Citation of this paper

A study on effect of rice bran and urea level on fermentation characteristics of fresh cashew apple silage

La Thi Thanh Huyen, Nguyen Thanh Van and La Van Kinh

Institute of Animal Sciences for Southern Vietnam, Hiep Thang, Binh Thang, Binh Duong Province, Vietnam
bakinh4@gmail.com

Abstract

The study was carried out to determine the effects of rice bran and urea level on the fermentation characteristics of fresh cashew apple silage. The experiment was arranged in a 4 x 2 factorial design with eight treatments and three replications per treatment. The factors were ratio of fresh cashew apple and rice bran (on fresh matter basis) and urea levels. Fresh cashew apple (CS) and rice bran (RB) ratios were 100%CS+ 0% RB, 90%CS+ 10%RB, 80%CS+ 20% RB, 70%CS+ 30% RB. Urea factor was used at level of 0 and 2.5% based on fresh matter of mixture silage. The results of study showed that the increase of rice bran level in silage raised dry matter content of silage while crude protein content increased by adding 2.5% urea. The losses of dry matter and crude protei were less in treatments including rice bran. Silages supplemented with urea tended to be higher in pH. The pH of mixture silage of 90% cashew apple and 10% rice bran remained quite stable at 4.0 during 60 days of fermentation, and increased to 4.25 at day 90 of ensiling. The 100% cashew apple silage and mixture silage of 90% cashew apple and 10% rice bran tended to be higher in lactic acid and lower in butyric and acetic acids than the other silages. Mixed silage consisting of fresh cashew apple 90% and rice bran 10% could improve the fermentation quality as evidenced by higher lactic acid content, lower pH value and fewer nutrient losses.

Key words: acetic acid, butyric acid, crude protein loss, dry matter loss, lactic acid

Introduction

In developing countries, research on processing, preservation and usage of agricultural by-products as feed source of domestic animals, especially ruminants plays an important role. These feed sources are not only cheap and abundant; but also of potentially high nutritional value for livestock. The lack of feed also is solved during the adverse weather such as drought, and storms. In Vietnam, there have been many studies on processing methods and using of crop residues (Chinh B V et al 1992; Giang V D and Trach N X 2001).

Cashew (Anacardium Occidentalo L,) is widely grown in Vietnam in. In 2005, cashew trees were planted in about 328,000 ha with production of 323,000 tonnes of nuts. With an average cashew nut and apple ratio of 1:4.5 (Kinh L.V. et al 1997), the amount of cashew apple can be estimated 1,453,000 tonnes. After cashew nuts are harvested, a massive amount of cashew apple is discarded into the environment. Fresh cashew apple is rich in soluble carbohydrates, about 54.7% DM (Kinh L.V et al 1997), which is an available energy source for ruminants. Antony et al (2020) indicated that fresh cashew apple is rich in carbohydrates, minerals, vitamins, amino acids, carotenoids, phenolic compounds, organic acids and antioxidants. Limiting fastors are the short harvest season (March and April) and the fresh cashew apples having a low dry matter content leading to spoilage through uncontrolled fermentation. The question is how to process and preserve fresh cashew apples for a long time after harvest to feed ruminants in times of feed shortage. In addition, the crude protein content of fresh cashew fruit is very low. Therefore, it is necessary to supplement non protein nitrogen such as urea to increase the crude protein content, thereby improving the feed value.

The present study aimed to determine fermentation attributes of mixed silage prepared with fresh cashew apple, rice bran and urea.

Materials and methods

Location and duration

The experiment was carried out in Binh Phuoc province Vietnam from March to June 2009.

Experiment design

Fresh cashew apples, after separation of the nuts, were collected from farms in Binh Phuoc and chopped immediately into four pieces for each apple. These were mixed with rice bran and urea and packed tightly into plastic bags inside 3-liter jars. The jars were closed, sealed with adhesive tape and placed in dark room at ambient temperature (25–30°C).

The experiment was arranged in a 4 x 2 factorial design with eight treatments and three replications per treatment. Each jar was considered as an experimental unit. The factors were ratios (%) of fresh cashew apple (CS) and rice bran (RB) of: 100:0, 90:10, 80:20, 70:30 CS:RB. Urea was at levels of 0 and 2.5% based on fresh matter of silage. Four storage periods were: 0, 30, 60 and 90 days.

Chemical analysis of silages and components

The proximal composition of ingredients and silages was determined using AOAC (1990) procedures (Tables 1 and 2). Total sugars (TS) of the silage was obtained by the Somogyi method (McDonald P and Henderson A R 1964). The pH was determined with a glass electrode meter, on a 10g sample after shaking with 100ml of distilled water for an hour. Organic acids (lactic, acetic and butyric) were measured by using the LepperFlieg method (AOAC 1988).

Data analysis

The data were subjected to the General Linear Model (GLM) procedures of Minitab Software version 2019 according to a 4 × 2 factorial arrangements in a completely randomized design. The statistical model included rice bran and fresh cashew apple ratio, urea level and their interaction. Differences among treatments were contrasted by the Tukey’s multiple comparison test at p < 0.05.

Results and discussion

The very high content of soluble sugars was the major characteristic of the cashew apple (Table 1). As expected, the DM content of the silages increased linearly with addition of rice bran (Table 2) and was not affected by addition of urea.

Table 1. Chemical composition of cashew apple and rice bran before ensiling (% DM basis except DM which is on fresh basis)
	DM	CP	TS	CF	EE

Rice bran	89.9	11.8	3.56	9.01	11.9
Fresh cashew apple	15.3	11.2	58.8	4.58	1.23
DM: Dry matter, CP: Crude protein, TS: Total Sugar, CF: Crude fiber, EE: Extract ether

Table 2. Mean values of DM content of the samples of silage
	Days of ensiling
	0	30	60	90

Rice bran, %
0	15.8^d	13.9^d	12.5^d	11.3^d
10	21.9^c	20.2^c	19.7^c	18.9^c
20	31.3^b	29.2^b	28.0^b	25.5^b
30	37.6^c	36.0^a	34.6^a	31.9^a
p	<0.001	<0.001	<0.001	<0.001
Urea, %
0	26.3	24.4	23.6	21.9
2.5	27.0	25.3	23.8	21.9
p	0.225	0.157	0.631	0.903
^{a, b, c, d} Means in columns with different superscripts are different at p<0.05

The crude protein content of the silages increased by a factor of between 2 and 3 according to the duration of the ensiling period (Table 3). As expected, the crude protein content decreased with a linear trend as the proportion of rice bran was increased. Unfortunately, the degree to which the crude protein was converted to true protein during the ensiling process could not be ascertained but is a logical objective for future research.

Table 3. Effect of rice bran and urea level on crude protein content of cashew apple silage (% on DM basis)
	Days of ensiling
	0	30	60	90

Rice bean, %
0	27.8^a	20.7^a	18.5^a	11.6
10	22.8^b	18.6^ab	15.0^ab	13.3
20	21.7^bc	17.6^b	15.4^ab	12.5
30	19.8^c	15.1^c	13.2^b	11.9
p -value	0.001	0.001	0.009	0.187
Urea, %
0	10.9	10.1	9.09	8.34
2.5	35.2	26.0	22.0	16.3
p -value	0.001	0.001	0.001	0.001
^{a, b, c, d} Means in columns with different superscripts are different at p<0.05

Irrespective of the addition of rice bran, or urea, the sugar content of the silages decreased to close to zero with the onset of fermentation (Table 4).

Table 4. Effect of rice bran and urea level on total sugar content of cashew apple silage (% on DM basis
	Days of ensiling
	0	30	60	90

Rice bran, %
0	56.5^a	1.98	2.21	1.27
10	35.2^b	2.26	1.76	0.98
20	25.0^c	2.57	2.07	0.76
30	19.2^d	2.26	1.98	1.91
p -value	0.001	0.732	0.851	0.547
Urea, %
0	35.0	1.90	2.09	0.90
2.5	33.1	2.63	2.48	1.20
p -value	0.028	0.061	0.075	0.288
^{a, b, c, d} Means in columns with different superscripts are different at p<0.05

This abrupt decline of total sugar content from the onset of the ensiling process was similar to that observed by Kinh L.V. et al (1997) when fresh cashew apple was ensiled with poultry litter.

The pH decreased immediately to below 4.5 after the silages were prepared with a tendency for the pH values to be slightly higher according to the added percentage of rice bran and urea (Table 5).

Table 5. Mean values of pH during ensiling
	Days of ensiling
	0	14	21	30	60	90

Rice bran, %
0	4.26^b	3.97	4.01^b	4.36^b	4.76^b	6.06^a
10	4.29^b	4.03	4.07^b	4.33^b	4.53^b	5.00^b
20	4.44^b	4.11	4.17^ab	4.49^ab	4.67^b	6.21^a
30	5.09^a	4.18	4.33^a	4.72^a	5.17^a	6.36^a
p -value	0.001	0.137	0.022	0.002	0.002	0.001
Urea, %
0	4.48	4.00	4.08	4.25	4.48	5.19
2.5	4.56	4.15	4.20	4.71	5.09	6.62
p -value	0.176	0.044	0.124	0.001	0.001	0.001
^{a, b, c, d} Means in columns with different superscripts are different at p<0.05

After 30 days of ensiling, the percentage of organic acids in the silage increased from 0.8 – 1.3% to 3.0-4.0% as the level of rice bran was increased with tendencies for acid levels to be slightly higher when urea was included in the silage (Table 6). Lactic acid accounted for the greater part (>70%) of the organic acids produced during the ensiling process; the levels were not affected by addition of rice bran and/or urea to the silage.

Table 6. Organic acid profiles of cashew apple silage with different rice bran and urea level at day 30 of ensiling
Rice bran %	Urea %	Organic acids (% in DM)	Of which (%)			Score #
Rice bran %	Urea %	Organic acids (% in DM)	Acetic	Butyric	Lactic	Score #

0	0	0.80±0.05	21.4±1.99	2.64±0.57	74.2±0.89	87.0±10.1
0	2.5	1.30±0.22	11.6±1.45	7.46±0.81	78.3±0.88	82.0±11.3
10	0	2.81±0.35	20.9±1.56	1.19±0.66	75.2±0.78	89.0±11.6
10	2.5	3.24±0.37	21.8±2.78	4.01±0.55	73.5±0.94	83.0±9.80
20	0	3.09±0.42	25.9±2.34	2.31±0.43	70.3±0.93	85.0±9.70
20	2.5	3.07±0.41	26.0±2.89	12.4±0.32	60.5±0.51	67.0±7.20
30	0	3.45±0.34	18.1±2.66	5.41±0.78	74.5±0.64	84.0±6.40
30	2.5	4.04±0.48	25.5±3.12	4.37±0.56	68.6±0.72	82.0±9.40
# Score of silage based on BAPH (2010)

Conclusions

According to the study results, mixed silage consisting of fresh cashew apple of 90% and rice bran of 10% could improve the fermentation quality as evidenced by higher lactic acid content, lower pH value and nutrient losses.
The current study data are practical importance for evidences of combination of agricultural by-products to produce feedstuffs for ruminants year-round.

References

Antony A P, Kunhiraman S and Abdulhameed S 2020 Bioprocessing with cashew apple and its by-products. In Book: Valorisation of Agro-Industrial Residues – Volume II: Non-Biological Approaches: 83-106.

AOAC 1988 Official Methods of Chemical Analysis, 4^th edition. Association of Official Agricultural Chemists. Washington DC (4th edition)

AOAC 1990 Official methods of analysis of the AOAC, 15^th edition. Association of official analytical chemists. Arlington, VA, USA.

Chinh B V, Ly L V, Tao N H, Thin P V and Preston T R 1992 Ammoniated rice straw or untreated straw supplemented with a molasses-urea block for growing Sindhi x Local cattle in Vietnam. Livestock Research for Rural Development, Volume 4, Article #27 Retrieved July 5, 1992, from http://www.lrrd.org/lrrd4/3/chinh.htm

Giang V D and Trach N X 2001 Effect of treatment with lime water and / or urea on the chemical composition, feed intake on the degradability of rice straw. Proceeding of Workshop on Improved utilization of by-products in livestock production in Vietnam –NUFU project on March, 2001

Kinh L.V., Do V V and Phuong D D 1997 Chemical composition of cashew apple and cashew apple waste ensiled with poultry litter. Livestock Research for Rural Development, Volume 9, Article #6 Retrieved October 1, 1997, from http://www.lrrd.org/lrrd9/1/kinh91.htm

McDonald P and Henderson A R 1964 Determination of water-soluble carbohydraies in grass. Journal of Science of Food and Agriculture 15: 395-398.