Azolla as a beneficial macrophyte for livestock feed: a review

Abstract

Livestock plays a significant role in the livelihood enhancement of the people, especially in rural areas. The requirement for dietary protein for people from the animal sources is expected to increase. However, due to problems of feed shortages and high costs of feed the livestock sector and its contribution to the country’s economy are threatened in many countries. To address this problem, exploration of alternative sources of cheap feed resources is imperative. Azolla is one of the cheapest feed resources grown in water bodies, mainly in tropical and sub-tropical countries. There are various species of Azolla used as a feed source for livestock. Azolla filiculoides, Azolla pinnata and Azolla microphylla are the main species of Azolla that contribute to livestock feed. Nutritionally, Azolla is a good source of amino acids, minerals, and vitamins. It is commonly used for feeding poultry, sheep, and goats, and dairy cattle. Azolla is used as a supplementary feed with other feed resources to increase feed intake, growth, egg production, and milk yield, as proven by many researches. Besides animal feeding, Azolla is also used for soil fertility improvement, bioremediation, compost making, and biogas production. Therefore, the production and utilization of Azolla in an appropriate, way particularly in wetland areas will contribute to improving livestock nutrition and productivity.

PUBLIC INTEREST STATEMENT

The demand for livestock products is increasing nowadays. For this increased demand, there should be production of enough livestock products. However, the productivity of livestock is limited due to feed shortages caused by the conversion of grazing land into farmland, urban expansions, and the high cost of agro-industrial by-products, and the lack of adoption of efficient feed production practices. Most of the livestock producers are based on roughages and agro-industrial by products. However, non-conventional feed resources (feed resources that have not been traditionally used as livestock feed) like Azolla can be used as livestock feed because of its easy cultivation, nutrient richness, and multipurpose advantage. In many wetland areas, Azolla is readily available and sometimes it disturbs aquatic organisms. Appropriate utilization of Azolla helps to improve the productivity of animals and reduce its negative impact on aquatic organisms.

Keywords:

• Azolla
• nutrient
• macrophyte
• non-conventional
• feed

REVIEWING EDITOR:

• Pedro González-Redondo, University of Seville, Spain

SUBJECTS:

• Agriculture
• Environmental Sciences
• Fisheries Science
• Botany
• Plant & Animal Ecology
• Nutrition
• Environmental Management

1. Introduction

Livestock plays a vital role in the livelihood of the people, providing food, cash income, traction power, manure, and other social and cultural functions (CSA, 2015; Shiferaw et al., 2011). In addition to this, in some countries, livestock, particularly cattle are used as a symbol of an individual’s wealth and status (Herrero et al., 2013). Globally, products obtained from livestock contribute 17% of kilocalorie consumption and 33% of protein consumption (Rosegrant et al., 2009). The demand for livestock products, mainly in developing countries, is increasing (Thornton, 2010). In many developing countries like Ethiopia, Tanzania, and Kenya, the products obtained from livestock are the essential source of nutrients for improving the nutritional status of the people (Engida et al., 2015; Molina-Flores et al., 2020).

Under this situation, livestock productivity is important for the producer’s income, and livelihood, and finally for the survival of the entire population that depends on livestock production (Lamy et al., 2012). Even though livestock have such huge benefits for the livelihood of the people, however, their potential benefit is restricted in some areas, like tropical countries, due to factors such as nutrition, climate, and health (Lamy et al., 2012). For example, in tropical countries, supplementation of feed during feed scarcity season mainly in extensive farming practices is not common. As a result of this, approximately 20–40% of seasonal body weight loss is occurs in animals at the onset of the dry season (Lamy et al., 2012).

Thornton (2010) indicated that poor nutrition and breed improvement challenges are the main factors for better animal production in Africa. For example, in Ethiopia, livestock productivity is still low due to constraints such as shortage of feed, poor genetic makeup of the animals, poor veterinary services, and other socioeconomic constraints (Tsegay et al., 2015; Yayneshet, 2010). Among these constraints, feed shortages are one of the bottlenecks for market-oriented livestock production (Tolera et al., 2012; Valbuena et al., 2015). Worldwide, the land use system, particularly pasture land and meadows utilized for livestock feed is declining (FAO, 2022). For example, the contribution of natural grazing land for livestock feed is reduced from 90% (Alemayehu, 1985) to 57% (CSA, 2013) due to the conversion of grazing land into cultivated land and overstocking (Danano, 2007).

In most developing countries, the production of concentrated animal feed for supplementation is in the form of cereals and grains. It is expensive, and the supply of feed ingredients is usually inadequate due to competition for human food (Negesse et al., 2009). The provision of supplementary feed in the form of agro-industrial by-products is also not common, as smallholder farmers cannot afford it (Tolera et al., 2012). The problem of supplementing concentrate feed is prominent in poultry production where there is no provision of supplementary feed, especially in rural areas. The sole source of feed for the poultry birds is through scavenging in agricultural fields (Gebeyew et al., 2015), resulting in low performance. Therefore, it is imperative to explore the possibilities of utilizing various non-conventional supplementary feeds that include oil palm by-products, poultry excreta, local brewery wastes, watery plants (Azolla), kitchen leftovers, coffee pulp, and fish offal (Negesse et al., 2009) to enhance the productivity of animals. As an alternative, nutritionist and the public sector should explore alternative high quality and cheap livestock feed resources to help address feed shortages and maximize profit for farmers (Amaefule & Obioha, 2021; Bhujel & Rizal, 2022).

The benefits of non-conventional feed resources are that they bridge the gap between feed supply and demand, decrease human-animal feed competition, and reduce feed and related costs. Thus, identifying cheaper and bulkier locally available non-conventional feed resources can improve the productivity of animals by improving the intake and digestibility of low-quality forages (Negesse et al., 2009).

Among the non-conventional feed resources available, Azolla is an aquatic free-floating fern belonging to the family Salviniaceae that grows in aquatic ecosystems (Kannaiyan & Kumar, 2006). Based on the classification by the Pteridophyte Phylogeny Group (PPGI), Azolla belongs to the family Salviniaceae (PPGI, 2016). According to Taylor (2009), the Salviniaceae is represented by two extant genera, Azolla and Salvinia, which are sometimes placed in two separate families, Azollaceae and Salviniaceae.

Azolla, which belongs to the Azollaceae family, is known for fixing atmospheric nitrogen because of Anabaena azollae (blue-green algae) in the lobes of Azolla leaves (Ramesh, 2019), and it is rich in protein and minerals (Maliwal, 2020; Patil & Patil, 2020). It is used as a livestock feed, soil fertility, green manure, and biofilter for the treatment of wastewater (Amit et al., 2016). It is the fastest-growing plant and a known source of protein, containing almost all essential amino acids, mainly lysine, which is scarce in other feed sources, particularly in poultry rations (Prabina & Kumar, 2010). The plant also contains very important minerals such as calcium, potassium, magnesium, and vitamins such as vitamin A and vitamin B12. The crude protein (CP) content of Azolla reaches 23–42%, depending on the species of Azolla (Buckingham et al., 1978). It is a beneficial plant for feeding sheep, goats, cattle, poultry, pigs, and fish (Hossiny et al., 2008).

Azolla is a cheap and alternative source of protein that can improve feed conversion ratio (FCR), energy efficiency, and animal performance without adverse effects on livestock and humans (Namra et al., 2010). It is the most economical and efficient feed substitute for livestock and increases milk and meat production (Pannaerker, 1988).

The inclusion of 10% of Azolla as a supplement in the diets of broilers increased the body weight of broilers from 122.37 g to 850 g compared to zero percent of Azolla supplements, which increased from 123.01 to 752 g within four weeks (Joysowal et al., 2018), which is due to the nutrient richness of Azolla. According to Joysowal et al. (2018), 10% inclusion of Azolla in the diets of broilers resulted in 850.8 g body weight gain compared to 752 g body weight gain that depends on no Azolla supplementation. Different authors also confirmed that Azolla in layers diet improves hen day egg production performance by 6.4% when 50 g kg⁻¹ Azolla is included without deleterious effect and can be used as a year-round fodder for chickens (Khatun et al., 1999). Besides its utilization as a livestock feed, Sisworo et al. (1990) indicated that Azolla plays a significant role as a buffer for soil nitrogen (N) availability and enhances N use efficiency through capturing excess N at an early stage and releasing it at a later stage of rice growth. Azolla has a special advantage because of its fastest-growing characteristics, ease of cultivation, and growing in controlled conditions with low production costs and higher productivity (Prabina & Kumar, 2010). Thus, many nutritionists such as (Katole et al., 2017) recommended supplementation with Azolla for livestock, particularly poultry production.

In contrast, studies have also indicated that Azolla is a weed and invasive plant in many countries (Hill, 2003) that causes harmful and irreversible impacts on wetlands (Sax et al., 2005). It also reduces the ecological quality of the wetlands through biological and physio-chemical changes in aquatic ecosystems (Boets et al., 2009; Devin & Beisel, 2007; Olenin et al., 2007). Under appropriate utilization and controlled production system, Azolla can be used as a sustainable and climate smart agriculture farming in wetland areas (Kollah et al., 2016).

In Ethiopia, Azolla was introduced in the wetlands in 2004 from India as a biofertilizer (Feyisa et al., 2013). The plant is a tropical plant that grows well in tropical environments. It is widely grown in Fogera Plain, mainly around Lake Tana. Farmers and researchers consider Azolla as a weed which is similar to water hyacinth (Tewabe & Asmare, 2020). The observation by the farmers revealed that during the introduction of Azolla in the areas, the farmers were not aware of the impact of Azolla on the ecosystem besides its appropriate utilization for livestock feed. Thus, understanding the benefits of Azolla in different sectors, mainly its use as a livestock feed, helps to create awareness among communities and livestock experts. In addition, researchers who are not familiar with the benefits of Azolla can also understand its cultivation and utilization practices. Therefore, this review work was aimed at investigating the benefits of Azolla as a potential livestock feed and its impact on the aquatic environment.

2. Materials and methods

The review work was conducted by collecting various data, information, ideas and explanations from different sources. The main source of the review work was obtained from journal papers, peer reviewed paper and books. For this review work, a total 114 different information sources were utilized. Of these information sources, 90 journals, eight books, one bulletins, three technical papers, five international project reports, two conference papers, two thesis reports, one case study and two proceedings were utilized. The publication year for these reviewed papers was three papers from 1954–1978, 11 papers from 1982–1999, 28 papers from 2000–2011 and 72 papers from 2012–2022.

3. Findings from the review

3.1. Characteristics of Azolla

Azolla is one of the fastest-growing aquatic plant resources on the planet, it grows without soil and provides high biomass and protein content. In tropical and subtropical regions of the world, it is abundantly available in ponds, ditches, and paddy fields (Bidya et al., 2018). The plant needs a continuous supply of phosphorus and a moderate temperature to survive. Under a good cultivation environment, it can grow in layers and form a thick mat that produces 10 kg of Azolla per 100 m² per day (Sjödin, 2012). It is easy to cultivate and provides high production yields compared to other legumes and grasses (Prabina & Kumar, 2010). Azolla is a fast-growing plant that can outperform other species of plants; as such, the plant should be cultivated and utilized under controlled conditions and with appropriate care (Sjödin, 2012). Nutritionally, Azolla is rich in protein, minerals, vitamins, and other elements, particularly lysine which is an essential amino acid. Lysine is the most important amino acid essential for animals and is deficient in most plant protein sources. Subsequently, Azolla is rich in lysine and other essential amino acids. On a dry weight basis, the crude protein content of Azolla consists of 25–35%, with insignificant amount of carbohydrate and oil contents (Pillai et al., 2002).

Feeding Azolla increases feed intake, body weight gain and the health status of animals, mainly young stocks. For example, Kamel and Hamed (2021) reported that the body weight gain of broiler chickens was 2237.7 g when they were supplemented with 12% of Azolla in their diet, compared to 2071.2 g without supplementation. Here, there is a body weight gain difference of 166.5 g because of the addition of Azolla. Thus, Azolla is an important supplementary feed for broilers diet.

Sinha et al. (2018) also reported that 53.2 eggs were obtained with high net profit when birds supplemented 100 g Azolla per bird per day, compared to 47 and 49.9 eggs under farmers’ feeding practices and concentrate feed supplements birds under the same management practices, respectively. Mathur et al. (2013) pointed out that when a dairy cow supplemented 1.5–2 kg of Azolla along with concentrate feed, it can increase milk yield by 20.96% compared to concentrate feed supplementation alone. This indicated that Azolla can reduce the cost of concentrate feed and related expenses. The milk yield of cross-breed dairy cows also increased by 11.87% under the same feeding practices when Azolla is included in their diet (Nidhi et al., 2015). It also increases milk yield in lactating animals and in poultry birds, it increases feed intake, body weight gain, FCR and egg laying capacity (Yanshi & Anshu, 2019). The inclusion of 10–15% of Azolla in broiler rations can also aid in obtaining better FCR (Wuthijaree et al., 2012). Azolla is also considered as mosquito repellant a it forms a thick mat above the water surface, reducing the breeding ground for mosquitoes. It is also a bio scavenger, and biofertilizer and it can accumulate heavy metals (Prabina & Kumar, 2010).

Azolla is currently produced and utilized as a commercial feed in China and Vietnam. According to Amit et al. (2016), Azolla was used as livestock feed in these two countries from some hundred years ago.

3.2. Environmental requirements for the production of Azolla

Azolla develops a unique symbiotic association with the blue-green algae Anabaena azollae, which helps to trap the atmospheric N for its growth, which contains a high protein content of over 20%. The main stem of Azolla plant grows at the bottom surface of the water with alternate leaves and adventitious roots at regular interval along the stem. The diameter of the plant is 1–2.5 cm and up to 15 cm for Azolla pinnata and Azolla nilotica, respectively (Kathirvelan et al., 2015). The ideal conditions for the growth of Azolla require a temperature of 20–28 °C and relative humidity of 65–80%. However, it can be grown at a temperature of 18–28 °C as reported by Gayathri and Vimalarani (2017) and Kathirvelan et al. (2015). Azolla requires standing water for its growth with a depth of 5–12 cm and pH ranging from 4–7.5 (Gayathri & Vimalarani, 2017). It can also survive a pH range of 3.5–10 (Kathirvelan et al., 2015). Azolla can be cultivated artificially by vegetative propagation and enough plants can be transplanted by propagating in a pond into a wetland within a short period (Kathirvelan et al., 2015).

3.3. Method of Azolla cultivation and its productivity

Azolla is grown in swampy areas and stagnant water such as ponds but it can be also cultivated in a trough dug in different dimensions depending on the requirements. During trough digging and preparation for Azolla cultivation, all the roots and debris are removed. The surface areas in every corner of the pit must be equal to have uniform water levels (Khare et al., 2014). To prevent weed growth in the trough, a high-density preferably 700 grams per meter (GSM) polyethylene sheet should be used up to the upper edge of the trough. Following it, 10–15 centimeters of fertile soil is added in the base of the trough (Khare et al., 2014). On the top of the soil, a small amount of manure mainly cow dung is used as fertilizer in addition to 30 grams of superphosphate. The trough is then filled with portable water at a depth of 15 cm and a small quantity of Azolla culture is inoculated in the trough. The trough is filled with fresh Azolla within not more than seven days (Kumari et al., 2021). Anitha et al. (2016) reported that 120 g of fresh Azolla can be harvested per day per meter square from the trough. On the other hand, a fresh biomass yield of 1–4.5 kg Azolla per meter square per month can be obtained but the yield depends on the season of the year (Zahran et al., 2007). A study conducted in India reported that 2.78 tons of DM/ha were harvested from Azolla plant (Hasan & Rina, 2009).

3.4. Type of Azolla species

According to Kannaiyan and Kumar (2006) Azolla was introduced in Vietnam date back in the 11^th century. Azolla was categorized either in the sub-genera or taxonomic section level. According to sub-genera categorization, it was categorized into two genera based on the sporocarp characters: Euazolla and Rhizosperma (Sadeghi et al., 2013). Further, Euazolla is classified into the taxonomic classification level (Saunders & Fowler, 1992). Based on taxonomic classification, there are five species including A. rubra, Willd (A. caroliniana), Lam (A. filculoides), Kaulf (A. microphylla) and Presl (A. Mexicana) as mentioned by Raja et al. (2012). According to Basak et al. (2002), there are six living species of Azolla in the world, of which four species viz., A. filiculoides, A. caroliniana, A. Mexicana and A. microphylla are found in North and South America, Mexico, West India and British Columbia.

The other species of A. pinnata is widely found in tropical Africa, South East Asia, Japan and Australia, while A. nilotica has been reported to occur in Central Africa, Uganda, Sudan and Namibia.

3.5. Chemical composition of Azolla

Analysis of metabolizable energy (ME) content of Azolla revealed that it is a low-energy source feed but it is a good source of macro and micro minerals and essential amino acids (Kavya, 2014). Table 1 presents the Dry Matter (DM), Crude Protein (CP), Ether Extract (EE), Crude Fiber (CF), Ash, Nitrogen Free Extract (NFE), Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF), Calcium (Ca) and Phosphorus (P) composition of different species of Azolla as cited by Kavya (2014) wherein different species of Azolla varies in their chemical composition. For example, Azolla microphylla and Azolla filiculoides have higher in (CP) content followed by Azolla pinnata.

Table 1. Chemical composition of different Azolla species source (Kavya, 2014).

Proximate value	Azolla filiculoides	Azolla pinnata	Azolla microphylla	Azolla pinnata
	Buckingham et al. (1978)	Parnrkar et al. (1986)	Anitha et al. (2016)	Alalade and Iyayi (2006)
DM	–	–	90	–
CP	23–42	15.63	25.33	21.4
EE	5.02	2.84	3.01	2.7
CF	–	13.01	11.6	12.7
Ash	15.54		23.59	16.2
NFE	–	52.7	16.91	47.0
NDF	39.16	52.76	40.36	36.88
ADF	26.58	–	25.24	47.08
Ca	0.937	1.64	1.7	1.16
P	0.487	0.56	1.05	1.29

NB: DM (Dry Matter), CP (Crude Protein), EE (Ether Extract), CF (Crude Fiber), NFE (Nitrogen Free Extract), NDF (Neutral Detergent Fiber), ADF (Acid Detergent Fiber)

The findings showed that the CP content of Azolla in different experimental areas ranges from 20–26.35%, which is promising for satisfying the protein requirements of different livestock species. The Ca and P composition of Azolla is also higher compared to other feed resources. Table 2 indicates the major chemical composition of Azolla in different areas.

Table 2. Major chemical composition of Azolla by different authors

Proximate composition	References
	Ahmed et al. (2016)	Ara et al. (2015)	Joysowal et al. (2018)	Bhatt et al. (2020)	Kumari et al. (2021)	Nidhi et al. (2015)	Roy et al. (2018)
DM	90.2				90.31		90.03
OM	80.35			79.7	84.3
CP	20	22.06	25.08	26.5	26.35	24.1	22.65
CF	14.25	14.3	14.39		15.16	15.1	11.03
EE	2.65	3.62	3.95	3.9	2.85	3.75	2.02
NFE	46.45	33.4	38.73		46.35	40.25	42.12
Ash	19.65	18.1	17.5	20.3	15.7	16.8	24.7
Ca	1.6	2.04	2.06	1.51		2.18
P	0.4	0.65	0.72	0.31		0.47
NDF	53.8			44.28	30.46
ADF	37			39.4	20.08
Cellulose	6.9
Hemicellulose	16.8
Lignin	5.7

NB: DM (Dry Matter), OM (Organic Matter), CP (Crude Protein), CF (Crude Fiber), EE (Ether Extract), NFE (Nitrogen Free Extract), NDF (Neutral Detergent Fiber), ADF (Acid Detergent Fiber)

3.6. Comparative nutritional composition of Azolla and other feed ingredients

Comparative evaluation of nutritional composition in some common feed ingredients that are used in livestock feed and Azolla are indicated in Table 3. The CP content of Azolla is higher than the many feed types indicated here. Surprisingly, Azolla is also higher in CP content than Vetch, which is a nutritious legume fodder crop utilized in livestock feed. This indicates the potential of Azolla in livestock feed if it is appropriately utilized.

Table 3. Comparative nutritional composition of Azolla and other feed ingredients

Proximate value	Azolla	Guinea grass	Wheat bran	Rice bran	Yellow Oats	Vetch (V. sativa spp.)
	Lal et al. (2022)	Aregheore (2001)	Tahir et al. (2002)	Tahir et al. (2002)	Alemayehu et al. (2021)	Tassew et al. (2022)
DM		35.20	89	91	90	87.7
CP	23.75	11.20	13.10	12.10	15.0	18.4
EE	3.01	1.80	4.40	15.10	8.3
CF	11.50	33.60	11.3	12.8	2.1
Ash	24.91				1.31.3	17.9
NFE		40.90
NDF			51	33.00		42.1
ADF			15	18.00		32.0
Ca	0.47–1.29	0.49
P	0.22–5.45	0.29

NB: DM (Dry Matter), CP (Crude Protein), EE (Ether Extract), CF (Crude Fiber), NFE (Nitrogen Free Extract), NDF (Neutral Detergent Fiber), ADF (Acid Detergent Fiber)

3.7. Advantages of Azolla in livestock farming

Azolla is low-cost and nutritionally rich feed resource for different livestock species, such as cattle, sheep, goats, poultry, and fish (El Naggar & El-Mesery, 2022). The detail of its purpose is described below.

3.7.1. Uses of Azolla for feeding fish

The diet supplemented with Azolla in fish has shown a positive effect on growth and performance and it can reduce the cost of feeding fish meal and fish oil. According to Mohanty and Dash (1995), the performance of Rohu fingerlings showed better weight gain (168.2%) when they were supplemented with Azolla at 60% inclusion level compared to 30, 40, and 50% inclusion levels in their ration. However, Panigrahi et al. (2014) reported that the weight gain of Labeo rohita fingerlings is 281.57 and 239.33% when they were supplemented with 40 and 50% inclusion levels of Azolla in their diet, which indicates a reduction of weight gain when the level of Azolla in the diet is increased. This difference is might be due to the poor digestibility characteristics of Azolla when its bulk is increased in the ration. This is because Gangadhar et al. (2017) studied that the dry matter digestibility (DMD) of Azolla fed to Labeo calbasu fish is 62.11, 50.29, 47.2, and 42.02% when the inclusion level of Azolla is 10, 20, 30 and 40%, respectively. Using Azolla in the diet of common carp attained a daily growth increment of 1.65 g/fish/day, compared to the control group that attained a growth increment of 0.42 g/fish/day using terrestrial weed feeds (Majhi et al., 2006). This indicates the feeding potential of Azolla for fish feed compared to other aquatic feed plants.

Basudha and Vishwanath (1997) reported that the integration of Azolla powder in a fish meal can enhance the weight and feed conversion efficiency. In addition to this the feeding, absorption, and growth rate of Tilapia mozambica are observed (Sithara & Kamalaveni, 2008). Therefore, the use of Azolla is the cheapest and easiest way to increase fish production, particularly in organic fish production, in addition to its better nutritional value (Yadav et al., 2014).

Magouz et al. (2020) also reported improvement in feed conversion efficiency and reductions of feed costs when Azolla is included at a 10–20% level in the ration. Feeding Azolla for fish also contributed to better fish production in aquaculture because of its contribution to pond culture. For example, Hasan and Rina (2009) and Salma and Ramachandra Naik (2020) indicated that Azolla was likely to increase the production of fish feces due to the consumption of large quantities Azolla which contributed to large fecal output (Majhi et al., 2006), which aids in increasing pond productivity and overall fish productivity. The overall better productivity of fish when it depends on Azolla feed is attributed due to better digestibility of Azolla (Gangadhar et al., 2017), better FCR (Majhi et al., 2006), and its highest nutritional contents (Prabina & Kumar, 2010).

3.7.2. Uses of Azolla for feeding poultry

Incorporation of Azolla as a feed ingredient in poultry rations up to 5% has shown better growth, feed conversion, and protein and energy utilization efficiency along with promising economic returns (Parthasarathy et al., 2001). A study conducted by Bidya et al. (2018) showed that supplementing the poultry feed with fresh Azolla enhanced the gain in body weight in backyard poultry birds by 446.95 g compared to 395 g fed concentrate feed and 285.1 g while fed foraging only (control group). The finding of Ara et al. (2015) study indicated that the final body weights were improved significantly in birds when fed with 5% Azolla than compared to birds that are fed with a basal diet made from different ingredients. A diet containing 10% and 5% Azolla was found best with a body weight gain of 850.8 g and 740.6 g in four weeks age of birds (Joysowal et al., 2018). Rai et al. (2012) also studied that a body weight gain of 1810 g was obtained when a broiler received an Azolla diet than birds received other feed types which results from only 1270 g. In another study, the application of 5% and 7% Azolla with a diet containing multivitamins and acidifiers is good in the production of profitable broilers due to reduced FCR, mortality, production cost, and improved net profit (Bholka, 2011; Islam & Nishibori, 2017; Naghshi et al., 2014). In an experiment conducted in broiler chicken fed 5% level of Azolla in Bangladesh is also better in body weight gain of 1637 g compared to other treatment groups 1579 g (Bhatt et al., 2020). Balaji et al. (2009) indicated that the percent giblet yield of birds fed with 4.5% Azolla is better than the control group and other treatments in their experiment investigating the effect of dietary inclusion of sun-dried and ground Azolla (Azolla pinnata) on production performance of broiler chicken. The body weight of poultry and net return was increased when poultry was fed Azolla in a diet (Rai et al., 2012) and it can replace commercial meals by up to 7% without causing a deleterious effect in hematological and blood biochemical parameters (Mishra et al., 2016). The better productivity of birds that depends on diets including Azolla is due to the better nutrient content of Azolla. Feeding Azolla for broiler chicken has a comparable result in growth and body weight change of chicken with that of mustard oil cake meal (Ashraf et al., 2015), which is promising to reduce the cost of expensive concentrate feeds (Nidhi et al., 2015).

The above studies indicated that the incorporation of Azolla in the diet of broilers increases body weight gain with lower feed costs than other feed types because of its richness in proteins and amino acids mainly lysine. In addition to this, better weight gain responses to the inclusion of Azolla in the broiler diet might be due to its benefit in increasing feed intake and better FCR (Yanshi & Anshu, 2019).

Similarly, layer birds were shown better egg production performance when Azolla was included in their diet. As Kannaiyan and Kumar (2005) studied, better egg production performance of layers was recorded, and concentrate feed cost was reduced when they fed 100 g Azolla/bird/day (Lakshmanan et al., 2017).

The carotene level of chicken and egg production was also improved in Asia when layers were fed Azolla powder (Ali & Leeson, 1995).

On average 53.2 eggs were harvested when birds supplemented 5% Azolla diet and 49.9 and 47 eggs when fed concentrate and foraged by themselves respectively (Bidya et al., 2018). Better performance in Azolla-supplemented birds might be due to higher amino acid availability in Azolla than other feed types (Kakhki et al., 2016) which increases egg production from 80.64 to 88.08% when digestible lysine was increased from 574 to 725 mg/bird/day. In addition, birds fed Azolla produced 197.6 eggs compared to 138.4 eggs in non-Azolla feeding birds in their 72 weeks of age (Rai et al., 2012). Azolla can be fed for egg type-pullets up to 10% inclusion level and better performance was obtained in a study conducted in Nigeria by Alalade and Iyayi (2006). Good egg mass and feed conversion efficiency was reported when chickens were fed 200 g/kg Azolla instead of sesame oil (Khatun et al., 1999) which might be due to better feed intake and digestibility of Azolla compared to sesame oil. As Azolla is rich in calcium content that resulted in good eggshell strength when azolla is included in the diet of layers (Austic & Neshiem, 1990). Better eggshells might be due to the high calcium content of Azolla. As the Ca content in the diet increases, egg shell quality also increases (Moreki et al., 2011).

3.7.3. Uses of Azolla for feeding sheep and goats

The supplementation of 300 g fresh Azolla with concentrate feed increases the growth rate of Osmanabadi goat kids in India including the chest girth, body height, and body length when compared to other treatments of feeding 100, 200-gram Azolla with concentrate feed (Toradmal et al., 2017). This result indicates increasing the level of Azolla in a ration helps for obtaining better results. Feeding Azolla at 20% levels for goats showed better body weight change compared to the control group and was economically profitable (Kumari et al., 2021). Feeding Azolla at a 6% level for replacing 25% linseed performs better in the growth performance of Corriedalie sheep without causing adverse effects (Ahmed et al., 2016). Another study conducted in India indicated that the body weight gain of lambs is 2.5 times higher compared to those reared in a semi-intensive system without supplementation and reduced the feed cost by 22% (Wadhwani et al., 2010). Thus, Azolla is a good feed source for sheep and goats for better growth performance and weight gain under optimum feed prices.

3.7.4. Feeding Azolla for cattle

Utilizing various levels of Azolla in the diets of dairy cows can improve body weight and milk yield (Golzary et al., 2018). According to Roy et al. (2016) feeding 5% dried Azolla instead of feeding a mixture of concentrate feed in heifers diet aids to improve feed conversion efficiency (FCE) by 20% and average daily gain by 15.7%. Better FCE and average daily gain in this study might be due to the richness of Azolla for having various nutrients particularly essential amino acids compared to conventional concentrate feeds (Djissou et al., 2016; Luo et al., 2022).

An increase of 6.9 and 7.23% of daily milk production was reported when a milking cow fed 0.977- and 0.609-gram Azolla per day for non-descript milking cows and 5.47 and 6.09% in cross-breed dairy cows in two districts of Odisha, India (Yadav et al., 2014). The variation in this study might be due to environmental differences, variations in husbandry practices, and breed variation. Supplementation of 1.5 kg Azolla per day for dairy buffalo has shown a 16.25% increase in daily milk production of 1.3 litter milk compared to the farmer’s feeding practice that mainly depends on straw, grasses, and cotton seed cake (Meena et al., 2017) which is due to the better nutrient content of Azolla than grasses and straw. The yield, fat content, and other quality of milk increased from 1–1.5 liters per day per animal when a dairy cow fed Azolla (Gayathri & Vimalarani, 2017; Kathirvelan et al., 2015; Yanshi & Anshu, 2019). Better fat content is due to the addition of concentrate feeds in a diet. At the same time, Kumar et al. (2020) indicated that the utilization of fresh Azolla as a supplement for dairy cows up to 1000 grams per day increased milk production by 7–13%. The variation in milk production might be due to genetic differences, the parity of dairy cows, and the stage of lactation. On the other hand, variation in milk yield might be due to differences in the nutrient content of basal feed provided for the cow, and differences in the nutrient content of the Azolla itself which might be also due to soil, harvesting method, stage of harvesting, and drying method differences. Therefore, through appropriate management, Azolla can be a good source of feed for dairy cows for increased milk production.

Yanshi and Anshu (2019) reported that milk yield and milk fat content have been increased when the Azolla ration is included in a dairy cow feed. The body weight and milk yield of indigenous Indian dairy cattle fed Azolla and mustard oil cake supplementation is higher compared to the control group that depends on the farmer’s feeding practices (Golzary et al., 2018). A study conducted in Bengal by Roy et al. (2018) in a desi cow indicated that supplementation of Azolla for 28 and 49 days increased by 0.61 and 0.8 litters of milk per day per cow respectively. This indicated that positive output is obtained when Azolla is supplemented for a long period which might be due to adaptation. In the same experiment, Azolla supplementation was increased by 0.95 liter of milk per day per cow when supplemented for 63 days (Roy et al., 2018). The study indicated that when supplementation of Azolla feeding days increased, the milk yield also increased. This might be when the animals are familiar with newly provided feed, feed intake also increases which thereby increase milk yield. Milk yield increased by 11.85% after Azolla supplementation in dairy cows was reported without harming the health of the animals and the palatability of Azolla mixed feed (Nidhi et al., 2015). A better increase in milk yield is might be due to better nutrient content and digestibility of the Azolla plant.

3.8. Limitations of Using Azolla for livestock feed

Even though Azolla is used as a livestock feed; however, large-scale utilization is not yet common (Brouwer et al., 2018). This might be due to a lack of adoption by the farmers because of its labor-intensive characteristics (Tamizhkumaran & Rao, 2012). The utilization practice of Azolla for different purposes is restricted because of factors such as lack of an initiative program to adopt this technology, lack of awareness in extension agents and farmers, lack of scientific research to develop Azolla strain for specific purposes, and restriction of Azolla propagation (Kollah et al., 2016).

4. Conclusion and recommendation

In recent days, the demand for livestock products has increased from time to time. However, the productivity of the animals is not enough to satisfy this increasing demand mainly due to feed scarcity and the high cost of agro-industrial by-products. Because of this searching for cheap and locally available feed is mandatory. Azolla feed is one of the feed resources that can be produced locally at low cost and in wetland areas; it can be harvested and produced easily. It is a good source of amino acids, minerals, and vitamins. When azolla is supplemented with other feed resources, it can increase body weight, feed conversion efficiency, and feed intake of broilers. In layers, it can increase egg production performance and egg quality. In large animals such as sheep, goats, and cattle; it can increase milk yield and overall performance of the animals without adverse health impacts. Therefore, the production and utilization of Azolla as a supplementary feed in the diet of sheep, goats, poultry, and cattle are possible to improving the productivity of the animals.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Sale Alebachew Chekol

Sale Alebachew received his BSc degree in Animal Production and Technology from Bahir Dar University, Ethiopia, and his MSc degree in Animal Production from Debre Markos University, Ethiopia. Presently, he is a lecturer and researcher at the Department of Animal Sciences, Debre Tabor University, Ethiopia. He has done various research in dairy science and fisheries. Currently, he has been studying the availability and utilization practices of Azolla in Fogera Plain, Ethiopia.

Teshager Zerihun Nigussie

Teshager Zerihun Nigussie received his BSc and MSc degrees in statistics from Hawassa University, Ethiopia. He also received a PhD in Statistics from Bahir Dar University. He is working on modeling various data from health sciences and agriculture. He is an assistant professor at the Department of Statistics in Debre Tabor University, Ethiopia. He has been working on data exploration and analysis of datasets from agricultural areas, spatial, and spatial modeling of health datasets.

Bernabas Aynshet Fenta

Bernabas Aynshet received his BSc degree in Animal Production and Technology from Debre Birhan University, Ethiopia, and his MSc Degree in Animal Production from Debre Markos University, Ethiopia. Presently, he is a lecturer and researcher at the Department of Animal Sciences, Woldia University, Ethiopia. He has done various researches in dairy science, animal nutrition, poultry science, and animal biotechnology.