Description of problem
Adding antibiotics in feed as growth promoter and health enhancer has been excluded in many developed countries (Afiouni et al., 2023). In the concern for antibiotic free livestock products, researches on potential feed additives as antibiotic alternatives have gained more attention in recent years (Landy and Kheiri, 2023). Among the alternatives, yeast is the promising potential candidate (Lin et al., 2023). Yeast and yeast fermented product have been used to improve body weight and feed utilization of livestock and poultry. The most important species of yeast, Saccharomyces cerevisiae has been recognized as probiotic potential (Fathima et al., 2023). Live yeast (LY) is the one to focus product created from micro-organism that has the potential to be used as dietary supplement (Moallem et al., 2009) as well as alternative to antibiotics for animals (Shen et al., 2009).It has beneficial role for enhancing growth and thus it became a potential candidate for antibiotic substitute in broilers nutrition (Yang et al., 2007) . Supplementation with yeast and yeast cell walls at 1.5 to 2 g/kg level could enhance growth and meat production of broilers (Ahiwe et al., 2020). Live yeast is known to be a feed with large concentrations of non-starch polysaccharide (NSP) along with mannose and glucans (He et al., 2021). Yeast could improve body immunity as well as intestinal nutrient digestibility (Samarasinghe et al., 2004), gut health by inhibition of harmful bacteria(Trevisi et al. 2015), enhance antioxidant capacity and diseases resistance (Bu et al., 2019). NSPs function as prebiotic substrates, selectively promoting the growth of beneficial gut microbiota such as Firmicutes while inhibiting pathogenic bacteria like Bacteroidetes, Escherichia coli, and Salmonella (Lin et al., 2023). The fermentation of NSPs by gut microbiota leads to the production of short-chain fatty acids (SCFAs) – primarily butyrate, acetate, and propionate – which confer multiple physiological benefits. Butyrate, in particular, serves as a primary energy source for intestinal epithelial cells, reinforcing the intestinal barrier by upregulating tight junction proteins such as occludin and claudin. This improves gut permeability and mitigates inflammatory responses by downregulating pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) (Ogbuewu et al. 2019). Furthermore, NSPs contribute to intestinal morphology adaptations by increasing villus height and improving the villus height-to-crypt depth ratio, thereby enhancing nutrient absorption efficiency and feed conversion ratio (Lin et al., 2023).
Yeast polysaccharide, beta glucan and mannan oligosaccharide were reported as prebiotics to regulate the immune function (Fadl et al., 2020) . Live yeast plays a part in producing lactic acid that inhibits the hazardous microorganisms in intestine (Ogbuewu et al. 2019) and can maintain sound gut health. Yeast derived polysaccharide (β-glucans) has many biological functions such as immuno-stimulating, anti-oxidant, antimicrobial, toxin-binder and growth enhancer (Stier et al., 2014). A recent study examined the effects of live weight performance, serum antibody production, and gut microbial composition of broilers fed with Saccharomyces cerevisiae hydrolysate at a rate of 250 mg to 500 mg/kg (Lin et al., 2023). The authors claimed to increase the body weight gain during d 15 to 28, with increased jejunum villi height and ratio of villi height to crypt depth. In addition, on microbial analysis there was a greater abundance of Firmicutes and a lower abundance of Bacteroidetes. Moreover, inclusion of yeast hydrolysate could downregulate the mRNA expression of immuno-modulatory genes (TNF-a, IL-1b, IL-6). Collectively authors stated that dietary Saccharomyces cerevisiae might be a functioning on improving the growth by changeable the gut immunity, barrier function, intestinal morphology that correlated with gut microbial alignment. Poultry farms usually exposed to multiple challenges includes dietary toxins, vaccination failure, higher disease susceptibility, poor meat or egg quality, etc. (Zhen et al., 2020) . Therefore, to reduce the challenges, dietary yeast supplementation as growth and health enhancer may be an effective strategy in broiler production. Even it is believed that the live yeast has beneficial role on human health, unfortunately the supplementation of live yeast in poultry diets are still under investigation in many developing countries like Bangladesh. In the light of sustainable poultry production, the purpose of this study was to investigate the potentiality of using live yeast (Saccharomyces cerevisiae) as an alternative for antibiotics for improving body weight, quality of meat as well as health condition of broilers with a view to produce organic meat for consumer market.
Materials and methods
Experimental design and dietary treatments
A total of 192 Arbor Acres (AA) male broilers were randomly divided into three groups: Control, Antibiotic, and Live yeast. Every group had eight replications of 8 birds. The broilers were weighed (40.25±2.45 g) at initiate of the experiment. The AA commercial broiler production manual guide was followed while creating the broiler diet, which included a starter feed for the first 21 days and a final one for the next 22 to 42 days. The feed was provided in pelleted form for all groups, ensuring uniform nutrient intake and digestibility. The control group received a standard basal diet, 100 mg chlortetracycline / kg of basal diet fed to the antibiotic group, and 600 mg/kg of live yeast powder was integrated to the basal diet for the LY group. Chlortetracycline (CTC) has a broad-spectrum action against gram-positive and gram-negative bacteria, and it is widely used as a feed growth promoter for broilers. The dosages for CTC was selected so that it could not contribute to antimicrobial resistance in chickens (Liu et al., 2021). LY was purchased from local market that contained the culture of Saccharomyces cerevisiae 2.8 × 108 CFU/g. The analyzed nutrient composition of Saccharomyces cerevisiae (DM basis) was found as follows: Crude Protein (CP): 37.4 %, Crude Fiber (CF): 3.5 %, Crude Fat (Ether Extract, EE): 2.3 %, Total Ash: 4.32 %, Nitrogen-Free Extract (NFE): 43.7 %, Gross Energy: 12.3 MJ/kg. Previous research has been conducted on live yeast in poultry diets using doses of 500 mg/kg and 1000 mg/kg (He et al., 2021). Considering the findings of previous research, we have selected the single lower dosage (600 mg/kg) of LY as the main treatment group in this experiment.
The nutrient contents and experimental feed ingredients utilized in this trial are all listed in Table 1.
Table 1. Nutrient composition of experimental basal diet1.
| Contents% | Starter Phase (Day 1- 21) | Grower Phase (Day 22- 35) |
|---|---|---|
| Maize | 58.00 | 61.40 |
| Soybean meal | 26.00 | 21.80 |
| Full fat soybean | 12.23 | 14.13 |
| Di-calcium phosphate2 | 1.60 | 1.50 |
| Limestone | 1.20 | 1.20 |
| Salt | 0.30 | 0.30 |
| L-Lysine-HCL2 (98 %) | 0.02 | 0.02 |
| DL-Methionine2 (98 %) | 0.14 | 0.14 |
| L-Threonine2 (98 %) | 0.01 | 0.01 |
| Vitamin-Mineral premixes | 0.50 | 0.50 |
| Total | 100.00 | 100.00 |
| Analyzed value | ||
| Crude Protein % | 19.90 | 18.60 |
| Ash % | 5.00 | 5.00 |
| Cal % | 0.95 | 0.98 |
| Av. Phosphorus % | 0.52 | 0.48 |
| Methionine (min) | 0.45 | 0.47 |
| Lysine (min) % | 1.05 | 1.03 |
| Threonine % | 0.88 | 0.85 |
| Calculated value | ||
| ME (Kcal/kg) | 2970.00 | 3100.00 |
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Live yeast (600 mg/kg) and antibiotic (chlortetracycline, 100 mg/kg) were mixed with premix and then mixed thoroughly with each basal diet.
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Commercially available.
Experimental site and managements
The experiment was conducted in the Sylhet Agricultural University, Sylhet-3100, with approval from the ethical council (Ethical number AUO2023026). Every broiler was grown in a temperature-controlled room with various environmental controls. For brooding purposes, the temperature was set at 37°C. However, it gradually dropped through 3°C every week before becoming stable at 25°C. In order to promote brooding, the broiler shed’s humidity was first adjusted to 50 % on day one, then increased by 5 % per week until it reached 70 %. Throughout the first week of the trial, the lighting was on for 24 h, and the remaining duration was 23 h. The broilers were raised in a bran rearing system, and each replicate was housed in a box. Each box measured 4 meters long and 2 meters wide, totaling 8 m², with each broiler occupying 1 m². During the brooding period, temperature, humidity, feeding, and watering were monitored every two hours of the day. After the brooding phase, the broilers were monitored every four hours and provided with necessary feed and fresh water as needed. The experimental broilers were given an ad libitum supply of feed and safe drinking water. The broilers received their vaccinations in accordance with standard immunization protocols. To secure young chicks from infecting Ranikhet, the broilers received vaccinations on days three and twenty-three. On day nine, they received the infectious bursal disease vaccine (IBD), which they boosted on day seventeen. All management procedures were done according to the recommendations for raising AA broilers (Aviagen 2018).
Chemical assessment of yeast and diets
The Association of Official Analytical Chemists (AOAC 2004) technique was used to test diets and yeast samples in emulate for DM, CP, CF, EE, Ash, Ca, and P. For successful laboratory testing, feed particles were grinded finely (0.01 mm). The Kjeldahl technique (protein content = nitrogen x 6.25) was used to calculate crude protein, while the Ankom Fiber Analyzer was used to calculate crude fiber. On the other hand, ash content was ascertained by ashing at 550°C for six hours in a muffle furnace. An automatic adiabatic oxygen bomb calorimeter (Parr 6400, Automatic Isoperibol alorimeter) has been employed to calculate gross energy. The ash content was subtracted from 100 to find the organic matter (OM) (Sultana 2020) . (Organic matter = 100 – Moisture % – Ash %). The NFE was computed as follows (Azila et al. 2022):
Calcium and phosphorus contents in feed were measured using optical emission spectroscopy and inductively coupled plasma (ICP2060T, Jiangsu, China).
Growth performance measurements
Data of feed intake and body growth were recorded throughout the study. Every week, the birds were weighed on a replication basis, and the mean weight of each replicate (8 birds from each of the 8 replicates) from every group was noted. The following formula was used to determine the growth performance metrics from the recorded data, including feed conversion ratio, average weight gain every day per bird, and average daily feed consumption.
Carcass characteristics and inner organs weight
In order to assess carcass attributes, and determine inner organ weight, one broiler was randomly chosen from each replicate (eight from each group) and killed on day 42 by cervical disarticulation. After the offals were removed, the weight of the eviscerated carcass was noted. All of the dead broilers’ thigh, drumstick, leg, wing, shank, and inner organs were taken out and weighed right away. Every live broiler was weighed before it was killed.
Assessment of quality of meat
The pH value of breast meat: Three sites of the breast muscle were monitored for pH by a portable pH meter (Starter 300 pH portable) at 45 min and 24 h after slaughtering. At room temperature, calibration buffers with pH values of 4.00 and 7.01 were used to calibrate the electrode. To ensure precision, the pH values were recorded twice (Akib et al., 2024).
Calculating drip loss % of breast meat: The procedure described by (Akib et al., 2024) was used to accomplish the drip loss percent. For this, blocks of roughly 100 gm breast meat were hung for seven days at 4°C within an inflated plastic zipper bag. The samples were taken out of the refrigerator, their surfaces cleaned with filter paper, and then they were weighed again after a day and a week to calculate drip loss. On the basis of the samples’ original weight and weights after hanging, the drip loss% was measured (Cheng et al., 2019).
Calculating the loss from cooking: The cooking loss was computed using chunks of breast flesh weighing about 100 grams each. The digital needle-tipped thermometer (H 1145, Hanna Instruments, Italy) was used to measure the meat’s interior core temperature, which were cooked in plastic bags submerged in a water bath that had been prepared to 70°C. Following the cooking process, the samples were taken out of the water bath and the bag’s extra water was drained. Before determining the final weights, the samples have been promptly cooled under the stream of water at 18°C for 30 min. Any remaining liquid was then wiped away with paper towels. The following formula was used to calculate cooking loss (Vargas-Ramella et al. 2022):
Collection of blood samples for hemato-biochemical parameter analysis
At 42 day of age, a broiler was arbitrarily chosen from every replicate. Then, two aliquots of blood were drawn from the broilers’ pierced wing veins for hemato-biochemical examination. For routine hematological assays, the initial sample was placed in a tube containing the EDTA. Standard hematological assays were employed to measure blood parameters. Without adding an anticoagulant, the second batch of samples was put in a tube. Serum was extracted from these samples and kept cold until it was analyzed. A commercially available test kit was used to evaluate the amounts of serum metabolites.
Cecal microbiota count
From each replicated broiler, one gram of cecal content was aseptically collected and transferred into an Eppendorf tube containing 900 μL of phosphate buffer solution (PBS). This was done to ensure proper homogenization and optimal suspension of the microbial cells. A series of 10-fold serial dilutions was then prepared using a sterile saline solution, creating a gradient of dilutions up to 10-7 that facilitated accurate quantification of the bacterial populations. Escherichia coli and Klebsiella cultures were cultured at 2 different concentrations (10-3 and 10-5). Following accurate absorption and coating, a 100-μL dilution was applied to the MacConkey Agar medium for inoculation. The number of colonies that resulted from 24 h of incubation at 37°C was counted. The same protocol was used to cultivate salmonella and shigella in SS (salmonella-shigella) agar, and lactobacillus in De Man-Rogosa-Sharpe (MRS) agar. In addition, total aerobic bacterial counts were determined by inoculating a 100-μL dilution (10-7) into nutrient agar, which supports a wide range of bacterial species and provides an overall measure of the microbial load in the cecal content. The data were recorded as colony-forming units per gram of sample (cfu/g) and expressed as log10 cfu/g to ensure consistency and comparability across samples. Each sample was analyzed in duplicate to guarantee the accuracy and repeatability of the results.
Statistical analysis
Each replication was considered a separate experimental unit. The information was recorded in a Microsoft Excel 2023 (Microsoft Corp., Redmond, WA, USA) and analyzed using SPSS version 27.0 (IBM Corp., Armonk, NY, USA) with a one-way ANOVA. Duncan multiple t-tests, with statistical significance at P value of less than 0.05, used to evaluate variances among group means.
Results and discussion
Performance of broilers
Table 2 demonstrates the consequence of live yeast (LY) on broiler growth performance. Across all age ranges, no statistically noteworthy differences (P > 0.05) in ADFI among the live yeast, antibiotic, and control groups. ADG exhibited significant variations across all age groups. From 1 to 21 days, the live yeast and antibiotic groups displayed considerably greater (P < 0.05) ADG than the control group while FCR does not show any significant differences at the beginning phase. On the other hand, during the grower phase (22-42 days), the LY group had considerably higher ADG than the control group, whereas FCR showed the reverse tendency. Interestingly both the live yeast and the antibiotic groups exhibited considerably higher ADG than the control group for the whole testing period. In addition, the control group’s FCR was larger than that of the LY and antibiotic groups. The control group had a lower final body weight (FBW) than the antibiotic and LY groups, despite the fact that the starting body weight (IBW) did not differ substantially.
Table 2. Effects of live yeast on the growth rate of broilers1.
| Broiler’s age | Control | Antibiotic | Live yeast | SEM | P-value |
|---|---|---|---|---|---|
| Average daily feed intake; ADFI (g/d) | |||||
| 1-21 day | 57.51 | 58.95 | 57.25 | 0.65 | 0.937 |
| 22-42 day | 118.5 | 113.7 | 115.3 | 1.05 | 0.531 |
| 1-42 day | 88.01 | 86.33 | 86.29 | 1.32 | 0.623 |
| Average daily weight gain; ADG (g/d) | |||||
| 1-21 day | 41.92b | 45.69a | 46.78a | 0.39 | 0.033 |
| 22-42 day | 54.34b | 56.33ab | 59.36a | 0.67 | 0.022 |
| 1-42 day | 48.12b | 51.01a | 53.06 a | 1.14 | 0.044 |
| Feed conversion ratio; FCR | |||||
| 1-21 day | 1.37 | 1.29 | 1.22 | 0.02 | 0.852 |
| 22-42 day | 2.18a | 2.01ab | 1.94b | 0.08 | 0.041 |
| 1-42 day | 1.83a | 1.69b | 1.63b | 0.04 | 0.033 |
| Initial Body Weight | 40.25 | 40.40 | 40.30 | 0.69 | 0.974 |
| Final Body Weight | 2061b | 2182a | 2269a | 42.14 | 0.002 |
a,bValues with various superscripts within uniform row indicate a significant variation at P < 0.05;.
SEM: stands for pooled standard error of the means. Significance level at P < 0.05.
Antibiotic: chlortetracycline, at 100 mg/kg; Live yeast: at 600 mg/kg basal diet.
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Data represented the mean value of 64 birds in every treatment.
Live yeast supplements to the feed have been shown in numerous trials to enhance animal growth performance (Yang et al., 2007; Ahiwe et al., 2020). The present investigation’s findings have shown that the average daily weight gain and FCR of broilers significantly improved when live yeast was added in diets in the growth phase. Notably, over the course of the entire time, the LY group surpassed the control group in terms of FCR by 10.9 % and ADG by 10.3 %. These results are consistent with earlier studies conducted by (Lin et al., 2023; Fathima et al., 2023), who reported that broilers fed diets containing yeast products improved growth performance. Several variables can be linked to the LY group’s increased growth performance. Firstly, it is well known that live yeast has significant concentrations of non-starch polysaccharides such glucan and mannose (He et al., 2021). These elements are essential for enhancing intestinal health and maximizing the absorption of nutrients. Live yeast has been shown to boost feed conversion rates and body growth in chicken by improving protein retention and the breakdown of fibrous components of feed (Moallem et al., 2009) . Secondly, live yeast’s probiotic properties support a favorable intestinal environment. According to (Ogbuewu et al., 2019), live yeast acts as a probiotic by suppressing pathogenic bacteria and promising the development of useful gut flora. As previously pointed out, LY may have an improved anti-inflammatory impact in animals, which might be responsible for some of its effects on growth promotion (Bu et al., 2019). Furthermore, it has been documented that live yeast can enhance growth performance through improving nutrient absorption, controlling gut microorganisms, and boosting nutrient digestibility (Samarasinghe et al., 2004). These possible processes are compatible with the improvement in growth performance that we found in our study.
Impact on visceral organ weight and carcass traits
Data on the impact of live yeast supplementation on the weights of several visceral organs and carcass traits in 42-day-old broiler chicks are shown in Table 3, Table 4. The relative weights of the visceral organs in broiler chickens at 42 days of age were not significantly affected by the addition of live yeast or antibiotics. Even though there were a few small numerical changes between the treatment groups, none of them were statistically significant (P > 0.05). Similarly, there was no discernible (P > 0.05) variation in carcass characteristics such as drumstick, shank, wing, thigh, and dressed weight across the experimental groups.
Table 3. Effects of live yeast on visceral organ weight of experimental broilers at 421.
| Contents | Control(g) | Antibiotic(g) | Live yeast(g) | SEM | P-value |
|---|---|---|---|---|---|
| Liver | 2.94 | 2.95 | 2.88 | 0.15 | 0.473 |
| Heart | 0.69 | 0.67 | 0.68 | 0.03 | 0.424 |
| Pancreas | 0.35 | 0.37 | 0.36 | 0.02 | 0.478 |
| Spleen | 0.17 | 0.16 | 0.14 | 0.01 | 0.158 |
| Proventriculus | 0.38 | 0.41 | 0.42 | 0.01 | 0.551 |
| Bursa | 0.18 | 0.16 | 0.18 | 0.01 | 0.521 |
| Gizard | 1.42 | 1.47 | 1.47 | 0.02 | 0.324 |
| Abdominal fat | 0.96 | 0.93 | 0.97 | 0.05 | 0.731 |
| Intestine | 5.82 | 5.73 | 5.68 | 0.31 | 0.732 |
SEM represent the standard error of the means. Significance level at P < 0.05.
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Data showed the average value of 8 samples in every treatment.
Table 4. Effect of live yeast on carcass characteristics in experimental birds at 421.
| Contents | Control(g) | Antibiotic(g) | Live yeast(g) | SEM | P -value |
|---|---|---|---|---|---|
| Slaughter weight | 96.65 | 96.57 | 97.2 | 0.27 | 0.536 |
| Dressed weight | 62.82 | 63.74 | 64.77 | 0.52 | 0.236 |
| Wing | 5.60 | 5.77 | 5.88 | 0.23 | 0.413 |
| Thigh | 8.77 | 8.93 | 9.15 | 0.22 | 0.813 |
| Drumstick | 8.10 | 8.52 | 8.62 | 0.13 | 0.447 |
| Shank | 3.82 | 3.78 | 3.81 | 0.08 | 0.514 |
SEM represents the standard error of the means. Significance level at P < 0.05.
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Data showed the average value of 8 samples in every treatment.
Feeding LY had no apparent effect on the relative weights of visceral organs or carcass characteristics which implies that changes in organ development or carcass composition are not related to the adverse effect of normal growth and health, which is consistent with the findings of (Ahiwe et al., 2020). Similarly, inclusion of 0.5, 1.5 and 2 % Saccharomyces cerevisiae did not affect the inner organs and dressing weight (Paryad and Mahmoudi, 2008).
Meat quality
At 45 min postmortem, broilers fed with antibiotics and LY mixed feed had a pH value on the breast muscle that was far more considerable than the control diet, as shown in Table 5. Furthermore, no considerable differences (P > 0.05) between the experimental groups in the drip loss % and the pH of the breast after 24 h were founded. On the other hand, the LY treatment group’s drip loss % at day 7 was considerably reduced (P < 0.05) than that of the control and antibiotic-fed broilers. Furthermore, the control and antibiotic groups showed a considerably more cooking loss % (P > 0.05) than the LY group.
Table 5. Effects of live yeast on meat quality of broilers at 421.
| Items | Control | Antibiotic | Live yeast | SEM | P -value | |
|---|---|---|---|---|---|---|
| pH | 45 min | 5.94b | 6.16a | 6.28a | 0.03 | 0.031 |
| 24 h | 5.71 | 5.83 | 5.84 | 0.06 | 0.243 | |
| Drip loss % | 24 h | 2.76 | 2.82 | 1.72 | 0.03 | 0.245 |
| 7th day | 4.49a | 4.44a | 2.97b | 0.17 | 0.031 | |
| Cooking Loss % | 26.2a | 24.17a | 21.28b | 1.49 | 0.042 | |
a,bValues with various superscripts within uniform row indicate a significant variation at P < 0.05;.
SEM: stands for pooled standard error of the means. Significance level at P < 0.05.
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Data represented the mean value of 8 samples in every treatment.
Meat qualitative indicators improved after LY supplementation in this study. The observed enhancement in water-holding capacity (WHC), indicated by reduced drip loss and cooking loss, may be linked to serum metabolic parameters, hematological response, and cecal microbiota composition of experimental chickens. In this study, broilers supplemented with live yeast exhibited significantly lower serum triglyceride and total cholesterol levels (P < 0.05, Table 6). These reductions suggest an improved lipid metabolism, which has been associated with enhanced cellular membrane stability and muscle water retention post-mortem (Bu et al., 2019). Additionally, the heterophil-to-lymphocyte (H/L) ratio, a marker of physiological stress, was significantly lower in the live yeast group (P < 0.05, Table 7). A lower H/L ratio correlates with reduced oxidative stress, which may explain the improved muscle protein integrity and reduced drip loss (Fadl et al., 2020). Cecal microbial analysis further supports this relationship. The live yeast group exhibited higher Lactobacillus spp. counts and significantly lower Escherichia coli and Salmonella spp. counts (P < 0.05, Table 8). A well-balanced gut microbiome has been linked to reduced systemic inflammation, which can positively influence meat quality by minimizing proteolytic enzyme activity that degrades muscle proteins post-slaughter (Lin et al., 2023). The LY group’s breast muscle had a higher pH value at 45 min post-slaughtered, which may have advantages for preserving the meat that can ensure good quality of meat. In contrast, according to the findings of (Aristides et al., 2018), Saccharomyces cerevisiae fermented product at 1,500 g/t could decline breast meat pH at 24 h post-slaughter. Our study observed that the pH decline trend from 45 min to 24 h post-slaughter remained within the acceptable range, suggesting that LY plays a crucial role in mitigating to decline rapid pH. This finding is significant because rapid declining the pH is associated with the accelerated denaturation of meat proteins, which can lead to paler meat and reduced water holding capacity (Cao et al., 2012) . Improved water-holding capacity and lessened protein denaturation might be linked to this higher starting pH (Akib et al., 2024). Distinguished results include the LY group’s reduced cooking loss rate and noticeably lower drip loss on day 7. These results suggest that adding live yeast to feed may increase meat’s water-holding capacity, an important aspect of meat quality and consumer acceptance. (Ahiwe et al., 2020). indicate that the higher gut health and nutritional utilization provided by live yeast could improve water retention.
Table 6. Effects of live yeast on serum metabolic parameters in broilers (42 day)1.
| Parameters | Control | Antibiotic | Live yeast | SEM | P -value |
|---|---|---|---|---|---|
| Blood urea nitrogen (mg/dl) | 0.35 | 0.25 | 0.28 | 0.02 | 0.451 |
| Serum glutamic pyruvic transaminase (u/l) | 12 | 9 | 9.2 | 0.35 | 0.852 |
| Total Cholesterol (mg/dl) | 265a | 296a | 187b | 29.5 | 0.002 |
| Triglyceride (mg/dl) | 87a | 98a | 73b | 4.14 | 0.031 |
a,bValues with various superscripts within uniform row indicate a significant variation at P < 0.05;.
SEM: stands for pooled standard error of the means. Significance level at P < 0.05.
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Data represented the mean value of 8 samples in every treatment.
Table 7. Effects of live yeast on hematological parameters of experimental broilers (42 day)1.
| Parameters | Control | Antibiotic | Live yeast | SEM | P-value |
|---|---|---|---|---|---|
| Hemoglobin (gm/dl) | 10.45 | 9.86 | 10.2 | 0.55 | 0.358 |
| Red Blood cells (Million/cmm) | 2.84 | 2.63 | 2.95 | 0.08 | 0.534 |
| PCV % | 35 | 34 | 33 | 1.73 | 0.165 |
| Mean corpuscular volume (fl) | 137 | 135 | 137 | 3.56 | 0.892 |
| Mean corpuscular Hemoglobin (pg) | 43 | 41 | 42 | 1.32 | 0.532 |
| MCHC (gm/dl) | 31 | 32 | 31 | 1.22 | 0.711 |
| RDW-CV % | 6.8 | 6.8 | 7.1 | 0.04 | 0.672 |
| WBC total count (k/cmm) | 129 | 127 | 127 | 6.88 | 0.758 |
| Heterophils % | 28 | 27 | 26 | 1.34 | 0.552 |
| Lymphocyte % | 61 | 62 | 63 | 2.33 | 0.653 |
| Monocyte % | 11 | 11 | 11 | 0.65 | 0.941 |
| Heterophils/Lymphocyte | 0.45a | 0.44a | 0.41b | 0.02 | 0.041 |
| Platelet (total count) (k/cmm) | 40 | 41 | 39 | 1.33 | 0.892 |
a,bValues with various superscripts within uniform row indicate a significant variation at P < 0.05;.
SEM: stands for pooled standard error of the means. Significance level at P < 0.05.
Abbreviations: PCV, Packed cell volume, MCHC, Mean corpuscular Hemoglobin concentration, RDW-CV, Red cell distribution width-coefficient of variation, WBC, White blood cells, Antibiotic: chlortetracycline, at 100 mg/kg; Live yeast at 600 mg/kg basal diet.
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Data represented the mean value of 8 samples in every treatment.
Table 8. Effects of live yeast cecal bacterial count log10 cfu/g in broilers (42 day)1.
| Microorganisms | Control | Antibiotic | OMSR | SEM | P-value |
|---|---|---|---|---|---|
| Escherichia coli | 7.63a | 6.68b | 6.31b | 0.27 | 0.026 |
| Klebsiella | 6.94 | 6.77 | 6.32 | 0.30 | 0.414 |
| Salmonella | 7.61a | 6.36b | 6.32b | 0.52 | 0.041 |
| Lactobacillus | 7.13b | 7.81a | 7.8a | 0.23 | 0.043 |
| Total aerobic Count (TAC) | 9.66 | 9.43 | 9.56 | 0.12 | 0.362 |
a,bValues with various superscripts within uniform row indicate a significant variation at P < 0.05;.
SEM: stands for pooled standard error of the means. Significance level at P < 0.05.
Antibiotic: chlortetracycline, at 100 mg/kg; live yeast at 600 mg/kg basal diet.
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Data represented the mean value of 8 samples in every treatment.
Serum metabolic profile
Table 6 exhibits the serum metabolic profile of the broilers on day 42. LY-fed broilers had significantly lower serum levels of total cholesterol (TC) and triglycerides (P < 0.05) than control and antibiotic-supplemented groups. Even though, blood urea-nitrogen and SGPT did not differ significantly across the experimental broiler groups. According to the serum metabolic profile examination of broilers given LY exhibited notably reduce triglycerides and total cholesterol in contrast to the control and antibiotic-supplemented groups. These outcomes are consistent with those of (Bu et al., 2019), who found that supplementing with yeast could improve broiler health and antioxidant capacity. The observed decrease in triglyceride and cholesterol levels implies that supplementing broilers diets with live yeast may improve their lipid metabolism. This may be helpful to meet the consumer expectations for lower-fat meat by creating healthier poultry products for human consumption. (Ogbuewu et al., 2019) suggest that the mechanism underlying this impact may be linked to yeast’s capacity to alter lipid metabolism or promote cholesterol excretion.
Hematological profile
Table 7 displays the hematological alterations in the experimental broilers on day 42. According to the study, LY-supplemented broiler meals resulted in considerably (P < 0.05) lower levels of lymphocytes/heterophils than both control and antibiotic-supplemented diets. However, other blood parameters including hemoglobin, red blood cells, PCV, MCV, MCH, MCHC, RDW-CV, TLC, and platelets in the experimental broiler groups exhibited statistically (P > 0.05) no differences. Although the majority of haematological indicators did not change, the LY group’s decreased heterophil /lymphocyte ratio is worth noted. This discovery might point to an adjustment of the immune system, which could enhance resistance to diseases. According to (Fadl et al., 2020), beta-glucan and mannan oligosaccharide, generated from yeast, have the ability to control immunological function in chickens. Our study’s better performance could possibly be attributed to the anti-inflammatory benefits of yeast supplementation seen in earlier research. It has been demonstrated that β-glucans generated from yeast can suppress cytokines that promote inflammation, namely IL-1β (Municio et al., 2013). According to other research, supplementing with yeast can prevent the overexpression of TNF-α, IL-6, and IL-1β (Superchi et al., 2012) . Although we did not assess these cytokines directly, our LY group’s decreased heterophil/lymphocyte ratio, which is consistent with our earlier findings, suggests a lower state of inflammation.
Bacterial number in cecum
Table 8 illustrates the cecal bacterial count (measured in Log10cfu/g) in experimental birds on day 42. Compared to the control diet, broilers supplemented with LY and antibiotics demonstrated a greater value (P < 0.05) for Lactobacillus spp. and a lower value for E. coli and Salmonella spp. counts. In contrast to the other experimental groups, LY did not significantly affect the total aerobic count (TAC) or the Klebsiella spp. count (P > 0.05). The cecal bacterial counts showed the most remarkable response to LY supplementation. Live yeast has the ability to positively alter the gut microbiota, as seen by the LY group’s higher abundance of Lactobacillus species and lower numbers of E. coli and Salmonella spp. This result supports the idea that LY can enhance gut health through increasing favorable microbes and suppressing possible bacterial infections, and it is in line with other researches (Lin et al., 2023). According to (He et al., 2021), changes in the cecal microbiota may have a significant impact on the function of the intestinal barrier and the inflammatory response. By opposing pathogens and the higher number of Lactobacillus spp. shown in our study may help to preserve the intestinal barrier (Servin, 2004) . This could therefore result in better gut structure and increased nutritional digestibility. Previous research has demonstrated that supplementing with yeast could increase the integrity of the intestinal epithelium, even though our study did not examine intestinal barrier function directly. According to (Tang et al., 2015), tight junction proteins such as occludin, claudin, and zonula occludens families primarily regulate the size of the gap between intestinal epithelial cells. These proteins are essential for controlling the intestinal barrier and protecting the intestinal epithelium from infections and antigens (Broom, 2018).
Conclusions and applications
In the light of current investigation, it can be concluded that
- 1.
Live yeast could improve broilers’ average daily gain, final body weight, and feed conversion ratio that can be used as feed additives for economic broiler production.
- 2.
Live yeast could decrease the cooking loss, drip loss of breast meat that can satisfy the consumer demands for safe, high-quality meat.
- 3.
LY ensured sound physiology of broilers by enhancing the number of beneficial Lactobacillus spp. in caecal ingesta and by reducing total cholesterol and triglycerides concentrations in serum.
- 4.
Therefore, live yeast at 600 mg/kg of basal diet supplements as a growth promoter and health enhancer can be potential feed additives for organic and sustainable broiler production.
Source: Science Direct
