A Novel Test for Poultry Welfare

Published: October 21, 2021

By: T.M. CROWLEY 1,2 / 1 MMR, School of Medicine, Deakin University, Geelong, Australia; 2 Poultry Hub Australia, University of New England, Armidale, Australia.

Summary

Welfare is of prime concern in the Australian Egg Industry and is highlighted with the ever-increasing demand for free range eggs. There have been huge changes in the egg industry in recent times to accommodate laying hens’ welfare, but what is driving this change? Some argue it is supermarket monopolies; others suggest it is people’s perceptions of hen welfare. Here we present a new scientific biomarker test that can used to determine the welfare and stress level of laying hens. The preliminary research presented in this report has surveyed cage, barn and free-range management systems to determine their welfare/stress state. This test has the potential to be used as an auditing tool for future investigations into the welfare/stress of laying hens.

I. INTRODUCTION

Heavily driven by public perception and large supermarket monopolies, welfare is of major concern for the poultry industry. The past few decades have seen development of poultry practices with a heavy focus on the welfare of poultry. There have been huge changes implemented to accommodate improvements in welfare, particularly in the layer industry. There are now a number of production systems including caged and free range which provide the consumer a conscious choice on how their eggs have been produced. These advances are closely regulated in most countries with regular inspections and audits to ensure the industry is committed to improving welfare standards. While these developments have undoubtedly facilitated an increase in perceived welfare standards, there is little research to confirm that there has been an actual increase in welfare standards and reduced stress on the birds. Many of the demands placed on the industry in terms of welfare are essentially based on public perception and interpretation, thus making it difficult to objectively assess the real welfare situation. Currently, there are a number of behavioural and other tests (cortisone levels) that have provided an insight into the welfare of poultry, but to date there is no clear scientific test that can be attributed to welfare.

Here we discuss a clear-cut test that will determine the welfare/stress on layers in various production systems. This will enable the industry to provide accurate scientific information on the welfare status of their production systems. This test will also enable auditors to directly test welfare during the course of their routine inspections. Over the last 30 years, a dramatic increase in society’s interest in the welfare of farm animals has arisen (Fraser, 2001; Coleman, 2008) and consequently there has been increasing scrutiny of the use of farm animals. A current weakness in studying animal welfare is that there are differing definitions of animal welfare (Fraser 2003; Sandøe et al., 2004). Together with a limited number of evidence-based assessments of welfare, there is need to develop further scientific quantitative assessments to allow producers and the industry to make decisions about the improvement of welfare in these systems. A commonly used biomarker of stress in avian species is measurement of corticosterone in blood. Corticosterone is the major adrenal glucocorticoid hormone that increases in birds under conditions of stress. Corticosterone has short-term effects on the physiology and behaviour of laying birds and also on their long-term performance. A wide variety of stressors, including environmental, temperature and humidity, housing space, feed and water restrictions and transport conditions, increase serum corticosterone concentrations in poultry.

Unfortunately, there are major practical difficulties with the measurement of blood concentrations of corticosterone as a biomarker of stress responses, due to the fact that the act of sampling serum from birds can have a profound effect on corticosterone levels as early as 45 seconds after restraint (Beuving and Vonder, 1978). Non-invasive techniques have been developed looking at the corticosterone in egg yolk and albumen (Singh et al., 2009; Royo et al., 2008) and faecal droppings (Rettenbacher and Palme, 2009; Rettenbacher et al., 2004). These techniques have reduced the sampling stress on the birds but can be time consuming and measure total corticosterone levels which does not distinguish between free (biologically active) and bound (not biologically active) corticosterone (Hemsworth and Coleman, 2011). Recently, a class of small non-coding RNAs, namely microRNAs (miRNA), that regulate gene expression and have a critical role in many biological and pathological processes, have been discovered. Studies investigating diseases in humans and other animals have shown clear differences in the expression patterns of miRNAs in serum from healthy compared to disease states (Chen et al.; Liu et al., 2011; Zhao et al., 2010; Gilad et al., 2008; Zhou and Verne, 2011; Schrauder et al., 2012). These studies suggest that the profile patterns of serum miRNAs are useful as biomarkers in a range of conditions, including welfare status. Serum miRNAs are packaged in exosomes and these encapsulated miRNAs have been found also in human breast milk (Zhou et al., 2012; Kosaka et al., 2010) and bovine milk (Chen et al., 2010; Hata et al., 2010). This paper will explore the use of these robust biomarkers as a means to identify stress in laying hens.

II. THE CURRENT STUDY

Here we present the first miRNA based stress test for laying hens. We believe that this test is ready for testing at the industry level. This test has the capacity to identify if hens are stressed at the flock level by using pooled samples and thus would provide real benefit for assessing stress in a range of farming and management systems. This test has the potential to play a role in the auditing of the stress/welfare of chickens across Australia.

Abstract presented at the 30th Annual Australian Poultry Science Symposium 2020. For information on the next edition, click here.

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