Egg production, egg quality, nutrient digestibility, and excreta microflora of laying hens fed with a diet containing brewer’s yeast hydrolysate

ABSTRACT

The objective of this study was to determine the effects of brewer’s yeast hydrolysate (BYH, Saccharomyces cerevisiae) on laying hens. A total of 288 Hy-line Brown laying hens were randomly assigned to 1 of 6 treatments with 8 replications (6 birds per replication). The treatment diets were supplemented with BYH at levels of 0, 0.05, 0.10, 0.50, 1.0 or 3.0%, respectively. The supplementation of BYH diets led to a significant linear (P < 0.05) effect on egg production, egg weight and egg mass during 37–41 and 42–46 weeks. The supplementation of BYH diets also led to a significant linear increase observed in internal egg quality: albumen height (37–41 and 42–46 weeks), Haugh unit (42– 46 weeks), and yolk colour (37–41 and 42–46 weeks), and a significantly linear increase in eggshell thickness (P < 0.05) during 37–41 and 42– 46 weeks. A linear increase was observed on dry matter and nitrogen at 46 weeks of laying hens, and linear increase and linear decrease were detected for Lactobacillus and E. coli at 46 weeks of laying hens, respectively. As a result, dietary BYH had beneficial effects on egglaying performance, egg quality, nutrient digestibility, and excreta microflora in laying hens.

KEYWORDS:

• Egg weight
• fecal Lactobacillus
• layer’s productivity
• nutrient retention
• Saccharomyces cerevisiae

1. Introduction

In many countries the use of antibiotics as growth promoters for poultry feed is banned due to existing resistance and potential effects on humans. Yeasts as probiotics products may serve as alternatives to antibiotics for growth promotion and disease resistance in poultry for several years (Jin et al. 1998), either the form of yeast by-products from breweries or commercial yeast products for animal feeding (Stone 2004; Araujo et al. 2017).

Brewer's yeast is the second-largest by-product originated by the food industry, and most of this is sold as animal feed at a low price (Amorim et al. 2016). Brewer’s/baker’s yeast is derived from the yeast species Saccharomyces cerevisiae (S. cerevisiae). Eckles and Williams (1925) first reported the use of S. cerevisiae as a growth promoter for ruminants. Brewing yeast is predominantly composed of proteins (35-60% of dry basis) that include all the essential amino acids and have high biological value. The second-highest compound in brewer’s yeast is carbohydrate which represents 35–45% of dry basis. In addition, there are other important biological substances, such as, minerals (5–7.5% of which, Ca, P, K, Mg, Fe, among others) lipids, immune-stimulating compounds such as nucleotides, β-glucan, mannan oligosaccharides, selenium, microbial nutrients (enzymes), and B-complex vitamins (Chae et al. 2001; dos Santos Mathias et al. 2014; Amorim et al. 2016). Yeast culture, and its cell wall extract containing 1,3-1,6 β-glucan and mannan oligosaccharide are the important natural growth promoters and immunomodulators with a strong positive effect on modern livestock and poultry production (Li et al. 2005). Brewer’s yeast (S. cerevisiae) has been proven to have a positive effect on growth performance, immune responses or anti-stress status of pigs, goats, poultry, cattle, and fish species (Huige 2006; Muthusamy et al. 2011; Chollom et al. 2017; Zhou et al. 2018).

Recently, the role of dietary proteins as physiologically active components has been increasingly recognized, such proteins or their precursors may occur naturally in raw food materials and exert their physiological action directly or upon enzymatic hydrolysis in vitro or in vivo. Several studies have demonstrated that yeast hydrolysate has physiological effects such as anti-obesity, anti-stress, and immuno-potentiating activities (Koh et al. 2002). For these reasons, yeast hydrolysate is receiving remarkable attention as a functional material in the diet food market. The continuing development of functional foods is likely to entail increased use of different protein sources known to contain bioactive components.

There are some reports about the usage of various yeast and yeast products such as inactive dried yeast, yeast culture, whey yeast, selenium yeast, chromium yeast and yeast cell walls in the diets of laying hens (Ayanwale et al. 2006; Hosseini et al. 2006; Yousefi and Karkoodi 2007; Yalçin et al. 2008). However, few studies have determined the effects of dietary supplementation of BYH in laying hens. Due to the lack of available information on the nutrition of lying hens and the use of hydrolyzed yeast in their diets. The objective of this was to investigate the effect of various level of brewer’s yeast hydrolysate (BYH) as a feed additive on egg production, egg weight, egg quality, nutrient digestibility, and excreta microflora in laying hens.

2. Materials and methods

The experimental protocols describing the management and care of animals were reviewed and approved by the Animal Care and Use Committee of Dankook University, South Korea.

2.1. Animals, diets, and housing

A total of 288 Hy-line Brown laying hens (37 weeks age) were used in this 10 weeks feeding trial. Hens were randomly assigned to 1 of 6 treatments with 8 replications (6 hens per replication). The replications were allotted equally into the upper and lower cages to minimize the effect of cage level. The experimental diets were formulated to meet or exceed the NRC (2012) nutrient requirements (Table 1). They were allowed to adjust to the environment for four days prior to the start of the experiment, during which the hens were fed on a control (CON) diet. The dietary treatments were a control basal diet without BYH or with 0.05, 0.10, 0.50, 1.0 or 3.0% BYH.

Table 1. Ingredient composition of experimental diets as-fed basis.

Ingredient	%
Corn	54.18
Corn gluten	5.92
Soybean meal	1.36
Sesame meal	17.88
Meat meal	3.00
Tallow	4.52
Molasses	1.63
MDCP	0.70
Limestone	9.48
Choline chloride 50	0.12
Salt	0.27
Vit. premix^1	0.10
Min. premix^2	0.10
Total	100.00
Calculated chemical composition (g/kg)
Crude protein	18.00
Crude fat	4.20
Crude fibre	3.55
Ca	4.00
P	0.61
Aval. P	0.34
ME, kcal/kg	2,760
Lys	0.73
Met	0.39
Analyzed chemical composition (g/kg)
Crude protein	17.92
Crude fat	4.23
Crude fibre	3.51
ME, kcal/kg	2,737

¹Provided per kilogram of diet: 12,500 IU vitamin A, 2500 IU vitamin D₃, 13 IU vitamin E, 2 mg vitamin K₃, 1 mg vitamin B₁, 5 mg vitamin B₂, 1 mg vitamin B₆, 0.04 mg vitamin B₁₂, 0.9 mg folic acid, 55 mg niacin, 14 mg Ca-pantothenate and 0.1 mg biotin.

²Provided per kilogram of diet: 50 mg Mn (as MnO₂), 620 mg Zn (as ZnSO₄), 5 mg Cu (as CuSO₄·5H₂O), 40 mg Fe (as FeSO₄·7H₂O), 0.3 mg Co (as CoSO₄·5H₂O), 1.5 mg I (as KI) and 0.15 mg Se (as Na₂SeO₃·5H₂O).

The hens were housed in a windowless laying house at approximately 21°C. The hens were individually caged and were subjected to a photoperiod of 16 h light and 8 h dark daily. All cages were equipped with nipple drinkers and common trough feed, experimental feed and water were provided ad libitum throughout the experimental period.

2.2. Source and manufacture of BYH

The brewer’s yeast used in our study was provided by Immunebio company (Eumseong, Korea). The brewer’s yeast contains 4,113 kcal/kg metabolizable energy (ME), 53.2% crude protein (CP), 1.8% crude fat (ether extract), 5.2% ash (Table 2).

Table 2. Ingredient composition of brewer’s yeast.

Items, g/kg	Brewer’s yeast, g/kg
Dry matter (kcal/kg)	4,113
Crude protein	532
Crude fat	18
Crude fibre	8
Ash	52
Moisture	68
Amino acids
Arginine	23
Histidine	15
Isoleucine	23.6
Leucine	29.6
Lysine	32.0
Methionine	8.8
Cysteine	5.3
TSAA	12.0
Vitamin B complex
Thiamin	35.0
Riboflavin	45.0
Niacin	300.0
Pyridoxine	23.0
Folate	1.3
Cobalamin (ug)	4.0
Mineral
Calcium	1.5
Phosphorus	11.1
Potassium	14.8
Chlorine	1.0
Magnesium	3.3
Sodium	0.8
Selenium (ppm)	9.1

S. cerevisiae was incubated in a liquid medium containing 2% glucose, 0.5% yeast extract, 0.5% soy peptone, 0.2% KH₂PO₄, 0.05% MgSO₄, and 0.1% FeSO₄ at 28°C for 5 days in a rotary shaker. The medium was then adjusted to pH 6.0 and hydrolyzed with amylase and protease for enzymatic digestion of particulate materials containing carbohydrate and protein. After incubation, the culture was centrifuged at 10,000 g for 20 min and ground in a colloid mill (model PUC60 Hankook Power Technology System, Seoul, Korea). The powder was treated with 0.1 M lactic acid for 60 min, followed by treatment with an enzyme mixture for cell wall lysis containing cellulase, hemicellulase, pectinase, glucanase, mannase, and arabinase at 50°C for 60 min.

2.3. Experimental procedures, sampling, and chemical analyses

Daily records of egg production, egg weight and feed intake were kept throughout the experimental period (10 weeks), and measured every 5 weeks. Egg mass output (g/bird/day) was calculated every 5 weeks by using hen-day egg production and egg weight record. Feed conversion ratio (FCR) was calculated as g feed consumption per d per hen divided by g egg mass per d per hen. A total of 180 (30 eggs per treatment) saleable eggs (no shell defects, cracks or double yolks) were randomly collected at 17:00 h on a weekly basis to determine the egg quality at 20:00 h the same day. The egg quality of the collected eggs was determined at 20:00 h on the day of collection. Egg weight was measured using an egg multi tester (Touhoku Rhythm Co. Ltd., Tokyo, Japan). Eggshell breaking strength was determined with the eggshell force gauge (model II, Robotmation Co., Ltd., Tokyo, Japan). A dial pipe gauge (Ozaki MFG. Co., Ltd., Tokyo, Japan) was used to measure eggshell thickness, which was determined based on the average thickness of the rounded end, pointed end, and the middle of the egg, excluding the inner membrane. Finally, egg weight, yolk colour and Haugh unit (HU) were determined using an egg multi-tester (Touhoku Rhythm Co. Lt., Tokyo, Japan).

Chromium oxide (Cr₂O₃, 2 g/kg) was added to the layer’s diets as an indigestible marker for a period of 7 days before fecal collection to determine apparent nutrient digestibility of dry matter (DM), nitrogen (N), and gross energy (GE). Fresh excreta samples from 8 birds (one bird per replication) per treatment were collected two times during the whole trial (5 week and finish) by putting the collection plates under the cage. Then excreta samples from each cage were pooled and stored at −20°C until the analysis. Before chemical analysis, the excreta samples were thawed and dried at 70.1°C for 72 h, then they were ground finely by 1 mm screen, later stored in the −20°C refrigerator until analysis. DM, N, and energy were conducted in accordance with the methods established by the AOAC (2000). Chromium levels were determined via UV absorption spectrophotometry (Shimadzu, UV-1201, Japan) according to Williams et al. (1962). The digestibility was then calculated using the following formula: digestibility (%) ={1 − [(Nf × Cd)/(Nd × Cf)]}×100, where Nf: nutrient concentration in excreta (%DM), Cd: chromium concentration in diet (%DM), Nd: nutrient concentration in diet (%DM), and Cf: chromium concentration in excreta (%DM).

At the 5 week and finish, excreta samples were collected from 48 layers randomly selected from each treatment (each treatment with 8 replication birds), then pooled on a cage basis and placed on ice and immediately transported to the laboratory for microbial analysis. One gram of the composite excreta sample from each replication was diluted with 9 mL of 1% peptone broth (Becton, Dickinson and Co., Rutherford, NJ) and homogenized. Viable counts of bacteria in the excreta samples were then determined by plating serial 10-fold dilutions (in 10 g/L peptone solution) onto MacConkey agar and Lactobacillus MRS agar to verify the Escherichia coli (E. coli) and Lactobacillus, respectively. The Lactobacillus MRS agar plates were incubated for 48 h at 39°C, and the MacConkey agar plates were incubated for 24 h at 37°C under anaerobic conditions. The bacteria colonies were counted immediately after removal from the incubator values reported as log₁₀ colony-forming units per gram.

2.4. Statistical analyses

Statistical analysis was performed by using the mix procedure in a completely randomized block design with the SAS software programme. Orthogonal comparisons were conducted using polynomial regression to measure the linear, quadratic, cubic, and quartic effects of increasing the dietary supplementation of brewer’s yeast. Results were expressed as the least squares means and standard error of means (SEM). Probability values less than 0.05 were considered significant.

3. Results and discussion

3.1. Egg production and broken egg ratio

The present study showed that dietary inclusion of BYH resulted in effect on egg production and egg mass during 37–41 and 42–46 weeks has significantly improved that is described in Table 3. In addition, there was a linear increase (P < 0.05) observed in egg weight with the dietary BYH during 37–41 and 42–46 weeks, which agrees with previous report, Yalçın et al. (2010). Meanwhile, Araujo et al. (2017) also indicated that supplementation of the diet of the breeder hens with the hydrolyzed yeast resulted in a 2.14% increase in egg production. However, earlier studies indicated contrary results, that yeast culture (S. cerevisiae), S. cerevisiae containing dried yeast, and S. cerevisiae fermentation product had no effects on egg production (Ayanwale et al. 2006; Hosseini et al. 2006; Yousefi and Karkoodi 2007; Yalçin et al. 2008; Sacakli et al. 2013; Blount 2016; Özsoy et al. 2018).

Table 3. Effects of brewer’s yeast hydrolysate supplementation on egg production in laying hens¹.

Items, %	BYH (%)						SEM^1	P-value
	0	0.05	0.1	0.5	1.0	3.0		Linear	Quadratic	Cubic	Quartic
37–41 week
Egg production (%)	90.0	90.4	91.2	92.6	93.8	93.6	1.3	0.02	0.82	0.80	0.51
Egg weight (g)	60.7	60.9	62.2	62.0	65.8	65.9	0.9	0.01	0.24	0.52	0.31
Egg mass (g/d/hen)	54.6	55.1	56.7	57.4	61.7	61.7	0.8	0.03	0.59	0.67	0.42
Feed intake(g)	115	125	127	124	126	130	1.8	0.43	0.85	0.92	0.78
Feed conversion	2.105	2.271	2.239	2.160	2.041	2.108	0.02	0.28	0.59	0.78	0.49
42–46 week
Egg production (%)	89.8	90.2	92.9	92.9	93.5	93.3	1.0	0.03	0.19	0.30	0.83
Egg weight (g)	61.3	62.4	62.4	62.7	63.5	64.2	0.7	0.01	0.82	0.61	0.59
Egg mass (g/d/hen)	55.0	56.3	58.0	58.2	59.4	59.9	0.9	0.04	0.64	0.79	0.58
Feed intake(g)	117	128	135	134	132	130	1.9	0.52	0.67	0.89	0.72
Feed conversion	2.125	2.274	2.329	2.300	2.223	2.170	0.02	0.34	0.64	0.78	0.58

¹Standard error of means.

Recently, Girma et al. (2012) and Özsoy et al. (2018) reported indicated that yeast products (S. cerevisiae) supplementation could be improve the egg weight. On the contrast, a previous study showed that the yeast and yeast product supplementation did not have significant effect on egg weight in laying hens (McKillop et al. 2006; Mohiti-Asli et al. 2007; Yousefi and Karkoodi 2007; Yalçın et al. 2014; Yalçın et al. 2015). However, we believe that dissolved yeast could be a significant effect on egg production. According to Amorim et al. (2016) Hydrolyzed yeast is a hydrolysate of yeast cells derived by acid, enzyme or other method of hydrolysis. It has been successfully used in feed for improved growth, improved immunity, altered gut microbial ecology or relieved the stress of broilers (Muthusamy et al. 2011). We understand, animals can hardly digest the cell wall of yeast. Moreover, BYH can break down the cell walls and transfer cell contents to better utilization (Zhou et al. 2018).

At the same time, other factors also contribute to the discrepancies among the above reports, such as chemical and biological characteristics of yeasts used, level of dietary yeasts, animal species, age of animals, and duration of the trial. Therefore, in the present study improvements in egg production and reduced egg broken ratio of lying hens fed diet supplementation with BYH. Our data representative that BYH can replace antibiotics as hens production promoter substitute thereby reducing the risk of antibiotic resistance issue and increasing safety to animals.

3.2. Egg quality

The effect of BYH supplementation on egg quality in laying hens is shown in Table 4. Data from this study revealed that inclusion of BYH diet supplementation linearly improved albumen height, Haugh unit, yolk colour, and eggshell thickness, that agree with earlier reports (Hameed et al. 2019). Previous study, Paryad and Mahmoudi (2008) stated that improvements were observed in internal egg quality (Haugh unit, yolk colour, and albumen height) could be due to the supply of BYH which contained a rich source of CP, crude fat, and minerals. It was found that S. cerevisiae can improved the plasma total protein, albumin in poultry. There were some similar results indicating that yeast products (S. cerevisiae) had positive effects on yolk colour (Girma et al. 2012); albumin weight and yolk weight (Yousefi and Karkoodi 2007); eggshell weight and yolk weight (Ayanwale et al. 2006); yolk diameter and Haugh unit (Özsoy et al. 2018). Meanwhile, vitamin E, vitamin B, and yeast phytase existing in the yeast are capable of increasing the bio-availability of certain minerals (Ca, Cu, Zn, Fe) and increasing the utilization of oxycarotenoids (Ayanwale et al. 2006; Girma et al. 2012). Additionally, Yousefi and Karkoodi (2007) specified that different levels of BYH presented significant improvement in eggshell thickness. Conversely, an earlier study stated that diet supplementation with that yeast (S. cerevisiae) did not have a significant effect on eggshell thickness (Ayanwale et al. 2006; Yalçin et al. 2008; Yalçın et al. 2010; Girma et al. 2012; Yalçın et al. 2014; Yalçın et al. 2015; Blount 2016). The contrasts between the results of this study and previous studies may be the age of hens, composition of dietary nutrients and level of yeast and yeast products. In the present study were in agreement Yalçin et al. (2008), Yalçın et al. (2014), Yalçın et al. (2015), Blount (2016) who found that yeast or S. cerevisiae supplementation did not affect eggshell breaking strength. In this result, we found that BYH (S. cerevisiae) have positive effect on egg weight, internal egg quality, and eggshell thickness. However, BYH (S. cerevisiae) supplementation did not affect the eggshell breaking strength. Various chemical substances found in BYH, such as such as protein, amino acid, nucleotides, mannan-oligosaccharide, and β-glucan, might be responsible for these positive effects in this experiment.

Table 4. Effects of brewer’s yeast hydrolysate supplementation on egg quality in laying hens¹.

Items, %	BYH (%)						SEM^1	P-value
	0	0.05	0.1	0.5	1.0	3.0		Linear	Quadratic	Cubic	Quartic
37–41 week
Albumen height, mm	7.7	8.4	8.6	8.6	8.5	8.6	0.2	0.02	0.02	0.15	0.93
Haugh unit	87.8	88.2	87.1	90.5	92.6	90.7	2.0	0.06	0.94	0.27	0.41
Yolk colour	6.5	6.8	6.7	6.7	7.1	7.5	0.2	0.01	0.33	0.54	0.54
Eggshell breaking strength, kg/cm^2	3.9	3.9	4.0	3.9	3.9	3.9	0.0	0.44	0.11	0.43	0.48
Eggshell thickness, mm^−2	47.8	48.7	50.9	52.2	51.3	51.4	0.6	0.01	0.01	0.50	0.07
42–46 week
Albumen height, mm	7.7	8.3	8.0	9.0	8.6	8.9	0.3	0.01	0.47	0.90	0.99
Haugh unit	84.9	90.4	90.2	92.2	91.3	93.3	1.8	0.01	0.21	0.24	0.83
Yolk colour	6.8	6.8	7.0	6.9	7.5	7.7	0.1	0.03	0.26	0.66	0.46
Eggshell breaking strength, kg/cm^2	4.5	4.6	4.6	4.6	4.6	4.9	0.1	0.10	0.57	0.37	0.65
Eggshell thickness, mm^−2	43.0	45.4	46.2	45.5	46.5	47.5	0.5	0.01	0.23	0.02	0.50

¹Standard error of means.

3.3. Nutrient digestibility

Earlier study reported that yeast and yeast products (S. cerevisiae) had improved the digestibility of DM, CP, and N in dairy cows (Erasmus et al. 1992; Robinson and Erasmus 2016); lamb (Haddad and Goussous 2005); rainbow trout (Rumsey et al. 1991); broilers (Paryad and Mahmoudi 2008); horses (Agazzi et al. 2011), respectively. In this present also observed dietary BYH supplementation had linear increase (P < 0.05) for nutrient digestibility of DM and N at week 46 of laying hens. Although, there are also some opposing results showed in the earlier studies, which indicate that yeast and yeast products (S. cerevisiae) had no effects on nutrient digestibility in sows (Veum et al. 1995; Shen et al. 2011); sheep (Fiems et al. 1993); and fish (Oliva-Teles and Gonçalves 2001; Ozório et al. 2010); broilers (Akhavan-Salamat et al. 2011). However, there were no significant difference on nutrient digestibility of energy (P > .05) in the present study (Table 5).

Table 5. Effects of brewer’s yeast hydrolysate supplementation on nutrient digestibility in laying hens¹.

Items, %	BYH (%)						SEM^1	P-value
	0	0.05	0.1	0.5	1.0	3.0		Linear	Quadratic	Cubic	Quartic
41 week
DM	73.17	73.58	73.50	73.66	73.90	73.88	0.85	0.51	0.91	0.95	0.81
N	64.82	65.06	65.04	65.11	65.27	65.29	0.88	0.68	0.96	0.96	0.90
Energy	74.27	74.32	75.06	74.56	75.07	75.17	0.82	0.37	0.93	0.91	0.90
46 week
DM	74.21	75.74	75.76	75.66	76.26	76.71	0.76	0.04	0.67	0.37	0.58
N	66.23	67.56	67.53	67.59	68.20	69.07	0.77	0.02	0.97	0.36	0.67
Energy	73.74	75.32	75.31	75.18	75.53	75.83	0.78	0.10	0.49	0.37	0.64

¹Standard error of means.

Morales-Lopez et al. (2009) and Zhang et al. (2005) reported that cell wall components of the yeast (S. cerevisiae) markedly enhance animal growth performance and beneficial impact on development of intestinal mucosal in broiler chicks. Also, β-glucans present in the hydrolyzed yeast has a high binding affinity for the pathogens present in the poultry digestive tract (Spring et al. 2000). In addition, β-glucans and α-mannans can protect the mucosa by preventing pathogens from binding to villi and allowing reduced antigens to be in contact with the villi (Gao et al. 2008). Suzuki et al. (1990) and Jeney and Anderson (1993) stated that diet supplementation of yeast can enhance specific and non-specific immune responses. In this analysis, the improved nutrient digestibility of hens fed hydrolyzed yeast supplement might be improved intestinal health of hens, that resulted in improved nutrient absorption by the hens for this reason to improved nutrient deposition in the eggs. Moreover, the nutrients deposited in the eggs were most likely improved for laying hens’ production development.

3.4. Excreta microflora

Intestine gut microbes are involved in the digestibility of nutrients and the animal health. The positive effects of yeast culture supplementation on the host animal's natural defense mechanism and on the biological control of its intestinal microflora and the direct effect of the probiotic on health or nutritional type have been reported earlier (Shareef and Al-Dabbagh 2009; Hassanein and Soliman 2010). In the current study revealed that dietary inclusion different levels of brewer's yeast hydrolysate supplementation linear increase on Lactobacillus count (P = 0.01) and significant reductions were observed for E. coli (P = 0.04) at week 46, respectively (Table 6). Hassanein and Soliman (2010) reported that the count of Lactobacillus bacteria increased and E. coli bacteria decreased due to adding 0.8% active live yeast into laying hens diets. Similarly, Özsoy et al. (2018) reported that the lowest coliform bacteria value was found in the group fed 0.2% yeast culture supplementation, and dietary yeast or their extracts had been reported to have beneficial effects in promoting the number of Lactobacillus (Ferreira et al. 2010). Gao et al. (2008) also indicated that yeast culture supplementation had a positive impact on immune functions, and intestinal mucosal morphology of broilers. The development of intestinal morphology could reflect the health status of the gastrointestinal tract of an animal. The Lactobacillus possess a major potential in bio-preservation strategies and antibacterial effect due to its bacteriocin. Therefore, we considered that brewer's yeast hydrolysate had positive effects on excreta microflora and gut health in laying hens. Meanwhile, in the current study, improved laying hens egg quality and nutrient digestibility may have resulted from improved excreta microflora and intestinal health resulting from supplementation with hydrolyzed brewer’s yeast.

Table 6. Effects of brewer’s yeast hydrolysate supplementation on excreta microflora in laying hens¹.

Items, %	BYH (%)						SEM^1	P-value
	0	0.05	0.1	0.5	1.0	3.0		Linear	Quadratic	Cubic	Quartic
41 week
Lactobacillus	7.30	7.35	7.33	7.43	7.37	7.44	0.17	0.18	0.90	0.92	0.82
E. coli	4.11	4.02	4.07	4.01	3.99	3.97	0.18	0.24	0.88	0.80	0.59
46 week
Lactobacillus	7.33	7.41	7.47	7.86	8.21	8.26	0.16	0.01	0.74	0.55	0.95
E. coli	4.29	3.88	3.94	3.76	3.67	3.63	0.17	0.04	0.89	0.96	0.59

¹Standard error of means.

4. Conclusion

In conclusion, the results found in this study indicated that BYH supplementation in lying hens diets has potential to improve the egg production, egg quality, nutrient digestibility of DM and N, and enhance the fecal microbiota of fecal lactobacillus and reduced E. coli counts. Therefore, we considered that the supplementation of BYH derived from S. cerevisiae has potential commercial applications to improve the production of high-quality eggs and animal health.

Disclosure statement

No potential conflict of interest was reported by the author(s).