The potential of Richardia scabra and fodder tree leaf meals in reducing enteric methane from dairy cows during dry season

Dyton Maselema and Fanny C Chigwa

Department of Animal Science, Lilongwe University of Agriculture and Natural resources. PO Box 219 Lilongwe Malawi
dmaselema@gmail.com

Abstract

In a study to evaluate enteric methane production and nutritional quality of locally available forages in dry season of Malawi’s central region, legume forages such as Arachis hypogaea (hay) and fodder tree leaf meals were found to produce less methane than the non- legumes. Out of the non-legumes, Richardia scabraa shrub which is locally available in both dry and rainy season had the least methane production and was not significantly different from the fodder tree leaf meals according to the following P-values; 0.411, 0.970 and 0.984 for Leucaena leucocephala, Sesbania sesban and Acacia anguistissima respectively. Arachis hypogaea hay had the least methane production as compared to all forages under study, however, the P-values show no significant differences from Leucaena leucocephala, Sesbania sesban and Acacia anguistissima; 0.746, 0.162, 0.133 respectively but rather different from the Rechardia scabra(P-value= 0.02).

Therefore, supplementation of Richardia scabra and fodder tree leaf meals in the dry season could be the best option not only for protein but also to reduce dietary energy losses through enteric methane.

Keywords: carbon footprint, in-vitro gas production, legume forages

Introduction

Dry season feed shortage leaves dairy farmers with no better choice than feeding low quality forages which require protein supplementation and regimes that reduces enteric methane production. Decline in feed availability during the dry season is one of the major challenges of smallholder dairy farming in Malawi (Kasulo et al 2013). In late dry season (early October to early November), most farmers run out of maize and rarely get maize bran to supplement dairy cows, forages becomes scarce due to drought and also since at this time most crop field are cleared in land preparation (Chingala 2006; Kasulo et al 2013).

The feeding of these low quality forages result in increased methane emmision and a reduction in milk production in ruminants; however, drought tolerant forages and those found in wetlands (Dambos) remain as the only option to dairy farmers (Kumwenda and Ngwira 2003).

There is need to develop feeding regimes that ensures increased milk production at the same time reduces enteric methane production. In ruminants methane is considered as a dietary energy loss and its also one of the greenhouse gasses influencing the current climate change (Shibata and Terada 2010).

It was therefore the aim of this study to evaluate the feeding quality of locally available forages for dairy cows in the dry season. The study evaluated a number of grasses and legume forages including fodder tree legumes for their contribution to enteric methane along with nutrient composition, in-vitro gas production and in-vitro true digestibility.

Materials and methods

Location of study Area

The study was conducted in Magomero Milk Bulking Group (MBG), Dedza district of Malawi. Magomero MBG is under Central Region Milk Producers Association (CREMPA), and lies close to Dzalanyama Forest which is defined by the latitudes 14⁰ 24’S and longitudes 33⁰38’E and lies on 1241 metres above sea level. The rainfall ranges from 800 to 1200 mm while temperatures are between 14 and 28⁰C.

Feed samples were collected in late November before the on-set of rainy season which is from November to March. Using a day to day feeding observation for a week, common dry season forages for dairy cows were identified.

Chemical analysis and the in-vitro true digestibility

The samples were dried at 60^oC for two days and then grinded to 1mm sieve size. Dry matter, ash, Acid Detergent Fiber (ADF), Neutral Detergent Fiber (NDF) and Crude protein (CP) content were determined according to AOAC (2000). CP analysis was done through Kjeldahl procedure. Table 1 shows the proximate analysis of the nutrient composition of the forages. In addition to this the in-vitro true digestibility was run to warant the feeding quality of the feed stuff under study.

In vitro gas production measurements and Methane gas estimation

The in-vitro gas production was done according to Tilley and Terry (1963) principle which was later modified by Menke et al (1979) and then compiled by Zaklouta et al (2011). Rumen liquor was collected from three fistulated local goats and taken to the lab in a pre-warmed sealed container. On arrival in the laboratory, the rumen fluid was filtered using a muslin cloth into a flask immersed in a water bath set at 39⁰C, and the fluid was continuous flashed with CO₂ to prevent aerobic conditions. The rumen inoculum was prepared using the following reagent solutions, micro-mineral solution, macro-mineral solution, buffer solution, resazurine solution, reducing solution and the filtered rumen liquor. Rumen inoculum of 30ml was pipetted into 100ml glass syringes containing the samples (n= 3) and then incubated in a water bath set at 39⁰C. The gas readings were taken at 0, 3, 6, 9, 12, 19, 22, 24, 27, 30, 48 and 72 hours after incubation.

At post incubation period, 4 ml of sodium hydroxide (NaOH) (10M) were introduced into the gas syringes to estimate methane production as reported by Fievez et al (2005), in this method NaOH reacts with carbon dioxide in the gas syringes such that the remaining gas is mostly methane gas. The literature present a number of methods for estimating enteric methane gas in ruminants some of which are the use of respiration chambers, sulphur hexafluoride (SF6) tracer gas techniques (Storm et al 2012) laser methane detector (LMD) (Chagunda et al 2009) and also using empirical equations (Bhatta et al 2007). However this method stands because it is less costly and reliable in ranking ruminant feed in terms of enteric methane production.

Statistical analysis

The data was analyzed for variance using Gen-stat Version 15 in a completely randomized design. Significant differences were established at p<0.05. The means were separated by Bonferon multiple range. The following was the statistical model; ϒ_ij =µ+β_i+ϵ_ij, whereϒ_ij is the observed variable andβ_i is the independent variable (forage type) and ϵ_ij isis the random error (normally distributed)

Results

Dry season feeding management

The study found out that dairy farmers commonly use grasses such asPennisetum purpureum (90%), Hyparrhenia species (80%), Saccharum officinarum leaves (70%) as basal feed. The most commonly used legumes for the dry season were Arachis hypogaea hay (100%) and Arachis hypogaea (shells) (50%). Some farmers (25%) were supplementing Leucaena leucocephala while others Sesbania sesban and Acacia anguistissima 20% and 20% respectively. Richardia scabra was found to be the most abundant shrub in both dry season and rainy season and about 93% of the farmers commonly used it as of the basal feed for dairy cows.

Nutrient composition and in-vitro true digestibility

The proximate analysis shows that folder tree leaf meals such as Leucaena leucocephala, Sesbania sesban and Acacia anguistissima were superior in terms of crude protein content CP range was 21.8 - 24.9%. The lowest CP levels were observed in Saccharum officinarum and Arachis hypogaea (shells) both 4.28%. In terms of ash, Richardia scabrawas superior (24.3%) to the rest of the forages, fodder trees had the lowest ash content (ranging from 5.87 to 10.6% of the DM). ADF values were in the range of 23.6 - 77.7 %, fodder tree leaf meals had the lowest (23.6 – 26.4%) while

In-vitro true digestibility

Figure 1. Summary on In-vitro True Digestibility

The results shows that Acacia anguistissima, Sesbania sesban and Pennisetum purpureum had a higher digestibility while Arachis hypogaea(hay),Richardia scabra, Leucaena leucocephala and Sacharum officinarum (cane leaves) had moderate digestibility. The lowest values were observed in Hyparrhenia species and Arachis hypogaea (shells).

In-vitro evaluation of the forages

The cumulative gas volume after 24, 48, and 72 hours was significantly different (p<0.05). As shown in table 2.

The cumulative gas volume at 24 hours ranked from the highest to lowest was as follows; Saccharum officinarum (Cane leaves),Hyparrhenia species, Arachis hypogaea (shell), Pennisetum purpureum, Arachis hypogaea (hay), Richardia scabra, Acacia anguistissima, Sesbania sesban and Leucaena leucocephala.

The fodder trees leaf meals and Richardia scabra had consistent lower gas production throughout the incubation period. At 24 hrs post incubation, Arachis hypogaea (hay) was ranked first in terms of gas production followed by Hyparrhenia species, Saccharum officinarum, Arachis hypogaea (shell) respectively. At 48hrs post incubation, Hyparrhenia species had the highest gas production followed by Saccharum officinarum, Arachis hypogaea (hay), Arachis hypogaea (shell) and Pennisetum purpureum, respectively.

Estimation of enteric methane

Figure 2. Estimated methane production

The study indicates that legume forages such as Arachis hypogaea (hay), fodder tree leaf meals and a local shrub Richardia scabra (a non-legume) result in lower methane production while, on the other hand, Hyparrhenia species, Sugarcane leaves, Pennisetum purpureum and Arachis hypogaea (shells) had the highest. There were no significant differences in methane production among Leucaena leucocephala, Sesbania sesban, Acacia anguistissima and Richardia scabra. The contrast test shows that methane gas from Arachis hypogaea (hay) was significantly lower than that of Richardia scabra (P = 0.02), however, was not statistically different from that of the fodder tree leaf meals (P-values = 0.746, 0.162, 0.133 for Leucaena leucocephala, Sesbania sesban and Acacia anguistissima respectively

Hyparrhenia species was not significantly different from Sugarcane leaves and Arachis hypogaea (shells) however, Pennisetum purpureum was superior to Hyparrhenia species but not significantly different from Saccharum officinarum and Arachis hypogaea (shells) in terms of methane production (see Table 4). 

The study established that methane production were associated with the gas production after 24 hours of incubation, such that the highest methane producers Hyparrhenia species (15.1ml), Sugarcane leaves (14.5ml) and Pennisetum purpureum (12.2ml) had also the highest gas production per 200mg substrate (107ml, 104 ml and 74.9 ml respectively) as shown in the following graph.

Figure 3. Relationship between CH4 and the in-vitro gas production

Discussion

Chemical composition and in-vitro true digestibility

The variations in chemical composition could be due to differences in forage species, stage of maturity as well as the selected edible portions of the forage. In case of fodder trees, the samples were mainly from new re-growth branches (as used by the farmers), on the other hand Arachis hypogaea (both hay and shells) are usually collected at late maturity stage (after harvesting), furthermore, grasses are always fed as whole (both leaves and stems),all these may have a bearing on chemical composition such as CP, ADF, NDF as well as digestibility as reported by Dewhurst et al (2009).

Methane estimation

The differences in methane production could be due to differences in protein solubility as reported by Preston et al (2015), it is reported that substrates with high soluble protein are asossiated with more gas and methane production in in-vitro rumen incubation than those with low protein solubility. Simillar studies by Meale et al (2012) also reported that substrates with high gas production in in-vitro rumen incubation are also assossiated with high methane production than those with low gas production. The assosiation between protein solubility and total gas or methane production comes because the higher the protein solubility the more fermentable is the substrates which result in more gas production and methane in particular.

The lower methane production in fodder tree leaf meals (Leucaena leucocephala, Sesbania sesban and Acacia anguistissima) could be as a result of high phenolic compounds (tanins) which supress microbial activities in the rumen as reported by Bhatta et al (2009) and Jayanegara et al (2011). However, this could not explain the low methane production in Arachis hypogaea(hay) and Rechardia scabra since there are no reported phenolic compounds.

Conclusion

• The high methane production in Hyparrhenia species, Pennisetum purpureum (Napier grass), Sacharum officinarum (cane leaves) and Arachis hypogaea (shells) signifies that dairy cows incur huge energy losses and probably contributes more to carbon footprint s when these are fed as a sole diet.
  
  
• Fodder tree leaf meals and Richardia scabra signifies a great potential to reduce dietary energy losses and also reduce carbon footprints if used as a supplement to these low quality forages especially in the dry season.
  
  
• The emphasis on Richardia scabra and the fodder treeleaf meals comes because unlike the Arachis hypogaea (hay) and most legume forages, these two are not seasonal; they are drought tolerant and available throughout the year hence could be the best option for smallholder farmers.

Acknowledgement

We would like to express our appreciation to Agroscope for funding the sample collection field work, Magomero field staffs for their cooperation in sample collection, LUANAR Animal Science staff especially at animal nutrition lab, Mr. Mindozo who assisted in rumen liquor collection.

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Received 11 May 2016; Accepted 26 January 2017; Published 1 March 2017

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