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By: Bilal Ahamad Paray, Mohamed F. El- Basuini, Mahmoud Alagawany, Moham- med Fahad Albeshr, Mohammad Abul Farah and Mahmoud A. O. Dawood *
“Several studies have found that aquatic animals’ performances showed improvements as a direct result of using yucca as feed or water additives. Dietary yucca increases protein metabolism in the fish body, with a possible reduction in ammonia excretion. The improvement in protein metabolism enhances feed utilization and results in a high feed intake and growth rate.”
Recently, food security agencies have called for limiting the usage of antibiotics and chemotherapies in poultry, livestock, and aquaculture production due to their negative impact on natural immunity, either in the animals or the human body and their hazardous environmental risks. Therefore, using natural alternative substances that act as growth promotors, immunostimulants, and antioxidative agents is urgently needed.
Yucca schidigera and its extracts are among the medicinal plants associated with plenty of beneficial effects when applied in aquaculture. Several studies found that aquatic animals’ performances showed improvements as a direct result of using yucca as feed or water additives.
Dietary yucca increases protein metabolism in the fish body, with a possible reduction in ammonia excretion. The improvement in protein metabolism enhances feed utilization and results in a high feed intake and growth rate.
Yucca has abundant amounts of saponin and resveratrol, which can eliminate the waterborne ammonia and lower its impacts on aquatic animals’ performance and health. Therefore, many commercial aquatic products include yucca and saponin in their formulation to be applied in aquaculture ponds and intensive systems. It enhances the water quality, feed intake, growth rate, antioxidative, and immune responses in aquatic species. Furthermore, yucca increases resistance against infectious bacteria and invaders.
The Nature, Sources, and Composition of Yucca
Yucca products (powder and juice) are commercially available, where they were approved in 1965 by the Food and Drug Administration (FDA) (21 CFR 172.510) and can be used as dietary additives or supplements due to their beneficial impacts on well being, growth performance, nutrient utilization, the removal of fecal odors and ammonia, hydrogen sulfide, and some other hazardous volatile compounds in human and animal excreta.
The main constituents of yucca powder or extract (YE) are steroi
dal saponins polysaccharides, and polyphenols, which possess antioxidant, anti-inflammatory, antiviral, antiprotozoal, antiplatelet, antimutagenic, anticancer, cholesterol reduction, and iNOS expression inhibiting activities.
Saponins have a direct impact on the permeability of intestinal cells, as well as the gastromicrobiota (antiprotozoal activity) by forming complexes with sterols (cholesterol) in cell membranes.
“The efficacy of yucca as a natural immunostimulant substance is attributed to its high content of bioactive components (e.g., alkaloids, terpenoids, saponins, steroids, phenolics, tannins, glycosides, and flavonoids).”
Yucca phenolic constituents include two stilbenes with antioxidant and anti-inflammatory potentials, where the first is yuccaol A, B, C, D, and E (trans-3,3’,5,5’-tetrahydroxy-4’ methoxystilbene) and the second is resveratrol (trans-3,4’,5 tetraxydroxystilbene)
Yucca as a Growth Promotor
The application of plant-based products to support the growth of aquatic organisms has become widely used. Dietary incorporation of yucca products has favorable effects on the growth performance, feed efficiency, and health of aquatic animals.
The improvement in growth as a result of yucca supplements may be linked to the enhancement in water quality and feed utilization, which relies on the intestinal status via modulating the gut flora, enzyme activity, and absorption.
In this context, Wang et al. evaluated the effect of dietary incorporation of Y. schidigera extract (YSE) at different levels on the growth performance of mirror carp (Cyprinus carpio). The boosted growth performance was linked to the alteration in the microbial population, which enhanced the feed digestion and utilization, regardless of the non significant alteration in intestinal digestive enzymes.
More over, Peterman et al. found a remarkable growth performance (higher weight gain and specific growth rate (SGR)) and feed utilization (lower feed conversion ratio (FCR)) after a 3 month feeding period in channel catfish.
“Furthermore, El-Keredy and Naena studied the growth of Nile tilapia (Oreochromis niloticus, initial weight of 20 g) infected with Pseudomonas aeruginosa in response to the dietary supplementation of YSE. The authors demonstrated that high levels of YSE in diets increases the saponin concentration.”
In a different approach, Abdel Tawwab et al. examined Nile tilapia’s (28–32 g) responses to YSE and/or the yeast Saccharomyces cerevisiae as water additives. The results of the Nile tilapia growth were improved (p < 0.05) due to the water additives and the highest growth was recorded in fish treated with YSE + yeast.
Furthermore, Elkhayat et al. studied the responses of European seabass (D. labrax) to YSE supplementation. The results of this trial showed an improved growth performance and wholebody protein content.
Moreover, Gaber examined the full substitution of fish meal protein in the control group (FMC) with the meal of soybean, cottonseed, sunflower, or linseed supplemented with YSE on the growth of Nile tilapia (O. niloticus). All groups fed diets with YSE showed a higher apparent protein digestibility coefficient, whole-body protein con- tent, and lower whole-body lipid content compared to the control.
In addition, Kelly and Kohler investigated the impact of a feeding regime with YSE on the growth performance of post-yolk-sac and juvenile channel catfish (I. punctatus). After the 12 week feeding period, post-yolk-sac channel catfish fry fed the YSE had the highest weight gain compared to the control.
For shrimp cultivation, Hernández Acosta et al. examined Pacific white shrimp (Litopenaeus vannamei, 2.6 g initial body weight) cultured in low salinity water and fed diets with Y. schidigera and Q. saponaria extracts (NTF). The increase in weights and decrease in FCR in response to Y. schidigera and Q. saponaria supplementation may be due to increased protein synthesis, digestive enzymes, and promotion of nutrient absorption.
Yucca as an Immunostimulant
Currently, ecofriendly natural strategies and/or alternatives to antibiotics, such as medicinal herbs and beneficial microorganisms (probiotics, prebiotics, and synbiotics), have become an area of interest of many studies.
“The efficacy of yucca as a natural immunostimulant substance is attributed to its high content of bioactive components (e.g., alkaloids, terpenoids, saponins, steroids, phenolics, tannins, glycosides, and flavonoids).”
The aquatic organisms treated with dietary yucca showed direct enhanced local intestinal immunity, which was correlated with a general immune system enhancement due to the influence of yucca as an antibacterial agent against pathogenic microorganisms in the gastrointestinal tract (GIT).
Accordingly, yucca reduces the GIT inflammation that is induced by pathogens and toxins and relieves the stress that results from unfavorable aquaculture conditions. Subsequently, treatment with yucca enhances aquatic animals’ resistance against infection by pathogenic microorganisms that may attack the organism in the ponds.
Indirectly, when the rearing water is treated with yucca extracts, the accumulation of ammonia is diminished and reduces the stressful impacts on fish, which could lead to immunosuppression and pathogenic invaders attacking if continued for a long time.
Yucca as an Antioxidative Agent
The antioxidant defense system is tightly linked to the health status and the immune system of fish. The aquatic animal antioxidant system is vulnerable to biotic and abiotic factors. Medical plants, with their numerous active components, are thought to possess different functions as immunostimulants and antioxidants.
The Yucca plant and its products have shown antioxidant activities that are attributed to its phenolic hydroxyl groups (hydrogen donors), which lowers the formation of hydroxyl peroxide.
A limited number of studies on the use of yucca and its products as an antioxidant in aquaculture have been done.
Yucca as a Natural Cleaner for Aquatic Water Quality
The accumulation of inorganic nitrogen compounds (NH4+, NH3, NO2-, HNO2, and NO3) resulting from the feces of aquatic organisms, organic matter, and the leftover feed affects the reproduction, growth, and resistance of fish to stressful conditions.
Specifically, exposure to NH4+ and NH3 (TAN) pollution can cause gill damage, anoxia, disruption of blood vessels and osmoregulatory activity (damage to the liver and kidneys), and a decrease in the effectiveness of the immune system. Severe ammonia toxicity induces several effects on the aquatic animals, including the decrease of feed consumption, deteriorated physiological functions, unstable breathing through the gills, oxidative stress, diminished immunity, and inflammatory features in the gills.
Yucca is applied mainly to reduce the levels of ammonia emissions in aquaculture ponds due to its content of steroidal saponin fractions, which has surface active properties and can bind to ammonia via glycol component fractions. The reduced levels of accumulated ammonia would result in the balance of protein metabolism in the fish body and a reduction in energy consumption.
“Hence, the feed utilization, growth performance, and physiological status of aquatic species can be improved using yucca.”
Additionally, yucca application results in the enhancement of the antioxidative, immunological, and anti-inflammatory responses in several aquatic animals. In this sense, yucca is an alternative approach to overcoming the excessive use of antibiotics for eco friendly aquaculture.
The inclusion of yucca extract improved the quality of rearing water and lowered the accumulated ammonia in the case of mirror carp Nile tilapia (O. niloticus), striped catfish (P. hypophthalmus), and European seabass juveniles (D. labrax).
Yucca extract has steroidal saponins and glycol with an active surface attributed to ammonia’s adsorption. Correspondingly, the reduction in ammonia levels is attributed to the binding of ammonia with steroidal saponins and glycols or the transformation of ammonia to nitrite and nitrate.
“The overall results provide impressive outcomes regarding using Y. schidigera in terms of potential interest in open-flow pond aquaculture and closed aquaculture systems.”
Correspondingly, Y. schidigera can be complementary to biofloc technology, which can also improve the growth and immune status of farmed fish via improving water quality parameters.
Concluding Remarks
Yucca can clearly enhance the quality of rearing water by reducing ammonia emissions that result from aquatic organisms due to its potential as a medicinal herb. Since aquatic organisms are known for their high sensitivity to environmental stressors, yucca’s application can be considered an active substance for the “blue clean aquaculture industry.”
Additionally, yucca showed growth-promoting effects when included as a dietary additive, with possible feed utilization potential. The enhancement of feed digestion and nutrient absorption activates the local intestinal immunity, which leads to improved immunity and high resistance against infectious diseases.
There are direct and indirect effects implicated for both axes involved in the aims of the present work: yucca can directly achieve improved water quality, but immunity and growth may be indirectly affected. The overall performances of aquatic organisms that were treated with yucca as a dietary additive or a water cleaner encourage performing further studies to prove its mode of action based on biochemical and biological techniques.
* This is a summarized version developed by the editorial team of Aquaculture Magazine based on the review article titled “Review Yucca schidigera Usage for Healthy Aquatic Animals: Potential Roles for Sustainability” developed by: Bilal Ahamad Paray, Mohamed F. El-Basuini, Mahmoud Alagawany, Mohammed Fahad Albeshr, Mohammad Abul Farah and Mahmoud A. O. Dawood. The original article was published on january 2021, through the Animals journal of MDPI under the use of a creative commons license. The full version can be accessed freely online through this link: https:// www.mdpi.com/951396
