Project topics and materials
Get Complete Project Material File(s) Now! »
Introduction
Most of the developed countries are in the temperate climates. To be profitable, animal production in these countries needs to be maximised through high quality feed ingredients that are rarely deficient in nutrients (Leng, 1995). Thus, the main aim of research in these countries is more related to fine tuning nutrient balances arising from the relative high digestibility and absorbability of feed nutrients to maximise animal production (Leng, 1995). In contrast, most of the developing countries are in the tropical areas with the focus based more on survivability, both for the animal as well as the farmer. Animals in these countries generally need to consume locally available feed sources that are deficient in nutrients (Leng, 1995). Roughages from these areas generally are of a low-quality, with a CP analysis of roughly 6% or lower and high fibre levels and digestibility values lower than 50% (Leng, 1990). Therefore, the production levels of these animals are well below its genetic potential, even with the aid of supplementation (Leng, 1995).
Supplementation recommendations from current feeding evaluation systems are generally based on low-quality temperate grasses and not necessarily on tropical grasses (Costa et al., 2013). In addition, most of the feeding evaluation systems do not describe the types of feed sources used in the developing countries as it is considered too low in nutritional value, such as straw, which is primarily used as bedding in temperate countries, whereas it frequently forms the basis of the diets in the tropical areas (Leng, 1995).
Leng (1995) suggested there is ample evidence that the production of ruminants, grazing low-quality tropical roughages, is low due to limiting or deficient nutrient profiles of the roughages, and not necessarily due to the low digestibility or degradability of the roughages per se. These deficiencies decrease the growth rates of the microbial population in the rumen, thereby decreasing fermentation and digestibility of the basal roughage. As such, the nutrients are used inefficiently by the ruminant, which increases the generated metabolic heat. The increase in metabolic heat might reduce the often already insufficient feed intake due to the general higher environmental temperatures and humidity associated with the tropical regions and the low nutritional value of the grasses (Leng, 1990). The authors further suggested that by supplementing these deficient nutrients, a more efficient rumen environment could be created, resulting in an increased and more efficient usage of the available roughage by the ruminant.
It is therefore imperative that the correct nutrients and/or nutrient combinations need to be identified in supplementing ruminants consuming low-quality tropical roughages. Although some efforts have been made in identifying animal requirements under tropical conditions (Costa et al., 2013), which had been incorporated into the more current feeding requirements (NRC, 2007), most of the feeds and feed principles are still based on temperate feeds and not tropical feeds (Costa et al., 2013). Recent studies suggest that supplementation have different effects on the rumen milieu depending on the type of grass (low-quality ropical grasses or temperate grasses), even though the chemical analysis of the grasses might be similar (Bohnert et al., 2011). In addition, it was established that different nutrients and/or nutrient levels used as supplements, could have different effects on roughage utilisation in ruminants consuming tropical grasses (Kanjanapruthipong and Leng, 1998; Detmann et al., 2009) compared to temperate grasses (Bohnert et al., 2011). Thus, supplementation strategies developed for ruminants consuming low-quality temperate grasses will differ to ruminants consuming low-quality tropical grasses (Bohnert et al., 2011). These differences will be discussed in more detail in this review.
Chapter 1
1.1 Introduction
1.2 C3 and C4 grass species: Differences in photosynthetic pathways
1.3 Anatomical differences between temperate C3 grasses and tropical C4 grasses and its effects on the nutritive value to herbivores
1.4 Effects of the anatomical differences between C3 and C4 grasses on the utilisation of lowquality roughages by ruminants
1.5 Influence of supplementation on low-quality tropical and temperate grasses: A literature overview
1.6 The effects of supplementation N compounds in the tropical roughage fed ruminan
1.7 Fermentable Energy
1.8 Effects of synchronisation of nitrogen and fermentable energy in ruminants consuming low-quality roughages .
1.9 Additional Notes on Microbial Nitrogen Synthesis
1.10 Summary .
Chapter 2 Substitution of rumen degradable nitrogen of sunflower meal with urea in supplements to sheep fed low-quality Eragrostis curvula hay
2.1 Abstract
2.2 Introduction
2.3 Hypothesis.
2.4 Materials and methods
2.5 Calculations.
2.6 Statistical analysis
2.7 Results and Discussion
2.8 Conclusion
Chapter 3 Supplementation of different levels of urea and starch to sheep fed low-quality Eragrostis curvula hay .
3.1 Abstract
3.2 Introduction .
3.4 Materials and Methods .
3.5 Results and Discussion
3.6 Summary
3.7 Conclusion
Chapter 4 Synchronisation of energy and protein supplementation in wethers fed low-quality Eragrostis curvula hay
4.1 Abstract
4.2 Introduction
4.3 Hypotheses .
4.4 Materials and methods
4.5 Results and Discussion
4.6 Summary and Conclusion .
Chapter 5 Review of supplementation studies conducted with sheep fed low-quality Eragrostis curvula hay at the University of Pretoria during 2007 – 2013 using meta-analytical techniques
Chapter 6 Practical aspects on rumen fermentation
Summary and Conclusion
References
