Lactoferrin (Lf), an iron-binding protein, plays a key part in host defence with diverse protective roles in infection and inflammation, including allergy. It is present in most mucosal secretions, including colostrum and milk. To quantify the levels of Lf in milk from New Zealand dairy goats, a sandwich enzyme-linked immunosorbent assay (ELISA) was established. Purified Lf, extracted from goat colostrum, was used to raise antibodies in rabbits and for ELISA standards. The ELISA method involved coating goat Lf antibody onto microtitre plates then sequential addition of standard or test samples, biotinylated-goat Lf antibody and streptavidin-biotin conjugate, with a colorimetric endpoint employing 3,3`,5,5`-tetramethylbenzidine. The intra and inter assay coefficient of variation was 4.1% and 7.8%, respectively. Average recovery of added Lf was 104.5%. Cross reactivity with bovine Lf was 40% and negligible for other milk proteins tested. In goat milk samples collected over the lactation season, the average Lf concentration was 31.8 ± 7.3 (standard error of the mean); 33.4 ± 5.2 and 821.8 ± 269.4 mg/L, in early, mid- and late season, respectively. An ELISA method has been developed that accurately and reproducibly measures Lf in goat milk samples. Lf levels in New Zealand goat milk are similar to those reported for the cow.
Proceedings of the New Zealand Society of Animal Production, Volume 68, Brisbane, Australia, 166-169, 2008
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