Feed intake and daily weight gain of cross-bred Sindhi cattle fed fermented rice straw and basal diet using soybean meal and dried brewer's malt

Phuong T B L¹, Khanh M Tran², Son V N², Hai T Nguyen¹, Hang T T Le³ and Khang N Duong¹

¹ Nong Lam University, HCMC, Vietnam
duongnguyenkhang@hcmuaf.edu.vn
² Department of Livestock, Veterinary and Fisheries of Long An province
³ An Giang University, Vietnam National University HCMC

Abstract

This experiment object to determine if fermented rice straw in total mixed ration (TMR) improves dry matter intake (DMI), average daily weight gain, and feed conversion (FCR) of cattle fed basal diet using soybean meal and dried brewer's malt (DBM) as additive. Substrates of fermentation consist of rice straw and 4% dry matter (DM) of DBM fermented with microbes BT4 at three levels. Forty cattle at 09 months of age were assigned randomly into four treatments and two replications in a feeding trial, lasted 90 days. The basal diet of experiment is mixture of soybean meal and dried brewer's malt was mixed ratio at 62% and 38% respectively. The treatments were as follows: (1) Control: basal diet at 65% DM + pure rice straw at 35% of DM, (2) FRSM30: 65% DM basal diet + 35% DM fermented rice straw from 30 liters of microbe’s biomass BT4, (3) FRSM40: 65% DM basal diet + 35% fermented rice straw from 40 liters of microbes biomass BT4, (4) FRSM50: 65% DM basal diet + 35% fermented rice straw from 50 liters of microbial biomass BT4. The results have shown that fermented rice straw have tend to improve crude protein compared to pure rice straw. Total DMI, voluntary CP intake, ADG and FCR was improved by feeding fermented rice straw compared to unfermented rice straw but there was no significant difference among FRSM treatments. However, growth cattle have a better trend found in FRSM40. These findings suggested that rice straws could improve palatable and weight gain of cattle by using microbes BT4 plus 4% DBM.

Keywords: palatable, biomass, weigh gain, microbes BT4

Introduction

The production and processing of agricultural products in Vietnam generate significant quantities of organic by-products, leading to environmental pollution through fermentation or post-harvest burning. According to the Department of Livestock Production's Draft on March 20, 2023, the Vietnam country annually produces an estimated 88.9 million tons of crop by-products in which include over 49.9 million tons of rice straw. In the sustainable agricultural circular chain, rice straw can be repurposed for cattle farming. However, it is very low crude protein content, limited animal intake, and poor performance have hindered its effective utilization. Additionally, the available feed resources for ruminants are seasonal. While dry rice straw can be stored to meet cattle feed needs during the dry season or when grazing areas are limited, straw harvested in the rainy season is often challenging storage due to mold growth. Therefore, pretreatment of rice straw is necessary to meet the needs of using straw for animals effectively.

Using microbial fermentation not only enhances the nutritional composition of straw but also supports fermentation activities in the rumen, making fermented rice straw environmentally friendly. The yeast Saccharomyces cerevisiae is commonly used in rice straw fermentation due to its effectiveness in crude fiber degradation, reducing neutral detergent fiber, and acid detergent fiber (Zayed et al 2018; Aquino et al 2020). Additionally, the yeast culture of Saccharomyces cerevisiae promotes the growth of ruminal bacteria that utilize lactate and digest cellulose (Callawa and Martin 1997). Therefore, the combination of Saccharomyces cerevisiae with lactic acid bacteria (LAB) in a starter culture can help stabilize the ruminal pH and support LAB growth in the rumen. To enhance the microbial fermentation of rice straw, it is recommended to add restricted feed additives as nutrient supplements to promote microbial growth and fermentation (Fattah et al 2020; Abo-Donia et al 2021). Probiotics have also been shown to alter rumen fermentation, primarily improving dry matter digestibility (Wang et al 2023) and significantly reducing acetate-to-propionate ratios (Astuti et al 2022). This suggests potential improvements in animal performance when using fermented rice straw in a feedlot diet of cattle.

Thus, this study aimed to evaluate the effect of supplementing fermented rice straw with a probiotic mixture (including Lactobacillus spp. and Saccharomyces cerevisiae) on feed intake and daily weight gain in cross-bred Sindhi cattle fed a diet consisting of soybean meal and dried brewer's grain malt as basal diet.

Materials and methods

Treatments and Experimental design

The feeding trial was conducted at the farm of Research and Technology Transfer Center, Nong Lam University of Ho Chi Minh City, from June to August 2024. Forty cattle were assigned randomly into four treatment and two replications in a feeding trial, lasted 90 days. The study compared rice straw versus three levels of fermented rice straw. The basal diet consisted of a mixture of 62% DM soybean meal and 38% DM dried brewer's malt.

The treatments were as follows: (1) Control: basal diet and pure rice straw; (2) FRSM30: basal diet + fermented rice straw from 30 liters of microbial biomass, (3) FRS40: basal diet + fermented rice straw from 40 liters of microbial biomass, (4) FRSM50: basal diet + fermented rice straw from 50 liters of microbial biomass.

Animal and feed preparations

The cross-bred Sindhi cattle in the experiment at nine months of age had an average initial weight of 231 ± 24.7 kg. During 10 days prior to starting the experiment, they were vaccinated against endemic diseases and treated for parasites by subcutaneous injection of Ivermectin; they were also adapted to experimental TMR (total mix ration). TMR of feeding trial included 35% DM of rice straw or fermented rice straw and 65% DM of basal diet (mixture of 62% soybean meal and 38% dried brewer's malt). TMR was mixed in the morning and fed throughout the day. Cattle were fed 3 times per day at 7 am, 11 am and 4 pm.

Microbes BT4 contain Lactobacillus spp. 3.4×106 CFU/ml and Saccharomyces cerevisiae 105 CFU/ml as starter culture. The microbial biomass solution was prepared twice by multiplying the microbial starter culture BT4 product prior to ferment with rice straw. Initially, one litter of microbial starter culture was multiplied by mixing with 0.1 kg of salt, 02 liters of molasses, and 50 liters of tap water. This mixture solution was then mixed well and incubated for 02 days. Subsequently, this entire solution was further incubated for 02 more days after adding 10 liters of molasses, 01 kg of salt, and tap water up to a total volume of 1000 liters. Fermented rice straw roll was incubated with 4% DM of dried brewer's malt and microbial biomass solution at different volumes: 30 liters, 40 liters, and 50 liters, for duration of 07 days in nylon bag. The microbial biomass solution volume for each fermented rice straw treatment would be mixed with 4% DM of dried brewer's malt before evenly sprinkling on the straw rolls. Once the fermentation ingredients are thoroughly prepared in the nylon bags, they would be rolled around to ensure even absorption. Furthermore, the fermented rice straw bags would be rolled once again on the third day of fermentation.

Data collection

Pure rice straw, fermented rice straw with different microbial biomass solutions (FRSM30, FRSM40, and FRSM50), and the mixture of soybean meal and dried brewer’s malts were measured with dry matter and crude protein (AOAC 2001.11-VF) every 14 days to establish TMR ration for cattle. Feed offers and feed residue were weighed to calculate the feed intake daily. Acid Detergent Fiber (ADF) and Non-detergent Fiber (NDF) of pure rice straw and fermented rice straw (FRSM30, FRSM40, and FRSM50) were measured according to E029.2021(Ref.ANKOMTechnology method12:2015) (VF) and GE030.2021(Ref.ANKOMTechnology method13:2015) (VF) respectively.

The body weight of the cattle was measured before the start of the experiment to distribute into experimental groups. Live weight gain was recorded every 14 days until the end of the experiment. The cattle were weighed in the morning prior to the first feeding.

Statistical analysis

The data were analysed with the general linear model (GLM) option in the ANOVA of the Minitab software (Minitab 19.2020). Sources of variation were treatments and error.

Results

Dry matter, crude protein, acid detergent fiber (ADF) and non-detergent fiber (NDF) in experimental feed

Pure rice straw has a high dry matter content but low crude protein (CP) content, which are nutritional limitations when used in cattle rations. After fermentation of rice straw with microbes BT4 and 4%DM of dried brewer's malt as additives, the CP content of fermented rice straw tended to improve (Table1). However, there was no discernible difference in CP content among the fermented rice straw treated by various levels of microbial biomass (FRSM30, FRSM40, and FRSM50). Fermented rice straw reduced ADF and NDF by up to 13-15.1% and 10.1-17.8%, respectively, compared to pure rice straw. In this feeding trial, a mixture of soybean meal and dried brewer's malt was used as basal diet with a CP of 19.6% to improve the low protein content of rice straw in cattle rations.

Feed intake

Rice straw was treated by fermentation with microbes BT4 and 4%DM of dried brewer's malt as additives showed improvement in dietary palatability as total DMI, DMI of BW, voluntary N intake, and CP intake all tended to be higher than the control. Total N intake and CP intake tend to increase from the FRSM30 to FRSM40, but they remain the stability in FRSM50 treatment. The DMI of BW ranged from the lowest 2.29 in control and the highest 2.45 in FRSM40 (Table 2).

Figure 1. Relationship of average daily gain (ADG) and unfermented/fermented rice straw in diet of cattle fed soybean meal and dried brewer's malt	Figure 2. Correlation of feed conversion rate and used microbial biomass in rice straw

Body weight gain

The average initial body weights among the treatment groups were not significantly different due to randomization and uniformity. The final body weights were also not significantly different, according to Table 3. However, the ADG curve had an R2 value of 0.99, indicating that the variation in weight gain explained by type of rice straw in the diet was substantial (see Figure 1). This reveal that the growth performance of cattle fed fermented rice straw was significantly increased compared to pure rice straw, leading to improved FCR of cattle fed fermented rice straw in the diet (Figure 2). When considering different microbes biomass used in fermented rice straw, no significant effect on ADG and FCR was found (Table 3).

Discussion

In developing countries, rice straw has traditionally been burned in the fields, leading to environmental pollution, or used sparingly as livestock feed due to its high dry matter content, low crude protein (4 to 4.7%), and low digestibility (Daniel et al 2019). Rice straw is typically used as a backup when there is a shortage of green fodder during the dry season or when there is limited cultivation area in households. Therefore, the objective of the experiment was to consider whether treating rice straw with microbes as feed would enhance productivity in cross-bred Sindhi compared to using pure rice straw.

Rice straw consists mainly of complex lignocellulose lead to low nutrient digestibility in rumen fermentation, hence rice straw require processes for pretreatment to enhance its utilization in cattle diet. In this study, rice straw treated with Lactobacillus spp. and Saccharomyces cerevisiae showed the main change in improving CP content while reducing acid detergent fiber (ADF) and neutral detergent fiber (NDF) compared to untreated rice straw. This positive impact is likely attributed to increasing the number of microbial cells by fermentation activities. The combination of Lactobacillus spp. and Saccharomyces cerevisiae was beneficial in degrading rice straw which is typically a low nutritional value feed source due to the slow and limited carbohydrate degradation of rice straw in the rumen. Yeast Saccharomyces cerevisiae could enhance the digestibility of DM and NDF when treated with alfalfa hay and coffee hulls. Additionally, yeast plays a role in consuming oxygen, creating a medium conducive to the growth of lactic acid bacteria (LAB). The lactic acid produced by LAB can be converted to propionate in the rumen (Cherdthong et al 2021; Phuong et al 2023), which serves as a precursor for glucose synthesis in cattle and reduces methane emissions (Astuti et al 2022). This study also incorporated a small amount of dried brewer's malt (4% DM) as a protein additive in the fermented rice straw. This addition further promoted fermentation efficiency by providing essential nutrients that compensate for the deficiencies present in raw rice straw (Abo-Donia et al 2021).

A positive outcome of this experiment was the increased palatability of cattle when fed the fermented rice straw diet, leading to a significant rise in total DMI, voluntary CP intake, DMI of BW, and subsequently ADG. Studies have shown that the growth performance of beef cattle was enhanced along with improved DM and CP consumption when fed fermented rice straw compared to unfermented one (Sukaryani and Mulyono 2019), enhanced digestibility and maintain milk composition were also found in dairy cows (Wang et al 2023). The hemicellulose hydrolytic action of Saccharomyces on rice straw during biotreatment was beneficial for the release of monosaccharide components within the fiber structure, as found in the experiment by Fonseca et al (2018), which contributed to the improvement of feed intake and nutrient utilization of fermented rice straw in cattle. In the current study, there was no significant difference in DM intake among fermented rice straw with varying levels of microbial biomass. However, a more favorable trend in CP intake was observed in the FRSM40 treatment. Additionally, the reintroduction of soybean meal into cattle feedlots of this study is recently noted due to the abundant supply resulting from the processing of soybean milk for human consumption in Vietnam. This is coupled with a decline in the availability of distilled by-products such as brewer's grain from beer factories due to changes in the needs of consumers. Soybean meal was considered a source of rumen escape protein for fattening cattle and increases dry matter intake and live weight gain (Nguyen and Preston 2021). Hence, combining it with rice straw would improve the utilization of rice straw and could maintain a positive ADG in the experiment. This aligns with the finding of Nazli et al (2018), who reported that incorporating rice straw at 40% in the basal diet of corn silage and PKC pellets still maintained a positive ADG.

Conclusions

In summary, cattle fed rice straw treated by microbial stater BT4 was improve total DMI, voluntary CP intake, ADG and FCR compared to pure rice straw. With the addition of rice straw/fermented rice straw up to 35% in basal diet including soybean meal and dried brewer’s malt, it maintained the weight gain of cattle from 452 to 607 g/day. Developing TMR rations from available by-products can help improve input costs in livestock farming as well as promote more effective use of rice straw, contributing to solving the problem of negative impacts on the environment.

Acknowledgments

We would like acknowledge Tran Trong Nhan, Huynh Kim Dat and Nguyen Khanh Hung, Dinh Huu Phuc, Nguyen Lai Quynh Nam for assistance with feed preparation. We also kindly acknowledge the support for this research from the AgriFoSe2030 project, SLU Global, Vice-Chancellor's Office, Agricultural Sciences for Global Development, Swedish University of Agriculture, Sweden.

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