Effects of Dietary Lactiplantibacillus pentosus and Salinomycin on Growth Performance, Meat Quality, Antioxidant Status, and Serum Parameters in Broilers Fed Diets Differing in Nutrient DensityABSTRACT
The study aimed to evaluate dietary Lactiplantibacillus pentosus [LP]-based probiotic as an alternative to in-feed antibiotics for broilers fed diets containing different nutrient densities. A total of 630 day-old male Ross 308 broiler chicks were randomly assigned to 42 pens (15 birds/ pen) in a 2×3 factorial design with three additives (none, salinomycin at 60 mg/kg, or LP at 1.0 × 108 cfu/kg) and two nutrient density levels (optimal [OPT] or reduced [DEF]). The OPT diets increased (p<0.05) body weight gain in relation to the DEF ones. The LP diet impaired body weight gain and feed intake compared with the control and salinomycin diets (p<0.05). The LP diet lowered feed conversion ratio in the OPT diet, but increased it in the DEF diet, leading to a significant interaction between the two factors (p<0.05). Breast meat yields were increased in the salinomycin group but decreased in the LP group as compared to the control group (p<0.05). CIE a* and b* values in breast meat and CIE a* value in thigh meat were highest in broilers fed salinomycin as compared to the control groups (p<0.05). The OPT diets increased cooking loss in breast meat and decreased CIE L* value in thigh meat (p<0.05) in comparison to DEF diets. Serum superoxide dismutase was higher in the salinomycin and LP groups than in the control group (p<0.05). The salinomycin diet lowered jejunal secretory immunoglobulin A compared with the control group (p<0.05). An interaction between additives and nutrient density on serum glutamic oxaloacetic transaminase was observed (p<0.05). Under the conditions of this study, dietary L. pentosus S14 increased serum SOD activity but impaired growth performance and breast meat yield; therefore, this strain cannot be recommended as a direct replacement for salinomycin without further dose optimization, strain validation, and challenge-model testing.
Keywords:
Lactiplantibacillus pentosus; growth performance; meat quality; antioxidant capacity; broiler chickens
INTRODUCTION
Nutrient density in diet is a critical consideration in commercial poultry production due to its significant impact on bird growth, health, and economic viability (Brickett et al., 2007; Wang et al., 2014). It has been reported that high nutrient densities could improve body weight gain, protein efficiency ratio, and energy efficiency ratio, but reduce feed intake and feed conversion ratio in both commercial and indigenous poultry (Wang et al., 2013). In contrast, providing high nutrient density diets to broiler chickens can lead to increase in feed costs, nitrogen excretion, fat deposition, and metabolic disorders (Li et al., 2010; Mirshekar et al., 2013).
Rising feed prices have been spurring interest in lowering dietary nutrient levels, particularly crude protein and metabolizable energy (Maynard et al., 2022). A cost-effective and environmentally sustainable strategy for poultry production involves achieving faster weight gain and heavier body weight with reduced feed usage (Brown et al., 2020; Nikbakhtzade et al., 2024). However, studies show that suboptimal nutrient concentrations in high-performing broilers can lead to reduced feed efficiency and retard growth rates (Nikbakhtzade et al., 2024; Ogunola et al., 2025; Zhang et al., 2025)
Probiotics have become a crucial ingredient in poultry nutrition, owing to their wide range of beneficial effects on animal health and performance (Park et al., 2016; Arsène et al., 2021). These live microbial supplements are known to improve performance and health of chickens via enhanced nutrient digestion/absorption, which then increases economic return in poultry production (Khan & Naz, 2013; Alagawany et al., 2018; Abd El-Hack et al., 2020). Most probiotics are derived from various species within the Lactobacillus and Bifidobacterium genera (Papizadeh et al., 2017). The Lactobacillus genus are abundantly present in the upper gastrointestinal tract of humans and animals, and are widely utilized as food additives for fermentation and preservation, owing to their unique properties and mechanisms of action distinct from conventional antibiotics (Ben Salah et al., 2012; Mokoena, 2017). Lactiplantibacillus pentosus (formerly known as Lactobacillus pentosus) (Zheng et al., 2020) is a highly adaptable probiotic strain for its strong environmental and gastrointestinal tolerance, antimicrobial activity, and folate biosynthesis, which are linked to nutrient metabolism (Ye et al., 2020; Tian et al., 2024). It also exerts anti-inflammatory effects by inducing Type 1 regulatory T cells that secrete interleukin-10, thereby modulating immune responses and inhibiting systemic inflammation (Kim et al., 2019). Additionally, L. pentosus enhances intestinal health by stimulating the production of short-chain fatty acids, which play critical roles in energy metabolism and gut integrity (Wang et al., 2021). In poultry, dietary multi-species probiotic formulations including L. pentosus have been reported to promote beneficial microbial growth, suppress enteric pathogens, and improve growth performance and feed efficiency (Altaher et al., 2015; Śliżewska et al., 2019). However, reduced nutrient density may alter substrate availability in the gastrointestinal tract, intestinal fermentation, microbiota balance, and nutrient absorption, thereby modifying the response to probiotic supplementation (Adedokun & Olojede, 2019; Jia et al., 2024; Dong et al., 2025). Under optimal nutrient supply, L. pentosus may primarily support gut function and feed efficiency, whereas under reduced nutrient density its effects may become more pronounced or different because the host and microbial ecosystem respond to a more limited nutrient environment. At this stage, dietary single-strain L. pentosus has not been tested in broilers, which prompted us to evaluate the interaction between L. pentosus-based probiotic and nutrient density in broiler chickens.
MATERIALS AND METHODS
Animal Care Approval
All animal care procedures were approved by Institutional Animal Care and Use Committee in Konkuk University (KU17048).
Animals, Diets, and Experimental Design
The experimental design employed a 2 × 3 factorial arrangement with three additives (none, salinomycin at 60 mg/kg, LP at 1.0 × 108 cfu/kg) and two levels of nutrient density. Corn gluten meal was used to formulate different nutrient density diets (Table 1). In the reduced nutrition density diet (DEF), the amount of corn gluten meal was reduced to 10 g/kg by replacing it with corn and cellulose. The DEF diet was primarily formulated to reduce metabolizable energy, crude protein, and limiting amino acids by an average of 2 to 7% compared with the OPT diet. No attempt was made to balance limiting amino acids between the OPT and DEF diets. The OPT diet was formulated to meet the requirements of the 2022 Korean Poultry Feeding Standard. The OPT and DEF diets (Table 1) were used throughout the experiment. Salinomycin was included as an antibiotic growth promoter because of its recognised effects on intestinal microbial regulation and performance outcomes, making it an appropriate comparator for assessing the efficacy of probiotic supplementation (Kairmi et al., 2022; Mohammad Naghizadeh et al., 2022). The probiotic strain used in this study was freeze-dried L. pentosus S14, which was isolated from pickled mustard leaves called burong mustasa and kindly provided by the Korean Food Research Institute (KFRI, Wanju-gu, Jeollabuk-do, Republic of Korea). It was verified that the L. pentosus probiotic preparation contained 1.0 × 108 CFU/g of viable cells, and it was thus added into the basal diets at 1 g per kg of diet to reach 1.0 × 108 CFU/kg of diets. Experimental diets were prepared weekly. No attempts were made to monitor the viability of the probiotic strain in the experimental diets.
A total of 630 day-old male broiler chicks (Ross 308) were obtained from a local hatchery, weighed upon arrival, and randomly allocated to 42 floor pens (2 × 1 m floor pens with fresh rice hull as the bedding material). Each treatment included 7 pen replicates with 15 birds each. Feed and water were provided ad libitum and lighting was maintained for 23 hours per day. The temperature was initially set at 34 °C for first the three days and gradually reduced to 24 °C at 21 days. The experiment lasted for 5 weeks.
Growth Performance and Sample Collection
Body weight and feed intake per pen were recorded at the beginning and the end of the experiment. Mortality was monitored daily and feed intake was adjusted for mortality. Mortality kept low and no more than 3 birds per treatment died during the experiment. At day 35, a bird per pen, close to the average body weight, was selected for sampling of the blood, right leg and breast meat, and the small intestine. Birds were euthanized using an overdose of carbon dioxide, and blood was immediately collected via cardiac puncture into a clot activator tube. Serum samples were obtained by centrifugation (200 × g) for 15 min and stored at -20 °C before analysis. Immediately after blood sampling, right breast and leg meats were sampled, weighed, and expressed as a percentage of body weight. Then, small intestine was excised and a 5-cm-long segment of jejunum, proximal to Meckel’s diverticulum, was collected for the determination of secretory immunoglobulin A.
Meat Quality of Breast and Leg Meat Samples
Breast and thigh meats were used to assess cooking loss, meat color, and pH. To evaluate water holding capacity, right breast and deboned thigh meat were vacuum-packaged and cooked in a water bath at 80 °C for 30 min, following the method described by Kim et al. (2020). After cooking, samples were cooled in ice-cold water for 10 min to room temperature, dried with a paper towel, and re-weighed to calculate cooking loss as a percentage of weight reduction. The pH values of breast and leg meats were measured in duplicates using a pH meter (Testo 205, Testo AG, Lenzkirch, Germany). Meat color was assessed at three points on the pectoralis major muscle using a portable spectrophotometer (CM-2600d, Konica Minolta, Ramsey, NJ, USA), with CIE lightness (L*), redness (a*), and yellowness (b*) components recorded from the SCE mode.
Determination of Tibia Breaking Strength
Both nutrient density (Ahmadi et al., 2024) and dietary probiotics (Mutuş et al., 2006) are known to affect tibia characteristics of broilers, which led us to measure tibia breaking strength in this study. The tibia was collected after removing all adhering muscle tissues and cartilage. The breaking strength of the tibia was assessed using an Instron Universal Testing Machine (Model 3342, Instron Corp., Norwood, MA, USA) with 50-kg-load cell at 50-kg load range and a crosshead speed of 50 mm/min, with the tibia supported on a 3.35 cm span.
Secretory Immunoglobulin A (sIgA) in Jejunal Mucosa
The jejunal segment sampled was opened longitudinally and rinsed with ice-cold phosphate-buffered saline (PBS). Jejunal mucosa samples were collected by scraping the mucosal surface of the jejunum using a tissue culture scraper, homogenized vigorously with ice-cold PBS, and centrifuged at 1,000 × g at 4 °C for 10 min. Then, supernatants were stored at -20°C until use. The concentrations of sIgA in the jejunal mucosa samples were determined using quantitative chicken IgA ELISA kits (Bethyl Laboratories, Inc., Montgomery, TX, USA) per the manufacturer’s instructions. The protein concentration in the supernatant was measured using a bicinchoninic acid (BCA) protein assay kit (Thermo Scientific, Waltham, MA, USA). The sIgA content was expressed as μg sIgA per μg of total protein.
Antioxidant and Immune Parameters in Serum Samples
The activity of superoxide dismutase (SOD) in serum samples as an indicator of antioxidant defense system was quantified using a commercially available SOD determination kit (Sigma, St. Louis, MO, USA). The concentrations of nitric oxide in serum samples as an indicator of innate immunity were measured as previously described by Lee et al. (2011). In short, equal volumes of serum samples and Griess reagent (Sigma, St. Louis, MO, USA) were added into a 96-well plate. The mixture was incubated for 10 min at room temperature and absorbance was read at 540 nm using a microtiter plate reader (Synergy2, BioTek, Winooski, VT, USA). Nitric oxide concentrations were calculated from a standard curve using sodium nitrite. The concentration of alpha-1-acid glycoprotein in serum sample as an indicator of innate immunity and inflammation was measured using a Chicken Alpha-1-acid Glycoprotein Assay Kit (Life Diagnostics, Inc., West Chester, PA, USA).
Serum Biochemical Parameters
Biochemical parameters including glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), glucose, total cholesterol, triglyceride, phosphorus, and uric acid were analyzed using an automated biochemical analyzer (Fuji DRI-CHEM 7000i, Fujifilm Co., Tokyo, Japan).
Statistical Analysis
Each pen was treated as an experimental unit. For growth performance, data were recorded on a pen basis. For carcass traits, meat quality, blood parameters, tibia characteristics, and jejunal measurements, one bird per pen was sampled, but the pen was retained as the experimental unit for statistical analysis. PROC UNIVARIATE (SAS 9.4, SAS Institute Inc., USA) was used to assess outliers and evaluate the normality of all variables. Data for all variables were analyzed using a two-way analysis of variance (ANOVA) with the model incorporating nutrient density and additives as the main factors and their interaction utilizing the general linear model of SAS (SAS 9.4, SAS Institute, Cary, NC, USA). When significant interactions were detected, simple-effect comparisons were performed to evaluate the effect of one factor within each level of the other factor. Duncan’s multiple range test was used to determine mean differences among treatments. Significant differences among treatments were pre-set at p<0.05.
RESULTS
Growth Performance
The impact of nutrient density and feed additives on body weight gain, feed intake, and feed conversion ratio is presented in Table 2. The OPT diets significantly increased (p=0.013) body weight gain in broiler chickens as compared to the DEF diets. Body weight gain was significantly decreased (p=0.04) in broilers on the L. pentosus-based diet in comparison to the control group. Salinomycin-fed broilers exhibited intermediate body weight gain. No interaction was observed between nutrient density and feed additives on body weight gain (p>0.05). Feed intake was not affected by nutrient density (p>0.05), but lowered by an average of 9.3% in broilers fed the L. pentosus-based as compared to the control groups (p=0.015). Feed intake showed a tendency for an ND × AD interaction (p=0.055), but this effect did not meet the significance threshold. A significant interaction between nutrient density and feed additives was observed on the feed conversion ratio. Dietary L. pentosus, but not salinomycin, tended to lower feed conversion ratio in broilers fed the OPT diet, but increased it in the DEF-fed broilers, showing a significant interaction (p<0.001) between the two factors.
Breast and Thigh Meat Quality
No interactions between nutrient density and feed additives on any of breast or thigh meat quality traits were found (Tables 3 and 4).
Nutrient density did not affect the relative breast meat yields of broiler chickens (p>0.05; Table 3). However, compared with the control group, breast meat yields were highest (p<0.05) in salinomycin-fed broilers, but lowest (p<0.05) in L. pentosus-based diet-fed broilers. Cooking loss was significantly higher (p<0.05) in broiler chickens receiving the OPT diets as compared to the DEF ones. None of the main factors affected (p>0.05) the pH or CIE L* (lightness) values of breast meats. CIE a* (redness) and CIE b* (yellowness) values in breast meats were not affected by nutrient density (p>0.05), but were significantly elevated in broiler chickens fed dietary salinomycin when compared with the control diets (p<0.05).
None of main factors (i.e., nutrient density and feed additives) affected thigh meat yields, nor the cooking loss, pH, and CIE b* values of thigh meats (p>0.05; Table 4). The CIE L* values of thigh meats were affected (p=0.018) by nutrient density, but unaffected (p=0.193) by dietary additives. Dietary salinomycin, but not dietary L. pentosus, increased the CIE a* values of thigh meats as compared with the control group (p=0.028).
Bone Strength
The effect of nutrient density and feed additives on tibia breaking strength is shown in Table 5. None of main factors or their interactions showed an effect on tibia breaking strength (p>0.05).
Jejunal IgA Concentrations
Nutrient density did not affect jejunal sIgA concentration in broiler chickens (Table 6).
However, jejunal sIgA was significantly lowered (p=0.016) in broilers fed the salinomycin-added diet compared with the control or L. pentosus groups. No interaction between nutrient density and feed additives on jejunal sIgA concentrations was observed (p=0.869).
Antioxidant and Immune Parameters in Serum Samples
The 2 × 3 interactions of nutrient density and feed additives did not affect the indicators of antioxidant defense system or innate immunity and inflammation (p>0.05; Table 6). The activities of SOD in serum samples assayed at 35 days were not affected (p=0.482) by nutrient density but were significantly elevated (p=0.027) in broiler chickens fed diets containing salinomycin and L. pentosus compared with the control group. NO and alpha-1-acid glycoprotein, the monitored indicators of innate immunity or inflammation in serum samples, were not altered by nutrient density and feed additives (p>0.05). However, alpha-1-acid glycoprotein in serum samples tended (p=0.071) to decrease by an average of 24.0% in salinomycin-fed broilers, and to increase by 17.1% in L. pentosus-fed broilers when compared with the control diet-fed control groups.
Serum Parameters
Serum parameters including GPT, glucose, total cholesterol, triglyceride, phosphorus, and uric acid were not affected by the main factors or their interactions (p>0.05; Table 7). However, the 2 × 3 interactions of nutrient density and feed additives affected the concentration of GOT in serum samples (p<0.05). Dietary salinomycin or L. pentosus did not affect the GOT concentration in broiler chickens fed the OPT diets, but tended to increase it in those fed the DEF diets, indicating that the effect of dietary additives on GOT levels is dependent on the nutrient density.
DISCUSSION
It has been reported that low nutrient densities lower body weight gain in broiler chickens as compared to higher ones (Delezie et al., 2010; Jia et al., 2024). In this study, we found that broilers fed the DEF diets were lower in body weight gain but had equal feed intake to those fed the OPT diets. Thus, the lowered body weight gain caused by the DEF diet is likely due to insufficient nutrient supply or inefficient nutrient utilization, as feed intake was not altered, thus leading to increased feed conversion ratio. Similar observations were reported by Strifler et al. (2023) and Kareem et al. (2025).
Against our expectations, dietary L. pentosus, but not salinomycin, lowered body weight gain and feed intake compared with the control group. Furthermore, dietary L. pentosus worsened FCR in the nutrient density-reduced diets. This negative effect by L. pentosus on growth performance seen in this study sharply contradicts its potential as a viable alternative to in-feed anbiotiotics. At this stage, although the plausible explanations are not readiliy available, assumptions can be proposed. First of all, reduction in body weight gain by dietary L. pentosus is in part due to a decrease in feed intake. Previous studies that showed probiotic-mediated decrease in feed intake (Amerah et al., 2013; Liu et al., 2025), either body weight gain or feed conversion ratio was improved, indicating an inhibitory effect of dietary probiotics per se on feed intake to be less likely. Secondly, it is likely that the dietary L. pentosus used in this study shifted the composition of gut microbiota, facilitating local inflammation at gut level. Indeed, we found that dietary L. pentosus tended to increase the concentration of alpha-1-acid glycoprotein in serum samples compared with the control groups, which may suggest a minor inflammation status in probiotic-fed broilers. L. pentosus strain isolated from pickled mustard leaves has been shown to exhibit antibiotic activities against food poisoning pathogens (data not shown). According to the study by Lee et al. (2010), different strains of B. subtilis with identical in vitro antibiotic activity could exhibit increase or decrease of immune markers, including serum alpha-1-acid glycoprotein, intestinal intra-epithelial lymphocyte subpopulations, and expression patterns of anti-inflammatory or proinflammatory cytokines in broiler chickens. Thus, a plausible explanation that cannot be excluded at this stage would be gut dysbiosis by dietary L. pentosus rather than its impact on balancing the gut microbiome. Although AGP tended to differ among additive treatments, this response did not reach statistical significance and should be interpreted only as a preliminary indication requiring confirmation. Further studies are warranted to disclose the role of dietary L. pentosus S14 strain in shaping gut microbiome of broiler chickens, which could help interpret the negative results obtained in this study. Finally, a significant 2 × 3 interaction of nutrient density and feed additives on feed conversion ratio was found, as dietary L. pentosus tended to decrease it under optimal nutrient diet but increased it in the deficient nutrient diet. Thus, it is likely that dietary L. pentosus aggravated nutrient digestion/utilization or reduced microbial diversity (i.e., dysbiosis) in broilers reared under compromised nutrition.
In line with the observed growth performance, dietary L. pentosus decreased breast meat yield compared with the control group. This reduction might be partly attributed to the decreased body weight gain in chickens fed dietary L. pentosus. In contrast, dietary salinomycin increased breast meat yield compared with the control group, which agrees with the results of Izat et al. (1991) and Qaid et al. (2021). In this study, broilers fed salinomycin-added diet tended to weigh and eat less but to show an increased feed conversion ratio compared with the control broilers. Thus, higher breast meat yield with the use of dietary salinomycin would not be caused by an efficient protein turnover but from an alteration of body composition. Indeed, Izat et al. (1991) reported that salinomycin-fed broilers had equal growth performance but had higher percentage of breast meat compared with those fed diets containing monensin or halofuginone.
The water-holding capacity of meat is one of the important traits of meat quality and affects color and tenderness of chicken meat, all of which influence consumer acceptance (Mir et al., 2017; Nikbakhtzade et al., 2024). In this study, the DEF diets decreased the cooking loss of breast meat as compared to the OPT ones, which agrees with previous findings by Benahmed et al. (2023) and Askri et al. (2025), who reported reduced cooking loss in broilers fed low protein diets. Dietary salinomycin, but not dietary L. pentosus, increased the a* and b* values of breast meat compared with the control group. Redness (a*) and yellowness (b*) are regarded as indicators of freshness for consumers (Khajeh Bami et al., 2020). In general, myoglobin and diet-originated carotenoids are known to affect breast meat a* and b* values in broilers (Suman & Joseph, 2013; Díaz-Gómez et al., 2017; Mir et al., 2017). However, since pigment deposition, heme iron, and myoglobin were not measured in this study, the mechanism underlying the observed color changes remains unclear. In this study, broilers fed the DEF diets exhibited higher thigh meat lightness (L*) values than those receiving the OPT ones, while broilers fed salinomycin-supplemeted diets showed the highest a* values for thigh meat. In contrast to our findings, Ndazigaruye et al. (2019) did not find an effect of low nutrition diets on thigh meat colors in broilers as compared to those receiving optimal diets. Dietary salinomycin, but not dietary L. pentosus, increased thigh meat a* values, indicating an increase in myoglobin, as noted in the breast meat in this study.
Broilers fed the salinomycin-added diet had decreased jejunal sIgA contents compared with the control groups. Given that sIgA serves as the first line of defense in intestinal mucosa against enteric pathogens and contributes to mucosal immune homeostasis (Peng et al., 2016; Lin et al., 2023), the reduction in jejunal sIgA in salinomycin-fed broilers may indicate reduced mucosal antigenic stimulation or altered local immune activity. However, because intestinal pathogen load, microbiota composition, and cytokine profiles were not measured, the biological meaning of this reduction remains uncertain. Naghizadeh et al. (2022) reported that dietary salinomycin exhibited an anti-inflammatory effect via improved gut integrity in Eimeria-challenged broilers. Similarly, anti-inflammatory response by dietary salinomycin has been reported in broilers reared on used litter (Lee et al., 2014), which supports the direct impact on controlling inflammation-inducing pathogens at gut level.
It is well established that superoxide dismutase (SOD) plays a critical role in detoxifying reactive oxygen species by catalyzing the conversion of superoxide anions to oxygen and hydrogen peroxide (Gao et al., 2013). In the present study, dietary supplementation of salinomycin and L. pentosus increased SOD activity in chickens, suggesting enhanced cellular protection against oxidative stress. The observed increase in SOD activity of probiotic-fed broilers aligns with earlier findings (Cao et al., 2019; Xiao et al., 2024; Yang et al., 2024) that demonstrated that lactic acid bacteria could strengthen the antioxidant defense system. Moreover, the improved SOD response by L. pentosus might be attributed to the inherent antioxidant enzymatic systems of lactic acid bacteria (Feng & Wang, 2020). In this study, dietary salinomycin also increased SOD activity as compared with the control group. Although dietary antibiotics could increase intracellular oxidation by increasing reactive oxygen species (Hu et al., 2022), dietary salinomycin is known to restore Eimeria spp.-induced decrease in SOD activity (Gordillo Jaramillo et al., 2021), and increase the SOD activity in broiler chickens (Sharma et al., 2025).
Our results showed that serum GOT levels were elevated in broilers fed diets containing either salinomycin or L. pentosus compared with the control group receiving the DEF, but not OPT diets, showing a significant interaction between dietary additives and nutrient density. Serum GOT level is commonly utilized as a biomarker for hepatic injury (Abou-Elkhair et al., 2020; Saleh et al., 2024), and elevated levels generally indicate liver impairment (Xu et al., 2021). A clear explanation is not readily available, as no other serum biochemical parameters (i.e. GPT, glucose, total cholesterol, triglyceride, uric acid, and phosphorus) were altered by the main factors. Furthermore, all values observed in this study fell within the normal range of serum GOT for chickens (84 IU/L to 342 IU/L, as reported by Zálešáková et al. (2025). Therefore, this finding should be interpreted as a treatment-dependent biochemical response rather than clear evidence of hepatic injury.
This study has some limitations. First, only one L. pentosus strain and one inclusion level were evaluated, so the findings cannot be generalized to other strains, doses, or probiotic formulations. Second, the study was conducted under non-challenged conditions, which limits conclusions about the use of L. pentosus as an alternative to anticoccidial or antibiotic feed additives under disease pressure. Third, gut microbiota composition, intestinal morphology, digestive enzyme activity, and inflammatory cytokines were not measured, limiting mechanistic interpretations of the reduced feed intake and growth performance in L. pentosus-fed broilers. Finally, probiotic viability in the final feed was not reported, which should be considered when interpreting the biological response.
CONCLUSION
It was demonstrated that broilers fed the optimal nutrient-density diet showed greater body weight gain and better feed conversion than those fed the deficient diet. Dietary L. pentosus S14 increased serum SOD activity but reduced feed intake, body weight gain, and breast meat yield, particularly limiting its practical value as a direct alternative to salinomycin under the conditions tested. Salinomycin improved breast meat yield and increased SOD activity, while reducing jejunal sIgA. The significant interaction for feed conversion ratio indicates that the response to feed additives depends on nutrient density. Further studies should evaluate different L. pentosus doses, confirm probiotic viability in feed, and include microbiota, intestinal morphology, and disease-challenge models before recommending this strain for commercial broiler production.
ACKNOWLEDGEMENTS
Viet Anh Vu was partially supported by the KUVEC-VNUA Joint Research Project, funded by Korea Institutional Cooperation Agency (KOICA).
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