Field methods for estimating serum immunoglobulin concentrations in newborn kids

Abstract

Serum samples were collected from 41 newborn kids between 48–96 h of age after consumption of colostrum at birth. Serum immunoglobulin (Ig) concentrations were determined using a quantitative, spectrophotometric zinc sulfate turbidity assay, and total serum protein was determined using a refractometer. A qualitative sodium sulfite precipitation test was also performed to evaluate Ig content using 14%, 16% and 18% sodium sulfite solutions. Failure of passive transfer of maternal immunity (FPT) in newborn kids was defined as a serum Ig content of less than 1200 mg/dl, and 1200 mg/dl or above as successful passive transfer (SPT). Based on these criteria, and using a total serum protein level of 5.4 g/dl as the cutoff point, refractometry correctly identified 17 of 17 kids (100%) with FPT and 20 of 24 kids (83.3%) with SPT. Four kids (6.7%) with adequate serum Ig levels were misidentified as FPT. Sodium sulfite precipitation at 14% correctly identified 17 of 17 kids (100%) with FPT, but only 3 of 24 (12.5%) with SPT. Twenty-one of 24 kids (87.5%) with adequate serum Ig levels were misidentified as FPT. Sodium sulfite at 16% correctly identified all 17 kids with FPT and 19 of 24 kids (79.2%) with SPT. Five of 24 kids (20.8%) were misidentified as FPT. Sodium sulfite at 18% correctly identified all 17 kids with FPT and 22 of 24 kids (91.7%) with SPT. Only two of 24 kids (8.3%) were misidentified as FPT. It was concluded that the sodium sulfite precipitation test, with an 18% solution, was a useful method for screening young goat kids for FPT or confirming SPT in the field. Total protein determination of refractometry using a cutoff value of 5.4 g/dl was also an acceptable screening method but less reliable than the sodium sulfite precipitation test. When using either method as a screening test, it is recommended that serum from individuals with a provisional diagnosis of FPT be submitted to a laboratory for a quantitative determination of Ig concentration to avoid cases of misidentification.