Effects of dietary methionine source on productive performance, blood chemical, and hematological profiles in broiler chickens under tropical conditions

Methionine sources at different dietary levels alters the growth and expression of genes related to homocysteine remethylation in the jejunum of broilers

Sulfur amino acids are essential for the proper development of broilers and are required throughout the bird's life to perform important physiological functions. Studies that seek to understand the actions of sulfur amino acids in the body of birds are essential. The present study evaluated the influence of sulfur amino acid supplementation using DL-Methionine (DL-Met) and DL-Methionine hydroxy analogue (DL-HMTBA), on the performance and expression of genes related to methionine metabolism, in the jejunum of broilers. Four hundred and fifty male broilers (Cobb-700 slow feathering) were distributed in a completely randomized design, in a factorial scheme (2x3), with two sources of methionine (DL-Met and DL-HMTBA) and three levels of methionine (deficiency, requirement and excess). The mRNA expression of the MAT1, MTR, BHMT, MTRR, CBG and GSS genes, and performance data such as feed intake, weight gain, and feed conversion were evaluated. DL-HMTBA increased the expression of BHMT (p = 0.0072) and MTRR (p = 0.0003) in the jejunum of the birds. Methionine deficiency increased the expression of BHMT (p = 0.0805) and MTRR (p = 0.0018). Higher expression of GSS was observed in birds that were supplemented with DL-HMTBA (p = 0.0672). Analyzing our results, it is preferable to supplement sulfur amino acids with DL-Met at the requirement level. Birds fed with DL-HMTBA showed worse weight gain (p = 0.0117) and higher feed conversion (p = 0.0170); methionine deficiency resulted in higher feed intake (p = 0.0214), lower weight gain (p<0.0001) and consequently higher feed conversion (p<0.0001). Based on the information found in this work, it is recommended to supplement sulfur amino acids with DL-Met at the level of compliance with the requirement.

A systematic review of metabolism of methionine sources in animals: One parameter does not convey a comprehensive story

The goal of this review article, based on a systematic literature search, is to critically assess the state of knowledge and experimental methodologies used to delineate the conversion and metabolism of the 2 methionine (Met) sources DL-methionine (DL-Met) and DL-2-hydroxy-4-(methylthio) butanoic acid (HMTBa). The difference in the chemical structures of HMTBa and DL-Met indicates that these molecules are absorbed and metabolized differently in animals. This review explores the methodologies used to describe the 2-step enzymatic conversion of the 3 enantiomers (D-HMTBa, L-HMTBa and D-Met) to L-Met, as well as the site of conversion at the organ and tissue levels. Extensive work was published documenting the conversion of HMTBa and D-Met into L-Met and, consequently, the incorporation into protein using a variety of in vitro techniques, such as tissue homogenates, cell lines, primary cell lines, and everted gut sacs of individual tissues. These studies illustrated the role of the liver, kidney, and intestine in the conversion of Met precursors into L-Met. A combination of in vivo studies using stable isotopes and infusions provided evidence of the wide conversion of HMTBa to L-Met by all tissues and how some tissues are net users of HMTBa, whereas others are net secreters of L-Met derived from HMTBa. Conversion of D-Met to L-Met in organs other than the liver and kidney is poorly documented. The methodology cited in the literature to determine conversion efficiency ranged from measurements of urinary, fecal, and respiratory excretion to plasma concentration and tissue incorporation of isotopes after intraperitoneal and oral infusions. Differences observed between these methodologies reflect differences in the metabolism of Met sources rather than differences in conversion efficiency. The factors affecting conversion efficiency are explored in this paper and are mostly associated with extreme dietary conditions, such as noncommercial crystalline diets that are very deficient in total sulfur amino acids with respect to requirements. Implications in the diversion of the 2 Met sources toward transsulfuration over transmethylation pathways are discussed. The strengths and weaknesses of some methodologies used are discussed in this review. From this review, it can be concluded that due to the inherent differences in conversion and metabolism of the 2 Met sources, the experimental methodologies (e.g., selecting different organs at different time points or using diets severely deficient in Met and cysteine) can impact the conclusions of the study and may explain the apparent divergences of conclusion found in the literature. It is recommended when conducting studies or reviewing the literature to properly select the experimental models that allow for differences in how the 2 Met precursors are converted to L-Met and metabolized by the animal to enable a proper comparison of their bioefficacy.

Absorption of methionine sources in animals-is there more to know?

This literature review evaluates the absorption of methionine (Met) sources such as 2-hydroxy-4-methylthiobutyric acid (HMTBa), its calcium salts (HMTBa-Ca), and DL-methionine (DL-Met) by focusing on the state of knowledge regarding the absorption mechanism, experimental methodology, and factors affecting their absorption. The 2 Met sources differ in mechanism and site of absorption due to differences in their chemical characteristics and enzymatic conversion. This review addresses diffusion- and transport-mediated absorption systems for amino acids and carboxylic compounds, best elucidated by in vitro, ex vivo, and in vivo experimental models. Opportunities and limitations in the use of radioisotopes to depict absorption sites as well as host and microbial metabolism are described. Physiological and environmental conditions that lead to changes in gut absorptive capacity and the impact of Met source absorption are also evaluated. This review concludes that any comparison between HMTBa and DL-Met should consider their different behaviors during the absorption phase. Hence, the chemical characteristics of these 2 molecules entail different absorption sites and mechanisms, from passive absorption in the case of HMTBa and HMTBa-Ca to active transporters for DL-Met, HMTBa, and HMTBa-Ca. In addition, the different conversion modes of these 2 molecules further differentiate their absorption modes. Considering these important differences, it is easier to understand the apparent divergence between the conclusions of existing publications. When comparing these 2 molecules, it is recommended to properly adapt to the conditions under which the absorption of Met sources is evaluated.

Increased Sulphur Amino Acids Consumption as OH-Methionine or DL-Methionine Improves Growth Performance and Carcass Traits of Growing-Finishing Pigs Fed under Hot Conditions

This study aimed to evaluate the impact of DL-Methionine (DL-Met) or OH-Methionine (OH-Met) when supplemented beyond the usually accepted requirements in sulfur amino acids (SAA) on the performance and carcass traits of growing-finishing pigs. Two hundred mixed sex pigs were distributed in a randomized block (body weight and sex), under a 2 × 2 factorial design with two methionine sources, DL-methionine, or OH-Methionine and two methionine doses (100% SAA or 120% of the SAA level present in the control). Diets were formulated to meet amino acids recommendations of the Brazilian Tables for Poultry and Swine (2017), except for SAA, which varied with the methionine doses. Daily feed intake, daily weight gain, and feed conversion were evaluated. Moreover, the carcasses were measured electronically for fat thickness (FT), longissimus dorsi muscle depth (LD), and lean meat (%). During the growing phase II (92 till 122 days of age), daily feed intake (p < 0.001) and daily weight gain (p < 0.05) increased with the high SAA levels. High SAA levels also provided greater daily weight gain during the entire period of the trial (0.90 versus 0.86 kg; p < 0.05) No significant interaction was observed between the methionine source and the SAA level for any carcass traits. However, animals that received OH-Met had greater (p < 0.05) loin depth (58.37 versus 55.21 mm) and those that received higher doses of methionine presented heavier (p < 0.05) carcass weight (78.16 versus 74.70 kg), and more (p < 0.05) lean meat weight (43.69 versus 41.90 kg). Taken together, these results demonstrated that supplementation of high sulfur amino acids levels under hot conditions provided heavier carcasses and more lean meat.

The effects of heat stress exposure on free amino acid concentrations within the plasma and the brain of heat-exposed chicks: A systematic review and meta-analysis

This study was conducted in order to investigate the effects of heat stress exposure on the concentrations of amino acids within the plasma and the brain of chicks. Methodology: Five electronic databases including; PubMed, Scopus, Web of Science, Embase and ProQuest were reviewed to find relative literature published until the March 8, 2019. A total of eight relative studies and 194 chicks were analyzed. The Random Effects model and the Fixed Effects model were performed. Using the Random Effects model for amino acids, a Standardized mean difference (SMD) of 2.05 and 1.46 was obtained for alanine and threonine concentrations respectively. This indicates a significant increase in the concentration of these amino acids within the plasma. An SMD of -2.68 and -2.46 was obtained for cysteine and proline concentrations respectively, this indicates a significant decrease in the concentration of these amino acids within the plasma. The pooled estimates regarding the effect of heat stress exposure on plasma amino acid concentrations for proline were -0.013. The SMDs obtained for amino acid concentrations within the brain (diencephalon) including leucine, methionine, valine and isoleucine were 1.799, 0.88, 2.11, 1.85, respectively, This indicates a significant increase in the concentration of these amino acids within the brain (P < 0.05). Comparing the SMD obtained for long-term heat exposure (two weeks) with the SMD obtained for short-term heat exposure shows that plasma amino acid concentrations including aspartic acid, glutamic acid, leucine, lysine, methionine, valine, isoleucine, tyrosine, glycine, proline, phenylalanine and threonine had all decreased. The relationship between heat exposure and changes in the concentration of some amino acids in the plasma is an important scientific finding.

Effects of Different Methionine Sources on Methionine Metabolism in the IPEC-J2 Cells

As one of the essential amino acids, methionine (Met) plays an important role in biological events such as methylation and antioxidant properties besides its function in protein synthesis. Different Met sources have been used in animal production, but their effects on Met metabolic pathways are not well understood. In the present study, we investigated the effects of different Met sources (L-Met, DL-Met, DL-2-hydroxy-4-(methylthio)butanoic acid (DL-HMTBA), and DL-methionyl-DL-methionine (DL-MM)) on the metabolism of Met in small intestinal porcine epithelial cell line (IPEC-J2) and the contents of extracellular Met sources. The results showed that concentrations of intracellular Met, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), and the ratio of SAM to SAH in the DL-HMTBA group were significantly lower than that in other Met source groups, while the content of 5-methyltetrahydrofolate (5-MTHF) was significantly higher. Moreover, the mRNA levels of MAT2A, AHcy, CBS, MTHFR, and MTR in the DL-HMTBA group were significantly higher than those in other Met source groups. Further study showed that the total content of extracellular Met sources was highest in the DL-HMTBA group, followed by DL-MM group, followed by L-Met and DL-Met groups. These results demonstrated that DL-HMTBA mainly affects the transmethylation and remethylation of Met and it can promote the trans-sulfur metabolism of Met when compared with other Met sources. In addition, most DL-HMTBA and a small amount of DL-MM can escape the intestinal first-pass metabolism and then provide more extracellular Met sources than L-Met and DL-Met. Therefore, this study can provide a theoretical basis for the selection of Met sources in livestock.

The effect of DL-, L-isomers and DL-hydroxy analog administered at 2 levels as dietary sources of methionine on the metabolic and antioxidant parameters and growth performance of turkeys

A hypothesis was verified that dietary methionine (Met) improves the growth and antioxidant status of turkeys, and that its effects depend on dietary inclusion levels and sources. A total of 816 female Hybrid Converter turkeys was fed wheat-soybean meal-based diets supplemented with 3 sources of Met: DL-, L-isomers and DL-hydroxy analog (DLM, LM, and MHA, respectively). In 4 4-week periods (from one to 16 wk of age), dietary Met content corresponded to NRC (1994) recommendations or was increased by approximately 50% (in one to 8 wk by 44 to 46% and in 9 to 16 wk by 55 to 56% vs. the NRC guidelines) to match the recommendations of some breeding companies. Increased Met content resulted in higher final body weights of turkeys (P = 0.002), an improved feed conversion ratio (P = 0.049), increased total glutathione concentration and ferric reducing ability of plasma (FRAP) values, and decreased malondialdehyde (MDA) concentration (all P < 0.001) in the blood plasma of turkeys. In comparison with DLM, LM and MHA contributed to an increase in plasma glutathione concentration (P = 0.001), a decrease in plasma triacylglycerol (P = 0.003) and uric acid (P = 0.001) concentrations, and a decrease in liver MDA (P = 0.001) levels. A decrease in plasma MDA (vs. DLM) and lipid peroxides (LOOH) (vs. DLM and LM) concentrations as well as a decrease in plasma superoxide dismutase (SOD) activity (vs. DLM and LM) also were noted in the MHA treatment (P = 0.016, P = 0.001 and P = 0.011, respectively). In conclusion, the results of the study indicate that the antioxidant status of turkeys could be affected by dietary Met levels and sources. The dietary Met content increased by 50% relative to NRC recommendations, improved the growth performance of turkeys, and strengthened their antioxidant defense system. In comparison with DLM, LM and MHA could be considered positive nutritional factors as manifested by a beneficial decrease in plasma and hepatic MDA concentrations as well as an increase in plasma glutathione levels, and the effect of MHA was more pronounced.

Estimation of broiler responses to increased dietary methionine hydroxy analogue [DL-2-hydroxy-(4-methylthio) butanoic acid] using linear and nonlinear regression models

As the first limiting amino acid in corn-soy broiler diets, methionine (Met) is supplemented using commercial synthetic sources as demanded to obtain economic feed formulations. The Met analogue DL-2-hydroxy-4-(methylthio)-butanoic acid (HMTBA) is largely utilized with that objective. This study intended to obtain responses of broilers fed with increasing levels of HMTBA, from 28 to 42 d, such that economic returns can be calculated. A total of 2,106 Cobb × Cobb 500 one-day-old male broilers was randomly placed in 81 floor pens (2.7 m2 each). Birds were fed conventional starter (zero to 14 d) and grower (14 to 28 d) diets. Starting at 28 d of age, pens of 26 birds were randomly allocated into 9 feed treatments with 9 replications having increasing supplementations with HMTBA (0.00, 0.07, 0.14, 0.21, 0.28, 0.35, 0.42, 0.49 and 0.56%). These were prepared by mixing different proportions of corn-soy dilution and summit diets, which had the same formulated concentration of nutrients and energy [19.7% CP, 0.90% Ca, 0.45% Av. P, 0.95% digestible Lys, and 3,150 kcal/kg AMEn], with the exception of HMTBA [0.56% in the summit but not supplemented in the corn-soy dilution diet (0.52% digestible TSAA)]]. Growth performance was evaluated until 42 d when carcass yield and commercial cuts were evaluated using 6 birds randomly taken from each pen. Body weight gain (BWG), feed conversion ratio (FCR), proportion of breast fillets, and abdominal fat were adjusted using linear broken-line, exponential asymptotic and quadratic polynomial regression models (P < 0.05). Estimations of maximum responses for supplemented HMTBA by the linear broken-line model were 0.17% for BWG, 0.14% for FCR, and 0.29% for breast fillets. Using exponential and quadratic regressions, optimized HMTBA supplementations were obtained at 0.34 and 0.35% for BWG, 0.20 and 0.33% for FCR, and 0.31 and 0.36% for breast fillets, respectively. Supplemental levels of HMTBA that optimize growth performance and breast meat in male broilers from 28 to 42 d, using different regression models, varied from 0.14 to 0.36%.

The effects of different protein levels in laying hens under hot summer conditions

The objectives of the present study were (1) to determine the extent to which the crude protein (CP) content of laying hen diets can be reduced, based on performance criteria, and (2) to determine how egg quality traits and blood biochemical parameters are affected by changes in dietary CP under hot summer conditions. The requirements for egg mass (EM) and feed utilisation (FU) were estimated using quadratic equations and broken-line regression models. Laying hens were raised for a 12-week period (42–54 weeks) in wire cages under a high ambient temperature in an open-sided housing system. A total of 144 Lohmann LSL laying hens were assigned to four treatments with six replicates of six birds each. The four experimental diets (11.51 MJ ME/kg) varied according to four CP levels: normal-CP diet (Control, 16% CP) and low-CP diets containing 13%, 14%, or 15% CP. All diets were fortified with DL-methionine, L-lysine, L-threonine and L-tryptophan at levels sufficient to meet dietary requirements. The results showed that under high ambient temperature conditions, all productive performance traits of birds fed 15% and 14% CP diets were similar to those of birds fed a Control diet (16% CP), whereas feeding a 13% CP diet negatively affected (P < 0.05) EM and FU. Estimations of requirements were of 15.13% and 14.56% CP for EM, and 14.86% and 14.38% CP for FU using quadratic and broken-line models, respectively. Haugh units, blood uric acid levels and albumin levels were significantly lower in birds fed a 13% CP diet compared with the Control group. In contrast, yolk colour index and blood triglyceride level were higher (P < 0.05) for the hens fed the 14% and 13% CP diets than for birds fed the Control diet. Overall, hens consuming 14% and 15% CP diets performed equally as well as the high protein diet group under hot summer conditions.

Protective potential of Lactobacillus species in lead toxicity model in broiler chickens

To alleviate adverse effects of heavy metal toxicity, diverse range of removing methods have been suggested, that is usage of algae, agricultural by-products and microorganisms. Here, we investigated lead (Pb) biosorption efficacy by two lactic acid bacteria species (LABs) in broiler chickens. In an in vitro study, Pb was added to culture medium of LABs (Lactobacillus pentosus ITA23 and Lactobacillus acidipiscis ITA44) in the form of lead acetate. Results showed that these LABs were able to absorb more than 90% of Pb from the culture medium. In follow-up in vivo study, LABs mixture was added to diet of broiler chickens contained lead acetate (200 mg/kg). Pb exposure significantly increased lipid peroxidation and decreased antioxidant activity in liver. The changes were recovered back to normal level upon LABs supplementation. Moreover, addition of LABs eliminated the liver tissue lesion and the suppressed performance in Pb-exposed chicks. Analysis of liver and serum samples indicated 48% and 28% reduction in Pb accumulation, respectively. In conclusion, results of this study showed that L. pentosus ITA23 and L. acidipiscis ITA44 effectively biosorb and expel dietary Pb from gastrointestinal tract of chickens.

Effects of dietary DL-2-hydroxy-4(methylthio)butanoic acid supplementation on growth performance, indices of ascites syndrome, and antioxidant capacity of broilers reared at low ambient temperature

This study examined the effects of dietary DL-2-hydroxy-4(methylthio)butanoic acid (DL-HMTBA) supplementation on growth performance, antioxidant capacity, and ascites syndrome (AS) in broilers reared at low ambient temperature (LAT) from 7 to 28 days of age. Eight hundred 7-day-old broilers were randomly assigned to two ambient temperatures (LAT and normal ambient temperature [NAT]), four supplemental DL-HMTBA levels (0.17, 0.34, 0.51, and 0.68 %) of the basal diet in a 2 × 4 factorial arrangement (ten replicate pens; ten birds/pen). LAT and NAT indicate temperatures of 12-14 and 24-26 °C in two chambers, respectively, and broilers were reared at these temperatures from 7 to 28 days of age. LAT significantly decreased body weight gain (P < 0.001), serum glutathione (GSH) content (day 14, P = 0.02; day 28, P = 0.045), glutathione peroxidase (GSH-Px) activity, and total antioxidant capacity (T-AOC) at 21 days (P = 0.001, 0.015) and 28 days (P = 0.017, 0.010) and increased feed conversion ratio (FCR) (P < 0.001), serum malondialdehyde (day 21, P = 0.000) and protein carbonyl Level (day 14, P = 0.003; day 21, P = 0.035). As for incidence of AS, there were significant effects of LAT on red blood cell (RBC) count (P < 0.05), hematocrit (HCT) (P < 0.05), and the right to total ventricular weight ratio (RV/TV) at 21 days (P = 0.012) and 28 days (P = 0.046). Supplementation of DL-HMTBA markedly decreased RV/TV at day 28 (P = 0.021), RBC (day 21, P = 0.008), HCT (day 21, P < 0.001), mean cell hemoglobin (day 14, P = 0.035; day 21, P = 0.003), and serum protein carbonyl level (day 21, P = 0.009), while significantly increased serum GSH content (day 14, P = 0.022; day 28, P = 0.001), SOD and GSH-Px activities at 21 days of age (P < 0.001 and P = 0.037). The optimal supplemental DL-HMTBA levels in basal diet of broilers aged from 7 to 28 days under low or normal temperatures were similar, so the authors recommended supplemental of DL-HMTBA level was 0.46 %.

The level and source of free-methionine affect body composition and breast muscle traits in growing broilers

Although dietary Met, as the first limiting amino acid (AA), has been extensively studied for poultry, little is known about how the supply and source of free Met affect tissue composition. The purpose of this study was to investigate the effect of feeding young broiler chickens with a deficient or sufficient TSAA (Met+Cys) supply, using either dl-Met (dl-Met+ and dl-Met-, for respectively diets sufficient and deficient in TSAA) or dl-2-hydroxy-4-methylthiobutyric acid (HMTBA+ and HMTBA-, for respectively diets sufficient and deficient in TSAA) as a Met source on tissue composition and breast muscle traits. For both Met sources, the deficient diets were formulated to provide true digestible Met:Lys and TSAA:Lys respectively 45% and 30% below that of the sufficient diets. Performance and tissue weights were affected by the Met supply but not by the Met source. In TSAA-deficient chickens, ADG and FCR, and protein content in empty body and pectoralis major muscles (PM) were lower than in TSAA-sufficient chickens (P < 0.05). Reducing the Met content of the diet increased the redness value of PM (a*) and the hue angle (H°; P < 0.01). The source of Met affected body AA composition and the partitioning of body Cys among tissues (P < 0.05). In TSAA-deficient birds, body Cys mass decreased in the commercial carcass and PM, but increased in the rest of the body (P < 0.01). The Met source also had an impact on the Cys mass, which was reduced in the commercial carcass and PM of dl-Met birds, but higher in the rest, especially in the feathers of TSAA-deficient birds (P < 0.05). The Met source, supply, or both altered the AA composition of the empty body, mostly in the commercial carcass. In conclusion, a dietary TSAA deficiency altered performance, tissue composition and quality traits of PM of broilers. There was no impact between dietary dl-Met and dl-HMTBA on performance or muscle weight, although the Met source affected the partitioning of Cys among tissues.

Effects of dietary crude protein and electrolyte balance on production parameters and blood biochemicals of laying hens under tropical summer condition

The objective of this study was to determine the effects of different levels of crude protein (CP) and dietary electrolyte balance (DEB) on productive performance, egg quality, and blood biochemical parameters of laying hens reared during hot summer months. The average minimum and maximum room temperatures recorded from 32 to 42 weeks of age were 27.2 and 36.5 °C, respectively, with relative humidity ranging from 48 to 56 %. A total of 144 Lohmann LSL-Lite laying hens were assigned to each of four dietary treatments with six replicate cages of six birds. The treatments were as follows: CP 15.4 % + DEB 165 mEq/kg (group 1), CP 15.4 % + DEB 250 mEq/kg (group 2), CP 13.9 % + DEB 165 mEq/kg (group 3), and CP 13.9 % + DEB 250 mEq/kg (group 4). In groups 3 and 4, feed conversion ratio and blood uric acid were decreased (P < 0.05); but the plasma triglyceride level was increased (P < 0.05) compared to groups 1 and 2. Low-CP diet with DEB 250 (group 4) also induced significant increases of average egg production and eggshell thickness compared to group 1. Blood pH, Na(+), and HCO3 (-) values were also higher (P < 0.05) in groups 2 and 4 than in the other groups. These results indicate that, under tropical conditions, using a DEB of 250 mEq/kg achieves a correction of the lay-induced metabolic acidosis and induces a positive effect on eggshell quality when the hens were fed low-protein diet.

The methionine precursor DL-2-hydroxy-(4-methylthio)butanoic acid protects intestinal epithelial barrier function

DL-2-hydroxy-(4-methylthio)butanoic acid (HMTBA) is a source of dietary methionine (Met) that is widely used in poultry nutrition. We have previously shown that HMTBA is preferentially diverted to the transsulfuration pathway, which gives antioxidant metabolites such as taurine and glutathione. Therefore, here we hypothesize that this Met source can protect epithelial barrier function in an in vitro model of intestinal inflammation of Caco-2 cells. The results show that HMTBA prevents the increase in paracellular permeability induced by H2O2 or tumour necrosis factor-α. This effect can be attributed to the increased production of taurine and reduced glutathione. Similar results were obtained for DL-Met, although the protective role of the amino acid was less pronounced than that of the hydroxy analogue. In conclusion, the diversion to the transsulfuration pathway means that this Met precursor is of greater value than previously thought, due to its capacity to improve intestinal homeostasis and the quality of poultry products destined for human consumption.

Effects of dietary inclusion of fermented cottonseed meal on growth, cecal microbial population, small intestinal morphology, and digestive enzyme activity of broilers

Two experiments were conducted to test the feeding value of fermented cottonseed meal (FCSM) in broilers. In experiment 1, 480 1-day-old male yellow-feathered broilers were allocated into 4 dietary treatments with 6 replicates (20 birds per replicate) to examine the effects of FCSM on the growth response of chickens. Experimental feeding was performed for 6 weeks in two phases (starter, days 0 to 21; finisher, days 22 to 42). FCSM was used at 0, 40, 80, and 120 g/kg levels to replace soybean meal in the basal diet. The dietary inclusion of 40 and 80 g/kg FCSM increased (quadratic (Q): p<0.01) the body weight gain of broilers in the starter and in the overall feeding periods. Experiment 2 determined the effect of FCSM on the cecal microbial populations, intestinal morphology, and digestive enzyme activity of broilers. The number of lactobacilli in the cecal digesta increased at day 21 (p<0.01) and day 42 (linear (L): p=0.01). Coliform bacteria counts decreased (L: p<0.05) with the increasing inclusion of FCSM at day 21. The inclusion of FCSM increased (L-Q: p<0.05) villus height in the duodenum and linearly elevated (p<0.05) villus height and the villus height to crypt depth ratio in the jejunum at day 21. Similar improvement (L: p<0.05) was noted in jejunal villus height at day 42. The inclusion of FCSM improved (p<0.05) the activities of amylase and protease at day 21, as well as protease at day 42. In conclusion, the appropriate inclusion of FCSM improves growth, cecal microflora, intestinal morphology, and digestive enzyme activity in yellow-feathered broilers.