Strategies to improve colostrum management and the transfer of passive immunity evaluation in dairy calves

Abstract

Colostrum management is essential to ensure an adequate transfer of passive immunity (TPI) to all dairy calves. It is equally important to routinely assess TPI in order to make the necessary corrections in colostrum management and to identify animals with lower levels of passive immunity, which are consequently more susceptible and therefore require more attention. This study aims to evaluate and improve strategies related to colostrum management and TPI on dairy farms. From 2020 to 2024, data and biological material (colostrum, blood and saliva) were collected from dairy farms in the Alentejo region. This information has led to the formulation of five chapters distributed according to their general objective. Variation in colostrum quality and its determinants were evaluated on dairy farms in Alentejo, a southern region of Portugal. Colostrum quality was assessed by Brix refractometry, which served as an indicator of total protein content, and by the microbiological composition, which served as an indicator of the hygiene practices during colostrum handling. A prevalence of 28.6% of poor-quality colostrum was observed and the main contributing factors were identified. It was also found that a significant percentage of calves (43%) received colostrum of poor microbiological quality. The factors involved in TPI were investigated and predictive models were developed. To test for association with serum IgG levels, calf, calving and colostrum data were collected. A good TPI (IgG ≥ 18 g/L) was associated with the provision of colostrum based on the calf's body weight, high microbiological quality, and the intake of a second colostrum meal within the first 24 hours of life, while the first colostrum intake should occur within the first three hours of life. The hypothesis of using saliva as an alternative fluid to blood for the assessment of TPI was tested. Given the novelty of the subject and the scarcity of information available, analyses were carried out to understand the dynamics associated with the transfer of immunoglobulins from colostrum to blood and saliva. Twenty calves were monitored during the first week of life and colostrum, blood, and saliva samples were collected to determine the chemical composition of colostrum, total protein concentration, IgG, IgA, IgM and other biomarkers of immunity, stress and redox balance in blood and saliva. The results suggested the transfer of IgG, IgA and IgM from colostrum to blood and subsequently to saliva. The transfer of immune system components was shown to be important in protecting the calf against enteric disease. A positive relationship between blood and saliva was also observed, demonstrating the potential of saliva to assess TPI in newborn calves. XV The optimisation of colostrum management through digital and instrumental applications was also evaluated. A predictive model for calf weight based on biometric measurements was developed and a web application was designed for easy application of the model. In addition, a digital Brix refractometer was tested to estimate colostrum quality at farm level, measured by several parameters and a tool to evaluate colostrum management was proposed. The calf body weight prediction model showed a high level of confidence (R2 = 0.96). The refractometer showed a high level of confidence in identifying colostrum of high-quality. In conclusion, significant advances were made to improve some of the strategies related to colostrum management. In addition, this study demonstrated the potential of saliva to assess the immune system of newborn calves, providing a non-invasive and easily to collect method that benefits both animal welfare and farm management.