Effect of urea treatment and preservation duration on chemical composition of rice straw offer for growing Sind crossbred cattle

Nguyen Thiet and Nguyen Trong Ngu¹

College of Rural Development, Can Tho University, Can Tho City, Vietnam
ntngu@ctu.edu.vn
¹ College of Agriculture, Can Tho University, Can Tho City, Vietnam

Abstract

This study was aimed to determine the effect of varying levels of urea treatment and preservation time on chemical composition of rice straw offer for growing beef cattle. First experiment was arranged with a completely randomized design with 04 treatments and 04 replicates. The treatments were U2: rice straw + 2% urea; U3) rice straw + 3% urea; U4: rice straw + 4% urea; U5: rice straw + 5% urea. Second experiment was arranged into a completely randomized design, consisting of three treatments and three replicates (3 animals/replicate). The treatments were control (C) 0.5 kg rice bran/100 kg body weight + natural grass ad libitum; U3: 0.5 kg rice bran/100 kg body weight + 1,5 kg natural grass/100 kg BW + 3% urea treated rice straw ad libitum; U5: 0.5 kg rice bran/100 kg body weight + 1,5 kg natural grass/100 kg BW + 5% urea treated rice straw ad libitum. The results from first experiment showed that there was not influence of urea treatment on DM and ADF contents. But CP level increased as urea added in rice straw increased (p<0.05). After 30 days’ incubation NDF and lignin levels were lower in U3, U4 and U5 as compared to U2 (p<0.05). Cattle supplemented with 3% or 5% urea treated rice straw did not affect on DMI and FCR, whereas improved final body weight and weight gain. It concluded that using 3% or 5% urea treated rice straw can replace up to 53.78% natural grass and improve animal performance.

Key words: beef cattle, performance, rice straw, urea

Introduction

According to the Department of Livestock Production beef cattle were from 677.873 heads in 2014 to 849.642 heads in 2019, which increased 1.25 times during 2014-2019 (GSO 2019). Rice straw is a major forage for ruminant in rice-producing areas. Rice straw can be treated in order to improve its nutritive value. Those treatments are designed to enhance feed intake and digestibility. Improving digestibility may be achieved through mechanical, chemical, heat and pressure treatments. Urea treatment is the easiest to apply. It can be done by smallholder farmers using plastic bags, with a 5% urea w/w solution and can increase digestibility by 18% (Van Soest 2006). Feeding rice straw to livestock reduces its environmental impact and makes the best use of rice as both an energy source and a protein provider. In short, rice straw has high indigestible fiber content and low protein and energy levels (Aquino et al 2019; Sarnklong et al 2010). They are common use as basal diet in ruminant. Additionally, intake capacity from animal is limited due to physical characteristics and low nutrition digestibility (Ravi et al 2019). Therefore, improvement of nutrition digestibility and intake are the main objectives when using rice straw provide for animal. The objectives of this study were to determine the effect of varying levels of urea treatment and preservation time on chemical composition of rice straw offer for growing beef cattle.

Materials and methods

Experiment 1: Effect of urea treatment and preservation duration on chemical composition of rice straw

Experimental design

The experiment was arranged with a completely randomized design, 4 treatments and 4 replicates. Samples were collected on days 1, 30, 60 and 90 after adding with urea. The treatments were as follows:

Treatment 1 (U2): rice straw + 2% urea

Treatment 2 (U3): rice straw + 3% urea

Treatment 3 (U4): rice straw + 4% urea

Treatment 4 (U5): rice straw + 5% urea

Urea treatment preparation

Dry rice straw was chopped into 7 to 10 cm long, then it was added with urea solution depending on the treatments. The mixtures were packed into polyethylene bags with a 50 kg capacity with air removed from inside the bags.

Sampling collection and analysis

The samples (400 g each bag) were collected on days 1, 30, 60, and 90 after adding with urea. All samples were dried in an oven at 65^oC until the weight was stabilized (24 hours), then analyzed for crude protein (CP), ash, and crude fiber (CF) contents according to AOAC (1990). Neutral detergent fiber (NDF), acid detergent fiber (ADF) and lignin were determined by the procedure of Van Soest et al (1991).

Experiment 2: Effect of urea treated rice straw on weight gain and FCR of Sind crossbred cattle

Experimental design

Twenty-seven growing cattle (Sind crossbred cattle), 11 months of age and 120.28±0.92 kg of body weight, were randomly selected and assigned to a completely randomized design with 3 treatments and 3 replicates (3 animals/replicate). The cattle were vaccinated against foot and mouth disease, de-wormed using Ivermectin before running the experiment. They were randomly allocated to treatments: control (C) 0.5 kg rice bran/100 kg body weight + natural grass ad libitum; U3: 0.5 kg rice bran/100 kg body weight + 1,5 kg natural grass/100 kg BW + 3% urea treated rice straw ad libitum; U5: 0.5 kg rice bran/100 kg body weight + 1,5 kg natural grass/100 kg BW + 5% urea treated rice straw ad libitum.

Urea treatment preparation

Dry rice straw was treated with 3% or 5% urea depending on the treatments. The solid urea was diluted in the water and sprayed on to the dry rice straw slowly, and incubated in plastic bags for 30 days before feeding. The chemical composition of feeds is presented in Table 1. Cattle were fed twice daily at 07:00 and 15:00 and had free access to water. All animals were kept in individual pens with cement floors. Animals were weighted at the beginning and the end of experiment, before morning feeding.

Data collection

Feed and feed refusal were recorded daily. At the end of the study, all samples were analyzed for dry matter (DM), ash, and crude protein (CP) according to AOAC (1990). All animals were weighed at the beginning of the experiment and once a month throughout the experiment period. Measurements were DM intake, body weight (BW), BW gain, and feed conversion ratio (FCR).

Photo 1. Rice straw was added with urea, packed into polyethylene bags and offered for growing crossbred Sind cattle

Statistical analysis

The data were subjected to analysis of variance using the General Linear Model procedure of Minitab software version 16.2.1. Tukey's pairwise comparisons (p<0.05) were applied to determine the differences between dietary treatments.

Results and discussion

Effect of urea treatment and preservation duration on chemical composition of rice straw

During 90 days, there were not influence of urea treatment on DM and ADF contents (Table 2; p>0.05) in this study. Similar findings were reported by previous studies (Trach and Tuan 2008; Fang et al 2012). But some studies found that urea treated rice straw decreased ADF content (Wanapat et al 2013). This study showed that urea treatment influenced the CP content of rice straw (Table 2, p<0.05). Adding from 2 to 5% in rice straw has increased CP level from 8.52% in U2 at day 1 to 13.94% in U5 at day 30. The increased CP level from urea treated rice straw was also reported by Pradhan et al (1996) and Gunun et al (2013). In contrast, from 30 to 60 days after incubation NDF and lignin levels decreased as urea levels increased (Table 2; p<0.05). The decrease in NDF content may be due to the reduction in hemicelluloses which was used by microorganism during fermentation (Wadhwa et al 2010) or the reduction in lignin content from present experiment. Similar results were reported by Sharma et al (2004) and Wanapat et al (2013). In short, urea treated rice straw can improve nutritive contents of rice straw by increasing CP content (U5 group) and decreasing NDF and lignin levels (U3, U4 and U5 groups) after 30 days’ incubation. Therefore, we prefer to 3% and 5% urea levels which will be added to dry rice straw and offered for growing cattle in second experiment.

Effect of urea treated rice straw on weight gain and FCR of Sind crossbred cattle

The result in current experiment showed that there was not influence urea treatment on DMI at first and third months. But cattle fed with 5% urea treated rice straw (U5 group) increased DMI as compared to other groups at second month from this study (Table 3; p<0.05). In principle, natural grass is more palatable than urea treated rice straw because it has high contents of indigestible fibers and anti-nutritional factors (silica and lignin). But this study found that cattle from urea treatment groups can replaced up to 53.78% natural grass (data not show) without negative effects on DMI. Chenost and Kayouli (1997) suggested that alkali agents can be absorbed into the cell wall and chemically break down the ester bonds between lignin and hemicellulose/cellulose and follow by making the structural fibers swollen. In addition, urea treatment also increased nutrients digestibility as suggested by previous studies (Gunun et al 2013; Wanapat et al 2013). These factors contribute to improve DMI in cattle fed with urea treated rice straw.

Cattle supplemented with urea treated rice straw with 3% (U3) or 5% (U5) were better final body weight, daily weight gain than those in the control (Table 4; p<0.05) or linear trends in improvement of live weight gain as the levels of treated rice straw increased (Figure 1, R² = 0.95). The improvement of BW or gain may be higher CP intake from urea treatment from this study or nitrogen from urea treatment could increase the activity of ruminal microorganism in degrading fibers of cell wall when energy was sufficient (Obara et al 1975) and nutrients digestibility (Gunun et al 2013; Wanapat et al 2013). Don Viet Nguyen and Lam Hoang Dang (2020) found that 2% urea treated fresh rice straw can be replaced from 33.33% (1/3) to 66.67% (2/3) green grass without the effects on final BW or gain in Sind crossbred cattle. But this study showed that 3% or 5% urea treated dry rice straw can replace up to 53.78% natural grass and improve final BW and gain. Although FCR did not differ among treatments (Table 4; p>0.05), but cattle fed with urea treatment were lower FCR than those as compared to control from 7.87% (U3) to 13.69% (U5). In addition, there was linear trend in improvement of FCR as the levels of treated rice straw increased (Figure 2, R² = 0.99). The FCR from this study was consistent to Don  and Dang (2020).

Figure 1. Effect of urea treatment on live weight gain in growing Sind crossbred cattle	Figure 2. Effect of urea treatment feed conversion ratio in growing Sind crossbred cattle

Conclusions

• Adding 3% or 5% urea to rice straw can improve nutritive contents of rice straw by increasing CP content and decreasing NDF and lignin levels after 30 days’ incubation.
  
  
• Cattle supplemented with urea treated rice straw with 3% (U3) or 5% (U5) can replace up to 53.78% natural grass without influence on daily DMI and FCR and improve final body weight, weight gain.

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