The recent trend in the feed business is currently directed toward the use of natural ingredients as alternatives to antibiotics, synthetic colors, and other chemicals. Spirulina (blue-green alga) is one of the high-quality natural feed additives that can be used in animal and poultry nutrition. 

There are two different species of Spirulina: Spirulina maxima and  Spirulina platensis, with varying distribution throughout the world. Spirulina platensis is more widely distributed and found mainly in  Africa, Asia, and South America. The blue-green algae (Spirulina platensis) have been used for hundreds of years as a food source for humans and animals due to its excellent nutritional profile and high carotenoid content.  

Spirulina is relatively high in protein with values ranging between 55-65% and includes all of the essential amino acids. The available energy content of  Spirulina has been determined to be 2.50- 3.29 kcal/gram and its phosphorous availability is 41%. Also, Spirulina algae are rich in thiamin, riboflavin,  pyridoxine, vitamin B12, vitamin C and carotenoids and have been used throughout the world as a feed component in broiler and layer diets to enhance yolk color and flesh. In addition, it is rich in nutrients such as vitamins, amino acids, gamma linoleic acid, phycocyanins,  tocopherols, chlorophyll, and β-carotenes.  

It has also been reported that spirulina has health benefits for conditions such as diabetes mellitus and arthritis. It has also been shown that Spirulina has immuno-stimulatory effects and antiviral activity. Spirulina has been shown to enhance immune function, and reproduction and increase growth. 

Less than 1% Spirulina added to chicken diets has been found to significantly enhance the defense systems for increased microbial killing, antigen processing, and greater T cell activity, reported that hens fed Spirulina-containing diets achieved superior productive and reproductive performance compared to the control birds.  Moreover, found that egg yolk color was significantly improved by the addition of Spirulina to laying hen diets.  

An early study found no adverse effect of dietary Spirulina supplementation on egg production, feed per egg, egg weight, body weight, or mortality rate. However, others reported did not record any effect on the reproductive performance of laying hens. In another study,  dietary Spirulina inclusion improved egg fertility, from 87% to over 96%. 

Recently, concluded that dietary inclusion of  Spirulina at a level of 0.05% can partially offset the adverse effects of 300 ppm aflatoxin on the growth rate and lymphoid organ weight of broiler chickens. More recently, found that  Spirulina may be helpful for reducing the tissue burden of arsenic in ducks.

Spirulina platensis algae is a feed additive for local laying hens:

Generally, the best results of the productive and reproductive performance or egg  quality in the present study may be related to one or more of the following points: 

• Spirulina has an excellent nutritional profile (high carotenoids, high protein with includes all of the essential amino acids and is rich in minerals and vitamins.
• Spirulina has been shown to enhance immune function, reproduction, and growth.
• Feeding Spirulina-containing diets may increase the lactobacillus population and enhance the absorbability of dietary vitamins.