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Passion fruit (Passiflora edulis) peel as feed for ruminants in Vietnam: Quantification, chemical composition and posibility to make silage

Tran Hiep, Bui Quang Tuan, Le Viet Phuong, Nguyen Hung Sơn, Le Van Ha¹ and Nguyen Xuan Trach

Vietnam National University of Agriculture, Hanoi, Vietnam
nxtrach@vnua.edu.vn
ORCID: 0000 -0001-67681590
¹ Tay Bac University, Son La, Vietnam

Abstract

A step-wise study was caried out to primarily assess posibility of using passion fruit peel as feed for ruminants. First, passion fruit peel was quantified based on the known quantity of fresh fruits by means of linear regression. Chemical composition of passion fruit peel as well as added materials were analyzed to provide a basis for design of silage formulae. There were 5 silage formulae consisting of passion fruit peel as the main component in different combinations with dry maize cobs, dry sugarcane bagasse, and molasses. The mixed materials for each formula were compacted layer by layer in 9 plastic vases of 10 liters each. Quality of the silage was evaluated after 30, 60, and 90 days of ensiling. It was shown that the passion fruit peel can be predicted with a high accuracy from the quantity of fruits. It had a low dry matter content (DM) but with relatively high protein content (14.1% in DM). The silages made from passion fruit peel alone or with 2% molasses had lower qualities with difficulty to preserve for a long time due to low DM content. Adding 20% of dry maize cobs and/or sugarcane bagasse together with 5% molasses to passion fruit peel increased dry matter content to an appropriate level (25.7-33.5%), ensuring good quality of the silage made and prolonged preservation. Therefore, the formula of 75% passion fruit peel, 20% dry maize cobs, 5% molasses and the formula of 75% passion fruit peel, 10% dry maize cobs, 10% bagasse, 5% molasses are considered suitable for making silage and selected for later step investigation in an on-farm feeding trial on dairy cattle.

Keywords: byproduct, cattle, feeding, environmental pollution

Introduction

Passion fruit is a new fruit tree in Vietnam and popularly planted in the central highland provinces of Dac Nong, Gia Lai, Lam Dong, Kon Tum, and in the northern mountainous province of Son La, which have fertile soil and perfect weather conditions for planting this fruit tree. Vietnam silagesnow has larger scale passion fruit plantations as well as processing companies, generating high economic income for local farmers and the companies. Passion fruit from Vietnam has been released to numerous countries around the world with numerous products of large quantity and high quality. However, the processing of passion fruits leaves large amounts of peel as a waste, which can cause serious environmental problems. Nevertheless, several previous studies have shown that passion fruit peel, either fresh or dehydrated, can be used as a good feed for ruminants (Alves et al 2015; Azevêdo et al 2012; Santos-Cruz et al 2013; Sena et al 2015). Therefore, making use of this byproduct as feed would help achieve double objectives, ie. better utilisation of a locally available cheep feed resource and environmental protection. The matter is that fresh passion fruit peel is too high in water content, making it difficult and expensive to dry for preservation. So far little information has been reported on making silage from this by product. Therefore, the present study was designed to test possibility of making silage from fresh passion fruit peel for use as feed.

Materials and methods

Materials

The main material for study was fresh passion fruit peel collected from a fruit processing campany in the mointainous province of Son La, North West Vietnam. In addition, dry maize cobs from a maize processing company, dry sugarcane bagases and molasses from a sugar factory were used as high dry matter content byproducts in combination with passion fruit peel of low dry matter content in silage making. Molasses was also used as easily fermentable supplement for passion fruit silage making.

Quantification of passion fruit peel as a byproduct

Passion fruits were collected from 50 households to determine the weight of peel in comparision with the whole passion fruit. Based on the measured data a prediction regression equation was developed to predict the amount of peel as a function of the amount of fruits. Total passion fruit peel in a locality was estimated from the production of passion fruits using the prediction regression equation.

Making silage of passion fruit peel

Passion fruit peel was made silage in 5 different combinations (SL) with the other ingredients: SL1 (only passion fruit peel), SL2 (98% passion fruit peel + 2% mollases); SL3 (75% passion fruit peel + 20% dry maize cobs + 5% mollases), SL4 (75% passion fruit peel + 20% dry sugarcane bagases + 5% mollases), SL5 (75% passion fruit peal + 10% dry maize cobs + 10% dry sugarcane bagases + 5% mollases). All the mentioned percentages were based on the weight of the ingredients as they were at the time of making silage. The passion fruit peel was chopped into 1-2 cm in length. The dry maize cobs were ground through a 0.5 cm sieve. The dry sugarcane bagasse was already fine from the factory. All the ingredients were well mixed together according to the silage formulae and then compacted layer by layer in 9 plastic vases of 10 liters each to make 3 replicates for each ensiling period of 30, 60 or 90 days. Samples of the silages were collected at the end of each ensiling period for quality evaluation based on colour, smell, mould, pH and chemical composition.

Chemical analysis

All the byproducts collected were subjected to predrying at 60ºC for 72 hours and ground in knife mill with 1mm pore diameter, for subsequent analysis of DM, crude protein (CP), crude fiber (CF), ether extract (EE), Ca, P, and total ash according to the respective methods of the AOAC (1990).

Samples of silage were tested for pH according to Hartley and Jones (1978).The organic acids were analysed with HPLC (high performance liquid chromatography). NH₃ -N was analysed with the Kjeldahl method using MgO to distill the NH₃ out of the sample solution. NDF, ADF and ADL were determined according to Van Soest and Robertson (1985).

Statistical analysis

The regression equations to predict the fresh and dry matter weights of peel from the whole fresh passion fruit weight were developed based on the partial least squares procedure in Minitab 16.0. Data on silage quality were statistically analysed with One-Way ANOVA, in which the sources of variation were silage formulae and error term. Tukey’s pairwise comparision was used to find significant differences between means at p <0.05.

Results and discussion

Quantification of passion fruit peel

As can be seen in Table 1, fresh peel as a by-product accounted for a very high proportion in the whole fruit (41.1%), even higher than the fruit content as the main part of passion fruit (38.2%). Seed as another byproduct of the passion fruit was relatively high (19.0%) in the whole fruit. The results indicate that residues (peel and seed) accounted for a large percentage of the passion fruit (more than 60%) and should be utilised as animal feed, avoiding environmental problems.

Table 1. Weights of the passion fruit and its components
	n	Mean	SD	Min	Max

Whole fruit (g)	50	62.36	8.39	39.20	80.70
Fresh peel:
Weight (g)	50	25.39	3.73	18.80	36.70
Percentage in fruit (%)	50	41.07	6.01	33.50	67.34
Fruit content
Weight (g)	50	23.96	4.90	10.50	30.80
Percentage in fruit	50	38.21	5.20	19.37	48.32
Seed
Weight (g)	50	11.92	2.73	4.20	17.20
Percentage in fruit	50	18.96	3.03	10.40	24.71
Processing loss (%)	50	1.76	3.25	0.00	19.81

It was possible to predict the weights of fresh matter and dry matter of passion fruit peel from the known weight of the fresh fruits based on regression equations as developed from the collected data (Figures 1 and 2).


Figure 1. Regression of fresh passion fruit peel weight on the fresh fruit weight	Figure 2. Regression of passion fruit peel dry matter on the fresh fruit weight

Chemical composition

With relatively high contents of crude protein (14.1%) and N-free extract (47.5%) (Table 2), fresh passion fruit peel could be used as an easily fermentable feed for ruminants.Alves et al (2015) and Almeida et al (2019) reported that the protein content of passion fruit peel and seed was 10.2% and 12% DM. Cruz et al (2011) and Silva et al (2015) showed that protein content of only passion fruit peel was 13.4% and 15.29% DM. However, Janaina et al (2015) and Oliveira et al (2016) reported that the passion peel ranged from 6,80 to 8,64% DM. The present result was higher than that reported by Janaina et al (2015) and Oliveira et al (2016) but comparable with that reported by Cruz et al (2011) and Silva et al (2015).

The low DM content (16.4%) would make it difficult for fresh passion fruit peel to be preserved as silage. Therefore, combinations of fresh passion fruit peel with the high dry matter ingredients would make the mixtures have DM contents better suitable for making silage (25-35%) as shown in Table 2.

Table 2. Chemical cmpositions of silage ingredients
Ingredients	DM %	Chemical composition (% in DM)
Ingredients	DM %	CP	CF	EE	Asch	NFE	NDF	ADF	ADL

Passion fruit peel	16.4	14.1	29.8	0.98	7.55	47.5	55.4	35.9	10.7
Maize cobs	91.9	2.57	35.3	0.22	1.62	60.3	79.1	42.7	4.55
Sugarcane bagasse	64.8	2.70	36.7	0.20	2.06	58.3	78.2	55.1	10.3
Molasses	78.0	11.0	0	0	7.50	81.5	0	0	0
N.B. DM: Dry matter, CP: Crude protein, CF: Crude fiber, EE: Ether extract, NFE: Nitrogen free extract, NDF: Neutral detergent fiber, ADF: Acid detergent fiber, ADL: Acid detergent lignin

Quality of passion fruit peel-based silage

Visible parameters

After 30 days of ensiling all the silages had a slight yellow colour with a soft texture, a slight sour smell, without any mould (Table 3). After 60 and 90 days, the silages became darker with some mould on one third of the surface. Especially, the silage made from fresh passion fruit peel only (SL1) or that from fresh passion fruit peel plus 2% molasses (SL2) became sour, very soft and slightly smashed, indicating a low quality. This phenomenon may have been due to low DM contents of the mixtures as shown in Table 3. The silages made from fresh passion fruit peel plus 20% dry sugarcane bagasse and/or dry maize cobs together with 5% molasses showed better results with longer times of ensiling.

Table 3. Visible parameters of silages after different ensiling times
Silage	Parameter	Ensiling time (days)
Silage	Parameter	30	60	90

SL1	Colour	Slight yellow	Brown yellow	Dark yellow
	Smell	Sour	Sour	Sour
	Texture	Soft	Soft, slightly smashed	Soft, slightly smashed
	Mould	-	+	++

SL2	Colour	Slight yellow	Brown yellow	Dark yellow
	Smell	Slight sour	Sour	Sour
	Texture	Soft	Soft, slightly smashed	Soft, slightly smashed
	Mould	-	+	+

SL3	Colour	Slight yellow	Brown yellow	Brown yellow
	Smell	Slight sour	Sour	Sour
	Texture	Soft	Soft	Soft
	Mould	-	+	+

SL4	Colour	Slight yellow	Brown yellow	Brown yellow
	Smell	Slight sour	Sour	Sour
	Texture	Soft	Soft	Soft
	Mould	-	+	+

SL5	Colour	Slight yellow	Brown yellow	Brown yellow
	Smell	Slight sour	Sour	Sour
	Texture	Soft	Soft	Soft
	Mould	-	+	+
N.B. SL1: only passion fruit peel, SL2: 98% passion fruit peel + 2% mollases, SL3: 75% passion fruit peel + 20% dry maize cobs + 5% mollases, SL4: 75% passion fruit peel + 20% dry sugarcane bagases + 5% mollases, SL5 (75% passion fruit peal + 10% dry maize cobs + 10% dry sugarcane bagases + 5% mollases. Mould: - : no mould; + : mould on 1/3 surface area; ++ : mould on 2/3 surface area; +++ : mould on all surface area

Changes in pH and chemical composition of silages

After 30 days the pH value of all the silages droped dramatically below 4.2 and maintained stable until 90 days of ensiling (Figure 3), indicating very good fermentation during the first month. Even without addition of any easily fermentable supplement (SL1), passion fruit peel could be made into silage and kept for a long time.

N.B. SL1: only passion fruit peel, SL2: 98% passion fruit peel + 2% mollases, SL3: 75% passion fruit peel + 20% dry maize
cobs + 5% mollases, SL4: 75% passion fruit peel + 20% dry sugarcane bagases + 5% mollases, SL5 (75% passion
fruit peal + 10% dry maize cobs + 10% dry sugarcane bagases + 5% mollases.

Figure 3. Changes in pH of silages after different ensiling times

Low DM contents of SL1 and SL2 (14.6% and 16.2%, respectively) (Table 4), should have resulted in lower quality of silage (Muck 1988). Adding dry sugarcane bagasse and/or dry maize cobs increased the DM content in SL3, SL4 and SL5 up to a level better for anaerobic fermentation. As a result, SL3, SL4 and SL5 had better organic acid profiles with higher proportions of lactic acid compared to SL1 and SL2. It could therefore be said that fresh passion fruit peel in combination with 20% dry maize cobs or 10% dry maize cobs and 10% dry sugarcane bagasse together with 5% molasses can be made into good silage based on the pH values and chemical composition.

Table 4. Chemical compositions of silages after different ensiling times
Ensiling time (days)	Silage	DM (g/kg)	Crude protein (g/kg DM)	NH₃-N (g/kg N)	Organic acids profile (%)
Ensiling time (days)	Silage	DM (g/kg)	Crude protein (g/kg DM)	NH₃-N (g/kg N)	Lactic acid	Acetic acid	Butyric acid

0	SL1	150	141	-	-	-	-
	SL2	162	138	-	-	-	-
	SL3	335	74.2	-	-	-	-
	SL4	257	89.3	-	-	-	-
	SL5	296	80.8	-	-	-	-

30	SL1	145	138	66.8	76.8	24.8	1.38
	SL2	157	134	62.3	84.9	25.7	1.22
	SL3	331	70.7	63.9	90.3	24.8	0.98
	SL4	253	86.2	64.5	92.7	25.2	0.84
	SL5	291	78.1	64.9	92.1	24.8	0.82

60	SL1	142	136	70.4	77.8	25.1	1.38
	SL2	154	131	62.6	87.1	24. 8	1.34
	SL3	328	68.5	66.2	94.1	25.6	0.81
	SL4	251	83.4	69.4	95.8	25.4	0.78
	SL5	289	75.2	68.3	96.1	24.9	0.84

90	SL1	138	135	73.5	77.8	24.6	1.36
	SL2	150	130	64.4	86.8	24.7	1.41
	SL3	324	64.5	70.9	94.0	25.3	0.92
	SL4	249	80.4	75.8	94.4	24.8	0.96
	SL5	285	74.1	73.9	95.0	24.8	0.98
N.B. SL1: only passion fruit peel, SL2: 98% passion fruit peel + 2% mollases, SL3: 75% passion fruit peel + 20% dry maize cobs + 5% mollases, SL4: 75% passion fruit peel + 20% dry sugarcane bagases + 5% mollases, SL5 (75% passion fruit peal + 10% dry maize cobs + 10% dry sugarcane bagases + 5% mollases

Based on the above results, fresh passion fruit peel can be ensiled to preserve for a long time. Further investigation to make passion fruit based silages as feed is warranted. It has been shown that ensiled banana acts as stimulant in diets of pigs (Caicedo et al 2020), so it is worth following this with passion fruit peel silage.

Conclusions

Fresh passion fruit peel accounted for a high percentage of the fruit and can be predicted with a high accuracy from the known quantity of fresh passion fruits.
Fresh passion fruit peel had a low DM content, but a relatively high contents of CP and NFE with low content of fiber.
Fresh passion fruit peel can be made into good silage when combined with 20% dry sugarcane bagasse and/or dry maize cobs together with 5% molasses.

Acknowledgements

The present study was supported under the Son La province funded project named “Applied study on improved utilisation of dry maize cobs, sugarcane bagasse and passion fruit peel as feeds for dairy cattle in Son La province”.

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Received 13 January 2020; Accepted 16 January 2020; Published 1 February 2020

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