Mare colostrum quality and relationship with foal serum immunoglobulin G concentrations and average daily weight gains.

Abstract

BACKGROUND: Foals suffer from total failure to transfer passive immunity (TFTPI) when serum immunoglobulin (IgG) is <4&#x2009;g/L, and partial failure to transfer passive immunity (PFTPI) when serum IgG is 4-8&#x2009;g/L. OBJECTIVES: To explore risk factors for poor serum IgG concentration. STUDY DESIGN: Retrospective observational study. METHODS: Data from 535 Thoroughbred foals born to 177 mares were analysed and included foal sex, birthweight, month and year of birth and colostrum Brix %. Associations between dam age and colostrum Brix (%); and between foal serum IgG and liveweight gains were also measured. Pre-suckle colostrum samples and foal blood samples were collected (by jugular venipuncture within 12-24&#x2009;h of birth). IgG was estimated in mare colostrum and foal serum using Brix refractometry and turbidimetric immunoassay, respectively. Foals were weighed within 20&#x2009;h of birth; daily until 7&#x2009;days of age and weekly until 130&#x2009;days of age. RESULTS: Mean foal serum IgG was 10.78&#x2009;g/L (SD&#x2009;=&#x2009;3.26) and mean mare colostrum Brix was 27.32% (SD&#x2009;=&#x2009;5.96). A number of colostrum samples (20.9%, n&#x2009;=&#x2009;112/535) measured <20% Brix and 20.4% of foals (n&#x2009;=&#x2009;109/535) had serum IgG concentrations &#x2264;8&#x2009;g/L, 2.2% of foals (n&#x2009;=&#x2009;12/535) had serum IgG less than or equal to 4&#x2009;g/L and 18.1% (n&#x2009;=&#x2009;97/535) had serum IgG between 4.1&#x2009;g/L and 8&#x2009;g/L. Foals had an average daily gain (ADG, kg) of 1.26&#x2009;kg (SD&#x2009;=&#x2009;0.14). Serum IgG (g/L) was associated with year of birth, birthweight (kg) and colostrum Brix (%). For every unit increase in foal birthweight (kg), there were small, significant increases in foal serum IgG (0.04&#x2009;g/L, p&#x2009;=&#x2009;0.04). Similarly, for every unit increased in mare colostrum Brix (%) there were small, significant increases in foal serum IgG (0.25&#x2009;g/L, p&#x2009;<&#x2009;0.001). Month of birth was significantly associated with colostrum Brix (%) and with average daily gains; with lower values for both outcome parameters with increasing calendar month. Increasing dam age at foaling was associated with lower colostrum Brix (%). MAIN LIMITATIONS: Retrospective design with missing data, small convenience sample. CONCLUSIONS: Several risk factors were significantly associated with foal serum IgG and mare colostrum Brix (%) in the current work.