excretion

what goes in, must come out!

After a chicken consumes food, the nutrients are absorbed by the body as it passes through the digestive tract. The leftover particles that were not absorbed are considered to be waste products, and these accumulate at the end of the digestive tract, in order to be excreted.


According to the online blog Living Homegrown by Theresa Loe, "Adult chickens poop about every 20 minutes" which indicates that chickens' metabolism is quick and efficient (Loe, 2015).


Chicken excrement can be of many colors, sizes, textures, and consistencies. A compilation of examples is shown below in Figure 38. Stool condition is strongly influenced by diet; as stated by Theresa Loe, "If you feed chickens a boatload of blackberries, they will have bright purple poop" (Loe, 2015). It is important to monitor the stool condition, as it may indicate dietary imbalances. Normal or regular chicken stool is brown, solid, and has white dustings (Hudson, 2021).

Figure 37. Chicken Poop 101: Everything You Should Know & Look Out For. Roberts, 2021. Retrieved on November 30, 2021 from https://www.knowyourchickens.com/chicken-poop/


Figure 38. The Complete Guide To Chicken Poop. Hudson, 2021. Retrieved on November 30, 2021 from https://cs-tf.com/chicken-poop/

In 2018, the components of chicken feces was extensively studied by researchers in China, who had the goal of investigating antimicrobial resistance genes (ARGs) in bacteriophages. Samples were gathered from thirty different farms located across northern, central, and southwest provinces of China. The samples were mixed with buffer solutions, centrifuged, and filtered in order to isolate phage particles.


The researchers found and identified twelve antimicrobial resistance genes in the samples' bacteriophages:

  • aac(6′)-Ib-cr

  • aph(3′)-IIIa

  • blaCTX-M

  • ermB

  • ermF

  • floR

  • mcr-1

  • qnrS

  • sul1

  • sul2

  • vanA

  • tetM

(Yang et al, 2020).

The researchers mentioned that the three most prevalent antimicrobial resistance genes were sul1, tetM, and aac(6′)-Ib-cr.


Additionally, they did not find any differences in the antimicrobial resistance gene detection rates relating to the varying geographical origins of the samples (Yang et al, 2020).


In the chart to the right, data regarding the abundancy of the antimicrobial resistance genes is displayed. The horizontal rows each represent one of the thirty samples taken from the participating farms.

Figure 39. Heat Map Showing The Abundance Of ARGs Detected In Different Chicken Feces. Yang et el, 2020. Retrieved on November 30, 2021 from www.sciencedirect.com/science/article/pii/S0048969719344377?via%3Dihub#s0075

possible uses for chicken excrement

Billions of chickens are raised each year to meet the high demands of the food production industry. Consider how each adult chicken defecates approximately every 20 minutes (Loe, 2015). Now, try to imagine how much excrement was produced by the 25 billion chickens raised in 2019 (Shahbandeh, 2019). It's impossible! Luckily, there are two things that chicken excrement could be used for.

organic fertilizer

Figure 40. How To Compost Chicken Manure & Use It In The Garden. Waddington, 2020. Retrieved on November 30, 2021 from https://www.ruralsprout.com/chicken-manure/

anaerobic digestion

Figure 41. Graphical Abstract. Beusang et al, 2020. Retrieved on November 30, 2021 from https://www-sciencedirect-com.jpllnet.sfsu.edu/science/article/pii/S0048969720330114

Chicken excrement contains decent NPK (nitrogen, phosphorus, potassium) ratios, making it a coveted product by avid gardeners. Elizabeth Waddington, a writer for the Rural Sprout, states that "Adding a well-aged chicken manure to your garden can not only increase its fertility but also improve soil structure" (Waddington, 2020). Because chicken excrement is so readily available, it is very inexpensive. A bag of chicken manure could cost as low as $3.00!

Figure 42. Example Of Chicken Manure For Sale. Home Depot, 2021. Retrieved on November 30, 2021 from https://www.homedepot.com/s/chicken%2520manure?NCNI-5

Poultry excrement can be detrimental to the environment if accumulated into large amounts and neglected. Some examples include eutrophication of water bodies, air pollution, and the spreading of pathogens (Beausang et al, 2020).


Anaerobic digestion (AD) occurs by placing organic matter, in this case it would be chicken excrement, into a reactor containing microbial communities that would break down the waste (EPA, 2021).


A study conducted in Ireland utilized a pre-existing AD facility and made modifications to plant parameters to accomodate the chicken excrement. It is mentioned that the first stage of anaerobic digestion takes 34 days to complete, and the second stage of pasteurization takes one hour to complete (Beausang et al, 2020).


The results of the study demonstrated that there was a net reduction of environmental burdens and risks (Beausang et al, 2020). Below are charts with the study's data. With the perspectives of protecting and preserving the environment, it would be of best interests to utilize methods of anaerobic digestion to eliminate poultry excrement.

Figure 43. Process contributions for the selected impact categories. Positive bars depict the incurred impacts and negative bars the avoided impacts. Beausang et al, 2020. Retrieved on November 30, 2021 from https://www-sciencedirect-com.jpllnet.sfsu.edu/science/article/pii/S0048969720330114

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