Development of an Acute Phase Protein Index as an objective indicator of sub-clinical disease status in pigs
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Research partners: SAC and University of Glasgow
Industrial partners: ABN Ltd, Pfizer Animal Health Ltd, JSR Genetics Ltd. QMS and BPEX
Sponsors: The above mentioned industrial partners with match funding from Scottish Government (RERAD) under the Sustainable Livestock Production LINK programme
Duration: February 2008 – November 2009
Currently, there are no markers to measure the extent of sub-clinical disease and its impact on performance in pig herds. This project aims to assess the feasibility of using selected serum acute phase proteins (APP) to develop an index as a marker for sub-clinical disease in pigs.
Two pilot studies identified that enterotoxigenic E. coli (ET) and Listeria monocytogenes (LM) were appropriate pathogen models for inducing local and systemic challenges, respectively. In the main study, pigs of around five weeks of age were repeatedly infected with 106, 108 and 1010 colony forming units (cfu), or sham-infected (controls). ET infection reduced feed intake and body weight gain at 1010 cfu, which was accompanied with temporally increased haptoglobin (plasma protein) levels. Levels of pig major acute phase protein, serum amyloid A, haptoglobin and C-reactive protein, as well as body temperature, increased with increasing LM infection pressure, although LM infection did not significantly affect feed intake or body weight gain. Modelling using both ET and LM data provided an APP Index with significant predictive power for classifying pigs as sub-clinically infected or not, with good specificity and moderate sensitivity. Feed intake in ET infected pigs could be predicted from a strategic combination of selected APP (haptoglobin, albumin and apolipoprotein-A1), with a correlation coefficient (r) of 0.69 between predicted and observed feed intake (where 1 indicates a strong correlation and 0 indicates that there is no correlation).
This feasibility study has shown that an APP Index can be constructed to objectively assess presence and extent of sub-clinical disease in pigs, although whether APP responses per se concur with sub-optimal performance remains inconclusive.
Whilst validation of the concept is still required, assessment of herd APP Index can be seen as a first step to assessing health status, with potential follow-up testing for specific pathogens if the APP Index deviates from baseline. Such early detection of sub-clinical disease could enable timely and informed management decisions, to reduce or overcome its possible associated penalty on growth performance. This will aid reducing economic losses, minimize environmental burdens arising from lower input requirements and nutrient losses, and promoting healthy pig production.
Executive summary report
Page last updated 29-Nov-2010