life. For days 2-42, calves were fed WM or MR-Nolg, as per experiment 1. For both experiments, blood samples and calf weights were taken at birth, 24 & 48 hours of age, day 7 and weekly thereafter for six weeks. Diarrhea (scours) levels, rectal temperatures and general health of calves were recorded daily for the first three weeks as well. Experiment 1 survival at 6 weeks of age was 11 out of 11 calves for Col/WM treatment, 8 out of 8 calves for MR-Hi/Lo treatment, 7 out of 8 calves for MR-Hi/No and a significantly lower (P>0.05) 7 out of 9 calves for MR-Nolg. In experiment 2, survival was 7 out of 8 calves for both Col/WM and MR-Lo-Inj treatments and a significantly lower (P>0.05) 4 out of 8 calves for MR-Nolg treatment. Calves on MR-Hi/No had significantly higher diarrhea levels than the other three treatments over weeks one and four in experiment 1. In experiment 2, calves which did not receive any Ig had significantly higher diarrhea levels over weeks three and four than calves which received Ig. Experiment 1 average daily gains (ADG) were significantly higher for calves on Col/WM, MR-Hi/Lo and MR-Hi/No treatments than for calves on MR-Nolg at six weeks of age. In experiment 2, six week ADG were significantly higher for calves on Col/WM and MR-Lo Inj treatments than for MR-Nolg. For both experiments, serum Ig levels of calves on Col/WM were significantly higher than calves on the other treatments at 24 and 48 hours of age. MR-Hi/Lo, MR-Hi/No and MR-Lo Inj calves trended to higher serum Ig levels than MR-Nolg calves but were not significantly different. Calves which received Ig, from colostrum, the Ig-fortified milk replacer or a subcutaneous Ig injection, had higher survival rates, lower diarrhea levels, less antibiotic treatment and higher average daily gains than calves hot receiving any Ig. It was concluded that immunoglobulins, administered either orally or parenterally, are an effective, alternative method, for providing passive immunity in neonatal calves. / Land and Food Systems, Faculty of / Graduate