Effects of season and species on in sacco degradability of plant species in the sub-humid subtropical savanna, South Africa. 71 Table 4.5 The effect of polyethylene glycol (PEG) on in vitro gas production kinetics for five browse species (experiment 2).
Background
High levels of CT in the diet decrease digestibility and voluntary DM intake (Decandia et al., 1999; Silanikove et al., 2001). This can be attributed to CT interactions with proteins, enzymes in the digestive tract, microbes and mucous membranes in the digestive tract (Silanikove et al., 2006).
Study objectives
Hypotheses
The use of trees and shrubs in ruminant nutrition
Diet selection
Knowing the function of food selection by small ruminants can be useful to introduce better pasture management. This knowledge based on feeding behavior is a key to understanding plant-herbivore interactions (Ungar, 1996; Dziba et al., 2003a), skillful management of rangeland systems and ultimately profitable livestock enterprises (Ungar, 1996).
Factors affecting goat feeding behaviour and diet selection
- Factors related to animals
- Factors related to plants
- Plant species composition
- Plant acceptability
- Plant chemical composition
- Tannins
- Mechanisms of tannin-protein complexes
- Factors affecting the formation of tannin-protein complexes
- Dissociation of the tannin-protein complexes
- Effects of tannins on rumen micro-organisms
- Effects of tannins on nitrogen metabolism
- Effects of tannins on nutritive value
- Effects of fibre and tannins on voluntary feed intake
- Effects of fibre and tannins on digestibilityof nutrients
Ruminants use protein more efficiently if it is prevented from bacterial deamination in the rumen (Ulyatt et al., 1975). This decrease compensates for an increase in the formation of protein-tannin complexes and tannin fiber (Terrill et al., 1992b).
Foraging on tannin-containing plants
This was confirmed by Baloyi et al. 2006) who suggested that the animal should avoid foraging on plants with high tannin content. It has been suggested that these proline-rich tannin-binding salivary proteins act as the first line of defense against tannins in the digestive tract (Mehansho et al., 1983).
Performance of ruminants foraging on tannin-containing plants
A number of studies reporting the positive effects of tannin in terms of animal productivity can be found in the literature. A number of studies reporting the negative effects of tannin in terms of animal productivity can be found in the literature.
Conclusions
A better understanding of tannin effects in ruminants is certainly needed to enable adequate use of the properties of tannins to improve animal production. Nevertheless, it is also evident that we are far from a definitive understanding of the role of tannins in animal performance.
- Introduction
- Material and methods
- Study area
- Experimental animal and plant species
- The relative abundance of woody species
- Diet selection and selection index
- Chemicals analysis
- Statistical analysis
- Results
- Diet selection
- Correlation between chemical composition and selection index
- Discussion
- Conclusions
Seasonal changes in forage availability and quality in the subhumid subtropical savanna influence diet choice (Fourie et al., 1986; Abate, 1996). Natural differences in leaf chemistry between different plant species influence diet choice (Scogings et al., 2004).
- Introduction
- Materials and methods
- Study area
- Relative abundance of woody species
- Species samples and chemicals analysis
- Diet selection and selection index
- Statistical analysis
- Results
- Diet selection
- Selection index
- Discussion
- Conclusions
Acidic detergent fiber reduction is a good way to explain preferences in the case of Acacia species (Jansen et al., 2007). Owen-Smith and Cooper (1988) showed that some plant species avoided in the rainy season may be acceptable in the dry season. This finding may be due to variation in leaf availability, as there are fewer leaves in the dry season than in the wet season.
Owen-Smith and Cooper (1988) showed that some plant species avoided in the rainy season may be acceptable in the dry season. These differences between seasons could be attributed to the higher number of leaves in the late rainy season.
Introduction
Legumes can provide valuable sources of protein to support ruminant production in tropical savanna (Ngwa et al., 2003). This is one of the biological methods that is currently being considered more in the evaluation of ruminant feeds (Getachew et al., 1998; Dijkstra et al., 2005). It has been commonly applied for the determination of nutritional value of feeds (Sallam, 2005; Pashaei et al., 2010).
Measuring gas provides useful information on the fermentation kinetics of both rapidly and slowly degrading fractions (Campos et al. Pashaei et al., 2010). Some in vitro studies indicate that some tannins are more active than others (Osborne & McNeill, 2001; Andrabi et al., 2005).
Materials and methods
- Plant species and chemicals analysis
- Gas production
- Statistical analysis
It was hypothesized that: (i) changes in the quality of forage caused by seasonal variations in the savanna may affect their rumen fermentation (Winrock, 1992; Larbi et al., 1998; Camacho et al., 2010); (ii) inherent differences in nutritional value among plant species may affect the outcome of rumen fermentation (Nsahlai et al., 1994; Ndlovu & .. Ndlovu & Nherera, 1997; Apori et al., 1998; Larbi et al., 1998) ; and (iii) since tannin can have negative effects on the nutritional value of feed by limiting intake and digestibility (Kumar & D'Mello, 1995), the addition of tannin agent such as PEG can reduce these negative effects on rumen fermentation performance (Makkar et al ., 1995a) of tannin-rich species. The acid-butanol-proanthocyanidin assay (Porter et al., 1985) was used to determine condensed tannin (CT) (Makkar, 1995). The adjusted data were fitted into the model by Schofield et al. 1994) to estimate the maximum GP and its rate of degradation.
These data were used to determine the GP kinetics by the model of Campos et al. The cumulative gas production (GP) was used to calculate the maximum GP velocity at the inflection point (μ) and the time required to half of the gas volume (T½) to be produced according to Sahoo et al.
Results
- Chemicals composition
- Effect of season and plant species on gas production parameters (Experiment 1)
- Effects of PEG on gas production parameters (Experiment 2)
- Effects of season and plant species on gas production kinetics (Experiment 1) 69
- Correlations between chemical composition and GP kinetics
Among the three seasons, GP was higher in the late wet season than in the early wet and dry seasons. It was longer in the dry season than in the late wet and early wet seasons. The maximum rate of GP (µ) was faster in the late wet season than in the early wet and dry seasons.
Dichrostachys cinerea had similar GP in the dry and the early wet seasons from where it increased in the late wet season. Dichrostachys cinerea had similar T1/2 in the dry and early wet seasons from where it decreased in the late wet season.
Discussion
The negative relationship between CT and GP has been reported elsewhere (Ngwa et al., 2003; Njidda, 2010). These results are consistent with the gas produced by the fiber fractions (Apori et al., 2000) for an 8-week re-growth leaf of C. This is consistent with Larbi et al. 2010) who showed that GP was negatively correlated with NDF content.
NDF and ADF), while Nsahlai et al. 2010) observed that the degradation rate can be limited by CT. These differences in chemical composition across seasons were reported by others (Larbi et al., 1998; Yayneshet et al., 2009).
Conclusions
The findings disagreed with Getachew et al. 2010) who reported that PEG treatment did not affect GP of both soluble and insoluble fractions for leaf species. 2000) suggested that the evaluation of the activity of tannins and their effects on the digestion process could be estimated as the degree of GP with the addition of PEG. In the literature, there were several responses to the PEG treatment of leaves of acacia species on the fermentation problem (Kamalak et al., 2005; Rubanza et al., 2005; Vitti et al., 2005). These differences in the degree of fermentation of acacia varieties may be due to differences in tannin type and concentrations (Dalzell &.
Based on Reed et al. 1990) it can be concluded that significant amounts of tannins in processed browse would be in the NDF and ADF fractions, where they bind to the cell wall and cell protein and appear to be involved in reducing digestibility. These results are consistent with the findings of Sallam et al. 2010) who found no effect of PEG on GP in alfalfa hay and Atriplex caseneace.
- Introduction
- Materials and methods
- In vitro degradability
- Short chain fatty acid
- Statistical analysis
- Results
- Effects of season and plant species on in vitro degradability (Experiment 1)
- Effects of PEG on in vitro degradability (Experiment 2)
- Discussion
- Conclusions
Among seasons, ApDeg and TrDeg were higher in the dry season than in the early wet and late wet seasons, while MY was higher in the early wet season than in the dry and late wet seasons. PF and DEF were higher in the early wet season than in the dry and late wet seasons. Chromolaena odorata had similar ApDeg in the dry and early wet seasons, from where it decreased in the late wet season.
The TrDeg was higher during the dry season than either the early or late stages of the wet season, which may be related to the fact that plant leaves in the early wet season had high CT and high CP, while the leaves in the late wet season had higher NDF level (Basha et al., 2012). This is in agreement with Guimarães-Beelen et al. 2006) who reported that the activities of microorganisms were significantly lower in the tannin-rich treatment compared to the low-tannin treatment.
- Introduction
- Materials and methods
- Plant samples and experimental animals
- In sacco degradability
- Statistical analysis
- Results
- Effects of season and plant species on in sacco dry matter degradation
- Effects of season and plant species on in sacco nitrogen degradation
- Correlation between chemical composition and in sacco degradability
- Discussion
- Conclusions
Among the three seasons, the soluble fraction was higher in the dry season than in the early wet and late wet seasons. PDdm and EDdm were higher in the dry season than in the early wet and late wet seasons. ltdm was longest in the late rainy season and shortest in the dry season.
Among the three seasons, an and EDn were higher in the early wet season than in the dry and late wet seasons. The greatest value of the slowly degradable fraction of DM (bdm) and CP (bn) in A. natalitia in the dry season and C. odorata in the two wet seasons and the lowest values of bdm and bn recorded in D. cinerea in respectively three seasons and in the early wet season.
- Introduction
- Methods
- Data
- Principal components analysis (PCA)
- Results
- Pattern of relationships by PCA
- Pattern of relationships by multiple regression model
- Discussion
- Conclusions
Physical defenses, such as spines, have been reported to influence diet choice by mammalian herbivores (Provenza & Balph, 1990; Illius et al., 1999). Contrary to expectations (Papachristou et al., 2003), spiny species have a positive contribution to diet selection index while invertebrate species have no contribution. Previous studies reported that evergreen and deciduous species were among the more and less preferred species (Dziba et al., 2003a; . Mkhize, 2008).
In addition to physical defense and phenology, the differences in chemical composition have been reported to influence diet selection by herbivores (Illius et al., 1999; Dziba et al., 2003a). Herbivores are able to balance diet selection by maximizing nutrient intake and minimizing plant secondary compounds (Jansen et al., 2007).
General discussion
The selection index was used to rank species according to selectivity in the field and this was instrumental in selecting the five top-ranked species for in vitro experiments presented in Chapters 4 and 5 and in sacco experiments in Chapter 6. Chapter 4 dealt with gas production and Chapter 5 concerned in vitro DM degradability. The main results of in vitro fermentation include the effects of season, plant species and their interaction. Based on the in vitro fermentation data, condensed tannins are the most important factor affecting the nutritional value of browse species by limiting the use of browse species by ruminants. 1997) pointed out that the presence of tannins and other phenolic compounds in a large number of shrub and tree leaves limits their utilization.
In Chapter 6, plant species had lower potential degradability in sacco DM compared to true in vitro degradability (TrDeg). Prediction of diet choice of browsing species using parameters of digestion was poor, as evidenced by the poor relationship between these parameters and diet choice.
Conclusions
Variations in bag degradability parameters were reported between seasons and between species browsed. Fiber concentration levels appear to be the main factor limiting the degradability parameters of the sack. In vitro gas production and solubility, and sac degradability parameters were weakly related to the species selection index browsed by goats.
However, the selection index was strongly and positively related to plant traits (thorniness, phenology) and CP;
Recommendations
Chemical composition, sacco decomposition and in vitro gas production of some plants in Ghnain. Relationships between chemical composition, dry matter decomposition and gas production in vitro in several ruminant forages. Effect of addition of polyethylene glycol (PEG 8000) on the in vitro gas production kinetics of leaves from tannin-containing trees.
Chemical composition and relation to in vitro gas production of indigenous Zimbabwean browse tree species. Effect of tannin with and without polyethylene glycol on in vitro gas production and microbial enzyme activity. Potential nutritive value of selected browse species from Kenya using in vitro gas production technique and polyethylene glycol.
In sacco dry matter degradability and in vitro gas production characteristics of some Ghanaian forages.
