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Article

Feed Intake and Growth Performance of Vietnamese Yellow Calves Fed Silages from Intercropped Maize–Soybean and Guinea Grass

by
Don V. Nguyen
1,2,*,
Beth Penrose
3,4,
Ngoc B. T. Tran
2,5,
Huyen T. T. Le
5,
Hong T. Trinh
6 and
Stephen Ives
7
1
School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia
2
Faculty of Animal Science, Vietnam National University of Agriculture, Hanoi 12406, Vietnam
3
Tasmanian Institute of Agriculture, University of Tasmania, Locked Bag 98, Hobart, TAS 7000, Australia
4
Research Institute for Northern Agriculture, Charles Darwin University, Darwin, NT 0909, Australia
5
National Institute of Animal Science, Hanoi 11913, Vietnam
6
Dien Bien Department of Agriculture and Rural Development, Dien Bien 32110, Vietnam
7
Tasmanian Institute of Agriculture, University of Tasmania, Locked Bag 1325, Newnham, TAS 7248, Australia
*
Author to whom correspondence should be addressed.
Ruminants 2024, 4(4), 602-612; https://doi.org/10.3390/ruminants4040041
Submission received: 14 September 2024 / Revised: 26 November 2024 / Accepted: 9 December 2024 / Published: 12 December 2024
(This article belongs to the Special Issue Feature Papers of Ruminants 2024–2025)
Browse Figure
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Simple Summary

Combining legumes with maize biomass or cultivated grass in silage offers a balanced source of carbohydrates and proteins, and can serve as a high-quality roughage during forage shortages. This study investigated the feed intake and growth responses of indigenous Yellow calves to diets with Guinea grass, Guinea grass–soybean, and maize–soybean silages. The results showed that replacing 30% of urea-treated rice straw with these silages significantly improved feed conversion ratios, total weight gain, and average daily gain in growing Yellow calves, although there were no significant effects on body conformation. These findings indicate that incorporating Guinea grass–soybean or maize–soybean silage into urea-treated rice straw diets can enhance growth in Yellow calves, supporting more sustainable mixed crop–livestock production systems.

Abstract

Combining soybeans with grass or biomass maize in silage holds promise in addressing the nutritional limitations of individual crops, providing a roughage with a good energy–protein balance. This study evaluated the effects of replacing urea-treated rice straw (UTRS) with silages made from intercropped maize–soybean and Guinea grass (GG) in calf diets on feed intake and growth performance. Sixteen native Yellow calves (130.7 ± 16.1 kg live weight and 12.8 ± 2.6 months old) were used; the experiment had a randomised complete block design with four dietary treatments: Treatment 1 (70% UTRS + 30% GG); Treatment 2 (40% UTRS + 30% GG + 30% Guinea grass silage); Treatment 3 (40% UTRS + 30% GG + 30% Guinea grass–soybean silage); and Treatment 4 (40% UTRS + 30% GG + 30% maize–soybean silage). The animals were fed 0.5 kg concentrate per 100 kg live weight daily, with unlimited access to forage and clean water, for 12 weeks after a two-week adaptation. The results indicate that silages containing soybean increased total weight gain and average daily gain (ADG) and decreased feed conversion ratio (FCR); however, silage replacements had no impact on dry matter intake and body conformation, suggesting that Guinea grass–soybean or maize–soybean silage can effectively enhance the ADG and decrease the FCR of growing calves fed UTRS-based diets.

1. Introduction

Yellow cattle are the predominant indigenous breed in Northwest Vietnam and are commonly raised both for beef and as a source of draught power [1]. As an indigenous breed, Yellow cattle are well adapted to the poor local feeding conditions and harsh climates and have a good reproductive capacity, but they have a low meat yield, with poor growth and a small body size [2]. In recent years, several genetic and nutritional studies have been conducted to improve those characteristics [2,3,4,5]. Both Nguyen et al. [4] and Dung et al. [5] stated that feeding protein–energy-balanced diets to Yellow cattle improved their general appearance, growth rate, carcass properties, and meat yield.
Small-scale Yellow cattle production in Northwest Vietnam has mainly relied on extensive grazing in forests and native pastures. Recently, many exotic forage species have been introduced and evaluated in traditional pasture areas of Vietnam to supplement the local feed source. The improved, higher-yielding varieties used for cut-and-carry production, such as elephant grass (Pennisetum purpureum) and Guinea grass (Megathyrsus maximus), were introduced in the last 20 years. In a trial conducted by Hue [6], Guinea grass achieved a yield of 74 tonnes dry matter per ha per year. However, the amount and (or) nutritional values of the forage vary greatly depending on season, grazing area, grazing intensity, grass species, fertiliser management, and focus of the small-scale farmer. Nguyen et al. [7] reported that, in winter or the dry season, natural and cultivated grasses only supply around 35–57% of the total forage demand. Consequently, supplemental feed including agricultural by-products from rice (Oryza sativa L.), maize (Zea mays L.) and cassava (Manihot esculenta Crantz) crops have been utilised to maintain ruminant nutrition [8]. In cold, dry winters, many livestock households in Northern Vietnam routinely provide their cattle with dry and/or urea-treated rice straw [7]. Many studies have tried to optimise the use of urea-treated rice straw as a substitute for fresh forage in cattle diets [4,9,10].
Maize is the predominant crop in the northwest region of Vietnam; in 2021, the largest cultivating area of maize in Vietnam was the Northern Midlands and mountains, with 414.4 thousand hectares, accounting for 45.9% of the country’s total maize-growing area [11]. Currently, maize is mainly grown for use as a grain in monocropping systems, and the vegetative parts of the plant are mainly left to dry and are then burnt. The monocropping maize systems deplete soil nitrogen reserves, reduce soil fertility, decrease soil pH and, when grown on steep slopes, increase soil erosion [12]. There is opportunity to intercrop the maize in these systems with a legume such as soybean (Glycine max L.) to replenish soil nitrogen, improve soil health, reduce soil erosion, and increase long-term productivity in intercropped systems [13,14]. Additionally, ensiling maize–soybean from the intercropped systems could provide a highly nutritious feed for cattle [15,16], which could be used in the winter/dry season feed gap.
Ensiling the vegetative soybean with maize biomass or cultivated grass could overcome the nutritional limitations of the individual crops. Soybean has a relatively small amount of fermentable sugars, and silage made of soybean only is a high-crude-protein (CP)-content feedstuff [17]. Vegetative soybean silage usually has a higher pH value compared to maize and maize–soybean mixtures [15,18]. As a result, proteins and amino acids are decomposed, leading to an unpleasant odor and the deterioration of silage [17,18]. Conversely, grass and maize silages have a low CP content [18,19]. Maize–soybean intercropping can also improve the soil’s biological and chemical properties, increase total biomass yield [20,21], and produce better quality silages compared to silages made of only grass, biomass maize, or soybean [16,18,22].
Generally, most recent studies have focused on silage characteristics, such as its microbial profile, nutritive values, and fermentation parameters [17,18,21]. Limited attention has been paid to the effects of the inclusion of maize–soybean silage on the responses of live animals, including effects on feed intake, digestibility, and growth performance. When Dorper × Santa Inês crossbred lambs were fed iso-nitrogenous (14% CP) and iso-neutral detergent fibre (16.5% NDF) diets, Bolson et al. [23] concluded that the maize–soybean intercropped silage increased the feed efficiency and growth of the lambs compared to monocultured soybean silage. Kang et al. [24] also reported that maize–soybean intercropped silage increased in vitro rumen fermentation, feed degradability, and milk quality of Holstein dairy cows; however, there is insufficient information available regarding the use of maize–soybean intercropping to make silage for cattle under small-scale production in Vietnam. Therefore, this study aimed to understand the impacts of incorporation of maize–soybean silage on growth performance of Yellow calves in comparison to other silages and fresh grass.

2. Materials and Methods

2.1. Silage and Rice Straw Preparation

In August 2021, three types of silage were prepared: Guinea grass, maize–soybean and soybean. Guinea grass was cut at 50 days old after its previous harvest. Maize–soybean was sown as an intercrop, while soybean was sown as a monocrop in May 2021, and both crops were simultaneously harvested at 90 days old. For the maize–soybean intercrop, soybean was sown in four rows with two rows of maize in between. Within the intercrop, maize was sown with 40 cm between rows whilst soybean was sown with 30 cm between rows. The distances between columns were 10 cm for soybean and 20 cm for maize. For sole-cropping soybean, row spacing was 40 cm, and the column spacing was 10 cm (Figure 1).
At 90 days of age, maize and soybean were at the seed-filling and 2/3 milk line stages, respectively. Guinea grass, maize, and soybean were cut and wilted on the field for 4–6 h to reduce moisture content. After wilting, they were chopped into 10–15 cm pieces and mixed according to the following formulations:
  • Guinea grass silage: 97% guinea grass + 2.5% cornmeal + 0.5% salt.
  • Guinea grass–soybean silage: 80% Guinea grass + 20% soybean.
  • Maize–soybean silage: 80% maize + 20% soybean.
The three silage mixtures were sealed in individual plastic bags (approximately 50 kg per bag). In the maize–soybean silage, the 4:1 (w/w) ratio reflects the approximate proportion of biomass maize and soybean yields harvested from the intercropped crop. The same percentage of soybean (20%) was used in the Guinea grass–soybean silage to facilitate direct comparison between the two silages. Urea-treated rice straw (UTRS) was also ensiled in August 2021. Dry rice straw was treated with 4% urea (as-fed basis) with the addition of 8 L clean water for every 10 kg dry rice straw and also sealed in individual plastic bags (approximate 40 kg per bag). All ensiled forages were anaerobically preserved and fed to cattle after at least four weeks of ensilage.

2.2. Experimental Design and Feed Compositions

The feeding trial was carried out in Dien Bien district, Dien Bien province, Vietnam from September to December 2021. Sixteen indigenous Yellow calves (130.7 ± 16.1 kg of LW, 12.8 ± 2.6 months old and balanced by sex) were used in the feeding trial. They were dewormed with Ivermectin (VIAMECTIN 25, Viavet Ltd., Hanoi, Vietnam) and immunised against foot-and-mouth disease before the experiment commenced.
The experiment followed a randomised complete block design. The calves were weighed and allocated to one of four blocks based on their LW. Subsequently, the four animals in each block were randomly assigned one of the four treatments below:
Treatment 1 (Control): 70% UTRS + 30% Guinea grass.
Treatment 2: 40% UTRS + 30% Guinea grass + 30% guinea grass silage.
Treatment 3: 40% UTRS + 30% Guinea grass + 30% guinea grass–soybean silage.
Treatment 4: 40% UTRS + 30% Guinea grass + 30% maize–soybean silage.
The experimental diets were formulated using the National Research Council feed standard system [25] to achieve an expected weight gain of 400–600 g per day. The calves were housed in separate pens and fed treatment diets individually for 14 weeks, which included a two-week adaptation period and a 12-week trial period. During the experiment, the calves were given ad libitum access to their allotted roughage treatment and clean drinking water, and were also given 0.5 kg of concentrate (as-fed basis) per 100 kg of LW per day at approximately 8.00 am before feeding roughage to ensure they received all the nutrients required for maintenance and growth. The ingredients of the concentrate mixture (as-fed basis) are displayed in Table 1. The amount of concentrate offered to individual animals was updated fortnightly based the change in their live weigh. Each roughage treatment was well mixed (as-fed basis) before being fed to the animals as a mixture.

2.3. Calculation of Feed Intake and Feed Analysis

Daily feed intake was calculated by weighing the offered feed and the residual feed. The concentrate mixture, ensiled mixtures, UTRS and Guinea grass were separately sampled on days 1, 42 and 84 of the 12-week trial period, and stored in a freezer at −20 °C until ready for feed analyses. At the end of the trial period, samples from each timepoint were dried at 65 °C in a fan-forced oven until their weight between two consecutive weighing times remained unchanged to ascertain the DM content. For each feed type, the three timepoint samples were pooled and then ground through a 1 mm screen using a CT 293 Cyclotec laboratory mill (Tecator, Höganäs, Sweden).
An elemental analyser (PE2400 Series II; Perkin-Elmer Corp., Waltham, MA, USA) was used to quantify total nitrogen content (N) for each feed type, which was then multiplied by 6.25 to determine CP content [26]. The samples were placed in a furnace for five hours at 550 °C to determine the total ash content according to the methods of AOAC [26]. An ANKOM XT15 fat/oil extractor (ANKOM Technology, Macedon, NY, USA) was used to quantify ether extract (EE). The neutral detergent fibre (NDF) and acid detergent fibre (ADF) content were quantified using an ANKOM 200 fibre analyser (ANKOM Technology, Macedon, NY, USA). Organic matter (OM) was computed as OM = 100 − Ash. Non-fibrous carbohydrate (NFC) was determined using equation NFC = 100 − (CP +NDF + EE + Ash) [27]. Total digestible nutrient (TDN) was computed utilising the equations established by Jayanegara et al. [28] TDN = 0.714CP + 1.594EE + 0.479NDF + 0.704NFC for forage and TDN = 0.885CP + 1.829EE + 0.323NDF + 0.883NFC for concentrate. Metabolisable energy (ME) was calculated by converting TDN to digestible energy (DE) = 0.01 × 4.4 × 4.185 × TDN), which was converted as ME = 0.82 × DE as per Nguyen et al. [4]. The concentrate ingredients and chemical compositions of feed used in the experiment are displayed in Table 1.

2.4. Measurements of Live Weight and Body Conformation

Animals were weighed fortnightly before morning feeding, by walking them over a calibrated Ruddweigh 200 electronic scale (Ruddweigh Electronic Scales, Guyra, NSW, Australia) with an increment of 100 g. Average daily gain was calculated as the total liveweight gain divided by the number of days on experimental feed. Feed conversion ratio (FCR) is an indicator of the efficiency with which an animal converts feed into body mass, and computed as the ratio of feed intake to live weight gain. The body conformation traits including chest girth, body length and wither height were also measured fortnightly using a plastic tape measure and a metal vernier equipped with two vertically sliding arms to record span. The detailed description of body measurements was provided by Nguyen et al. [4]. To maintain, accuracy, consistency and repeatability, the same researcher implemented all measurements throughout the experiment. During the measurements, the animals were restrained in a relaxed state with their four legs stabilised on flat ground and their head comfortably erect.

2.5. Statistical Analyses

The feed intake, ADG and FCR of each calf were calculated using linear regression, based on individual data collected from the start to the end of the feeding trial. Summary descriptive statistics, including means and standard errors of mean, were computed and carefully examined for any potential data entry errors. Version 16.2 of Minitab statistical software [29] was used to analyse all collected data. Analysis of variance (ANOVA) was employed to analyse the data through a general linear model, incorporating various forage mixtures as a fixed effect and blocks as a random effect, while dependent variables included growth traits, feed intake, and body measurements. Tukey’s probability pairwise comparison tests were applied to identify significant differences at the p < 0.05 threshold.

3. Results

3.1. Feed Intake

There were no significant differences in feed intake (as-fed basis) between the four treatments (p > 0.05; Table 2). Similarly, DMI and DMI per 100 kg LW were not influenced by the treatments (p > 0.05), with values ranging from 3.4 to 3.7 kgDM per day per head and from 2.36 to 2.57 kg, respectively. Replacing 30% UTRS with different silages had no significant effects on both CP and ME intakes (p > 0.05). Moreover, dietary treatments did not cause any significant variation (p > 0.05) in concentrate to forage ratios, ranging from 0.21 to 0.28.

3.2. Live Weight Gain and Conversion Ratio

Calves fed diets containing Guinea grass–soybean silage and maize–soybean silage (treatments 3 and 4, respectively) had considerably higher total weight gain (p = 0.035) than those fed the control and Guinea grass silage diets (treatments 1 and 2, respectively) (Table 3). No significant differences in total weight gain were observed between the two groups fed diets without soybean (treatments 1 and 2), or between the two groups fed soybean-containing diets (treatments 3 and 4) (p > 0.05). Similarly, significant differences (p = 0.035) in ADG were observed between the calves fed soybean-containing diets (0.38 for Treatment 3 and 0.37 kg per day for Treatment 4) and those that received diets without soybean (0.32 kg per day for treatments 1 and 2). Average daily gain was similar between treatments 1 and 2, or between treatments 3 and 4 (p > 0.05). The best feed conversion ratios (FCR) were observed from the calves fed the soybean-containing diets (9.3 and 9.6 in treatments 3 and 4, respectively). These ratios were substantially better (p < 0.05) compared to the FCR observed in Treatment 1 (11.5).

3.3. Body Conformation Traits

The initial and final body conformation traits (chest girth, body length and wither height) among treatments did not significantly differ (p > 0.05). Similarly, dietary treatment did not cause any significant change (p > 0.05) in body measurements (Table 4).

4. Discussion

The results illustrate that although no significant differences were detected in DM, CP and ME intakes for the native Yellow calves fed the different dietary treatments, the inclusion of vegetative soybean in silages enhanced ADG, resulting in greater overall live weight gain. The higher ADG of the animals fed diets containing Guinea grass–soybean silage or maize–soybean silage might be in part due to the higher rumen degradability of soybean-containing silage, which could stimulate microbial growth and nutrient digestibility. Urea, a non-protein nitrogen source, is widely utilised as a substitute for feed protein in ruminant diets due to its cost effectiveness [30]. In the absence of a rumen-protected coating, however, urea may be inadequately utilised as a nitrogen source for microbial protein synthesis because it is rapidly hydrolysed to ammonia by bacterial ureases in the rumen and it often exceeds the use capacity by rumen bacteria with the surplus being absorbed through the rumen wall into the blood [31]. This can reduce the availability of protein in the rumen, which then negatively affects the protein syntheses of the bacterial community.
While UTRS boosts the overall CP percentage, it does not provide the same nutritional value as true protein sources found in other forages [32]. Dewhurst and Newbold [33] concluded that ammonia nitrogen concentration alone does not fully explain the effects of degradable protein on microbial growth. They emphasised that rapid growth of rumen bacteria is supported by true protein sources, such as peptides and amino acids. Based on the effects on fibre digestion, Calsamiglia et al. [34] highlighted that true proteins are essential for proper rumen function, including enhanced fibre digestion. Furthermore, Weimer [35] pointed out that branched-chain volatile fatty acids, which are the primary products of peptide and amino acid fermentation, serve as an important nutrient source for cellulolytic and hemicellulolytic bacteria. Aquino et al. [36] also affirmed that the digestibility of the protein in UTRS remains lower compared to other forages and this can limit the efficiency of protein utilisation by ruminants. When mixing vegetative soybean with corn stover at various ratios, Cheng et al. [37] concluded that increased vegetative soybean levels resulted in an enhanced nutritive value of the silage, demonstrated by increased CP and ME values. This trend is consistent with the present study when comparing those values between Guinea grass silage and Guinea grass–soybean silage. Similarly, Gandra et al. [38] reported that Jersey heifers fed diets containing maize–soybean silage (either 3:1 or 1:1) had higher digestibility of DM, organic matter, CP, and NDF than those on a diet containing maize silage.
The daily feed intake of the animals in this study were within the range recommended by Kearl [39], who found that a 100–200 kg beef cow would need to consume DMI of approximately 2.3–2.8% of their liveweight to achieve a 0.25–0.50 kg weight gain per day. Our findings align with those reported by Dung et al. [5] whose young male Yellow cattle increased 0.51 kg per day when consuming DMI at 2.7% of their liveweight. The smallest feed conversion ratio (9.3) was observed in the animals fed a diet containing Guinea grass-soybean silage, the observation was comparable to that found by Nguyen et al. [4] and Vu et al. [40] when feeding native Yellow and Sindhi x Yellow crossed cattle, respectively. Therefore, our findings align with previous studies suggesting that the addition of legume and sorghum mixed silage in diets increases growth performance of beef cattle [41,42]. Both Song et al. [21] and Zeng et al. [15] stated the combination of maize and soybeans in silage offers a good balance of carbohydrates and proteins, which is beneficial for ruminant production as a reliable source of high-quality roughage during periods when fresh forage is limited or unavailable.
The findings in the present study support the development of management strategies aimed at achieving more sustainable mixed-crop livestock production systems. Incorporating legumes such as soybean in maize production systems could lead to soil benefits including improved nitrogen cycling and fertility, and reduced erosion, especially on steep slopes [14,43]. Furthermore, maize–soybean intercropping could disrupt pest lifecycles and reduce plant pathogens and disease spread, leading to healthier crops and increased yields [44]. Incorporating legumes into agricultural systems offers practical, cost-effective and environmentally sustainable methods for the crop-livestock sustainable agriculture production by reducing reliance on external inputs while enhancing soil nutrient levels, maintaining availability of good forage for ruminant production.
There are some limitations in research and extension services that provide region-specific guidance on best practices for maize–soybean intercropping and silage making [15]. In Vietnam, while numerous agronomic studies have optimised spatial arrangements and planting densities to maximise biomass yield, control weeds, and reduce pesticide use [12,45,46], investigations into silage fermentation characteristics, ruminal digestibility, and the biochemical responses of animals to intercropped maize–soybean silage remain insufficient. Additionally, resource constraints have led to small sample sizes in various studies, including the current one, potentially compromising the validity of their findings [47,48]. Extension services, essential for translating scientific knowledge into practical applications and improving mixed crop-livestock systems, are also underdeveloped in remote areas of Vietnam [49,50]. Consequently, farmers, particularly small-scale producers, often lack training and knowledge in production costs, resource management, pest control, ensiling techniques, and dietary silage inclusion.
To maximise the potential benefits of silage made from maize–soybean intercrop-ping, future research should employ larger sample sizes to validate findings and provide more robust conclusions. In addition, it is important to investigate other factors influencing the characteristics and quality of maize–soybean silage, and the biochemical responses, health and productivity of animals fed the silage. Substantially expanding the extension network and enhancing extension agents’ knowledge and skills are essential to making extension services more effective and responsive, ultimately benefiting farmers and communities. Finally, comprehensive economic analyses are required to evaluate the cost–benefit ratio of maize–soybean silage systems and their impact on farm profitability.

5. Conclusions

The feed conversion ratio, total weight gain and average daily gain of growing Yellow calves were significantly improved by substituting 30% urea-treated rice straw with Guinea grass–soybean silage or maize–soybean silage; however, the silage substitution had no considerable effect on feed intake and body conformation traits. It is therefore recommended that replacing 30% Guinea grass–soybean silage or 30% maize–soybean silage in urea-treated rice straw-based diets of calves over an 84-day feeding period could represent an effective strategy to enhance average daily gain and feed conversion ratio. Furthermore, maize–soybean intercropping for silage could deliver environmental co-benefits such as reducing fertiliser requirements and improving soil health. Future research should include a larger number of animals to provide more robust findings and focus on improving intercropped silage quality, ruminant responses, extension services and conducting economic analyses to assess profitability.

Author Contributions

Conceptualization, D.V.N., N.B.T.T., H.T.T.L. and S.I.; methodology, D.V.N., N.B.T.T., H.T.T.L., H.T.T. and S.I.; formal analysis, D.V.N., B.P. and S.I.; investigation, D.V.N., N.B.T.T. and H.T.T.; writing—original draft preparation, D.V.N.; writing—review and editing, D.V.N., B.P., N.B.T.T., H.T.T.L. and S.I.; visualization, D.V.N.; supervision, H.T.T.L., B.P. and S.I.; project administration, H.T.T.L. and S.I.; funding acquisition, H.T.T.L. and S.I. All authors have read and agreed to the published version of the manuscript.

Funding

The research was financially supported by the Australian Centre for International Agricultural Research (ACIAR, http://aciar.gov.au/, accessed on 18 November 2024) through LPS/2015/037: “Intensification of beef cattle production in upland cropping systems in Northwest Vietnam” and SMCN/2014/049: “Improving maize-based farming systems on sloping lands in Vietnam and Laos”.

Institutional Review Board Statement

The welfare of all experimental animals was maintained in compliance with the 2013 Australian Code of Practice for the Care and Use of Animals for Scientific Purposes. All procedures were approved by the University of Tasmania Animal Ethics Committee (Permit No. A0017801).

Informed Consent Statement

Not applicable.

Data Availability Statement

Dataset available on request from the authors.

Acknowledgments

We are grateful to Provincial Extension Centre for Livestock Breeds and Crop Varieties, Dien Bien, Vietnam for their cooperation, experimental forage and facility supplies. We acknowledge Fiona Brodribb from University of Tasmania, Australia for her assistance in English editing and proofreading.

Conflicts of Interest

The authors declare no conflicts of interest.

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Ruminants 04 00041 g001
Figure 1. Row and column spacings for (a) intercropped maize–soybean and (b) monocropped soybean.
Figure 1. Row and column spacings for (a) intercropped maize–soybean and (b) monocropped soybean.
Ruminants 04 00041 g001
Table 1. Concentrate ingredients and feed chemical compositions.
Table 1. Concentrate ingredients and feed chemical compositions.
ItemConcentrateUrea-Treated Rice StrawFresh Guinea GrassGuinea Grass SilageGuinea Grass–Soybean SilageMaize–Soybean Silage
Ingredient (g per kg) (as-fed basis)
Corn flour595
Rice bran260
Soybean140
Premix5
Chemical composition
Dry matter (DM) (%)88.642.319.332.030.329.2
Organic matter (%DM)96.086.688.587.487.294.4
Crude protein (%DM)12.38.36.15.97.57.9
Ether extract (%DM)6.52.12.62.73.23.3
Crude fibre (%DM)10.829.830.638.235.726.9
Neutral detergent fibre (%DM)17.768.949.348.649.753.0
Acid detergent fibre (%DM)6.137.628.424.226.324.1
Total ash (%DM)4.013.411.512.712.95.6
Non-fibrous carbohydrate (%DM)59.57.330.530.125.728.2
Total digestible nutrient81.047.453.652.053.958.2
Digestible energy (MJ·kg−1 DM)14.98.79.99.49.910.7
Metabolisable energy (MJ·kg−1 DM)12.27.28.07.68.28.7
Premix includes vitamin A (4100.000 IU·kg−1), vitamin D3 (350.000 IU·kg−1), vitamin E (8 g·kg−1), vitamin B1 (850 mg·kg−1), vitamin B2 (1.6 g·kg−1), vitamin B6 (1.7 g·kg−1), vitamin B12 (6 mg·kg−1), vitamin K3 (350 mg·kg−1), niacin (12 g·kg−1), folic acid (250 mg·kg−1), biotin (16 mg·kg−1), iron (30 g·kg−1), copper (30 g·kg−1), manganese (13 g·kg−1), and other minerals (Zn, Se, I, Co) (380 mg·kg−1).
Table 2. Daily feed intake.
Table 2. Daily feed intake.
Treatment 1Treatment 2Treatment 3Treatment 4SEMp
(n = 4)(n = 4)(n = 4)(n = 4)
As-fed basis
Concentrate (kg)0.680.690.750.660.020.878
Forage (kg)9.09.09.710.10.370.231
Total intake (kg)9.79.710.410.80.380.238
Dry matter basis
Concentrate (kg)0.600.610.660.590.020.960
Forage (kg)3.12.72.93.00.110.875
DMI (kg)3.73.43.63.60.120.889
DMI/100 kg LW (kg)2.572.402.362.400.080.447
Daily CP intake (kg)0.310.260.290.300.010.933
Daily ME intake (MJ)30.228.430.330.61.000.705
Concentrate to forage ratio0.210.280.270.210.010.866
Treatment 1 = 70% urea-treated rice straw (UTRS) + 30% Guinea grass; Treatment 2 = 40% UTRS + 30% Guinea grass + 30% Guinea grass silage; Treatment 3 = 40% UTRS + 30% Guinea grass + 30% Guinea grass–soybean silage; Treatment 4 = 40% UTRS + 30% Guinea grass + 30% maize–soybean silage; ADG = average daily gain; CP = crude protein; DMI = dry matter intake; LW = live weight; ME = metabolisable energy; SEM = standard error of the mean.
Table 3. Live weight gain and feed conversion ratio of experimental animals.
Table 3. Live weight gain and feed conversion ratio of experimental animals.
Treatment 1Treatment 2Treatment 3Treatment 4SEMp
(n = 4)(n = 4)(n = 4)(n = 4)
Initial LW (kg)130.3125.8134.4132.55.10.954
Final LW (kg)157.5152.5166.3163.96.60.856
Total weight gain (kg)27.3 a26.8 a31.9 b31.4 b0.90.035
ADG (kg per day)0.32 a0.32 a0.38 b0.37 b0.010.035
Feed conversion ratio (kg DMI per kg ADG)11.5 a10.4 ab9.3 c9.6 bc0.350.047
Treatment 1 = 70% urea-treated rice straw (UTRS) + 30% Guinea grass; Treatment 2 = 40% UTRS + 30% Guinea grass + 30% Guinea grass silage; Treatment 3 = 40% UTRS + 30% Guinea grass + 30% Guinea grass–soybean silage; Treatment 4 = 40% UTRS + 30% Guinea grass + 30% maize–soybean silage; LW = live weight; ADG = average daily gain; DMI = dry matter intake; SEM = standard error of the mean. Means bearing distinct superscript letters in the same row significantly differ (p < 0.05).
Table 4. Body conformation measurements.
Table 4. Body conformation measurements.
Treatment 1Treatment 2Treatment 3Treatment 4SEMp
(n = 4)(n = 4)(n = 4)(n = 4)
InitialChest girth120.5117.0121.0122.01.80.813
Body length112.0110.3108.0114.33.00.917
Withers height99.5101.3101.8101.31.40.954
FinalChest girth 131.0129.3132.3131.82.10.971
Body length128.3120.3129.0126.53.00.784
Withers height108.8106.0107.3106.51.50.931
ChangeChest girth 10.512.311.39.81.00.870
Body length16.310.021.012.31.70.096
Withers height9.34.85.55.00.80.179
Treatment 1 = 70% urea-treated rice straw (UTRS) + 30% Guinea grass; Treatment 2 = 40% UTRS + 30% Guinea grass + 30% Guinea grass silage; Treatment 3 = 40% UTRS + 30% Guinea grass + 30% guinea grass–soybean silage; Treatment 4 = 40% UTRS + 30% Guinea grass + 30% maize–soybean silage; SEM = standard error of the mean.
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MDPI and ACS Style

Nguyen, D.V.; Penrose, B.; Tran, N.B.T.; Le, H.T.T.; Trinh, H.T.; Ives, S. Feed Intake and Growth Performance of Vietnamese Yellow Calves Fed Silages from Intercropped Maize–Soybean and Guinea Grass. Ruminants 2024, 4, 602-612. https://doi.org/10.3390/ruminants4040041

AMA Style

Nguyen DV, Penrose B, Tran NBT, Le HTT, Trinh HT, Ives S. Feed Intake and Growth Performance of Vietnamese Yellow Calves Fed Silages from Intercropped Maize–Soybean and Guinea Grass. Ruminants. 2024; 4(4):602-612. https://doi.org/10.3390/ruminants4040041

Chicago/Turabian Style

Nguyen, Don V., Beth Penrose, Ngoc B. T. Tran, Huyen T. T. Le, Hong T. Trinh, and Stephen Ives. 2024. "Feed Intake and Growth Performance of Vietnamese Yellow Calves Fed Silages from Intercropped Maize–Soybean and Guinea Grass" Ruminants 4, no. 4: 602-612. https://doi.org/10.3390/ruminants4040041

APA Style

Nguyen, D. V., Penrose, B., Tran, N. B. T., Le, H. T. T., Trinh, H. T., & Ives, S. (2024). Feed Intake and Growth Performance of Vietnamese Yellow Calves Fed Silages from Intercropped Maize–Soybean and Guinea Grass. Ruminants, 4(4), 602-612. https://doi.org/10.3390/ruminants4040041

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