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

Background

Foals suffer from total failure to transfer passive immunity (TFTPI) when serum immunoglobulin (IgG) is <4 g/L, and partial failure to transfer passive immunity (PFTPI) when serum IgG is 4–8 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 h of birth). IgG was estimated in mare colostrum and foal serum using Brix refractometry and turbidimetric immunoassay, respectively. Foals were weighed within 20 h of birth; daily until 7 days of age and weekly until 130 days of age.

Results

Mean foal serum IgG was 10.78 g/L (SD = 3.26) and mean mare colostrum Brix was 27.32% (SD = 5.96). A number of colostrum samples (20.9%, n = 112/535) measured <20% Brix and 20.4% of foals (n = 109/535) had serum IgG concentrations ≤8 g/L, 2.2% of foals (n = 12/535) had serum IgG less than or equal to 4 g/L and 18.1% (n = 97/535) had serum IgG between 4.1 g/L and 8 g/L. Foals had an average daily gain (ADG, kg) of 1.26 kg (SD = 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 g/L, p = 0.04). Similarly, for every unit increased in mare colostrum Brix (%) there were small, significant increases in foal serum IgG (0.25 g/L, p < 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.