Effect of potassium nitrate and urea on feed intake, digestibility, N balance and methane production of goats fed a basal diet of Gliricidia (Gliricidia sepium) and Mimosa (Mimosa pigra) foliages supplemented with molasses

Phonevilay Silivong, O Xaykham, O Aloun and T R Preston*

Souphanouvong University, Lao PDR
silipvl@yahoo.co.th
* Finca Ecologica, TOSOLY, UTA (Colombia) AA#48, Socorro, Santander, Colombia

Abstract

Four weaned female goats, with an initial body weight of 8 kg and 4-5 months of age, were assigned to 4 treatments on a 2*2 factorial design in a 4*4 Latin square. The treatments were: foliages of Gliricidia or Mimosa and potassium nitrate or urea as the source of NPN.  

DM intake, coefficients of apparent digestibility of DM and crude protein and N retention tended to be higher for goats fed Mimosa compared with those fed Gliricidia. By contrast, methane .emissions were much lower (by 70%) when Gliricidia was the forage source. There were tendencies for higher values for daily N retention (P=0.27), N retention as percent N intake (P=0.077) and N retention as percent of N digested (P=0.16) when the NPN source was potassium nitrate compared with urea. Potassium nitrate reduced the methane: carbon dioxide ratio when Mimosa was the forage source but had no effect  when Gliricidia was fed. Methane:carbon dioxide ratios were much lower on Gliricida than on Mimosa.

Key words: Carbon dioxide, climate change, greenhouse gases, NPN, N retention

Introduction

In SE Asia, most farmers raise livestock for their main source of income and draft power.  According to FAO (2005) over 75% of the populations in Lao PDR rely on agriculture as their primary source of income.

In Lao PDR the populations of cattle, buffalo and sheep-goats have increased significantly from year 2002 to 2007 at the rates of 1.9, 0.61 and 9.46 % per annum, respectively (Anon 2007). However, a number of impediments and constraints have been shown to affect livestock productivity and efficiency. The main feed resources for the ruminants in Lao PDR are native grasses, legumes and tree leaves that are available in the natural grassland and forests (Phonepaseuth Phengsavanh and Ledin 2003). The availability of these feed resources is seasonally limited and both feed availability and quality are low, especially in the cropping season.   

Preston and Leng (2009) and Leng (1997) have emphasized that the most appropriate ways to improve feed resources for ruminants are through efficient utilization of crop residues and tree/shrub foliages.  However, to optimize performance correct feeding methods need to be applied ensuring that rumen function is efficient and secondly ensuring efficient assimilation of nutrients by providing a source of bypass nutrients (Preston and Leng 2009).

Mimosa pigra is an invasive weed of the genus Mimosa in the family Fabaceae. This plant is considered to be one of the worst environmental weeds of the Mekong River basin (Storrs et al 2001). In Tram Chim National park in Dongthap Province in the Mekong delta, there is growing concern over the rapid growth of the Mimosa pigra plant, that has taken over more than one seventh of the 7,600 ha of the park (Tran Triet et al 2007; Viet Nam-VNS). However, recent research (Nguyen Thi Thu Hong et al 2008) has shown that mimosa foliage is an excellent feed for goats, supporting growth rates when given as the sole feed of almost 100 g/day. It was hypothesized that the presence of condensed tannins would confer bypass properties on the protein in the Mimosa and that this could explain its high nutritive value.

Gliricidia (Gliricidia sepium)  is a medium-sized tree and can grow to 10 to 12 m high. The bark is smooth and its color can range from a whitish gray to deep red-brown. It has composite leaves that can be 30 cm long. Each leaf is composed of leaflets that are about 2 to 7 cm long and 1 to 3 cm wide. The flowers are located on the end of branches that have no leaves. The tree grows well in acidic soils with a pH of 4.5-6.2. The tree is found on volcanic soils in its native range in Central America and Mexico. However, it can also grow on sandy, clay and limestone soils. http://search.yahoo.com/search?p=Gliricidia&ei=UTF-8&fr=moz35 

Gliricidia sepium has been used as a protein supplement for low quality forages and resulted in improved ruminant productivity (Norton 1994). This is because of its high crude protein (CP) content and forage availability throughout the year. Gliricidia contains (in DM)  on average 22 % CP (Topps 1992).

In an in vitro study (Silivong et al 2012), it was shown that gas production and methane produced per unit substrate solubilized was the same when leaves from Gliricidia or Mimosa were the major sources of protein, and that with both foliages supplementation with potassium nitrate reduced methane production compared with urea as NPN source.

The hypotheses to be tested were:

• Feed intake, digestibility and N balance of goats fed Gliricidia (Gliricidia sepium) or Mimosa (Mimosa pigra) foliages will be increased when the foliages are supplemented with potassium nitrate rather than urea.
• There will be decreased methane emission when potassium nitrate replaces urea

Material and methods

Location and duration

The experiment was carried out at the animal science farm of  Souphanouvong University, which is located about 7.5 km from Luang prabang city. The experiment was conducted from September to November 2011.

Treatments and experimental and design

Four growing goats were used to compare four treatments arranged in a 2*2 factorial design within a 4*4 Latin square with 10 days per period: 5 days for adaptation and 5 days for collection of feed refusals, feces and urine.

The factors were:

Source of NPN:

·         Potassium nitrate (KN) or Urea (U)

Source of forage:

·         Gliricidia sepium (GD) or Mimosa pigra (MP)

Individual treatments were:

• MP-U:  Urea (1.83% of diet DM) + Mimosa

• GD-U: Urea (1.83% of diet DM) + Gliricidia

• MP-KN:  Potassium nitrate (6% of diet DM) + Mimosa

• GD-KN: Potassium nitrate (6 % of diet DM) + Gliricidia

 Animals and management

Four female weaned goats (local breed) with initial live-weight of 8 kg and 4-5 months of age were used. These animals were purchased from farmers around the Luang Prabang district.  They were housed individually in metabolism cages made from bamboo (dimensions of width 0.8 m, length 0.9 m and height 0.9 m) designed to collect separately feces and urine (Photo 1). The goats were vaccinated against Pasteurellosis and foot and mouth disease and treated with Ivermectin (1ml/33 kg live weight) to control internal and external parasites. They were gradually introduced to the cages and diets over 7 days before beginning the experiment.  

 Feed and feeding

 Molasses diluted to a Brix (content of sugars) of 30 was used as the carrier for the NPN sources. The diluted molasses was fed in a plastic bucket and hung above the feed trough and was given ad libitum. The Gliricidia and Mimosa foliages (Photo 2 and Photo 3) were collected daily from natural stands in the University campus and were fed at 3% of live weight on DM basis. They were hung in bunches above the feed trough. Feeds offered and residues were weighed every morning.  

Measurements

Live weight was recorded in the morning before feeding at the beginning and at the end of each period. Feeds offered and refusals  were collected daily during the 5 days of the collection period. Urine was collected in buckets with 20 ml of a solution of sulphuric acid (10% sulphuric acid concentrate + 90% distilled water). Feces were collected daily and stored at -18ºC and at the end of each period, sub-samples were mixed together and ground with a coffee grinder. Ratio of methane to carbon dioxide was measured on the last day of the experiment, 2h after feeding in the morning. A sample of rumen fluid was taken by stomach tube on the last day of the 2nd and 4 th period 2h after feeding in the morning.

Chemical analyses

The sub-samples of feed offered and refused and of feces were analysed for DM, N and ash according to AOAC (1990) methods. The pH of rumen fluid was measured immediately after collection, using a glass electrode and digital pH meter. A drop of concentrated sulphuric acid was then added to preserve the samples prior to analysis for ammonia by steam distillation (Nguyen Van Lai and Ly 1997). N solubility was measured by shaking 3g  of dried leaves with 100 ml of M NaCL for 1 h, then filtering and determining nitrogen in the filtrate (Whitelaw et al 1963). The ratio of methane and carbon dioxide was measured by Gasmet infra-red meter following the proceduure method described by Madsen et al (2010) and Silivong et al (2011) (Photo 4).

Statistical analyses

The data were analyzed by the General Linear Model option in the ANOVA program of the Minitab Software (Minitab 2000). Sources of variation in the model were: goats, periods, treatments, NPN source, foliage source and error.  

Results and discussion

Leaves and stems were higher in crude protein and DM in Mimosa than in Gliricidia (Table 2). Compared to other published data, the DM and crude protein levels of Mimosa in the leaves and stem were higher than the value (33.3% and 34.8% DM and 13% and 5% CP in DM) reported by Sitone et al (2011).  The solubility of the nitrogenous fraction was low implying that both foliages would likely be good sources of bypass protein.

Intakes of Gliricidia and Mimosa foliages were not affected by source of NPN as potassium nitrate or urea. Total DM intake as g/kg LW tended (P=0.12) to be higher when Mimosa was the source of forage compared with Gliricidia (Table 3; Figure 1).

Apparent coefficients of digestibility of DM and crude protein tended to be higher (P=0.13 and P=0.18) for Mimosa than Gliricidia, and for supplementation with nitrate compared with urea in the case of DM (P=0.048) but not for crude protein (P=0.57). Daily N retention and N retention as percent of N intake were higher for Mimosa than Gliricidia but  there was difference for N retained as percent of N digested (Table 4). There were tendencies for higher values for daily N retention (P=0.26) when the NPN source was potassium nitrate compared with urea. The differences were significant for N retention as percent of N intake (P=0.015) with a tendency for N retention as percent of N digested to be higher for nitrate rather than urea (P=0.078)

Rumen parameters and ratio of methane and carbon dioxide  

There were no differences among treatments in the pH and concentration of ammonia in rumen fluid (Table 5). The ratio of the concentration of methane to carbon dioxide in the mixed eructed gas and air was decreased markedly on the Mimosa diet when potassium nitrate replaced urea; by contrast, on the Gliricidia diet, overall ratios of methane to carbon dioxide were much lower than on the Mimosa diet  and were not affected by the source of NPN (Table 6; Figure 5).

Discussion

The reduction in methane missions due to feeding nitrate rather than urea has been reported in studies with sheep by Nolan et al (2010) and Van Zijderveld et al (2010a), in goats (Nguyen Ngoc Anh et al 2010) and in cattle (Hulshof et al 2010; Van Zijderveld et al 2010b; Do Thi Thanh Van et al 2010; Sangkhom et al 2011). The major reduction in methane emissions when Gliricidia replaced Mimosa foliage is difficult to explain.  In an in vitro incubation, Ho Quang Do et al (2012) reported lower rates of production of methane when leaves from Sesbania grandiflora and cassava  were the source of forage compared with water spinach and sweet potato vines. These authors related this to differences in protein solubility which were lower for Sesbania (33%) and cassava (35%) compared with water spinach (70%) and sweet potato vines (70%).  In contrast with the results of the present experiment, Mimosa reduced methane emissions in goats fed foliage of Melia azedarach (Bui Phan Thu Hang et al 2012).

The apparent reduction in methane production with Gliricidia compared with Mimosa is also in conflict with the results for apparent digestibility and N retention all of which favored Mimosa over Gliricidia. Further research is needed with these two foliages in order to resolve these conflicting findings.

Conclusion

• DM intake, coefficients of apparent digestibility of DM and crude protein and N retention tended to be higher for goats fed Mimosa compared with those fed Gliricidia. By contrast, methane emissions were much lower (by 70%) when Gliricidia was the forage source.

• There were tendencies for higher values for daily N retention (P=0.27), N retention as percent N intake (P=0.077) and N retention as percent of N digested (P=0.16) when the NPN source was potassium nitrate compared with urea.

• Potassium nitrate reduced the methane: carbon dioxide ratio, compared with urea,  when Mimosa was the forage source but had no effect when Gliricidia was fed.

Acknowledgements

This research was done with support from the MEKARN program financed by Sida.  Acknowledgement is made to Mr. Sisomesouk and Mr. Phoudthavong  who provided valuable help in the laboratory. The authors also thank the  Faculty of Agriculture and Forest Resource, Souphanouvong University for providing the facilities to carry out this research.

References

AOAC 1990. Official Methods of Analysis. Association of Official Analytical Chemists. 15th Edition (K Helrick editor). Arlington pp 1230.

Do Thi Thanh Van, Duong Nguyen Khang and Preston T R 2010 Methane emission in yellow cattle fed diets based on NaOH treated rice straw, cassava root and leaf meal,  supplemented with sodium nitrate or urea as sources of non-protein nitrogen. http://www.mekarn.org/workshops/pakse/abstracts/van.NIAS.htm

Hulshof R B A A,  Berndt  J J,  Demarchi A,  Gerrits W J J and  Perdok H.B  2010 Dietary nitrate supplementation reduces methane emission in beef cattle fed sugarcane-based diets. Greenhouse Gas Conference Banff Canada , page 81 http://www.ggaa2010.org/pdfs/ Proceedings_Abstracts.pdf

Leng R A 1997 Tree foliage in ruminant nutrition. FAO, Animals Production and Health Paper. 139 http://www.fao.org/docrep/003/w7448e/w7448e00.htm

Madsen J, Bjerg B S, Hvelplund T,  Weisbjerg M R and Lund P 2010  Methane and carbon dioxide ratio in excreted air for quantification of the methane production from ruminants. Livestock Science . Volume 129, (1) 223-227 http://www.livestockscience.com/article/PIIS1871141310000181/fulltext

Minitab 2000 Minitab Software Release 13.

Nguyen Ngoc Anh, Khuc Thi Hue, Duong Nguyen Khang and Preston T R 2010 Effect of calcium nitrate as NPN source on growth performance and methane emissions of goats fed sugar cane supplemented with cassava foliage. http://www.mekarn.org/workshops/pakse/ abstracts/anh grrc.htm

Nolan J V, Hegarty J,  Godwin I R and Woodgate R 2010 Effects of dietary nitrate on fermentation, methane production and digesta kinetics in sheep. ASAP special issue (Volume 50, issue 5-6): Livestock production in a changing environment

Norton B W 1994 Antinutritive and toxic factors in forage tree legumes. Tropical Tree Legumes in Tropical Agriculture. CAB International, pp 202-215

Phonepaseuth Phengsavanh and Ledin Inger 2003 Effect of Stylo 184 (Stylosanthes guianensis CIAT 184) and Gamba grass (Andropogon gayanus cv. Kent) in diets for growing goats; Livestock Research for Rural Development 15 (10). http://www.lrrd.org/lrrd15/10/seut1510.htm

Preston T R and Leng R A 2009 Matching Ruminant Production Systems with Available Resources in the Tropics and Sub-Tropics/ http://www.utafoundation.org/P&L/preston&leng.htm

Silivong P, Preston T R and Leng R A 2011 Effect of sulphur and calcium nitrate on methane production by goats fed a basal diet of molasses supplemented with Mimosa (Mimosa pigra) foliage. Livestock Research for Rural Development. Volume 23, Article #58. http://www.lrrd.org/lrrd23/3/sili23058.htm

Sophea Iv and Preston T R 2011: Effect of different levels of supplementary potassium nitrate replacing urea on growth rates and methane production in goats fed rice straw, mimosa foliage and water spinach. Livestock Research for Rural Development. Volume 23, Article #71. Retrieved June 16, 2011, from http://www.lrrd.org/lrrd23/4/soph23071.htm

Topps J H 1992 Potential, composition and use of legume shrubs and trees as fodders for livestock in the tropics. Journal of Agricultural Science, Cambridge 118: 1- 8.

Tran Triet, Le Cong Kiet, Nguyen Thi Lan Thi and Pham Quoc Dan  2007 The invasion by Mimosa pigra of wetlands of the Mekong Delta, Vietnam. [on-line]. Available from:  http://www.ento.csiro.au/weeds/pdf/mimosa_ symposium/07Trietetal.pdf

Van Zijderveld S M, Gerrits WJ J, Apajalahti J A, Newbold J R, Dijkstra J, Leng  R A and Perdok H B  2010a Nitrate and sulfate: effective alternative hydrogen sinks for mitigation of ruminal methane production in sheep. Journal of Dairy Science. Volume 93, 5856-5866 http://download.journals.elsevierhealth.com/pdfs/journals/0022-0302/PIIS0022030210006387.pdf

Van Zijderveld S M, Dijkstra J, Gerrits W J J,  Newbold J R and  Perdok H B  2010b Dietary nitrate persistently reduces enteric methane production in lactating dairy cows. In Greenhouse gases and animal agriculture conference. October 3-8, 2010 Banff, Canada, T119, page 127 http://www.ggaa2010.org/pdfs/Proceedings_Abstracts.pdf

Whitelaw F G, Preston T R and Dawson G S 1962 The nutrition of the early-weaned calf:  a comparison of commercial groundnut meal, heat-treated groundnut meal and fish meal as the major protein source in the diet. Animal Production Volume 4. http://www.utafoundation.org/publications/whitelaw&preston 1962.pdf

Received 20 June 2012; Accepted 17 July 2012; Published 1 August 2012

Go to top