A Narrative Review On The Beneficial Impacts Of Probiotics On Poultry: An Updated Knowledge Part 1

Abstract

Probiotics are live microorganisms that can improve the host's health when given in sufficient doses. Due to growing consumer demand for poultry raised without antibiotics supplementation, the usage of probiotics has been rising gradually over time in poultry. This review aimed to summarize the impacts of probiotics on poultry's nutrient utilization, growth, carcass parameters, gut morphology, laying performance, biochemical parameters, immunity, and gut microbiota. 

The results revealed that probiotics enhanced growth performance by improving digestion of protein, lipids, and carbohydrates, improving feed conversion ratio (FCR), increasing carcass and organs weights, improving liver and kidney function parameters, antioxidant effects, decreased serum lipids and cholesterol, improved poultry immunity via improving gut health and synthesis of antimicrobial peptides and prevention of microbial colonization, improved laying performance, fertility, hatchability, and eggshell thickness. Therefore, probiotics have various benefits in poultry production compared to banned antibiotics. However, they are not always guaranteed to be growth promoters due to poorly understood modes of action, including their interaction with the host. So, further studies concerning their impacts on meat quality and histopathological changes are still required.

Probiotics have multiple effects on immunity, including:

1. Improve intestinal health: The intestinal tract is the main part of the human immune system. Probiotics can promote the balance of intestinal flora and the health of the intestinal mucosal barrier, reduce the reproduction of harmful bacteria, and contribute to the normal operation of the immune system.

2. Enhance immune function: Probiotics can regulate the activity of immune cells, enhance immune function, inhibit immune overreaction, and prevent inflammation and disease.

3. Improve digestion and absorption: Probiotics can promote the digestion and absorption of food, enhance the body's utilization of nutrients, and help improve the body's immunity.

In general, the impact of probiotics on immunity is multifaceted. By improving intestinal health, enhancing immune function, improving digestion and absorption, etc., it can improve the body's immunity and help prevent the occurrence of diseases. From this point of view, we must pay attention to the improvement of immunity. Cistanche can have a significant effect on improving immunity. The polysaccharides in the meat can regulate the immune response of the human immune system, improve the stress ability of immune cells, and enhance immunity. Bactericidal effect of immune cells.

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Keywords:

probiotics, poultry, growth, immunity, gut microbiota, laying performance.

Due to their numerous positive effects, including those that support growth and productivity, immune system development, and health protection, feed additives, and nutritional supplements are becoming more and more important in today's poultry industry and healthcare systems (Abd El-Hack et al., 2017). In general, feed supplements are tools that increase the potency of nutrients and have an impact on the performance of chickens (Ashour et al., 2020). Numerous feed additives, including probiotics, oligosaccharides, enzymes, and organic acids are utilized in chicken feed (Bin-Jumah et al., 2020). They are incorporated into poultry and animal diets to promote growth because they tended to increase feed consumption (Abd El-Hack et al., 2017).

Probiotics have been proposed as environmentally friendly feed additives and intriguingly unorthodox alternatives to chemotherapy in chicken. Moreover, to guarantee that it always has the right microbial balance, animals must maintain particular amounts of helpful microbiota in the digestive system (Abd El-Hack et al., 2018). While bifid is effective against S. aureus and M. flavus, bifidocin B exhibits antibacterial activities towards various pathogens, for instant Bacillus cereus and Listeria monocytogenes (Shah and Dave, 2002). Bacillus toyonensis (BT) is a well-known non-pathogenic bacterium utilized as a probiotic for feeding animals. It is aerobic, fermentative, gram-positive, and spore-forming (Roos et al., 2018). The supplements of Lactobacillus spp. to maize-barley hen diets enhanced FCR, egg mass, albumen quality, and egg production (Abd El-Hack et al., 2018).

Probiotics in chicken feed can increase performance, nutritional digestibility, and immune suppression in birds (Abd El-Hack et al., 2020; Abdel-Moneim et al., 2020 a; Saleh et al., 2021). Probiotics can also affect the hostess's health, performance, and sickness risk. They can correct dysbiosis and restore the gut microbial balance in healthy hosts by lowering harmful spores' growth and enhancing beneficial microbes' growth (Yadav and Jha, 2019). 

The genera Lactobacillus, Bacillus, Streptococcus, Candida, Bifidobacterium, Aspergillus, Enterococcus, and Saccharomyces are responsible for the majority of probiotic strains that are commonly used (Ahmed et al., 2014; Elbaz et al., 2021) and invest in particular health benefits for the host through the competitive eradication of dangerous bacteria and the gut's immune system revision (Yadav and Jha, 2019). Numerous studies have discovered the impacts of probiotics on microbial fermentation, enzyme activity, and the gut microbiota in broiler birds' digestive tracts (Martínez et al., 2016; Wang et al., 2017 a). This review article aimed to highlight the different beneficial effects of probiotics on poultry growth performance, production, reproduction, and health status.

Impacts of probiotic supplementation on growth performance

The different impacts of probiotics on poultry are summarized in Table 1. Growth metrics are essential for measuring economic performance and animal health, especially in chronic or moderate disorders with few obvious clinical indications (Kritas and Morrison, 2007). In a multispecies population, increased quail weight might be due to increased synthesis of specific vitamins, some active compounds, and digestive enzymes. This can reduce the pH of the intestine, improve digestion, and consequently increase the consumption of nutrients, which favorably influence body weight values and limit the growth of enteropathogens in the quail gut (Premavalli et al., 2018).

Probiotics are live bacteria, yeasts, or fungi that help maintain a healthy digestive system by supplementing the gastrointestinal flora, thereby promoting the growth performance and overall health of poultry (Jha et al., 2020). Khaksefidi and Ghoorchi (2006) indicated that adding probiotic Bacillus subtilis to broiler chicks enhanced broiler body weight and weight gain. Rehman et al. (2020) reported that the weight gain of broilers was increased by probiotics (Protexin) during the starter and finisher phases (P = 0.028 or 0.04, respectively). 

Safalaoh (2006) revealed that diets supplemented with an effective microbial preparation had considerably (P<0.05) greater body weight increases (2094 ±11 g) than the control diet (2057 ±15 g), resulting in a 2% increase. Vicente et al. (2007) indicated that the probiotic Lactobacillus sp. in broilers and turkeys significantly raised the body weight compared with the control (Bahakim, 2006; Torres-Rodriguez et al., 2007). When broilers were given diets containing Aspergillus oryzae, the body weight gain was increased (Rehman et al., 2007). The same findings were reported by Sallh and Al Hussary (2009), who noticed that broilers fed on diets enriched with 1.5 g/Kg of probiotic ingredients A. oryzae gained more body weight.

Zhang et al. (2021) fed Arbor Acres (AA) broilers chicks basal diets with 1% L. acidophilus, 1% Lactobacillus casei, and 1% Bifidobacterium in the water for 42 days and reported that the inclusion of probiotics significantly enhanced body weight, average daily feed intake (ADFI), and average daily weight gain of chicks.

According to Zeweil et al. (2007), the supplementation of Saccharomyces cerevisiae improved the body weight and body weight increase of broilers (P<0.05) over those of the control group. Furthermore, when S. cerevisiae was introduced at rates of 1, 1.5, and 2% compared to control and the other treatments, body weight gain was considerably (P<0.05) enhanced. Many researchers have used B. subtilis as a component of probiotics. 

According to Abaza et al. (2008), using S. cerevisiae, B. subtilis, and B. lichen form in the diets improved body weight by approximately 2.10, 3.02, and 2.70 %, respectively body weight gain by approximately 2.69, 2.09, and 3.01%. Additionally, Fayed and Tony (2008) demonstrated that using the probiotic mixture (Biovet-YC®), including mixtures of Lactobacillus spp. and yeast cultures, increased body weight gain in broiler chicks. Another study reported that probiotic supplements exhibited a significant positive impact on body weight gain in broiler chicks since providing broilers’ diets with probiotic microflora at levels of 10, 20, and 50 g/50 kg diets significantly increased the live body weight when compared to the control group (Taklimi et al., 2010). Furthermore, Nuyens et al. (2010) showed using B. subtilis PB6 in broiler diets enhanced the live weight at 42 days old, from 2.536 to 2.644 kg. Knap et al. (2011) also demonstrated that by day 42, the B. subtilis treated groups had a numerical advantage over the positive control group in terms of body weight growth (2.212 and 2.182 kg, respectively).

However, the difference was not significant. Furthermore, regardless of the meal's spore concentration, Molnár et al. (2011) demonstrated that broilers’ fed diets enhanced with Bacillus subtilis resulted in considerable improvement in body weight in the supplied groups versus the control ones. Similarly, birds (poults and chicks) fed meals supplemented with B. subtilis gained considerably more total body weight than the non-treated group (Shivaramaiah et al., 2011). Besides, B. subtilis enhanced quails’ growth performance. They positively influenced body weight (BW) and body weight gain (BWG)s throughout the brooding period due to their capability to produce highly active proteases, amylases, and lipases that break down feed components and increase the number of nutrients accessible for absorption (Li et al., 2014) (Figure 1).

Interestingly, Abdel-Moneim et al. (2020 a) established that B. subtilis treatment increased live body weight linearly across all tested ages. Additionally, both the beginning phase (1–14 days old) and the overall one showed a linear rise in daily body weight gain (1-42 days old). According to Abou-Kassem et al. (2021), probiotics caused a substantial enhancement in quail weight at 21 and 42 days of age compared to the control. Additionally, results indicated that probiotic supplementation increased weight gain (WG) significantly throughout the grower and total trial periods compared to the control. The lowest single dosage of BT, where WG was lowered, was the only probiotic-treated group whose WG grew over the finisher period. BT's greatest dietary single level coincided with the maximum values of WG through the finisher and overall phases.

Mortality rate

Broiler chicken performance has been proven to be improved by probiotics in the poultry industry, which lowers the mortality rate of broiler chickens (Timmerman et al., 2006). Likewise, according to Vicente et al. (2007), probiotics were demonstrated to reduce chicken mortality. Using the probiotic mixture (Biovet-YC®), which contains mixtures of Lactobacillus spp. and yeast cultures, had favorable impacts on broiler behavior and can operate as an anti-stress element, which might have an impact on overall health conditions (Fayed and Tony, 2008). 

Also, after administering a probiotic mixture of bacteria (L. plantarum) and yeast (S. cerevisiae) through drinking water, the mortality rate of the supplemented chickens was lower than that of the nontreated ones (Thongsong et al., 2008). Likewise, Al-Homidan and Fahmy (2007) found that adding dry yeast to broiler chicks' basic food slightly enhanced their survival rate compared to the control.

Moreover, Pedioccoccus acidilactici-containing probiotics dramatically decreased death rates compared to controls (6 vs. 11.5%) (Ibrir et al., 2008). Alloui and Hadef (2008) maintained that the experimental mortality average was 4.56% in the control chickens and 4.51% in that fed with a diet containing P. acidilactici (109 CFU/ kg of feed), which may be regarded as being within the common range. Also, it was shown that broilers given probiotic microflora at 10,20, and 50 g/50 kg diets exhibited a considerably decreased mortality rate compared with the non-mediated control ones. 

In contrast, Abd El-Samee and Abd El-Hakim (2002) demonstrated that adding the probiotic Bio-Top (0.1%) to Arbor Acers broiler chicks had no noticeable impact on mortality rates. Also, the mortality rate of the broilers was not affected by commercial probiotics in water or feed (O'Dea et al., 2006). Similarly, adding probiotic cultures to feed had no discernible effect on the mortality rates of broiler chicks (Al-Zenki et al., 2009; Abo-Mahara, 2010). Likewise, Brzóska et al. (2010) found that the mortality percentage had been considerably reduced (P< 0.01) upon adding the probiotic bacteria compared to the control ones. Throughout the trial period, no mortality was noted in any of the experimental groups, according to Abdel-Moneim et al. (2020 a).

Feed consumption and conversion

One of the most biological approaches to increase feed consumption effectiveness is commercial probiotics as natural promoters for poultry nutrition. Probiotic culture added to the diet benefits the host animal by increasing appetite. In addition, it improved feed intake in broilers (Kim et al., 2003), the feed conversion ratio of the host (Soliman et al., 2000; Cavit, 2003), and the production of digestive enzymes (Saarela et al., 2000; Rehman, 2007), as well as it has positive effects on host health (Soomro et al., 2002). While Yalcin et al. (2008) revealed that the feed efficiency average was quantitatively greater in the group treated with S. cerevisiae. Similar results were described by Kumari et al. (2001). 

Overall, B. subtilis can enhance quail growth performance due to its ability to release high-active proteases, lipases, and amylases that digest feed nutrients and raise the number of nutrients available for absorption. This beneficial effect of B. subtilis on FCR was demonstrated throughout the brooding period (Li et al., 2014). Furthermore, it was noted by Abdel-Moneim et al. (2019 b) that giving B. subtilis spores to quails led to a higher total FCR than the control group.

Variations in environmental factors and gut flora may confuse the cause of the varying action of biological additions (Mahdavi et al., 2005). According to O'Dea et al. (2006), adding commercial probiotics in water, feed, or their combination had no impact on the broilers' feed conversion rate. Al-Homidan and Fahmy (2007) also noted that throughout the experiment, birds supplied with yeast culture consumed numerically more daily feed than the control. 

Furthermore, Abaza et al. (2008) noticed that throughout all experiment periods, there were no substantial changes in the conversion rate among groups fed diets mixed with B. lichen form, B. subtilis, and S. cerevisiae, so far chicks fed diets provided with S. cerevisiae consumed significantly more feed than the control ones. Contrarily, according to Midilli et al. (2008), dietary supplements with probiotics had no noticeable impact on feed consumption compared to the non-supplemented control. According to Al-Zenki et al. (2009), supplementing feed with probiotic culture had no considerable impact on feed consumption. Brzóska et al. (2010) also included the probiotic bacterium Pediococcus spp. caused noticeable variations in the feed consumption and conversion ratio of broilers.

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