Incidence of Inadequate Transfer of Passive Immunity in Dairy Heifer Calves in South Australia.

Simple Summary: Calves are born with an underdeveloped immune system, and therefore must absorb immune components, such as immunoglobulins, from their dam's first milk (colostrum) to help fight infectious disease. If they do not receive enough good-quality colostrum within 24 h of birth, their immune status is compromised, and they are more likely to have poor growth and health in their first 12 weeks of life. Colostral immunoglobulin uptake can be estimated by measuring serum total protein with a digital refractometer in calves 1–7 days of age. The aim of this study was to estimate the uptake of colostral immunoglobulin in female dairy calves from five pasture-based dairies in the southeast of South Australia to evaluate the proportion of calves that did not receive an adequate amount of colostrum. The objective of this observational study was to estimate the incidence of inadequate transfer of passive immunity (ITPI) on five pasture-based dairy farms in South Australia. Heifer calf uptake of colostrum was evaluated within the first 1–7 days of age (n = 2638) using a digital refractometer to estimate each calf's serum total protein concentration, as an indicator of colostrum uptake. Results of <51 g/L indicated inadequate transfer of passive immunity (ITPI). The data showed that the incidence of ITPI on the farms was 6.5%, 31.3%, 48.8%, 49.7% and 52.4%. The incidence of ITPI was calculated in relation to the age of the calf at testing and the breed of calf, and no significant differences were found. A significant difference was found in the incidence of ITPI when comparing the calf's first feed after separation from the dam (colostrum versus a colostrum-transition milk mixture). The farm with the lowest incidence of ITPI collected calves twice a day, measured colostrum quality on farm with a Brix refractometer and ensured that each calf received an appropriate amount of high-quality colostrum soon after collection. Further studies are required to establish the risk factors of ITPI in South Australian dairy heifers. [ABSTRACT FROM AUTHOR]