Evaluation of Passive Transfer Immunity and Predicting Survivability in Newborn White-Tailed Deer Fawns

Immunoglobulin gamma (IgG) is used as a marker for the success or failure of passive transfer in neonates that rely on the maternal transfer of immunoglobulins through the consumption of colostrum. Industry standards for successful passive transfer have been established for major livestock species; however, benchmarks have yet to be determined for pen-raised white-tailed deer fawns (Odocoileus virginianus). The objectives of this study were to determine an on-farm methodology to indicate successful passive transfer of immunity and to identify methods to characterize physical status that may be used to predict the survivability of pen-raised white-tailed deer fawns. Fawns (n=153) born to 88 white-tailed does (1.5 to 7.5 yr, 40-80 kg) from an established herd (3-S Whitetails, Bedias, TX) were utilized in this study. Measurements including BW, body length, and cannon bone length were obtained biweekly from birth to six wk of age. At 24 h of age, blood samples (6 mL) were obtained via jugular venipuncture. Blood was analyzed on-farm using a handheld digital refractometer (MISCO PA201). Both whole blood and serum were analyzed for total protein concentration, IgG concentration, and a Brix value which was determined using a scale adapted for on-farm use on dairies. Serum IgG concentration was also quantified by radial immunodiffusion (RID) that was validated for use in cervids. Data were analyzed using the LOGISTIC, MIXED, and CORR procedures of SAS. During the trial, fawn morbidity rate was 75.8% and mortality rate was 21.6%. The logistic procedure indicated that serum Brix values (P<0.01) and serum IgG concentration (P<0.02) at birth were useful for predicting survivability of fawns. Fawns that survived had greater serum Brix values (8.93±0.17 vs 7.55±0.35 °Brix) and serum IgG concentrations (9.51±0.66 vs 6.80±1.40 g/L) than fawns that died. In addition, there was a strong positive relationship (P<0.01) between all on-farm serum measurements and results of the RID (r=0.87). Body measurements obtained were not predictors of survivability (P≥0.12); however, there were differences between fawns that survived and those that died. Fawns that survived had a greater (P<0.02) cannon length (18.39±0.10 vs 17.79±0.23 cm) and BW (2.74±0.05 vs 2.33±0.12 kg) at birth than fawns that died. These results indicate that serum IgG concentration and Brix values measured on-farm using a handheld electronic refractometer may be used to help predict passive transfer of immunity and survivability in white-tailed deer fawns. These results also indicate that certain physical characteristics of newborn fawns may be related to survivability.