Thoroughbred breeding: passive immunity transfer in the newborn foal

Serum samples from eleven Thoroughbred mares were collected during the last 3 weeks of pregnancy until delivery with the purpose to evaluate immunoglobulins contents (IgG, IgG(T), IgM, IgA) and total proteins levels. In order to evaluate some possibile correlations usefull for an early prediction of immunotransfer deficiency from mare to foal, colostrum and foals serum samples were also collected at different time to analyze immunoglobulins and serum proteins fractions. IgG’s mean mare serum concentration was 1672 mg/dl at 3 weeks with a trend to decrease near foaling. Total serum proteins mean level was 6.77 g/dl at delivery and 6.04 g/dl one week later. Mare serum IgG(T) were predominant immunoglobulins class in all samples and their levels were 682 mg/dl as mean. IgGa and IgGb mean values were 310 and 300 mg/dl. IgM mean level was 44 mg/dl. Colostral IgG level at foaling was more than 8000 mg/dl (48% TP) and only 330 mg/dl 24 hours after foaling, then 138 mg/dl at 15 days and 117 mg/dl at 30. A good correlation was noted between mare serum at delivery and 24 hours colostrum IgG levels. Mare serum IgA collected one week before foaling were strictly correlated with 24h colostrum IgA. Foals serum IgG mean values were nearly 40 mg/dl in the samples collected within three hours from the first suckling until reaching 1058 mg/dl (about 20% TP) at 24 hours. IgGa and IgGb subclasses showed the same evolution. IgG(T) were significantly correlated with IgG at 24h and showed highest values at 24 hours (261 mg/dl). IgM and IgA contents also showed highest values at 24h (14 and 46 mg/dl). Foal serum á-2 globulins level significantly increased between birth, 24 hours (about 0.40 g/dl) and one week (0.70 g/dl). Foal serum total ã-globulins concentration significantly increased between 0h (0.64 g/dl), 24h (1.68 g/dl) and one week. A/G ratio decreased between 0h (1.68) and 24h (1.20), following ã-globulins concentration.