Prevalence of failure of passive transfer of immunity in dairy calves in a Mediterranean pasture-based production system of the south-west region of Western Australia

Highlights

• This study determined the prevalence of failure of passive transfer of immunity (FPTI) in dairy calves in a region of Australia with a mediterranean pasture-based production system.

• The established that FPTI in dairy calves in south-west of Western Australian dairy herds was low with a prevalence of 8.7%.

• The refractometer refractometer was not a reliable indirect method for determining passive transfer of immunity in calves.

Abstract

The objective of this study was to estimate the prevalence of failure of passive transfer of immunity (FPTI) in dairy calves in the south-west region of Western Australia herds. A cross-sectional study was conducted in 26/140 dairy farms and serum samples were collected from 495 healthy 2–7 day-old calves. A radial immunodiffusion (RID) test was used to determine the concentration of serum IgG and calves were classified as having FPTI if the IgG concentration was less than 10 mg/mL. Estimation of FPTI was also assessed using two indirect methods using serum total protein (STP) and a brix refractometer. The estimated prevalence of FPTI was found to be 8.7% (43 calves out of 495) by RID with the concentration of IgG ranging between 0 and 6.2 mg/ml. The STP was found to vary from 46 to 96 mg/mL and using a cut-off point of 55 mg/mL the calf level prevalence was estimated as 7.1% (33 calves). Using the brix refractometer, the prevalence was found to be 13.1% (65 calves) with the refractometer reading ranging 6–14% of IgG. In the present study there was no association between calf-level factors (age, sex and breed) and FPTI. There was a higher correlation of the RID test results and the STP results compared to the RID and brix refractometer results. It is concluded that the prevalence of FPTI in dairy calves in the south-west region of Western Australia is low (8.7%) and the brix refractometer is not a reliable indirect method for determining passive transfer of immunity to calves.

Introduction

Calves are born hypogammaglobulinemic and acquire passive immunity through the ingestion of colostral IgG (Larson et al., 1980; Weaver et al., 2000). The lack of or insufficient consumption of IgG results in the failure of passive transfer of immunity (FPTI), defined as serum IgG < 10 mg/mL (Calloway et al., 2002). Important factors that contribute to the successful transfer of passive transfer of immunity (PTI) include ingestion of high quality colostrum with an immunoglobulin concentration > 50 mg/mL of IgG, ingesting an adequate volume of colostrum with at least 150 mg of IgG, prompt ingestion of colostrum within 4 h from birth, and minimising colostrum bacterial contamination (Godden et al., 2019; Weaver et al., 2000). FPTI in calves not only causes significant negative impacts on their early life for instance reduced growth-rate, morbidity and mortality but also has adverse long-term negative effects on reproductive performance and milk production in the first and second lactations (Chuck et al., 2018; Donovan et al., 1998).

Given the benefits of colostrum, investigating the status of PTI in calves ≤7 days old is an important herd health component in dairy production systems. In North America, the prevalence of FPTI in dairy calves ranged from 19% to 37% (Beam et al., 2009; Trotz-Williams et al., 2008). In Australia, a prevalence range of 8% to 42% has been reported but these studies have only included sampling from the intensive dairying regions of the eastern states (Chuck et al., 2017; Phipps, 2016; Vogels et al., 2013). There is a lack of information on this important aspect within the pasture-based dairying regions of Australia such as Western Australia. Dairying in Western Australia is unique with a Mediterranean climate and with larger dairies compared with other states in Australia (Aleri and Laurence, 2020). The objective of this study was to estimate the prevalence of FPTI in the Mediterranean pasture-based dairying region of Western Australian dairies, and to further assess the accuracy of two indirect methods (serum total protein [STP] and brix refractometer) for assessing PTI compared with a direct method of determining serum IgG concentration using the radial immunodiffusion (Vishnu et al., 2015) test.