Effect of NPN source, level of added sulphur and source of cassava leaves on growth performance and methane emissions in cattle fed a basal diet of molasses

Le Thuy Binh Phuong, Duong Nguyen Khang and T R Preston*

Nong Lam University, Viet Nam
binhphuongty27@yahoo.com
* TOSOLY, AA#48 Socorro, Colombia

Abstract

The objective of this study was to determine the effect of potassium nitrate versus urea, and of supplementary sulphur, on growth performance of cattle fed molasses and cassava foliage. Sixteen growing Laisind female cattle (Red Sindhi*local “Yellow” breed) with á range of initial live weight of 187-234kg were divided into two blocks according to live weight and within blocks were allocated at random to 8 treatments arranged as a 2*2*2 factorial with 2 replications. The factors were source of NPN (potassium nitrate: 6 % of diet DM basis or urea: 1.8 % of diet DM basis), level of added sulphur (0 or 0.8% S) and source of cassava foliage (fresh foliage or dried leaf meal).

DM intake was not affected by NPN source, but was depressed by adding 0.8% sulphur and was lower for the treatment with fresh cassava foliage compared with leaf meal. After correcting the data by covariance for differences in initial live weight, growth rate was depressed by adding 0.8% sulphur to the diet but was not affected by source of NPN or source of cassava foliage. The ratio of methane to carbon dioxide was reduced by feeding potassium nitrate rather than urea and by fresh cassava foliage compared with cassava leaf meal.

Key words: Feed conversion, foliage, leaf meal, potassium nitrate, urea

Introduction

Earlier studies in my laboratory showed that nitrate salts, replacing urea as the NPN source, and supplementary sulphur as sodium sulphate reduced methane production in an in vitro incubation with molasses and cassava leaf meal as the substrate (Phuong et al 2012a, b).  

The objective of the following experiment was to determine if these dietary modifications would result in improved performance of growing cattle fed a basal diet of molasses and cassava foliage, since it is known that enteric methane production results in 8-12% loss of the gross feed energy resulting from the ruminant digestion process (Blaxter and Clapperton 1965).

Materials and methods

Location and duration

The experiment was conducted at the cattle research station in Binh Duong province, Viet Nam, from November 2011 to January 2012.

Experimental design

Sixteen growing Laisind (Red Sindhi*local “Yellow” breed) with á range of initial live weight of 187-234kg were divided into two blocks according to live weight and within blocks were allocated at random to 8 treatments arranged as a 2*2*2 factorial with 2 replications. 

The factors were:

Source of NPN:

·         Potassium nitrate (6% of diet DM basis) or urea (1.8% of diet DM basis)

Level of added sulphur:

 0 or 0.8% S

Source of cassava foliage:

Fresh foliage or dried leaf meal

Basal diet

Molasses derived from sugar cane was fed ad libitum. Fresh native grass  was fed at 2 kg/day. Cassava foliage (fresh or as leaf meal) was supplied at 1% of LW (DM basis).

Animals

The cattle had individual  access to feed troughs containing the molasses and the forage. Water and salt were always available. The cattle were vaccinated against foot and mouth disease and were de-wormed before starting the experiment.

Feeding system

The additives (potassium nitrate, urea and sodium sulphate) were dissolved in the molasses. The grass was harvested in the morning and chopped by machine prior to feeding it at 15.30. Fresh cassava foliage was also harvested in the morning, from plants of 4 to 5 months maturity, and was offered in the fresh state at 07.15. Cassava leaf meal, purchased from a local feed company, was given at the same time.  

Prior to starting the experiment, the cattle were adapted gradually over a 2-week period to the NPN source and the sodium sulphate. Fresh molasses was offered 3 times every day (07.15, 11.00 and 15.30). The prescribed quantities of fermentable N sources (urea, nitrate) and the sodium sulphate were dissolved in the molasses offered at 07.15 and 11.00). Before each morning feeding, the feed residues were removed from the troughs and weighed to determine feed intake.

Data collection and measurements

The cattle were weighed every 14 days using an electronic balance. Feed samples were collected every two weeks for DM and N analysis. Live weight gain was calculated from the linear regression of weight (Y) on days of experiment (X).

Chemical analysis

The DM and N contents of the feeds were analyzed according to AOAC (1990). Samples of eructed gas were collected and  analyzed by GASMET infra-red analyser (Gasmet Company, Finland) for methane and carbon dioxide using the method described by Silivong et al  (2011).

Statistical analysis

The data were analyzed by the General Linear Model option in the ANOVA program of Minitab (2000). Sources of variation were: blocks, NPN source, level of sulphur, source of cassava foliage, interaction NPN*sulphur level and error.

Results and discussion

As expected the crude protein content of the leaf meal was slightly higher than in the fresh foliage (Table 1). 

 Molasses represented 53-57% of the DM intake (Figure 1) with cassava foliage providing 34%.

DM intake was not affected by NPN source, but was depressed by adding 0.8% sulphur and was lower for the treatment with fresh cassava foliage compared with leaf meal (Table 2).

Growth rates of the cattle were uniform throughout the experiment (Figure 2). There were differences in initial live weight between NPN sources and source of cassava foliage. After correcting the data by covariance for differences in initial live weight: (i) adding 0.8% sulphur to the diet reduced the final weight and the live weight gain (Figure 3); and (ii) sources of NPN and cassava foliage had no effect on final live weight or live weight gain. DM feed conversion was poorer when 0.8% sulphur was added to the diet but was not affected by source of NPN or source of cassava foliage.

 The ratio of methane to carbon dioxide ratios was reduced by feeding potassium nitrate rather than urea and by fresh cassava foliage compared with cassava leaf meal (Table 3; Figure 4). 

 It appeared that the effect of nitrate in reducing methane production was greater when 0.8% sulphur was added to the diet (Figure 5).

Figure 5. Effect of NPN source and level of sulphur on the ratio of methane to carbon dioxide in eructed gas from cattle fed molasses and cassava foliage

There are many reports showing reductions in methane production when nitrate salts replace urea in in vitro incubations with a range of substrates (Phuong et al 2011;  Du Thuy Thanh et al 2011;  Inthapanya et al 2011).  Reports from in vivo experiments show similar responses in cattle (Van Zijderveld et al 2010), in goats (Nguyen Ngoc Anh et al 2010) and in sheep (Nolan et al 2010).

However, the hypothesis that the reduction in methane would be accompanied by better animal performance was not proven in the present study, nor was such an effect observed in the experiments  reported  by Zijderveld et al (2010); Nguyen Ngoc Anh et al (2010) and Nolan et al (2010). However, in a recent experiment in which local "Yellow" cattle were fed a basal diet of lime-treated rice straw and fresh cassava foliage, the reduction in methane - resulting from supplementation with potassium nitrate replacing urea - was accompanied by better live weight gain and feed conversion (Inthapanya et al 2012). More research is needed to elucidate the feeding strategy required in order that the theoretically greater efficiency of  energy utilization from reducing enteric methane emissions will be reflected in improved animal performance.

Conclusions

• The ratio of methane to carbon dioxide ratios was reduced by feeding potassium nitrate rather than urea and by fresh cassava foliage compared with cassava leaf meal.
  
  
• Live weight gain was not affected by replacing urea with potassium nitrate as NPN source, nor by the source of cassava foliage.
  
  
• Adding 0.8% sulphur to the diet reduced the live weight gain and resulted in poorer feed conversion.

References

AOAC 1990 Official methods of analysis. Association of official Analysis (15^th edition). Washington, D.C, USA.

Phuong L T B, Preston T R and Leng R A 2011  Mitigating methane production from ruminants; effect of supplementary sulphate and nitrate on methane production in an in vitro incubation using sugar cane stalk and cassava leaf meal as substrate. Livestock Research for Rural Development. Volume 23, Article #22. http://www.lrrd.org/lrrd23/2/phuo23022.htm

Blaxter K L and Clapperton J L 1965 Prediction of the amount of methane produced by ruminants. British Journal of Nutrition.  19: 511–522.

Du Thuy Thanh, Preston T R and Leng R A 2011  Effect on methane production of supplementing a basal substrate of molasses and cassava leaf meal with mangosteen peel (Garcinia mangostana) and urea or nitrate in an in vitro incubation. Livestock Research for Rural Development. Volume 23, Article #98. http://www.lrrd.org/lrrd23/4/than23098.htm

Inthapanya S, Preston T R and Leng R A 2011  Mitigating methane production from ruminants; effect of calcium nitrate as modifier of the fermentation in an in vitro incubation using cassava root as the energy source and leaves of cassava or Mimosa pigra as source of protein. Livestock Research for Rural Development. Volume 23, Article #21. http://www.lrrd.org/lrrd23/2/sang23021.htm

Inthapanya S, Preston T R, Khang D N and Leng R A 2012  Effect of potassium nitrate and urea as fermentable nitrogen sources on growth performance and methane emissions in local “Yellow” cattle fed lime (Ca(OH)2) treated rice straw supplemented with fresh cassava foliage. Livestock Research for Rural Development. Volume 24, Article #27. http://www.lrrd.org/lrrd24/2/sang24027.htm

Minitab 2000 Minitab Software Release 13.2

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. MEKARN Conference on Live stock production, climate change and resource depletion (Editors: Reg Preston and Brian Ogle). Pakse, Laos, November 7-9 2010.http://www.mekarn.org/workshops/pakse/abstracts/anh_grrc.htm

Nolan  J V, Hegarty R S, Hegarty J, Godwin I R and Woodgate R  2010 Effects of dietary nitrate on rumen fermentation, methane production and digesta kinetics in sheep. Animal Production Science 50 (8) 801–806

Phuong L T B, Khang D N, Preston T R and Leng R A 2012a  Mitigating methane emissions from ruminants; comparison of three nitrate salts as sources of NPN (and sinks for hydrogen) in an in vitro system using molasses and cassava leaf meal as substrates. Livestock Research for Rural Development. Volume 24, Article #17. http://www.lrrd.org/lrrd24/1/phuo24017.htm

Phuong L T B, Khang D N, Preston T R and Leng R A 2012b  Mitigating methane production from ruminants; effect of supplementary sulphate and nitrate on methane production in an in vitro incubation using molasses and cassava leaf meal as substrate. Livestock Research for Rural Development. Volume 24, Article #18. http://www.lrrd.org/lrrd24/1/phuo24018.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

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

Received 6 March 2012; Accepted 27 March 2012; Published 2 April 2012

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