Project topics and materials
Get Complete Project Material File(s) Now! »
Calculated ratios
The E. curvula hay that was used in this study was of low quality, characterized by low crude protein, low fat content and high fibre portions, suggesting that it is a poor-quality roughage that warrants improvement in terms of its utilization. In this study, the intent was to test the effectiveness of the plant extracts on CH4 emission reduction associated with fermentation of such feeds without adversely affecting digestibility.
Extracts of P. betle and A. vera increased TGP, CH4 volume and IVOMD. The presence of biochemical catalysts such as amylase and lipase (Abrahim et al. 2012; Basak & Guha 2015; Ray et al. 2015) in their leaf samples could be partly responsible for the high volume of gases recorded at all dosage levels. Higher gas production from in vitro fermentation has been attributed to a faster rate of substrate degradation in the rumen. Increased digestibility and gas production could be due to the phytochemicals (amylase and lipase) present in the plant extracts used in this study. These phytochemicals have been reported to support fibrolytic microbes in the rumen by increasing the proximity between substrates and microbes (Morgavi et al. 2000), causing a faster rate of fermentation and subsequent degradation of substrates (Beauchemin et al. 2003), and rapid stimulation and reproduction of bacterial activity in the rumen (Beauchemin et al. 2003). Higher CH4 volumes recorded for all dosages of P. betle could be owing to higher fermentation activities and the digestion process stimulated by the phytochemicals present in the leaf sample, which according to Prabhu et al. (1995) had a significant stimulatory influence on intestinal lipase and amylase activity when tested in rats.
The corresponding increase in TVFA with increasing dosage level in A. vera and P. betle could be traced to higher concentrations of such biochemical catalysts in the treatment, an indication of faster rate of organic matter degradation from the fibrolytic microbes (Menke et al. 1979), which resulted in a reduction in rumen retention time when these extracts were administered. However, feeding a higher dosage level could alter the microbial population and could become toxic to the animals. Furthermore, the presence of anthraquinone, a phenolic compound present in the medicinal plants used in this study, might have played a stimulating effect on the bowels and served as an effective antibiotic agent, which could have generated more gas through its laxative effects. Anthraquinone is employed massively as a digester in paper making (Haddad et al. 2009). It works as a redox catalyst on E. curvula hay by forming a complex with the reducing end of polysaccharides in cellulose and hemicellulose and accelerating the rate of delignification through the cleavage of the β-phenyl ether bond of lignin. A. vera and other plant extracts used in this study contain varied quantities of naturally occurring anthraquinone glycosides. These plants have been used traditionally to relieve chronic and serious digestive problems. P. betle contains a variety of biologically active enzymes that can speed up digestion, two of which are catalase and diastase. Diastase breaks down complex starch polymer into its monomers, whereas catalase influences the conversion of hydrogen peroxide to water and hydrogen.
The high volume of CH4 gas recorded for P. betle could be due to a faster rate of degradation and subsequent production of hydrogen in the rumen, which enables the methanogens to convert H2 to CH4, according to Dey et al. (2014). Although P. betle and A. vera improved IVOMD at all dosages, the resultant CH4 produced per unit of IVOMD was higher than the control (Figure 2.1) with the exception of A. vera at 25 mg/kg DM feed. Extracts of P. betle and A. vera have been used in various studies as laxative agents (Abrahim et al. 2012; Nouri et al. 2014). The higher IVOMD and lower TGP and CH4 volumes for A. indica, J. curcas, M. oleifera and M. oleifera pods in low dosages (25 and 50 mg/kg DM feed) could be attributed partly to the presence of azadirachtin (Harry-Asobara & Samson 2014), curcin (Oskoueian et al. 2014), and alkaloids (Gautam et al. 2007; Ojiako 2014), respectively. Non-toxic azadirachtin has been used as a feed inhibitor and pesticide. Curcin and protease inhibitors have been reported to be present in J. curcas, whereas leaves and pods of M. oleifera are both rich in alkaloids, which have a bitter taste, making them undesirable for some microbes. Total gas produced, which is an indication of forage degradation characteristics and kinetics of fermentation, has not been affected negatively by all plant extracts used in this study, as evidenced by their digestibility compared with the control.
Significant CH4 reductions recorded for J. curcas could be attributed partly to the presence of inhibitory agents. The effectiveness of this plant at reducing CH4 in the rumen might be related to its purgative, anthelminthic and antiseptic properties (Liu et al. 2015; Kumar et al. 2016). The extract would have reduced CH4 production by combating the methanogens. The findings of Oskoueian et al. (2014) showed a significant suppression in rumen microbial population by direct effects of phorbol esters or other metabolites present in J. curcas, which might have occurred by damaging membrane proteins or by causing increased membrane permeability, which finally results in leakage of cytoplasmic constituents. M. oleifera leaf and pod extracts contain alkaloids, tannins, saponins and flavonoids, which are strong antioxidants that are capable of inhibiting rumen microbes by bonding with their membranes. Phenolic compounds from this plant were found to be active against bacteria such as Staphylococcus aureus, Escherichia coli and Salmonella typhi, which might have been responsible for the suppression of CH4-producing microbes in the rumen. A. indica had been researched for effectiveness against methanogens (Pal et al. 2015). The results of this study were in agreement with those obtained by Pal et al. (2015). The presence of limonoids such as azadirachtin, salannin, meliantriol and nimbin was responsible for the antimicrobial properties of A. indica. The M. oleifera leaf tested in vitro significantly reduced CH4, with an increase in VFA and organic matter digestibility, which corresponds with findings of Dey et al. (2014). There was a linear relationship between dosage and digestibility until it peaked at 75 mg/kg DM feed. This was true of the results obtained from using various plant extracts by Dey et al. (2014) and Marhaeniyanto and Susanti (2014). The mechanism of increased in vitro digestibility in A. indica, J. curcas and T. diversifolia may be due to their antimicrobial properties and laxative properties (Harry-Asobara & Samson 2014) by making the rumen more conducive to beneficial organisms to degrade the substrates. According to Oskoueian et al. (2014), the presence of phorbol esters could have contributed to the reduction of rumen methanogens, in addition to the alkaloids, saponins, tannin and saponin glycosides that have been attributed to CH4 reduction (Bhatta et al. 2012), whereas the improvement in IVOMD shows the dosage used in this study was not toxic to rumen microbes.
Tithonia diversifolia and C. papaya reduced CH4 partly because of the presence of alkaloids, flavonoids, phenol sesquiterpenes, monoterpenes and diterpenes in the leaf extracts. A dosage of 25 mg/kg DM feed effectively reduced CH4 production. Agidigbi et al. (2014) confirmed the antibacterial activities of T. diversifolia extracts when tested at 20 mg/mL through inhibitory actions against S. aureaus and E. coli. Improved digestibility, and individual VFA and TVFA were positively related in this study. The response of C. papaya could be traced to the presence of papain in papaya leaf extract, which aided in the breaking down and subsequent digestion of E. curvula hay. A higher partitioning factor obtained across the treatments is an indication of huge microbial biomass synthesis, which could indicate non-toxicity of plant extracts and increased fermentation of feedstuff.
Collection and preparation of plant extracts
Plant materials were collected, authenticated and transported as reported in Section 2.2.1. Fresh samples of 4 kg each of AV, AZ, TD, CP, JA and MO were harvested from growing trees, washed and freeze-dried until constant weight was achieved. Dried samples were milled through 1-mm sieve and extracted by dissolving 200 g dried plant materials in flasks containing 2000 ml methanol. The mixture was placed on a shaker at 20 °C for 96 hours, and the contents of the flask were filtered by squeezing through a 150 μm aperture. The excess methanol in the filtrate was evaporated in the fume chambers and then transferred to the freeze dryer for complete dryness. All extracts recovered were in powder form except those from AV, which yielded a stiffened jelly-like substance. The crude extracts were stored at 4 °C for further use.
CHAPTER ONE Literature review
1.1 Introduction
1.2 Methanogenesis in the rumen
1.3 Mitigation strategies for methane emission from ruminants
1.4 Potential use of medicinal plants to mitigate enteric methane production
1.5 Chemical compounds and methane reduction potentials of medicinal plants used in this study
1.6 Conclusion from the review of literature
1.7 Hypothesis tested
CHAPTER TWO Effect of certain medicinal plant extracts and dose rate on in vitro organic matter digestibility, gas and methane production of Eragrostis curvula hay
Abstract
2.1 Introduction
2.2 Materials and methods
2.3 Results and discussion
2.4 Conclusion
CHAPTER THREE Associative effect of plant extracts on anti-methanogenic properties, volatile fatty acids and organic matter digestibility of Eragrostis curvula hay
Abstract
3.1 Introduction
3.2 Materials and Methods
3.3 Results and Discussion
3.4 Conclusion
CHAPTER FOUR Effects of substrate and storage time on the efficacy of plant extracts used as an environmentally friendly alternative additive to monensin to modulate rumen fermentation and reduce enteric methane emission
Abstract
4.1 Introduction
4.2 Materials and methods
4.3 Results and discussion
4.4 Conclusion
CHAPTER FIVE Oral dosage of medicinal plant extract as an additive reduced methane emission without negatively affecting feed utilization and performance of South African Mutton Merino sheep
Abstract
5.1 Introduction
5.2 Materials and methods
5.3 Results and discussion
5.4 Conclusion
CHAPTER SIX Effect of plant extracts of Moringa oleifera, Jatropha curcas and Aloe vera supplementation on haematology, serum biochemistry and overall performance of SA Mutton Merino sheep
Abstract
6.1 Introduction
6.2 Methodology
6.3 Results and discussion
6.4 Conclusion
CHAPTER SEVEN Conclusions and recommendation
7.1 General conclusion and recommendation
7.2 Critical review
REFERENCES
