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Passion fruit (Passiflora edulis) peel as feed for ruminants in Vietnam: use of passion fruit peel silage in the diet of dairy cattle

Tran Hiep, Bui Quang Tuan, Nguyen Hung Son, Le Van Ha1 and Nguyen Xuan Trach

Vietnam National University of Agriculture, Hanoi, Vietnam
nxtrach@vnua.edu.vn
1 Tay Bac University, Son La, Vietnam

Abstract

Two on-farm feeding trials were carried out to test response of heifers and milking cows to rations using passion fruit peel (PFP) silage to replace whole crop maize silage (CTL) as an ingredient of the ration. PFP was madeinto silage according to a formula consisting of 75% PFP, 20% dry maize cobs, and 5% molasses. It was used to replace 50% (PFS50) or 100% (PFS100) of the maize silage in a total mixed ration, normally formulated by the farm (control ration) for Holstein heifers or milking cows. In each feeding trial, a total of 15 animals were randomly allocated to 3 groups of 5 each to be fed 3 rations. Results showed almost no significant differences in feed intake, feed conversion ratio (FCR), changes in body weight (BW), milk yield (MY) and milk quality were found among groups in the trials. It was therefore concluded that PFP silage can be used to replace whole crop maize silage in the ration without losses in growth performance (heifers) or milk yield and milk quality (milking cows).

Keywords: byproduct, cows, feeding, heifers, milk


Introduction

Passion fruit (Passiflora edulis) peel is a byproduct with large volumes from passion fruit processing (Hiep et al 2020). However, it has been mostly left as a waste, causing serious environmental problems, despite of several studies showing that passion fruit peel can be used as a good feed (Azevêdo et al 2012; Santos-Cruz et al 2013; Alves et al 2015; Sena et al 2015a,b). In Vietnam, the passion fruit industry has dramatically grown recently but also raised concerns of environmental pollution. In order to make use of passion fruit peel as feed, studies on quantification, analysis of chemical composition and making silage of this byproduct have been conducted with encouraging results. A conclusion was drawn that passion fruit peel can be made good silage according to a formula consisting of 75% passion fruit peel, 20% dry maize cobs, and 5% molasses (Hiep et al 2020). As a step to follow for later on practical application, the present study was designed to test if it was possible to use PFP silage to replace whole crop maize silage as an ingredient in the diets of heifers and milking cows.


Materials and methods

Study site and time

Two feeding trials were carried out on farm at Moc Chau Dairy Cattle Breeding Joint Stock Company located in the mountainous province of Son La, North West of Vietnam, from September 2018 to January 2019.

Materials

The two feeding trials were conducted on Holstein heifer and milking cow to test if it was possible to replace whole crop maize silage with PFP silage in their diets. Most of the feedstuffs used in the feeding trials (Table 1) were those normally used by the farm, except for PFP silage. Maize and elephant grass were grown by the farm. Whole crop maize was made into silage. Elephant grass was fed fresh after cutting. Molasses was bought from a local sugarcane factory. There were two types of concentrate, concentrate mix for heifers and concentrate pellets for milking cows, which were produced by the Company. The concentrates consisted of ground corn, ground cassava, ground soybean cake, ground rape cake, ground palm cake, palm oil, mineral-vitamin premix, NaHCO3, lime, and common salt.

Table 1. Mean contents of dry matter (DM), crude protein (CP), total ash (Ash), crude fiber (CF), ether extract (EE), and metabolizable energy (ME) of the feedstuffs used in feeding trials

Feedstuffs

DM
(% as fed)

CP
(%DM)

Ash
(%DM)

CF
(%DM)

EE
(% DM)

ME
(MJ/kg DM)

Passion fruit peel silage

32.6

8.20

6.60

29.8

0.89

8.49

Whole crop maize silage

30.4

7.53

6.17

29.6

1.49

8.74

Elephant grass

18.0

12.0

9.89

34.3

3.78

8.69

Concentrate mix

87.3

23.9

9.22

5.46

3.09

11.3

Concentrate pellets

89.9

19.5

8.92

5.60

4.18

11.5

NB. Concentrate mix for heifers; Concentrate pellets for milking cows

Fresh passion fruit peel was collected from a fruit processing company located nearby. It was made into silage according to a formula selected from the different formulae tried by Hiep et al (2020), viz. 75% PFP + 20% dry maize cobs + 5% molasses based on the weight of the ingredients as they were at the time of making silage. The PFP was chopped with a chopping machine into 1-2 cm in length. The dry maize cobs were ground with a grinding machine through a 0.5 cm sieve. All the ingredients were well mixed together and then compacted layer by layer with a tractor in concrete pits, which were then covered airtight. After 30 days of ensiling the silage was used as an ingredient of the rations in the feeding trials on heifers (Table 2) and milking cows (Table 3).

Feeding trial on heifers

A total of 15 Holstein heifers 6-7 months of age with an average body weight of 172 ± 3.42kg were allocated to 3 groups of 5 each according to a completely randomized design to be fed 3 different rations (Table 2). One group was fed the ration without PFP as normally used by the farm (CTL). The second group was fed PFS50, in which 50% of the maize silage in the control ration was replaced with PFP silage. The third group was fed PFS100, in which 100% of the maize silage in the CTL ration was replaced with PFP silage. Except for the two silages, which accounted for 65% dry matter (DM) of the rations, all the other ingredients (elephant grass, concentrate mix) were the same for all groups. Chemical composition in terms of DM, crude protein (CP), crude fiber (CF), and metabolizable energy (ME) were almost the same for the three rations.

Table 2. Design of rations in the feeding trial on heifers

CTL

PFS50

PFS100

Ingredient composition (% on dry mater basis):

Passion fruit peel silage

0.00

32.5

65.0

Whole crop maize silage

65.0

32.5

0.00

Elephant grass

15.0

15.0

15.0

Concentrate mix

20.0

20.0

20.0

Chemical composition:

Dry matter (%)

31.3

32.0

32.7

Crude protein (% DM)

11.5

11.7

11.9

Crude fiber (% DM)

25.5

25.6

25.6

Metabolizable energy (MJ/kg DM)

9.25

9.17

9.09

The main period of experiment was 12 weeks after 2 weeks of adaptation. The animals were kept in individual stalls and fed twice daily at 8am and 4pm. Before each feeding, elephant grass was chopped into 1-2 cm in length and mixed thoroughly with all the other diet ingredients. The supplied amounts were adjusted so as to maintain the individual leftovers at around 10% of the total supplied. Water was supplied freely at all times.

Feeding trial on milking cows

A total of 15 Holstein cows in 2-3 months of lactation with an average milk yield of 19.4 ± 4.31 kg/day,  milk solid not fat (SNF) of 8.59 ± 1.98 %, milk fat of 3.54 ± 0.80%, and milk protein of 3.48 ± 0.76% were selected for the feeding trial. The cows were allocated to 3 groups of 5 each according to a completely randomized design to be fed 3 different rations (Table 3). One group was fed the ration without PFP as normally used by the farm (control ration). Two other groups were fed PFS50 and PFS100, in which PFP silage replaced 50% and 100% maize silage in the CTL  ration, respectively. Except for the two silages, which accounted for 40% DM of the rations, all the other ingredients were the same for all groups. Chemical composition in terms of DM, CP, CF, and ME were almost the same for the three rations.

Table 3. Design of rations in the feeding trial on milking cows

CTL

PFS50

PFS100

Ingredient composition (% on dry mater basis):

Passion fruit peel silage

0.00

20.0

40.0

Maize silage

40.0

20.0

0.00

Elephant grass

15.0

15.0

15.0

Concentrate pellets

45.0

45.0

45.0

Chemical composition:

Dry matter (%)

37.8

38.4

39.1

Crude protein (% DM)

13.6

13.7

13.9

Crude fiber (% DM)

19.5

19.6

19.6

Metabolizable energy (MJ/kg DM)

9.97

9.92

9.87

The main period of experiment was 12 weeks after 2 weeks of adaptation. The animals were kept in individual stalls and fed around the times of milking. Before each feeding, elephant grass was chopped into 1-2 cm in length and mixed thoroughly with all the other diet ingredients. The supplied amounts were adjusted so as to maintain the individual leftovers at around 10% of the total supplied. One third of the morning or afternoon portion was supplied just before milking and the rest after milking. Water was supplied freely at all times.

Measurements
Feed intake:

Total feed offered, and refusals, were measured every day for each animal during the whole feeding trials to determine intake. Samples of feed offered and refusal were taken before the last morning feeding of each week. After homogenization, an amount of about 0.5kg of feed offered was taken for each cow and put into a plastic bag. Feed refusals were mixed well together, then an amount of 10% was taken into a plastic bag for each animal. All the feed and refusal samples were stored at -18oC in freezers immediately after collection until the end of the experimental period. After thawing, the composite samples were made and then dried in a forced-ventilation oven at 60ºC for 72 h. Subsequently, they were processed in a knife mill with 1 mm sieve and stored in glass bottles at room temperature for later chemical analyses of DM, CP, CF, and EE according to the respective proximate methods of the AOAC (1990). ME was then calculated according to Wardeh (1981). Dry matter intake (DMI), ME intake (MEI), and CP intake (CPI) were calculated by difference between the amount offered and the amount left in refusals.

Body weight gain:

The heifers were weighed before the morning feeding on the first two days and the last two days of the trials using an electronic balance (RudWeight, Australia) to determine weight gain, which was calculated as the difference between the two average weights for each animal. In addition, intermediary weightings were performed in 4-week intervals throughout the experimental period to monitor the animal performance and identify any possible anomalies.

Milk yield:

The cows were milked twice daily starting at 6am and 3pm using a portable bucket milking machine (Bartech-Turkey). The amounts of milk from individual cows were weighed after milking using a 50 ± 0.3kg analog scale and recorded for the whole experimental period. Daily milk yield (MY) was calculated for each cow as sum of the morning and afternoon milk yields. Fat corrected milk yield (FCMY) was also calculated for the purpose of comparison among the groups.

Milk quality:

Fresh samples of milk from each cow were collected in the morning and afternoon milkings on 3 first consecutive days of week 3, 7, and 11. The samples were stored in 25 mL plastic tubes in freezers at -180C before chemical analysis for fat, protein, and SNF at the Central Laboratory of the Faculty of Animal Science, Vietnam National University of Agriculture.

Statistical analysis

Data were statistically analyzed using Proc GLM in MINITAB software. The sources of variation were ration and error term. Tukey’s pairwise comparison was used to find significant differences between means at p <0.05.


Results and discussion

As can be seen in Table 4, body weights and weight gains of heifers were similar among the three rations. The similar changes in body weight can be explained by similar intakes of DM, CP and ME as well as their conversion ratios among the rations as shown in Table 5.

Table 4. Changes in body weight (BW) of heifers during the feeding trial

CTL

PFS50

PFS100

SEM

p

Initial BW (kg)

172

173

170

1.38

0.318

Final BW (kg)

248

248

246

1.67

0.628

Total BW gain (kg)

76.0

75.5

76.3

1.07

0.852

Average daily gain (kg/day)

0.84

0.84

0.85

0.01

0.852



Table 5. Dry mater intake (DMI), ME intake (MEI), crude protein intake (CPI), dry mater conversion ratio (DMCR), metabilizable energy conversion ratio (MECR), and crude protein conversion ratio (CPCR) by heifers fed different rations

CTL

PFS33

PFS65

SEM

p

DMI (kg/day)

4.83

4.79

4.85

0.03

0.389

MEI (MJ/day)

44.6

43.5

44.5

0.31

0.062

CPI (g/day)

554

570

568

3.93

0.058

DMCR (kg DM/kg BW gain)

5.72

5.65

5.79

0.07

0.427

MECR (MJ/kg BW gain)

52.9

51.3

53.1

0.67

0.168

CPCR (g CP/kg BW gain)

657

673

677

8.52

0.252

For milking cows, milk yields (MY and FCMY) and milk quality (SNF, fat, and protein) did not differ among the rations, although on the average there was some better milk yield and milk quality for the groups fed PFP silage (Table 6).

Table 6. Milk yield (MY), fat corrected milk yield (FCMY), and milk quality of milking cows fed different rations

CTL

PFS50

PFS100

SEM

p

Milk yield

Initial MY (kg/day)

22.3

22.6

23.0

2.40

0.783

Average MY of 12 weeks (kg/day)

20.8

21.0

21.4

0.60

0.793

Average FCMY of 12 weeks (kg/day)

19.3

19.6

19.9

0.55

0.726

Milk quality

Solid not fat (%)

8.55

8.59

8.62

0.18

0.980

Protein (%)

3.45

3.51

3.48

0.08

0.913

Fat (%)

3.52

3.54

3.55

0.09

0.897

Table 7 shows that dry mater intake (DMI), ME intake (MEI) and crude protein intake (CPI) were almost the same for all groups. DMI in all groups reached nearly 3.4% BW, which is normal for milking cows at this stage of lactation (after milk peak). The conversion ratios of DM, ME and CP were not different among the groups. These similarities could explain the similar milk yield and milk quality among the three groups as shown in Table 6.

Table 7. Dry mater intake (DMI), ME intake (MEI), crude protein intake (CPI), dry mater conversion ratio (DMCR), metabilizable energy conversion ratio (MECR) and crude protein conversion ratio (CPCR) by milking cows fed different rations

CTL

PFS50

PFS100

SEM

p

DMI

kg/day

17.8

17.9

18.0

1.99

0.682

% BW

3.33

3.34

3.36

0.02

0.627

MEI (MJ/day)

177

178

177

19.8

0.784

CPI (kg/day)

2.41

2.46

2.49

0.27

0.476

DMCR (kg DM/kg FCM)

0.85

0.85

0.84

0.01

0.351

MECR (MJ/kg FCM)

8.50

8.46

8.30

0.06

0.103

CPCR (g CP/kg FCM)

116

117

116

0.88

0.613

From the results of the two feeding trials it can be said that PFP silage is at least as good as whole crop maize silage as feed for dairy cattle. That may be due to the fact that PFP silage had good quality (Hiep et al 2020) with similar chemical composition and ME values compared with those of the whole crop maize silage as shown in Table 1. Therefore, PFP can and should be utilized to substitute maize silage wherever and whenever it is available to reduce feeding costs and minimize environmental pollution at the same time. Moreover, the formula of PFP silage making would pay the way for better utilization of dry corn cobs and molasses as locally available cheep byproducts for feeding dairy cattle.

The above results of the two feeding trials are in agreement with several previous studies on use of PFP as feed used for other types of ruminants. Sena et al (2015a) and Almeida et al (2019) show that dehydrated passion fruit by-product is a good option for partial replacement of sorghum silage (75%) as feed for lambs. In another experiment by Sena et al (2015b), PFP can substitute Tifton 85 (Cynodon spp.) in diets for Santa Inês × Dorper rams at approximately 30% without impairing performance and carcass traits. Especially, Alves et al (2015) report that steers fed passion fruit by-product showed higher feed intake, digestibility, and body weight gain than those fed sorghum silage. These all together indicate that PFP can be used in different ways as an excellent feed for ruminants.


Conclusions


Acknowledgements


References

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Received 5 March 2020; Accepted 7 March 2020; Published 1 April 2020

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