BackgroundDairy cows are at the highest risk of developing clinical and subclinical diseases and disorders in the first few weeks following parturition. During the periparturient period, from approximately 30 days before calving to 30 days postpartum, the immune system of the dairy cows undergoes a multitude of changes to prepare for parturition, colostrum production and lactation. One such change is the transfer of a large amount of immunoglobulin G proteins, especially subclass IgG1 to colostrum, leading to a reduction of IgG1 in the blood. As IgG1 and IgG2 need to maintain a balance to protect animals from intracellular and extracellular pathogens, a disruption of this balance compromises the immune protection of the animals. Rapid tests that can detect these immunological changes may be potentially useful for predicting the risk of dairy cows developing infectious diseases and other adverse health conditions following parturition. ResultsWe report here a new rapid test to detect certain immune status changes in the blood serum of dairy cows. This test uses a nanoparticle probe to evaluate the relative quantity of IgG1 and IgG2 in a sample. The nanoparticle probes are aggregated together upon interaction with bovine IgG2, while bovine IgG1 inhibits such interactions. The nanoparticle aggregates are detected by monitoring the color change of the assay solution using a handheld device. We tested the serum samples from 230 dairy cows collected during periparturient period, from 14-7 days before calving to 7-14 days postpartum. Results show that the test clearly detected an immune status change associated with IgG1/IgG2 relative quantity change around the time of parturition. Data analysis using mixed liner model in SAS (Statistical Analysis System) revealed a significant difference (P value = 0.042) in their test responses between healthy cows and cows with mastitis and/or lameness. ConclusionThe new rapid test we report here can be used to detect and monitor certain immune status change in dairy cows during the periparturient period. The test results may be potentially used to evaluate and predict the health risk of the dairy cows following parturition.

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