The Effects of Yucca Schidigera Extract and Multi-carbohydrase in Different Crude Protein Diets on Growth Performance, Nutrient Digestibility, Carcass Parameters and Excreta Noxious Gas Contents in Broilers

ABSTRACT The scarcity and increase in the price of animal feeds have attracted the attention of nutritionists to address this issue. The inclusion of plant extracts and enzymes to protein-reduced diet could be a feasible strategy to reducing the feed cost. Therefore, the purpose of this study was to assess the impacts of Yucca schidigera extract and multi-carbohydrase in low crude protein (CP) diets of broiler on growth performance, nutrient digestibility, carcass metrics, and noxious gas levels in the excreta. A total of 480, 1-d-old ROSS 308 were randomly allocated into 4 dietary treatments, six replication, and 20 birds/cage. Phase 1, T1(CP 21%, ME 2,969 kcal/kg); T2 (CP 19%, ME 2,863 kcal/kg + 0.02% Yucca); T3 (CP 17%, ME 2,865 kcal/kg + 0.02% Yucca); T4 (CP 17%, ME 2,861 kcal/kg + 0.02% Yucca + 0.1% multi-carbohydrase). Phase 2, T1 (CP 19%, ME 3,086 kcal/kg); T2 (CP 17%, ME 2,977 kcal/kg + 0.02% Yucca); T3 (CP 15%, ME 2,978 kcal/kg + 0.02% Yucca); T4 (CP 15%, ME 2,978 kcal/kg + 0.02% Yucca + 0.1% 0.1% multi-carbohydrase). Although the addition of YS and multi-carbohydrase to the low CP diets on the growth performance did not improve, it revealed the positive result on the nutrient digestibility, carcass parameters, and noxious gas emission. Overall, broilers supplemented with YS 0.02% and multi-carbohydrase (0.1%) demonstrated the best production performances compared to the other treatment groups. Thus, a combination of YS and multi-carbohydrase could be added to the diets with low CP to boost broiler production performance.


INTRODUCTION
Feed costs account for 70-80% of farm expenses, making poultry feeding one of the most essential areas of the poultry industry (Olugbenga et al., 2015).Moreover, protein is the most costly component of feed.Lowering crude protein (CP) level in diets is one of the current ways attempted by the poultry industry to address this issue.Evidence shows that feeding broiler chickens with low-CP diets increases nitrogen (N) efficiency and decreases N excretion, consequently this reduces the environmental impact and carbon footprint of poultry production (Belloir et al., 2017).However, changing CP levels in isoenergetic diets is connected with changes in energy-to-protein ratios, and can have significant effects on body composition, such as body fat content (Swennen et al., 2004).Therefore, adding prebiotics, probiotics, toxin binders, Phyto-biotics, enzymes, oligosaccharides, symbiotic, organic minerals, organic acids, and other feed additives to the low CP diets improve the feed energy and they don't harm broilers or consumers (Yadav et al., 2016).Incorporating plant extracts and exogenous enzymes into animal diets that are low in some nutrients, particularly CP, has demonstrated good outcomes.Numerous plants and their derivatives have been studied as a replacer of feed additives in various farm animals (Farag et al., 2018).Among those, Yucca schidigera (YS) is considered as one of the possible plant extracts to be used in livestock diet.Normally, YS extract is utilized in the food and beverage industry as a natural medicine and flavor enhancer, whilst in the poultry, swine, and cattle industries is used as a natural feed additive (Cheeke et al., 2005).Supplementing the diet of broilers with YS has shown to improve their growth rate and feed conversion (Ranjbar et al., 2014).Moreover, there are various beneficial effects of YS in livestock and poultry production such as: therapeutic activities like anti-inflammatory, antioxidant, immunostimulatory, anticarcinogenic, growth stimulant, hypocholesterolemic, and hypoglycemic (Gupta et al., 2014).YS could also be used to minimize fecal odors and ammonia emissions emanating from poultry farms and their surroundings (Vlckova et al., 2017), thus this might help in improving the animal health by decreasing N emission.Additionally, YS has a growth-promoting impact on animals (Cheeke & Otero, 2005).Cereals and soybean meal are used in poultry feed worldwide, this is due to the rising prices and price of poultry feed ingredients that have resulted in more diets being formulated with high-fiber ingredients.This makes the diet contain a considerable amount of indigestible fractions.In fact, plant-based ingredients contain high amounts of nonstarch polysaccharides (NSP, 10 to 20%) (Annison & Choct, 1991), which reduces the digestibility of nutrients in the diets and can result in poor growth and performance of birds.To alleviate this problem, supplementing multi-enzymes into broiler diets can be a possible strategy.Previous studies have reported that the addition of multi-enzymes improves nutrient utilization, resulting in weight gain and improved feed conversion ratio (FCR) (Sharifi et al., 2013).This can reduce feed costs and benefit from local alternative feed ingredients.To the best of our knowledge, no studies on the effects of combination YS extract and multi-carbohydrase in broilers have been conducted.It is reasonable to hypothesize that the inclusion of YS extract and multi-carbohydrase in a low CP diets of broilers could lead to positive changes in carcass parameters and affect health and performance more than YS or multi-carbohydrate alone.Therefore, the present study intention was to investigate the effects of YS extract and multi-carbohydrase in low CP diets on growth performance, nutrient digestibility, carcass traits and excreta noxious gas contents in broilers.

MATERIALS AND METHODS
The experiment was conducted at Dankook University's Swine Research Unit in South Korea.The trial protocol was reviewed by animal care and use Committee of Dankook University in the Republic of Korea (DK-1-2030).

Sampling and Measurements
At 1, 21, and 35 days of age, broiler chicks were weighed per cage.Feed intake (FI) was also observed over the study period.Body weight gain (BWG), FI, and FCR ratio were all calculated using this data.
12 broilers (3 chicks per cage) were randomly selected from each treatment group one week prior to the completion of the experiment and caged in line with treatments for the measurement of nutrient digestibility.Chromium oxide (Cr 2 O 3 ) as an indigestible

The Effects of Yucca Schidigera Extract and Multicarbohydrase in Different Crude Protein Diets on Growth Performance, Nutrient Digestibility, Carcass Parameters and Excreta Noxious Gas Contents in Broilers
marker, was supplemented to the diets of broilers at a level of 0.2%.Excreta samples were collected at the end of the trial (day 35) and stored at -20°C until further examination.Excreta samples were dried in a forced-air drying oven (70°C) for 72 hours before being ground through a 1-mm screen sieve to determine dry matter (DM) and N digestibility.The AOAC's methods for analyzing DM were followed (2007).UV absorption spectrophotometry was used to investigate chromium (Shimadzu, UV-1201, Shimadzu, Kyoto, Japan).A Kjeltec 8600 analyzer was used to determine the N (protein) content (Foss Tecator AB, Hoeganaes, Sweden).The digestibility of nutrients was determined according to the formula used by (Munezero & Kim, 2022).An amino acid (AA)analyzer was used to evaluate the AA contents in the excreta and experimental diet after 24 hours of acid hydrolysis with 6 N HCl at 110°C (Beckman 6300, Beckman Coulter, Inc., Fullerton, US).After cold performic acid oxidation overnight and subsequent hydrolysis, sulfur-containing amino acids were evaluated.Following that, the excreta samples, as well as the feed samples, were examined in accordance with the AOAC guidelines (2007).
At the end of the trial, 12 broiler chicks were chosen randomly from each treatment (3 broilers per replication cage) and terminated via cervical dislocation.All of the following carcass parameters were manually dissected and recorded: Leg, liver, breast, and abdominal fat, as well as the adipose tissues lining the proventriculus and gizzard.To eliminate variances in cutting techniques, all procedures were carried out by the same, experienced personnel.
Excreta samples were collected and frozen throughout the last three days of the experiment to examine noxious gas emission.Excreta samples were kept in 2.6-L plastic boxes.A small hole in the middle of one of the side walls of each box was sealed with adhesive plaster.The samples were fermented for seven days at 30°C and measured on days one, three, five, and seven.On days 1, 3, 5, and 7, NH3, RSH, and acetic acid were measured using a multi-gas meter (MultiRAE Lite model PGM-6208, RAE, USA).The adhesive plaster was punctured for this measurement, and 100 mL of headspace air was sampled at a height of 2.0 cm above the samples.Each box was wrapped with adhesive plaster again after air sampling.Every 48 hours, headspace measurements were taken again.

Statistical analysis
All data were analyzed using SAS's General Linear Models (GLM) procedure and a one-way ANOVA (SAS Institute, 2008).The GLM approach was used to assess significant differences in mean values among dietary treatments using repeated measurements and Duncan's tests.The significance level was set at p<0.05.

Growth performance
The results of broiler growth performance after adding the YS and multi-carbohydrase on broiler growth performance on day 21 and 35 are presented in Table 2. Broilers supplemented with YS and multicarbohydrase exhibited no significant differences in growth performance during both phases.However, numerically broilers fed the YS 0.02% + α-1,6-galactosidase and β-1,4-mannanase multicarbohydrase 0.1% had higher BWG and FI compared to others and T1 showed the lowest value for FCR during the entire experiment.

Nutrient digestibility
Table 3 indicates the effect of supplementing YS and multi-carbohydrase in a reduced CP diets of broilers on nutrient digestibility.T4 broilers had a notably higher nutrient digestibility of DM and Nthan other treatments throughout the trial.Besides, the digestibility of AAwere significantly higher in T1 as compared to other treatments.Means in the same row with different superscripts differ (p<0.05).

Carcass parameters
The effects of reducing dietary CP and supplementation of YS and multi-carbohydrase on broiler carcass yield are presented in Table 4.In comparison to other treatments in the entire experiment, T4 broilers supplemented with yucca and multi-carbohydrase showed the greatest value of breast yield percentage, indicating the best carcass features.Aside from that, T3 broilers had the highest abdominal percentages.

Gas emission
The effect of reducing dietary CP and supplementing with yucca and multi-carbohydrase on broiler noxious gas emission characteristics is shown in Table 5. T4 dietary treatment supplemented with Yucca 0.02% + α-1,6-galactosidase and β-1,4-mannanase multicarbohydrase 0.1% has significantly reduced the NH3 on day 5 and 7.However, there was no difference observed on RSH (mercaptans) and acetic acid throughout the trial.Means in the same row with different superscripts differ (p<0.05).

Growth performance
Growth performance is a critical metric for assessing broiler production.According to (Yeo & Kim 1997;Begum et al., 2015), adding yucca extract to broiler diets had no impact on the birds' feed consumption or feed efficiency.Similarly, in the present study, broilers treated with 0.2% YS extract and 0.1% of α-1,6-galactosidase and β-1,4-mannanase multi-carbohydrase did not improve the growth performance during the entire trial.The findings were inconsistent with previous researchers who found that supplementing YS in the diet of broiler improved growth performance (Ranjbar et al., 2014;Sahoo et al., 2015).The effect of YS was also evaluated in laying hens, swine and rabbits, and researchers discovered a considerable improvement in growth performance (Al-Bar et al., 1992;Wang & Kim, 2011;Gebhardt et al., 2019).The presence of steroidal saponins in YS, which have a beneficial effect on the digestive tract by activating digestive enzymes and increasing villus height (Cheeke, 2000), could be the reason for increased growth performance in the earlier investigation.Normally, multi-enzymes are hypothesized to increase performance by lowering the anti-nutritive effect of non-starch polysaccharides (NSP), diminishing the cell wall's nutrient encapsulating effect, and alleviating viscosity difficulties associated with certain NSP (O'Neill et al., 2014).Variations between earlier researches and the present work could be due to inconsistencies of pig utilized, the type of diet used, and the amount of supplementation employed in those studies.

Nutrient digestibility
Throughout the experiment, T4 broilers had significantly higher nutrient digestibility of DM and N, and T1 broilers had the highest AA digestibility.Similarly, previous research has shown that broiler chicks supplemented with yucca schidigera had significantly higher protein digestibility (Sahoo et al., 2015).Additionally, Chen et al. (2021), found that introducing yucca extracts to the diets of late gestating and lactating sows greatly increased DM digestibility.Contrary to our findings, Alghirani et al. (2021)  documented that the inclusion of yucca schidigera in broiler diets significantly lowered the digestibility of DM.According to Htoo et al. (2007), a reduction in CP can lead to a decrease in AA digestibility, therefore adding YS and multi-carbohydrase might be the answer.Meng et al. (2004) previously described the beneficial effect of carbohydrase addition on nutrient digestibility, which is in agreement to the present study, in which an increase in digestibility was observed as the result of multi-carbohydrase treatment.In general, phytogenic feed additives containing steroidal saponins, such as yucca schidigera, have been proven to enhance intestinal health and reduce microbial pressure while preventing intestinal disease, perhaps leading to improved nutrient digestibility and absorption (Begum et al., 2015).

Carcass parameters
Body weight, as well as carcass weight, and dressing percentage, have a significant correlation (Chung et al., 2021).In the present experiment, combining YS and multi-carbohydrase improved carcass yield.Sahoo et al. (2015) found that the yucca schidigera treatment broiler group had higher breast meat yield which is in line with the present findings.Nevertheless, Azadegan et al. (2014) have found no significant differences in the carcass characteristics of broilers fed saponin-containing diets.The variations between earlier research and the current work could be due to differences in the bird strains utilized, the type of diet used, the saponin source used, and the amount of supplementation placed in those studies.

Gas emission
The poultry production is accompanied by considerable environmental pollution with NH3.The higher concentrations of gaseous NH3 are the most common contaminant in the poultry farming, affecting performance, bird welfare, and consequently, human health (Costa et al., 2012).The usage of natural products such as a yucca schidigera extract product, which can assist the moderation of ammonia supply, is the key to dealing with the ammonia problem in the poultry sector.Saponin, the major steroidal chemical element of YS extract, does this by physically binding ammonia and lowering its amount (Ayoub et al., 2019).In the current study, supplementation of YS and multi-carbohydrase on the broiler diets significantly affected the reduction of NH3.When 100 ppm of yucca extract was introduced to layer diets, there was a substantial decrease in ammonia generation and emission in laying-hen barns (Chepete et al., 2012).Additionally, YS in broiler diets lowered ammonia concentrations considerably without affecting broiler performance (Cabuk et al., 2004).However, other authors have demonstrated no effects of Yucca extract on ammonia N concentrations in ruminants (Hristov et al., 1999).A supplementation of multi-carbohydrase could decrease the excretion of ammonia.Sun & Kim (2019) have reached an agreement on this where they found that adding multi-enzyme to corn-soybean meal-DDGS-based diets reduced excreta ammonia emissions while having no negative influence on production performance.The higher digestibility of N could account for the lower NH 3 emissions seen in this study.

CONCLUSION
Except for growth performance, which has not been impacted, broilers treated with yucca schidigera extract 0.02% and α-1,6-galactosidase and β-1,4mannanase multi-carbohydrase 0.1%, outperformed the other treatment broilers in terms of nutrient digestibility, carcass metrics, and gas emissions.Based on the results obtained, there is an interactive effect on overall performance of broilers when the diets with low CP are supplemented with the yucca extract and multicarbohydrase.Therefore, the full benefit potential of supplemental yucca extract and multi-carbohydrase can be realized by using feed lower in CP, thereby improving the production performance of broilers.

Table 1 -
Composition of experimental diets.

Table 2 -
Effect of reducing dietary crude protein and supplementation of Yucca and multi-carbohydrase on growth performance in broilers.

Table 3 -
Effect of reducing dietary crude protein and supplementation of Yucca and multi-carbohydrase on nutrient digestibility in broilers. a,b,c

Table 5 -
Effect of reducing dietary crude protein and supplementation of Yucca and multi-carbohydrase on noxious gases emission characteristics of broiler. a,b,c

Table 4 -
Effect of reducing dietary crude protein and supplementation of Yucca and multi-carbohydrase on carcass yield of broiler.