Livestock Research for Rural Development 24 (4) 2012 Guide for preparation of papers LRRD Newsletter

Citation of this paper

Effect of potassium nitrate or urea as NPN sources associated with Mangosteen peel (Garcinia mangostana) on methane production, rumen parameters and growth performance of Phan Rang sheep in the Mekong Delta of Vietnam

Vo Duy Thanh, Nguyen Van Thu and T R Preston*

Can Tho University, Vietnam
vothanh69@gmail.com
* Finca Ecologica, TOSOLY, AA#48, Socorro, Santander, Colombia

Abstract

Twelve female Phan Rang sheep with an initial weight of 21.3 ± 0.2 kg at 4 months of age were allocated in a 2 x 2 factorial design with 3 replicates. The first factor was non protein nitrogen source (urea or  potassium nitrate); the second factor was Mangosteen peel meal at 0 or 1.5% of the diet DM.

 

 Feeding potassium nitrate rather than urea decreased the ratio of methane to carbon dioxide in the eructed air from the sheep. There was a tendency for methane production to be reduced by supplementation with Mangosteen peel. There was no effect of the NPN source, nor of the supplementation with Mangosteen peel, on apparent digestibility, N retention, and growth performance.

Key words: Ammonia, digestibility, climate change, feed conversion, greenhouse gases, live weight gain, VFA


Introduction

Sheep husbandry is practiced throughout the majority of the inhabited world, and has been fundamental to many civilizations. However, as for other ruminants sheep produce methane which has 21 times the impact of carbon dioxide in forcing global warming (The CattleSite News Desk, 2000). Therefore developing technologies of reducing greenhouse gas emissions from the rumen is very important for sheep production. Particularly the Mekong delta is one of the regions in the world, which is seriously vulnerable with the global climate changes and predicted sea level rise.

 

In a recent review, Leng (2008) postulated that nitrate could replace carbon dioxide as an electron acceptor in the rumen with the generation of ammonia instead of methane. In this reaction, nitrate is reduced to nitrite and then to ammonia, resulting in lower methane gas emission. As reported previously by Trinh Phuc Hao et al (2009) and Le Thi Ngoc Huyen et al (2010) nitrate could be fed safely to goats and cattle as the source of NPN for the rumen fermentation. Several studies have now shown that nitrate effectively inhibits methane production (Nolan et al 2010, Jeong et al 2005, Bozic et al 2009, Kluber and Conrad 1998, Guo et al 2009, Guangming et al 2010, Mohanakrishnan et al 2008).

 

Previous studies with Mangosteen peel were aimed at modifying the rumen fermentation (Suchitra Kanpukdee and Wanapat 2008). Supplementation with Mangosteen peel decreased the acetic: propionic acid ratio and it was predicted that this would have resulted in a reduction in methane production.  Currently, in Vietnam Mangosteen is mainly distributed in the Mekong Delta with a total area of 4,900ha with a total yield of fruit of about 4,500 tonnes (about 1 tonne/ha) (http://www.rauhoaquavietnam.vn). The peel of the Mangosteen peel is mostly thrown away in the canals causing pollution of the environment. Therefore its utilization for purposes such as animal production could be beneficial economically and environmentally.

 

There have been no studies on the effect of Mangosteen peel on rumen methane production in sheep. Phan Rang sheep have been mainly raised in Ninh Thuan province of Vietnam for meat production by the Cham ethnic group.  In recent years, sheep production in Mekong Delta has been also developed because the ecological conditions and feed resources in the region are suitable.Thepresentinvestigation was therefore aimed to determine the effects on methane production, rumen parametersand growth in Phan Rang sheep of supplementing the basal diet of molasses and para grass with Mangosteen peel in combination with potassium nitrate or urea as source of NPN.


Materials and methods

Location and duration

The experiment was carried out at the farm of Cantho University, Cantho City, Vietnam, from September to December, 2011.

Experimental design

Twelve female Phan Rang sheep with an initial weight of 21.3 ± 0.2 kg at 4 months of age were used for this experiment. They were allocated in a 2 x 2 factorial design with 3 replicates. The first factor was non protein nitrogen source (urea or potassium nitrate); the second factor was Mangosteen peel meal (0 or 1.5% of diet DM).

Animals and housing

The sheep were kept in individual pens. Vaccination was done against epidemic diseases and the sheep were drenched against internal parasites before the commencement of the experiment.

Feeding and management

The diets (Table 1) were introduced gradually during a 14 day period of adaptation, followed by 90 days for the feeding trial. The sheep were fed two times a day (8:00 and 14:00). Clean fresh water was available at all times. The NPN salts were dissolved in the molasses which was fed in two equal portions in the morning (08:00) and afternoon (14:00). The Mangosteen peel was mixed with the soybean meal and offered in two equal portions after feeding the molasses. The Operculina turpethum was fed in the morning and the Para grass in the afternoon following the other feeds. Both forages were chopped to a length of 2-3 cm and fed in the fresh state.

Table 1. Composition of the diets (% DM basis)

 

Urea (MP0)

K-Nitrate (MP0)

Urea (MP1.5)

K-nitrate (MP1.50

Para grass

44.2

35.8

41.0

39.0

Operculina turpethum

12.5

12.5

12.5

12.5

Molasses

15.9

15.8

15.3

16.3

Soybean meal

24.8

31.2

28.2

27.8

Mangosteen peel

0.00

0.00

1.50

1.50

KNO3

0.00

4.00

0.00

4.00

Urea

1.8

0.0

1.8

0.00

Total

100

100

100

100

Proximate analysis, %

       

OM

87.5

85.8

86.6

86.7

CP

22.3

22.5

22.4

22.4

NDF

39.3

34.9

37.3

36.8

ADF

23.1

21.6

22.3

22.4

Ash

9.56

9.12

9.45

9.23

Measurements
Methane, CO2, pH, NH3-N and Volatile fattyacid (VFA)

During the feeding trial period, rumen samples were taken on day 45 and 85 at 1 hour before feeding and at 3 hours after feeding for analyzing pH, NH3-N, and VFA. The methane: carbon dioxide ratio was determined at 85 days of the experiment using the Gasmet equipment (GASMET 4030 Gasmet Technologies Oy, Pulttitie 8A, FI-00880 Helsinki, Finland). Rumen volatile fatty acids (VFA) were determined by the procedure of Barnett and Reid (1957); rumen pH was measured using a glass electrode pH meter. Rumen ammonia concentration was determined by distillation and titration with 0.1N sulphuric acid (http://mekarn.org/labman/Amoniac.htm).

Sampling procedure for feeds and feces

Feeds offered and refusals were measured daily to calculate feed intake. Feces and urine were collected separately during 5 days from 45 to 50 days and from 85 to 89 days of the experiment. H2SO4 was added to the urine container to avoid gaseous ammonia losses during the sampling period. Feed samples and feces were analyzed for DM, Ash and N, and urine analyzed for N, according to the standard methods of AOAC (1990).

Digestibility and nitrogen balance 

Apparent digestibility coefficients for DM, OM and NDF and ADF were determined by the methods described by McDonald et al (2002).

Live weight change

The sheep were weighed  in the morning prior to feeding, at the beginning and end of each week during the experimental period.

Statistical analysis

The data were analyzed using the General Linear Model option in the ANOVA program of the Minitab (2000) software. The sources of variation were NPN source, Mangosteen peel, interaction NPN*Mangosteen peel and error.


Results and discussion

Chemical composition

The chemical composition of the feed ingredients is shown in Table 2.

Table 2. Chemical composition of feed ingredients

   

Ingredients

DM

OM

CP

EE

NDF

ADF

Ash

(%)

(% in DM)

Para grass

18.7

87.7

10.2

4.29

66

31.7

12.3

Operculina turpethum

9.7

86

13.6

6.5

38.8

30.7

14

Molasses

73.6

93.1

2.72

     

6.88

Soybean meal

83.2

90.6

42

2.43

28.7

19.2

9.4

Mangosteen Peel

82.3

95.3

18

4.09

61.9

60.3

4.67

Urea

100

 

282

       

KNO3

100

 

86.9

       

DM: Dry Matter, OM: Organic matter, CP: Crude protein, NDF: neutral detergent fiber, ADF: acid detergent fiber

Feed intake

 

DM intake was reduced when potassium nitrate was the NPN source compared with urea, but was not affected by the feeding of Mangosteen peel (Table 3).

Table 3. Feed intake of sheep (g DM/head/day) in the experiment

 

NPN

 

Mangosteen peel

 

P

 

 

Urea

KN

 

NonMP

MP

 

NPN

MP

MP*NPN

 

Molasses

57.7

47.9

 

49.7

55.9

 

0.001

0.001

0.350

 

Operculina turpethum

60.4

62.2

 

64.0

58.6

 

0.698

0.265

0.531

 

Para grass

273

214

 

233

253

 

0.002

0.163

0.785

 

Soybean

108

124

 

119

112

 

0.001

0.025

0.005

 

Total DM

517

478

 

486

509

 

0.045

0.200

0.253

 

Apparent digestibility

There were no differences in coefficients of apparent digestibility of DM, OM, CP, NDF and ADF due to source of NPN or supplementation with Mangosteen peel after 45 and 85 days of the feeding trial (Tables 4 and 5). However, the apparent digestibility of CP was higher at the end of the feeding trial (85 days) than at the midway point (45 days) (Table 6).

 Table 4. Coefficients of apparent digestibility in sheep fed forage diets supplemented with nitrate or urea as NPN source and with or without Mangosteen peel (MP) after 45 days of the feeding trial

 

NPN

 

Mangosteen peel

   
 

Urea

KNO3

P

No-MP

MP

P

SEM

DM

60.1

58.6

0.74

58.4

60.3

0.68

3.17

OM

61.2

59.2

0.65

59.2

61.2

0.60

3.10

CP

50.2

46.1

0.12

47.5

48.8

0.77

1.59

NDF

55.6

50.8

0.45

52.3

54.1

0.97

4.29

ADF

45.9

37.7

0.34

41.6

42.0

0.94

5.76

 


Table 5.
Coefficients of apparent digestibility in sheep fed forage diets supplemented with nitrate or urea as NPN source and with or without Mangosteen peel (MP) after 85 days of the feeding trial

 

NPN

 

Mangosteen peel

   
 

Urea

KNO3

P

No-MP

MP

P

SEM

DM

62.1

59.2

0.49

61.5

59.7

0.66

2.80

OM

63.1

60.2

0.46

62.3

61.0

0.74

2.73

CP

54.6

51.3

0.16

53.6

52.3

0.56

1.50

NDF

58.5

59.2

0.89

59.0

58.7

0.95

3.18

ADF

47.4

43.9

0.63

46.7

44.7

0.79

4.97


Table 6. Coefficients of apparent digestibility in sheep fed forage diets supplemented with nitrate or urea as NPN source and with or without Mangosteen peel (MP) after 45 and 85 days of the feeding trial

 

45 days

85 days

SEM

P

DM

59.3

60.6

1.9

0.63

OM

60.2

61.7

1.9

0.58

CP

48.1

52.9

1.3

0.02

NDF

53.2

58.8

2.4

0.10

ADF

41.8

45.7

3.4

0.43


In contrast with the findings in the present study, Diaz et al (1993) and Klita et al (1996) demonstrated that high levels of saponins and/or tannins in diets resulted in decreased apparent digestibility, especially of crude protein. The reason for these differences may lie in the concentration and the source of the saponins/tannins used by these workers. In the study of Ngamsaeng and Wanapat (2005) it was also concluded that tannins decreased protein degradability by complexing with feed protein, which may lead to inhibition of protein degradation in the rumen.

Rumen parameters

In general, the parameters of rumen fermentation were within the normal range for ruminants fed tropical forage diets (Nguyen van Thu 2010). Supplementation with Mangosteen peel and with nitrate or urea as source of NPN had no effect on  rumen pH, ammonia or total VFA at the midpoint of the experiment (Table 7). However, after 85 days rumen ammonia was lower with nitrate than urea supplementation (Table 8).

Table 7. Mean values for rumen pH, ammonia and volatile fatty acids at the middle  of the experiment (45 days feeding trial)

 

NPN

 

Mangosteen peel

SEM

P

 

Urea

KN

NonMP

MP

NPN

MP

NPN*MP

pH at 0h

6.52

6.47

6.44

6.55

0.042

0.541

0.821

0.916

pH at 3h

6.32

6.33

6.28

6.36

0.023

0.618

0.038

0.215

N-NH3 at 0h, mg/100 ml

31.7

29.6

30.7

30.6

0.961

0.539

0.127

0.548

N-NH3 at 3h, mg/100 ml

42.3

41.6

42.1

41.8

0.756

0.149

0.924

0.776

VFA at 0h, mmol/L

86.4

84.9

83.6

87.7

1.690

0.395

0.101

0.13

VFA at 3h, mmol/L

112

109

110

111

2.354

0.446

0.923

0.846


Table 8. Rumen pH, ammonia and volatile fatty acids at the end of the experiment  (85 days feeding trial)

 

NPN

 

Mangosteen peel

SEM

P

 

Urea

KN

NonMP

MP

 

NPN

MP

NPN*MP

pH at 0h

6.58

6.60

6.61

6.57

0.022

0.647

0.191

0.45

pH at 3h

6.27

6.31

6.30

6.28

0.036

0.437

0.682

0.594

N-NH3 at 0h, mg/100 ml

32.3

28.9

30.4

30.8

1.106

0.066

0.805

0.595

N-NH3 at 3h, mg/100 ml

43.4

41.7

42.5

42.6

0.497

0.049

0.890

0.927

VFA at 0h, mmol/L

89.4

86.8

86.9

89.3

1.298

0.200

0.233

0.874

VFA at 3h, mmol/L

119

115

117

118

2.424

0.242

0.707

0.576

Nitrogen balance and daily weight gain

The dietary treatments had no effect on N retention, live weight gain or DM feed conversion (Table 9).

Table 9. Nitrogen intake, live weight and feed conversion of sheep in experiment 2

 

NPN

Mangosteen peel

SEM

P

 

Urea

KN

No MP

MP

NPN

MP

NPN*MP

N balance, g/day

               

  Intake

19.0

18.3

19.1

18.3

0.675

0.484

0.408

0.210

  Retention

9.72

9.30

9.57

9.45

0.518

0.585

0.877

0.058

Live weight, kg

               

  Initial

21.3

21.3

21.6

21.0

0.212

0.789

0.088

0.002

  Final

27.0

26.8

27.2

26.6

0.489

0.762

0.352

0.064

  Daily gain, g

61.3

55.4

58.4

58.3

3.584

0.275

0.980

0.959

DM conversion

7.60

8.13

7.75

7.98

0.196

0.090

0.424

0.310

The ratio of methane to carbon dioxide in the breath of the sheep

Feeding potassium nitrate rather than urea decreased the ratio of methane to carbon dioxide in the eructed air from the sheep (Table 10; Figure 1). There was a tendency (P=0.18)for methane production to be reduced by supplementation with Mangosteen peel (Figure 2).


Table 10.
Concentration of methane and carbon dioxide in the outside air and in the eructed breath of sheep fed a forage-based diet with potassium nitrate or urea and with or without Mangosteen  peel (MP); ratios of methane to carbon dioxide are calculated according to the proposal of  Madsen et al (2010)

 

K-nitrate

Urea

P

With MP

Without MP

P

SEM

Air

             

  CO2

414

414

 

414

414

   

  CH4

2.31

2.31

 

2.31

2.31

   

Animal

             

CO2

755

611

 

698

668

 

70.5

CH

30.8

46.5

 

28.6

48.7

 

4.63

CH4/CO2#

0.100

0.257

0.017

0.140

0.217

0.180

0.037

#Ratio  CH4/CO2 = (CH4animal– CH4 air)/(CO2animal-CO­­2air), where the values in animal breath and air are in ppm

 

Figure 1. Effect of potassium nitrate compared with urea on the ratio of methane to carbon dioxide in eructed breath of sheep fed a forage-based diet with (MP) and without (No-MP) mangosteen peel

Figure 2. Effect of mangosteen peel on the ratio of methane to carbon dioxide in eructed breath of sheep fed a forage-based diet with potassium nitrate or urea

 

The reduction in methane production by feeding a nitrate salt instead of urea  is in agreement with many reports in sheep (Nolan et al 2010;Van  Zijderveld et al 2010a), goats (Nguyen Ngoc Anh et al 2010) and cattle (Van  Zijderveld et al 2010b). The lack of response in growth  performance, despite the reduction in methane, is also in agreement with the results reported by the above researchers. 


Conclusions


Acknowledgments

This research was submitted by the Senior Author to Cantho University in partial fulfillment of the requirements for the MSc degree in Animal Production "Specialized in Response to Climate Change and Depletion of Non-renewable Resources".


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Received 5 March 2012; Accepted 25 March 2012; Published 2 April 2012

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