Abstract
The study's goal was to evaluate the impact of concentrate diets containing fermented cassava pulp with yeast waste (CSYW) with various roughage to concentrate ratios (R:C) on ruminal fermentation, nutritional digestibility, milk production, and milk composition in lactating cows. Four mid-lactation Thai crossbred dairy cows were randomly assigned a 2 × 2 factorial arrangement in a 4 × 4 Latin square design, weighing 440 ± 60.0 kg (75% Holstein Friesian and 25% Thai native breed), and having 90 days-in-milk (DIM). The different dietary treatments consisted of the following: factor A: soybean meal (SBM) and replacing SBM with CSYW at 100% dry matter (DM) in the concentrate diet, whereas factor B consisted of varying the R:C ratio from 60:40 to 50:50. An interaction effect between protein source and R:C ratio on intake was not observed (P > 0.05). The CSYW-diet did not affect the intake of concentrate and rice straw. However, when the R:C ratio was changed to 50:50, there was a significant increase in the apparent digestibility of neutral detergent fiber and acid detergent fiber (P < 0.05). There was no evidence of an interaction effect between CSYW and the R:C ratio on the parameters of the rumen, the microorganisms in the rumen, or blood urea-nitrogen. The concentration of ammonia-nitrogen in the rumen, however, significantly increased (P < 0.05) when animals were given a concentrated diet containing CSYW. Total VFA, C2:C3 ratios, acetic acid (C2), propionic acid (C3), butyric acid (C4), and methane levels were unaffected by the replacement of SBM with CSYW in concentrate diets or the R:C ratio given to lactating cows (P > 0.05). There was no evidence of an interaction between CSYW and the R:C ratio across any and all milk-related parameters (P > 0.05). The R:C ratio had no effect on milk production or composition (P > 0.05). With the exception of milk protein (P < 0.05), milk yield and milk composition were not affected by replacing SBM with CSYW in concentrate diets (P > 0.05). The concentration of protein in milk produced by animals fed a CSYW-diet increased from 3.05 to 3.25%. On the basis of this research, it is recommended that CSYW be used as a protein source in a concentrate diet in place of SBM with a R:C ratio of 60:40 or 50:50.
Keywords: Yeast waste, Cassava pulp, Ruminal fermentation, Dairy cow, Saccharomyces cerevisiae
1. Introduction
The primary elements that contribute to effective and profitable dairy production, particularly on farm systems, are feed quality and supply. In the northeast of Thailand, dairy cattle are starting to dominate the ruminant population. Feed expenditures account for almost 70% of overall operating costs, with concentrated spending accounting for the majority (65–80%) [1]. Livestock productivity is becoming ever more limited because of a shortage of feed and the expensive price of feed based on the present trend of rising feed costs and economic inflation [2,3]. There is significant work to reduce the cost of feeds by using inexpensive feed resources, such as agro-industrial by-products [4,5]. Cassava pulp, a fibrous byproduct of the cassava processing industry, has recently gained attention as a cellulosic biomass because it is a cheap, abundant, and sustainable agricultural product. Currently, cassava pulp is typically utilized as cheap livestock feed. However, cassava pulp typically has a low CP and high fiber content, which results in poor animal utilization [6,7]. Thus, improving the utilization efficiency of cassava pulp for animal feed should be developed, specifically through biotechnology innovation.
Saccharomyces cerevisiae, a biotechnology innovation, has long been used successfully to improve the quality of animal feed [[7], [8], [9]]. To increase crude protein content, commercial baker's yeast containing S. cerevisiae could be fermented with various agro-byproducts. Cassava bioethanol waste (CBW) fermented with S. cerevisiae (bakers' yeast) has the potential to increase CP by 25% DM [10]. Furthermore, Sommai et al. [7] demonstrated that fermenting cassava pulp with S. cerevisiae increased CP content by 23.3% and significantly improved rumen fermentation, feed utilization, and bacterial population in Thai beef cattle. Nevertheless, utilizing commercial yeast products could result in higher feed expenditures. Therefore, a different source of yeast should be considered as well.
S. cerevisiae is now used to ferment molasses in bioethanol plant facilities, producing liquid yeast waste. Yeast waste (YW) produced a sizable amount of waste that could have an adverse effect on the environment, despite the fact that ethanol was the main product [11]. Under consideration of this, it seems that any remaining yeast can be transformed into animal feed. Moreover, yeast waste contains 25–30% crude protein (CP) and 60–70% of yeast cells [11,12]. Dagaew et al. [13] reported that yeast waste fermented cassava pulp could increase protein content from 23.0 to 53.7% (compared to no fermented) and substitute SBM in concentrate diets for Thai native beef cattle by up to 100% shown without adverse effect. However, the feeding trial in lactating cows’ work is determined to study the fermented cassava pulp with yeast waste (CSYW) product. It was hypothesized that when fed to lactation cows, CSYW has a similar impact including, feed efficiency, ruminal fermentation and milk production.
Hence, this study's objectives were to measure the effect of substation SBM by CSYW in the concentrate diets and the difference ratio of roughage concentrate on rumen fermentation, nutrient digestibility, milk production, and milk profiles in lactating cows.
2. Materials and methods
2.1. Animal care and experiment location
Four Holstein-Friesian crossbreed lactating cows’ management was investigated in this study, as well as other relevant procedures, and was carried out in accordance with the Animal Ethics Committee of Khon Kaen University with approval from the National Research Council of Thailand's Guidelines on the Ethics of Animal Experimentation no. IACUC-KKU-108/63. The Division of Dairy Cattle Farm, Khon Kaen University, Khon Kaen Province, Thailand (16.46° N 102.82° E; altitude, 169 m above sea level) was the site of this experiment.
2.2. Fermented cassava pulp with yeast waste (CSYW) preparation
Following the method developed by Dagaew et al. [14], fermented cassava pulp with yeast waste (CSYW) was prepared. Khon Kaen Sugar Industry Public Co., Ltd. supported yeast waste (YW). A local shop supplied cassava pulp (CS), commercial-grade urea, and molasses. The following media and solutions were developed: (1) CSYW was made by weighing 10 L of YW into a flask containing 10 L distilled water, then mixing and incubating at room temperature for 2 h; (2) the solution of medium was produced by mixing 2.4 kg of molasses and 5.0 kg of urea in 10 L of distillation water, and the pH was adjusted with H2SO4 until the final pH was 3.5–5; (3) after mixing (1) and (2) in a 1:1 ratio, the mixture was flushed with oxygen for 18 h; (4) CS was thoroughly combined with the yeast medium solution (3) at a 20 kg to 10 L ratio after 18 h; (5) the product fermented for 14 days under anaerobic conditions in a plastic silo, was sealed, and sun dried for 72 h to keep moisture below 10% before being used as a protein source to replace SBM. Table 1 displays the experimental diet ingredients and chemical composition. The final CSYW product had a CP content of 53.7%.
Table 1.
Feed ingredients and chemical composition used in the experimental ration.
| Item | SBM | CSYW | CSYW feedstuff | Rice straw |
|---|---|---|---|---|
| Ingredient, % dry matter | ||||
| Cassava chip | 40.0 | 40.0 | ||
| Rice bran | 11.8 | 12.0 | ||
| Palm kernel meal | 11.0 | 11.0 | ||
| Soybean meal | 19.0 | – | ||
| CSYW3 | – | 19.0 | ||
| Mineral premix | 0.5 | 0.5 | ||
| Urea | 1.2 | 1.0 | ||
| Molasses | 3.0 | 3.0 | ||
| Corn gain | 12.0 | 12.0 | ||
| Di-calcium | 1.0 | 1.0 | ||
| Salt | 0.5 | 0.5 | ||
| Feed cost ($US/kg) | 3.1 | 2.6 | ||
| Chemical composition | ||||
| Dry matter (%) | 90.6 | 91.2 | 34.9 | 92.4 |
| ------- Dry matter (%DM) ---------- | ||||
| Organic matter | 95.8 | 90.2 | 84.5 | 86.5 |
| Ash | 4.2 | 9.8 | 15.5 | 13.5 |
| Crude protein | 16.3 | 16.5 | 53.7 | 2.3 |
| Neutral detergent fiber | 15.0 | 27.2 | 24.3 | 75.5 |
| Acid detergent fiber | 9.2 | 18.3 | 11.3 | 55.3 |
SBM = Soybean meal; CSYW = Fermented cassava pulp with yeast waste treatment; CSYW feedstuff = Fermented cassava pulp with yeast waste feedstuff.
2.3. Animals and experimental design
A 2 × 2 factorial arrangement in a 4 × 4 Latin square design was randomly assigned to four 440 ± 60.0 kg multiparous mid-lactation crossbred dairy cows with more than 90 days-in-milk (DIM) (75% Holstein Friesian and 25% Thai native breed). The different dietary treatments consisted of the following: factor A: soybean meal (SBM) and replacing SBM with CSYW at 100% dry matter (DM) in the concentrate mixture, whereas factor B consisted of varying the R:C ratio from 60:40 to 50:50. At 7:00 a.m. and 4:00 p.m. each day, the animals were fed two equal meals of a concentrate combination and rice straw. Every day, the feed intake and milk production of all dairy cows were recorded. Throughout the experiment, there was always access to mineral blocks and pure, fresh water.
2.4. Feeding and samples collection
The research was carried out over the course of four 21-day intervals. Weighing the offered and residue feeds during the morning feeding provided for the daily recording of individual intakes of rice straw and concentrate. The first 14 days were for adaptation. During the final five days of each period, samples of feed offered and feed refused were taken at the morning and afternoon feedings. The samples of feces were collected using the spot technique (last 5 days of each period) at 5% total fresh weight. The fecal samples were separated into two portions and composed of 5% of the total fresh weight: the first part was used to measure the amount of dry matter (DM) produced each day, and the second portion was refrigerated and pooled by the cow at the conclusion of each period for chemical analysis and nutrient digestibility calculations. All samples were dried at 60 °C after collection, ground to pass through a 1 mm sieve, and then their dry matter (DM), ash, and CP contents were analyzed according the AOAC method [15]. Organic matter (OM) was obtained by subtracting the ash percentage from 100. The Ankom Fiber Analyzer (Ankom Technology) was used to analyze neutral detergent fiber (NDF) and acid detergent fiber (ADF) according to the Van Soest et al. [16] method. To determine the apparent digestibility, acid insoluble ash (AIA) was determined using Van Keulen and Young's methods [17].
Every day, samples of each animal's milk production were taken. On the final five days of each cycle, samples of milk from the morning and afternoon milking were gathered and combined (60 ml in the morning: 40 ml in the afternoon is the ratio used). Milk samples were preserved with 2-bromo-2-nitropropane-1, 3-dial and kept at 4 °C. According to the AOAC [15], the milk samples' fat, protein, lactose, total solids, and solids-without-fat contents were measured using infrared methods (Milko- Scan 33; Foss Electric, Hillerod, Demark). The formula used to determine fat-corrected milk (FCM) was 3.5% FCM = 0.35 milk yield (kg) + 15 fat yield (kg). The milk urea nitrogen (MUN) was examined using an industrial kit (Sigma kits#640, Sigma Diagnostics, St. Louis, MO).
Each time, on the day before and 4 h after feeding, blood was drawn from the jugular vein of each cow and kept in a tube containing EDTA. Plasma was then retrieved, spun down at 500 g for 10 min, and stored at −20 °C for blood urea nitrogen analysis (L type Wako UN, Tokyo, Japan). Before and 4 h after feeding, a portion of the ruminal fluid was sampled using a vacuum pump linked to a stomach tube to collect 50 ml of rumen fluid. HANNA Instruments HI 8424 (Singapore) was used to measure the rumen's temperature and pH immediately. Three groups of rumen fluid samples were generated. To prevent nitrogen volatilization of ruminal fluid, 45 mL were combined in a second portion with 5 ml of 1 M H2SO4. VFAs and NH3N concentration analysis using centrifuged for 15 min at 16,000×g. Fifty percent of H2SO4 at 0.3 ml mixing with centrifuged of rumen fluid 0.8 ml, 0.8 ml of 5 mmol/L 2–5- Methylvaleric acid and diethyl ether at 1.6 ml. After that, the substance was spun for 15 min at 2500 rpm. After that, 1 mL of the ether layer was transferred to a test tube and allowed to stand for 5 min. The amount of NH3–N was measured using a spectrophotometer (UV/VIS Spectrometer, PG Instruments, London, UK). The gas chromatograph (GC2014, Shimadzu, Tokyo, Japan) used for measuring VFA concentrations was fitted with a flame ionization detector and a 25-m-by-0.53-mm capillary column (BPX5, SGE Analytical Science, Victoria, Australia). The VFA proportion was calculated for the methane (CH4) concentration. The stoichiometric model used to estimate CH4 from VFA composition followed the Moss et al. [18] equation: CH4 = (0.45 × acetate) - (0.275 × propionate) + (0.40 × butyrate). In order to count the ruminal bacteria and protozoa with a hemocytometer slider (Boeco) under microscopic (150 × ) conditions, 1 mL of rumen fluid was preserved with 9 ml of formalin in a bottle container [19].
2.5. Statistical methods
This study was conducted using the SAS [20] with General Linear Models (GLM), and an ANOVA was performed on all the data for a 2 × 2 factorial arrangement in a 4 × 4 Latin square design. Using Duncan's new multiple range tests, it was established that P < 0.05 was significant, suggesting statistically significant differences.
3. Results
3.1. Chemical composition of diets
The chemical composition and feed ingredients are displayed in Table 1. In the current study, the CP concentration of the CSYW product was 53.7% of DM, which was greater than the typical CP level of SBM (44–45%DM). CP in diets was comparable between the two concentrates, ranging from 16.3 to 16.5% of DM, which may be attributed to the fact that the high CP content in CSYW can balance CP in concentrate diets. In comparison to the SBM-diet, the fiber content of concentrate diets including NDF and ADF, was increased by 12.2% and 9.1%, respectively. This may be because CSYW has a high fiber content, resulting in high fiber-in-concentration diets.
3.2. Feed utilization efficiency
Table 2 displays the consumption of concentrates, rice straw, and total DM. Protein source and R:C ratio did not have an interaction effect on consumption (P > 0.05). The CSYW-diet did not affect the intake of concentrate and rice straw. Additionally, the total DM intake (kg/day) was improved by the CSYW. Moreover, there was no effect of the R:C ratios on feed intake (P > 0.05).
Table 2.
Effect of substitution of soybean meal (SBM) with fermented cassava pulp with yeast waste (CSYW) in concentrate diets with various roughage (R) to concentrate (C) ratios on feed intake in lactating dairy cows.
| Protein source | R:C ratio | Daily intake, %DM |
||||||
|---|---|---|---|---|---|---|---|---|
| Rice straw, kg/day | Rice straw, g/kg BW0.75 | Concentrate, kg/day | Concentrate, g/kg BW0.75 | Total intake, %BW | Total intake, kg/day | Total intake, g/kg BW0.75 | ||
| CSYW | 60:40 | 9.9 | 97.7 | 6.6 | 49.3 | 3.2 | 16.5 | 146.9 |
| 50:50 | 8.4 | 81.7 | 8.4 | 46.8 | 2.7 | 16.9 | 128.5 | |
| SBM | 60:40 | 9.1 | 94.3 | 6.0 | 40.2 | 2.9 | 15.2 | 134.5 |
| 50:50 | 7.7 | 79.4 | 7.7 | 43.5 | 2.7 | 15.4 | 122.9 | |
| SEM | 0.37 | 4.12 | 0.25 | 2.52 | 0.13 | 0.62 | 6.24 | |
| P-value | ||||||||
| Protein source | 0.64 | 0.68 | 0.65 | 0.95 | 0.96 | <0.05 | 0.89 | |
| R:C ratio | 0.05 | 0.47 | 0.07 | 0.31 | 0.31 | 0.43 | 0.21 | |
| Interaction | 0.76 | 0.82 | 0.92 | 0.76 | 0.92 | 0.07 | 0.17 | |
SEM = standard error of the mean.
Table 3 demonstrates the effect of substitution of SBM with CSYW in concentrate diets with various R:C ratios on nutrient intake and digestibility. An interaction effect between CSYW and the R:C ratio on nutritional intake was not observed (P > 0.05). The nutritional intake of OM, CP, NDF, or ADF was unaffected by increasing CSYW (P > 0.05). In addition, the apparent digestibility of DM, OM, CP, NDF, and ADF was unaffected by the level of substitution (P > 0.05). However, when the R:C ratio was changed to 50:50, there was a significant increase in the apparent digestibility of NDF and ADF (P < 0.05).
Table 3.
Effect of substitution of soybean meal (SBM) with fermented cassava pulp with yeast waste (CSYW) in concentrate diets with various roughage (R) to concentrate (C) ratios on nutrient intake and digestibility.
| Protein source | R:C ratio | Nutrient intake, kg/d |
Apparent total-tract digestibility, % DM |
|||||||
|---|---|---|---|---|---|---|---|---|---|---|
| OM | CP | NDF | ADF | DM,% | OM | CP | NDF | ADF | ||
| CSYW | 60:40 | 12.5 | 2.9 | 4.3 | 3.5 | 63.9 | 67.2 | 50.5 | 63.0 | 54.5 |
| 50:50 | 12.8 | 2.8 | 4.2 | 3.4 | 63.5 | 66.5 | 51.8 | 69.4 | 55.9 | |
| SBM | 60:40 | 11.9 | 2.6 | 3.9 | 3.2 | 62.5 | 66.3 | 51.0 | 66.8 | 54.3 |
| 50:50 | 12.7 | 3.0 | 4.0 | 3.3 | 63.8 | 65.7 | 52.2 | 70.3 | 57.0 | |
| SEM | 0.90 | 0.22 | 0.70 | 1.22 | 4.30 | 1.67 | 0.86 | 3.85 | 0.86 | |
| P-value | ||||||||||
| Protein source | 0.68 | 0.94 | 0.94 | 0.94 | 0.83 | 0.02 | 0.76 | 0.72 | 0.22 | |
| R:C ratio | 0.57 | 0.58 | 0.35 | 0.89 | 0.60 | 0.98 | 0.56 | <0.05 | <0.05 | |
| Interaction | 0.80 | 0.27 | 0.44 | 0.76 | 0.46 | 0.91 | 0.67 | 0.22 | 0.17 | |
DM = Dry Matter; OM = organic matter; CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; SEM = standard error of the mean.
3.3. Rumen ecology, rumen microbes, and blood urea-nitrogen
Table 4 provides a summary of the rumen fermentation characteristics and concentration of blood urea nitrogen (BUN) of lactating cows fed various doses of CSYW and various R:C ratios. The rumen's characteristics, its microbes, or BUN were not shown to be affected by an interaction between CSYW and R:C ratio. The rumen's pH and temperature, which were steady at 6.63 and 7.01 and 38.80 and 39.01 °C, respectively, were unaffected by the R:C ratio or the replacement of SBM with CSYW (P > 0.05). However, when animals received a concentrate diet containing CSYW, the concentration of NH3–N in the rumen considerably increased (P < 0.05). BUN was not impacted by the treatments (P > 0.05). Furthermore, neither the CSYW nor R:C ratios had an impact on the overall amount of bacteria or protozoa (P > 0.05), with values ranging from 4.75 to 5.50 × 1011 and 2.05 to 3.00 × 107, cells/ml, respectively.
Table 4.
Effect of substitution of soybean meal (SBM) with fermented cassava pulp with yeast waste (CSYW) in concentrate diets with various roughage (R) to concentrate (C) ratios on rumen ecology, microorganism, and fermentation.
| Protein source | R:C ratio | pH | Temperature, °C | NH3–N, mg/dl | BUN, mg/dl | Rumen microbes, cells/ml |
|
|---|---|---|---|---|---|---|---|
| Bacteria, × 1011 | Protozoa × 107 | ||||||
| CSYW | 60:40 | 7.01 | 38.80 | 16.64 | 12.35 | 5.50 | 2.05 |
| 50:50 | 6.93 | 38.88 | 17.55 | 11.78 | 5.12 | 2.50 | |
| SBM | 60:40 | 6.87 | 38.86 | 16.08 | 11.42 | 4.50 | 2.99 |
| 50:50 | 6.63 | 39.01 | 16.37 | 12.53 | 4.75 | 3.00 | |
| SEM | 0.16 | 0.20 | 0.21 | 0.35 | 0.35 | 0.05 | |
| P-value | |||||||
| Protein source | 1.84 | 0.65 | <0.05 | 0.80 | 0.39 | 0.37 | |
| R:C ratio | 0.26 | 0.88 | 0.12 | 0.26 | 0.07 | 0.75 | |
| Interaction | 0.99 | 0.57 | 0.16 | 0.45 | 0.86 | 0.79 | |
NH3–N=Ammonia-nitrogen; BUN = Blood urea-nitrogen; SEM = standard error of the mean.
3.4. Rumen fermentation characteristics
Table 5 shows the impact of replacing SBM with CSYW in concentrate diets with different R:C ratios on ruminal VFA concentration and VFA characteristics. The substitution of SBM with CSYW in concentrate diets and the R:C ratio administered to lactating cows did not influence any of the investigated parameters (P > 0.05). The amounts of acetic acid (C2), propionic acid (C3), butyric acid (C4), C2:C3 ratios, and CH4 were also unaffected by both factors (P > 0.05).
Table 5.
Effect of substitution of soybean meal (SBM) with fermented cassava pulp with yeast waste (CSYW) in concentrate diets with various roughage (R) to concentrate (C) ratios on ruminal volatile fatty acid (VFA).
| Protein source | R:C ratio | Total VFA, mM/L | Acetate (C2, %) | Propionate (C3, %) | Butyrate (C4, %) | C2:C3 ratio | Methane, mmol/100 mol |
|---|---|---|---|---|---|---|---|
| CSYW | 60:40 | 74.04 | 63.49 | 22.49 | 14.02 | 3.27 | 27.88 |
| 50:50 | 73.60 | 65.38 | 23.22 | 11.39 | 4.01 | 27.59 | |
| SBM | 60:40 | 70.62 | 64.90 | 22.09 | 13.00 | 3.69 | 28.33 |
| 50:50 | 74.75 | 64.52 | 22.24 | 13.22 | 3.05 | 28.20 | |
| SEM | 1.21 | 1.69 | 1.24 | 1.63 | 0.44 | 0.89 | |
| P-value | |||||||
| Protein source | 0.37 | 0.82 | 0.59 | 0.81 | 0.55 | 0.56 | |
| R:C ratio | 0.08 | 0.47 | 0.82 | 0.81 | 0.14 | 0.93 | |
| Interaction | 0.15 | 0.61 | 0.72 | 0.47 | 0.90 | 0.81 | |
SEM = standard error of the mean; CH4 = (0.45 × acetic acid) - (0.275 × propionic acid) + (0.40 × butyric acid) [18].
3.5. Milk production and content
Table 6 shows the effect of substitution of SBM with CSYW in concentrate diets and different R:C ratios on milk yield and milk composition. There was no evidence of an interaction between CSYW and the R:C ratio across any and all milk-related parameters (P > 0.05). The R:C ratio had no effect on milk production or composition (P > 0.05). With the exception of milk protein (P < 0.05), milk yield and milk composition were not affected by replacing SBM with CSYW in concentrate diets (P > 0.05). The protein content of the milk produced by animals fed a CSYW-diet increased from 3.05 to 3.25%.
Table 6.
Effect of substitution of soybean meal (SBM) with fermented cassava pulp with yeast waste (CSYW) in concentrate diets with various roughage (R) to concentrate (C) ratios on milk composition in lactating dairy cows.
| Protein source | R:C ratio | Milk yield, kg/d | Milk yield, 3.5%FCM*, kg/day | Milk compositions, % |
MUN, mg/dl | ||||
|---|---|---|---|---|---|---|---|---|---|
| Fat | Protein | Lactose | SNF | TS | |||||
| CSYW | 60:40 | 12.25 | 12.59 | 3.02 | 3.17 | 5.44 | 8.38 | 11.44 | 12.72 |
| 50:50 | 12.68 | 11.30 | 2.83 | 3.32 | 5.56 | 8.54 | 11.84 | 13.02 | |
| SBM | 60:40 | 12.76 | 12.35 | 3.11 | 3.05 | 4.39 | 8.23 | 11.10 | 11.88 |
| 50:50 | 12.76 | 12.34 | 3.12 | 3.05 | 5.64 | 8.54 | 11.88 | 12.40 | |
| SEM | 1.32 | 1.39 | 0.39 | 0.04 | 0.80 | 0.11 | 0.32 | 0.82 | |
| P-value | |||||||||
| Protein source | 0.71 | 0.67 | 0.63 | <0.05 | 0.55 | 0.50 | 0.64 | 0.39 | |
| R:C ratio | 0.98 | 0.81 | 0.82 | 0.14 | 0.49 | 0.52 | 0.56 | 0.62 | |
| Interaction | 0.98 | 0.80 | 0.80 | 0.12 | 0.40 | 0.06 | 0.09 | 0.89 | |
SNF=Solid-not-fat; TS = Total solid; MUN = milk urea-nitrogen; SEM = standard error of the mean; 3.5% FCM = Fat corrected milk = 0.35 × milk yield (kg) + 15 fat yield (kg).
4. Discussions
The CSYW product has a high nutritional content, especially nitrogen, which may be needed by animal hosts and rumen microbes. This could be the main influence of the medium solution's urea level of 5.0 kg, which indicated a greater concentration of N in the CSYW. Nevertheless, yeast carrying YW may replicate during fermentation as single-cell proteins, which could affect the enhance in protein [14].
The chemical composition of the concentrate diets suggested by the NRC for nutrient value is shown in Table 1 [21]. In brief, the dry matter intake (DMI) of dairy cows given CSYW in a concentrate mixer met the energy requirement for growth and production [21]. Mertens [22] suggested that the appropriate level of NDF in a dairy cattle diet should be at least 35%, while the NRC [21] recommends that NDF content in dairy rations be a minimum of 25–33%.
Feed utilization was unaffected by the addition of CSYW as a source protein in concentrate diets, such as intake, digestibility, milk yield, and milk composition. The results indicate that the CSYW product is comparable to SBM when added to a lactating cow concentrate diet. Despite possessing such little nutritional benefit, fermenting cassava pulp with leftover yeast could enhance flavor and digestion. The amount of feed consumed may increase if molasses-containing yeast waste encourages animal ingestion of feed [23].
The breakdown of cassava pulp could be significantly accelerated by the use of CSYW, which contains yeast cells and urea. According to Suntara et al. [24], the fiber content of cassava pulp can be broken down by fibrolytic enzymes that yeast might release. Furthermore, an additional method to improve feed digestion would be to utilize CSYW with a high urea concentration. As a result of the alkaline agents created by urea during the fermentation step of CSYW, the hemicellulose-lignin compound in cassava pulp swells [3]. Concentrated alkaline chemicals can physically expand structural fibers by chemically dissolving the ester bonds in them. Interestingly, a previous in vitro experiment found that in vitro dry matter digestibility remained unchanged when SBM was substituted with 100% CSYW. According to Dagaew et al. [13], feeding cattle a concentrate feed containing 100% CSYW showed no adverse influence on feed consumption or nutrition digestibility in in vivo experiments. Similarly, Promkot et al. [25] found that dry matter intake (DMI) was higher during the 14-day prepartum period and higher during the 60-day postpartum period in Holstein crossbred dairy cows fed a YEFECAP diet compared to a control diet. Furthermore, Chuelong et al. [6] found that YFCP supplementation at 20 g/d had no effect on cattle feed intake.
The digestibility of NDF and ADF increased by 10% and 5%, respectively, when the percentage of a concentrated diet went from 40% to 50%. According to Dagaew et al. [14], this was consistent with the increase in concentrated diet from 30% to 70%. As a result, DM and ADF had increased in vitro digestibility of 449 and 308 g/kg, respectively, and more commonly accessible energy that facilitated improved bacterial growth and digestion [10]. Also, this study confirmed the fact that a concentrated dietary supplement increased microorganisms in the rumen by 55%.
Ruminal pH and temperature were not influenced by CSYW in a concentrate diet and were reported in the optimal range between 6.63 and 7.01, and ruminal temperatures ranged from 38.80 °C to 39.01 °C [26,27]. This might be a result of the fact that the CSYW production process uses yeast waste as its main ingredient, producing a product with a high live yeast content. A slight shift in the R:C ratio (60:40 vs. 50:50) may also have no bearing on the pH of the rumen. Through its connection with lactate-using bacteria (LUB), yeast has been shown to be crucial in maintaining a healthy rumen environment. High levels of LUB in the rumen prevent a lactate-producing bacterium from functioning, regulate the rumen's pH, and prevent lactic acid from accumulating [28]. According to Dagaew et al. [13], feeding Thai native beef calves a concentrate diet containing 100% CSYW helps to keep the rumen's pH and temperature stable. Similar research by Cherdthong and Supapong [10] revealed that ruminal pH and temperature were unaffected by the addition of 20% yeast-fermented cassava bioethanol waste (YECAW) to the concentrate diet. Furthermore, Chuelong et al. [6] found that when cattle were given 20 g/d of YFCP, ruminal pH and temperature did not change.
As the levels of CSYW increased, so did the concentration of NH3–N. This could be because when the amount of CSYW is raised, microorganisms break down the increased CP from the substance into considerable amounts of NH3–N. The range of NH3–N levels, from 6.3 to 25.5 mg/dl, was within the usual range. It was possible for microbial activity to be beneficial since the NH3–N concentration was lower than what was needed for bacterial growth and microbial activity [29] (those associated with maximum performance). These findings were consistent with those of Amin et al. [28] and Dagaew et al. [13], who found that dairy calves and beef cattle fed rice straw and supplemented with YECAW or CSYW had ruminal fluid ammonia-nitrogen levels that were optimal for microbial development between 13 and 16 mg/dl. Furthermore, Promkot et al. [25] reported that YEFECAP can cause several impact in the rumen, especially enhanced NH3–N concentration in dairy cows. Furthermore, in terms of the R:C ratio, as there was a small alteration, the results did not significantly modify rumen characteristics.
As part of the investigation into the relationship between ruminal NH3–N and utilization of protein, a BUN concentration was also established. Our results indicate that BUN did not change with different treatments. This could be due to the fact that NH3–N concentrations in cows receiving CSYW were related to feed intake due to insufficient substrate and/or bacteria that used NH3–N for growth in the rumen. These findings indicate that there are no adverse effects of CSYW on BUN concentrations. According to reports, beef cattle generally have plasma UN concentrations of between 11 and 15 mg/100 ml [2]. Similarly, Dagaew et al. [13] demonstrated that 100% of CSYW in a concentrate diet has no effect on BUN concentration in Thai native beef cattle. Moreover, according to Cherdthong et al. [23], feeding dairy calves YECAW up to 20% of the time had no effect on their BUN levels. In contrast, Musco et al. [30] discovered higher levels of BUN as the R:C ratio increased in a study on dairy cows from 90 days DIM until 60 days after the trial. The difference between groups gradually disappeared, implying a transitory utilization of protein as an energy substrate due to the lower energy in the diet.
It has been shown that a high-concentrated diet ratio results in a high C3 concentration. When the ratio of R:C in the diet of cattle was changed from 60:40 to 40:60, Phesatcha et al. [9] found that the concentration of C3 increased from 24 to 28%. On the other hand, the current research did not find any changes in C3 caused by the effects of the proportion of R:C, which could be because there was only a minor shift in the R:C ratio. The VFA profile was unaffected by CSYW replacement SBM. These findings show that CSYW can be utilized as a substitute element in animal feed and does not adversely impact on the rumen's ability to produce VFA. Similarly, to the above, the amounts of butyric acid (C4), acetic acid (C2), or propionic acid (C3) as well as the total VFA were not affected by feeding YECAW to dairy calves, according to Cherdthong et al. [23]. Dagaew et al. [13] observed that adding CSYW to concentrated diet meals increased the C3. In concentrate diets, C3 in cattle was improved when replacement SBM by CSYW at 100%. Additionally, according to Chen et al. [31], adding protein from yeast-fermented cassava chips to meals that contain concentrates greatly increases the ratio of C2 to C3, while also increasing the amounts of total VFA and C3. In ruminants, propionate fermentation results in significant changes to CH4, and production decreases with yeast supplementation [32]. Nevertheless, CSYW has no impact on CH4 in this result. Likewise, Bayat et al. [33] found that yeast had no effect on CH4 emissions.
On a concentrated diet, 100% SBM replacement with CSYW had no negative impacts on feed consumption, rumen fermentation, digestion, or microbial communities. Up to 100% of the protein in a concentrated diet can be supplied by CSYW. It is possible to reduce feed costs, environmental pollution, and the risks associated with incorrect waste disposal.
The increase in dietary protein consumption was what caused these modifications. Lactating dairy cows on high protein diets had increased nitrogen intake and BUN levels, according to Barros et al. [34]. Several studies show a positive correlation between ruminal NH3–N, BUN, and MUN [35]. The results of this study were consistent with Hwang et al. [36] summary that cattle produce milk with levels of MUN that are between the normal ranges of 11 and 17 mg%.
Milk yield, milk fat, lactose, and solid-not-fat were not significantly affected when using CSYW in a concentrate diet. In this study, CSYW supplementation enhanced milk protein. This might be because the addition of CSYW increases the amount of protein from yeast cells and nitrogen from NPN available to the bacteria growing in the rumen. The well-known effect of yeast on rumen fermentation and nutritional digestibility, which increases ammonia uptake and promotes microbial protein production, could account for the greater milk protein content in the experimental group [37]. This could have been caused by proteins that were taken in by the rumen and proteins made by bacteria in the milk [38].
5. Conclusion
Based on this study, it was possible to conclude that enhancing the level of concentrated feed increased the digestibility of neutral detergent fiber and acid detergent fiber. The various R:C ratios had no impact on milk output, rumen parameters, or feed utilization. The inclusion of CSYW in concentrate diets can be comparable to the SBM-diet, while total intake and milk protein were higher in cows fed the CSYW-diet than in cows fed the SBM-diet. As a result, it is suggested that CSYW be used as a protein source in a concentrate diet in place of SBM with a R:C ratio of 60:40 or 50:50.
Author contribution statement
Gamonmas Dagaew; Anusorn Cherdthong; Sawitree Wongtangtintharn; Rittikeard Prachumchai: Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data; analysis tools or data; Wrote the paper.
Sawitree Wongtangtintharn: Contributed reagents, materials, analysis tools or data; Wrote the paper.
Funding statement
Gamonmas Dagaew was supported by Thailand Science Research and Innovation [PHD62I0020].
Data availability statement
Data included in article/supplementary material/referenced in article.
Declaration of interest’s statement
The authors declare no conflict of interest.
Acknowledgments
Thanks to Tropical Feed Resources Research and Development Center (TROFREC), Department of Animal Science, Faculty of Agriculture, Khon Kaen University.
Footnotes
Supplementary data to this article can be found online at https://doi.org/10.1016/j.heliyon.2023.e14585.
Appendix A. Supplementary data
The following is the Supplementary data to this article.
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