An update on biomarkers and biosensors for monitoring real time data on poultry health and welfare


One of India’s fastest-growing agricultural areas is poultry farming. It is now the world’s third-largest producer of eggs and seventh-largest producer of chicken meat. The Indian poultry industry should concentrate on generating high-quality eggs and meat due to the high demands of the global trade market. All appropriate health, nutrition and welfare criteria must be implemented to ensure high-quality production. The recording of real-time data on all of these factors is difficult, but because to technology improvements and the discovery of some biomarkers, real-time data on health, production and welfare is now feasible. These types of data are always valuable for early and quick detecting the common vulnerabilities as well as it also help, to better planning to minimize the risk of any future crisis. This article attempts to summarise the current solutions for real-time monitoring of poultry health and welfare.

Biomarkers for monitoring health and welfare:   

Intensive selection and nutritional supplementation have been two major focus areas of the poultry industry for the past 50 years in order to achieve optimal production. It revealed that, a significant changes have been formulated in genetic characteristics and feeding patterns. Genetic alteration and feeding patterns induced intestinal physiological stressed, particularly by environmental stress, dietary excess or some feed ingredients. Hippocrates also has been proposed 2500 years ago a healthy gut has long been crucial to overall health and that all disease originates from the stomach.  Welfare of animal is a emerging concerned in society, it is defined by the World Organization for Animal Health, “An animal is in a good state of welfare if it is healthy, comfortable, well nourished, safe, able to express innate behavior, and if it is not suffering from unpleasant states such as pain, fear and distress”. Recently some phenotypic biomarkers, intestinal health biomarkers, and pro inflammatory liver acute phase proteins used for monitoring flock health and welfare.

Fig: Common stressor of poultry and their real time monitoring techniques  

  • Phenotypic biomarkers associated with health and welfare: Physiological indicators such as body temperature, respiratory rate, heart rate, blood pressure and body weight are must be altered during any stress or diseases conditions. Measurement of these parameters is very simple by invasive monitoring techniques.
  • Structural biomarkers associated with intestinal health:   
  • Phenotypic analysis of intestinal villous and crypt

This is the golden standard test of poultry for monitoring the effect of feed ingredient    and feed additive. In this examination, height of intestinal villous and depth of intestinal crypt are measured by the histopathological examination. The villus length (VL)  measured from tip to the base of lamina propria, villus width (VW) at one-fourth, two-fourths, and three-fourths of the villus length and crypt depth (CD)  measured from the base of the villus to the mucosa.  The ratio of VL to CD was calculated by dividing the obtained values of VL by the CD VL by the CD. Villus surface area (VSA) of duodenum, jejunum, and ileum are also can calculated using the following formula

                      Villus surface area=2π× (average villus width/2) ×villus length

  •  Serum biomarkers associated with intestinal health

Infectious agent and oxidative stress are the major threats that tigers the inflammatory chain reaction with or without showing serious clinical symptoms. Due to prolong  inflammatory chain reaction  it can be change phenotype of intestinal epithelium cell, resulting change in expression of genomic presentation  and secrets various chemicals  that can be used as early biomarkers for monitoring intestinal health of poultry.

  1. Intestinal alkaline phosphates:  It is a negative biomarker of intestinal health. It generally expressed as defense molecules in serum.
  2. Increased in entroendocrine L-cell density:  The density of entroendocrine L-cell in the ileal mucosa positively indicates about intestinal health.  
  3.  Alterations in intracellular junction’s  allow to  bacteria  reach  to blood circulation  and at early stage   in liver  it lead to production of acute phase protein
  4. Total bacterial count in liver used as biomarker of intestinal permeability
  5. Detection & quantification of LPs in serum could be elegant indicator of increased paracellular permeability but technique to measure LPs are not very reliable.
  6.  D- Lactate concentration is serum used as biomarker of intestinal permeability.
  7.  Enzyme diaminooxidase concentration in chickens indicates damage of intestinal epithelium cell.
  8. Fecal biomarkers
  9. Dysbiosis of fecal microbiota: Fecal microbiota is quantitevely & functionally most developed in cecal part fecal microbiota used as proxy of intestinal microbiota; there are 100 to 1000 species more specific signature of dysbiosis bacteria belong to group fermicutes can be used. Quantification of entrobacteriaceae using Q PCR or other means may be use to measure dysbiosis in poultry.
  10. Terminal metabolites of fecal microbiota: Terminal feacal microbiota metabolites like propionate & butyrate concentration directly indicate intestinal health.Key enzyme butyryl -CoA acetate CoA, transferase indicate improper intestinal health. Investigation of poultry volatile fecal compounds like antitrypsin inhibitor is a potential biomarker of gut permeability. Intestinal fatty acid binding proteins is cytoplasmic protein exclusive to the intestinal enterocytes and can be regarded as a biomarker. Other potential biomarkers also have been identified includes lipocalin 2, ovotransferrin superoxide dismutase, fibronectin and intestinal alkaline phosphatase etc.

 (E) Acute phase proteins biomarkers associated with health and welfare

Acute phase proteins as diagnostic markers have the great value in identifying health problems associated with various metabolic disorders, inflammation, infectious diseases and stress. APPs are plasma proteins, mainly synthesized by hepatocytes, as part of the acute phase response (APR), and mediated by the major pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β) and interleukin-6 (IL-6), which are released during inflammation at the site of injury (Schrodl et al., 2016). APPs described in poultry as:

  1. α1-acid glycoprotein (AGP) :

AGP is one of the most important binding proteins in plasma, carrying out important anti-inflammatory and immunomodulatory roles to control inflammation (Luo et al., 2015). Elevated serum AGP levels have been observed in chickens infected with various bacterial or viral pathogens (Packialakshmi et al., 2016).

  • Serum amyloid A (SAA): 

SAA belongs to a family of apolipoproteins which is incorporated into high-density lipoprotein (HDL) and then it is released into the circulation (Benditt and Eriksen, 1977). In mammals, multiple SAA genes have been described but in chicken just one SAA gene has been identified (Ovelgonne et al., 2001). Persistently elevated serum SAA levels in chicken may result in the formation of AA amyloid protein, a SAA precursor. The accumulation of this precursor is able to cause joint amyloidosis, showing signs similar with chronic arthritis (Woldemeskel, 2012).

  • Haptoglobin-like protein  

Hp is the major hemoglobin-binding protein found in mammals. PIT54 (mammalianlike Haptoglobin) has been associated with Staphylococcus gallinarium and S. aureus infections (Garcia et al., 2009), E. coli and Eimeria tenella infections (Georgieva et al., 2010) and IBV infections (Asasi et al., 2013).

  • C-reactive protein (CRP):

 CRP was the first APP been described and is one of the major APP in humans and dogs (Eckersall and Bell, 2010).CRP has also been identified in birds with E. coli, Pasturella multocida, S. aureus infection (Patterson and Mora, 1964), IBV (Seifi et al., 2014), birds infected with Salmonella typhimurium (Rauber et al., 2014) and in birds exposed to heat stress (Sohail et al., 2010).

  • Ovotransferrin (OVT) :

In poultry, transferrin protein is an acute phase protein, which occurs as two forms with the same gene sequence expressed in liver and oviduct, called ovotransferrin (OVT). In chicken, OVT is a positive APP, increasing its circulating concentration in response to a stimuli and remaining elevated as long as inflammation persists

  • Micro RNAs

MiRNAs have been identified in animal species as markers for various biological processes. They play key roles in immune system, act as specific targets for inflammation and contribute for the diagnosis of a variety of diseases and stress disorders

g) Stress hormones:  Measurement of cortisol hormone can be used to assess welfare.

E)  Biosensors associated with poultry health and welfare: Sensor based technology also very useful emerging tools for monitoring health and welfare of poultry.

  1. Environmental Sensors:

It have been proven in many research exposure to elevated levels of temperature, relative humidity, and air quality  mainly  noxious gases like carbon dioxide and ammonia is reduce growth, feed conversion, and immunological response. Current advances in sensing technology, with higher capabilities at affordable prices, permitted to allow adopting some useful environmental sensor. Availability of multi-sensing systems to monitor environmental variable and air quality are highly relevant to provide a comfortable environment for poultry. These sensors based data can be used for developed a good prediction model to calculate the health and performance of poultry.

  • Acoustic Sensors

Acoustic sensors are mainly based on sounds emitted by living organisms and poultry have a social interaction between each other by producing voice alarm signaling. These some forms of acoustic signaling can also be considered as reliable stress indicators that might be reliable welfare assessment indicators. Current available bioacoustics software, like Raven software animals 2016, has made this type of analysis somewhat easier, thus, becoming a practical tool for behavioral and welfare studies.

  • Movement Sensors

High density or less spacing housing system always restricted movement of poultry lead to lameness. Currently some piezoelectric crystal based sensors used to determine locomotion differences like symmetry of the peak force in each foot that led to uneven walking which is a first approach towards real time broiler gait assessment. Movement of poultry is a direct indicator of the welfare status in poultry.

  • Thermal Sensors: Heat stress is crucial issue for poultry health as well as welfare aspect. It may impact on behaviour, immunity, and physiological processes and can cause major mortalities. Infrared thermal imaging (IRTI) technology creates infrared images showing the body’s superficial temperature distribution from the infrared radiation emitted by objects that is converted into electrical signals. In the thermal image, each colour expresses a specific temperature range related to the defined scale, thus it is a practical, non-invasive tool to study welfare aspects related to thermoregulation.
  • Electrochemical sensor:  Electrochemical sensor is a device that transforms chemical information, such as the concentration of a specific sample component or total compositional analysis into an analytically useful signal. It used to detect some pathogenic microorganism.