Serum opsonic activity and neutrophil phagocytic capacity of newborn lambs before and 24-36 h after colostrum uptake.

Neutrophil (PMN) counts, immune complex (IC) uptake by PMN, and serum opsonising activity for promoting yeast uptake were used to evaluate infection clearing capacity in 16 lambs prior to colostrum feeding (two lambs fed bovine colostrum, 14 suckled lambs) and at 2 days of age. At 2 days of age lambs had more circulating PMN than they had prior to colostrum uptake (P less than 0.01). Colostrum feeding caused a significant increase in the percent of lamb PMN phagocytosing IC, although at Day 2 the percent phagocytosis was significantly lower (32.2%) than for adult controls (90%). Yeast opsonophagocytosis was greater when 24-36 h post-feeding serum was the source of opsonin than when pre-feeding serum was used (P less than 0.001). When adult serum was the opsonin, yeast opsonophagocytosis was approximately twice the phagocytosis mediated by 24-36 h post-feeding serum. The peripheral neutrocytosis and the enhancement of opsonophagocytosis generated by absorption of either ovine or bovine colostrum did not differ. The results of this study suggest that the parameters evaluated may be used for indicating the presence (or absence) of passively acquired protective immunity.

A simple method for the demonstration of factors in bovine colostrum capable of causing anaemia in lambs reared free from maedi on bovine colostrum.

Previous studies demonstrated that the anaemia encountered in lambs reared on bovine colostrum and a milk substitute was associated with the presence of immune complexes on lamb erythrocytes. In the present study the usefulness of a panel of 20 sheep sera for the detection of "anti-sheep" factors in bovine colostrum by double immunodiffusion in agarose was investigated. Utilising this method, 353 batches of bovine colostrum have been examined, 132 of which were declared safe for use in the rearing of lambs. When fed to lambs, only 2 samples (1.5%) caused anaemia as compared with up to 20% before this test was introduced. Experiments designed to determine whether the bovine colostra, declared anaemia-prone, would indeed cause anaemia when fed to lambs, showed our method to fully discriminate between safe and unsafe colostra for the rearing of lambs. In a follow-up collaborative study, set up to cover most of the Netherlands, the general validity of the test system described was demonstrated, using 114 batches of safe colostrum to feed 723 lambs. Further experiments are needed to determine the exact nature of the factor(s) involved in this phenomenon.