nutritional needs & digestion
what do chickens eat?
Figure 5. Food Chain. Ahintz, May 16, 2012. Tech At Gattis, 2012. Retrieved on November 27, 2021 from http://gattistech.blogspot.com/2012/05/food-chain-in-kidspiration.html
Chickens are natural omnivores and their diet consists of seeds, bugs, fruits and vegetables, grains, and even sometimes smaller animals (Telkamp, 2018).
According the the University of Georgia, chickens have many nutritional needs. A chicken's diet needs to include carbohydrates, fat, protein, vitamins, minerals, and water (Fowler et al, 2015).
Carbohydrates could take many forms, some examples are glucose, sucrose, and cellulose. Although carbohydrates make up the majority of a chicken's diet, an excess of carbohydrates can be detrimental by causing intestinal issues.
Fats or triglycerides are found in oils and can be absorbed by a chicken's body without using energy.
Proteins are made up of amino acids, which can be rearranged upon consumption to create different or more useful proteins.
Vitamins are used by the chicken's body to conduct the chemical reactions required to process carbohydrates or fats or proteins. Vitamins naturally occur in edible foods and intake can be increased with supplements.
Minerals such as calcium, sodium, and phosphorus are important parts of a chicken's diet, because they allow for bone formation and development. Minerals are not as naturally occurring as other components of a chicken's diet, so chickens are often provided with mineral-rich supplements derived from limestone or oyster.
Water is essential to all living things; a chicken must have sufficient access to fresh and uncontaminated water to drink from.
According to the Merck Veterinary Manual, a lack of Vitamin E and/or selenium can cause myopathy. This can affect skeletal, cardiac, and smooth muscle of chickens by approximately four weeks of age (Van Wettere, 2020).
To meet the high demands of the meat industry, researchers have studied ways of maximizing the nutritional value in poultry diets. In a review from Animal Nutrition, it is mentioned that protein serves many purposes in a chicken's body: it is involved with metabolic processes, hormones, blood, and more; and it is the most expensive ingredient when creating a proper diet (Beski et al, 2015).
The review analyzed different sources of protein, with the goal of finding options that are more available and feasible than plant-based sources of protein.
One option that satisfied the researchers was spray-dried porcine plasma. This source of protein is derived from blood meal, which is made by collecting and dehydrating by-products of slaughterhouses. The researchers found that the spray-dried plasma contains high nutritional value and minimal anti-nutritional factors, and that making a diet with 1-4% of it being blood meal can improve the poultry's performance (Beski et al, 2015).
Figure 31. Typical Nutrition Concentrations for Various Types of Poultry. Fowler, 2015. University of Georgia, 2020. Retrieved on November 27, 2021 from https://extension.uga.edu/publications/detail.html?number=C954&title=Nutrition%20for%20the%20Backyard%20Flock
the digestive tract is also known as the foregut
Figure 32. Parts Of The Digestive Tract Of A Chicken. Saad A Naji, January 2016. Research Gate, 2016. Retrieved on. November 27, 2021 from https://www.researchgate.net/figure/Parts-of-the-digestive-tract-of-a-chicken_fig5_316699373
When a chicken eats, food first travels from the mouth to the crop. The crop has mucuous glands and the capacity to store food particles, where they are moistened and prepared for chemical digestion in the proventriculus. Beyond the proventriculus is the ventriculus, commonly known as the gizzard and equivalent to the stomach, is comprised of the mucuous membrane, the submucuousa, the muscle tunic, and the serosa. The pH levels of the gizzard are dependent on the type of food that the chicken consumes (Rodrigues et al, 2018). Food then passes further along the digestive tract, so that the body can absorb nutrients.
Over time, the domestication of chickens and the use of commercial feeding practices have caused chickens to evolve with decreased functionality in their crops and gizzards. The crops are storing less food and the gizzard undergoes less mechanical digestion (Rodrigues et al, 2018).