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

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

Table 2. Chemical composition of feed ingredients
Ingredients	DM	OM	CP	EE	NDF	ADF	Ash
Ingredients	(%)	(% 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	SEM	NPN	MP	*NPNMP**
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	SEM	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

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".

References

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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

Introduction

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

Animals and housing

Feeding and management

Measurements

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

Sampling procedure for feeds and feces

Digestibility and nitrogen balance

Live weight change

Statistical analysis

Results and discussion

Chemical composition

Feed intake

Apparent digestibility

Rumen parameters

Nitrogen balance and daily weight gain

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

Conclusions

Acknowledgments

References

The cattle site news desk 2000 Reducing Greenhouse Gas Emissions. http://www.thecattlesite.com/news/29799/reducing-greenhouse-gas-emissions


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

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

Introduction

Materials and methods

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

Results and discussion

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

Conclusions

Acknowledgments

References

The cattle site news desk 2000 Reducing Greenhouse Gas Emissions. http://www.thecattlesite.com/news/29799/reducing-greenhouse-gas-emissions

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