AbstractsBiology & Animal Science

The potential of pods from tree legumes as supplement to low quality roughages for ruminants.

by Ngwa Asanji. Thomas




Institution: University of KwaZulu-Natal
Department: Animal and poultry science
Degree: PhD
Year: 2014
Keywords: Animal and poultry science.
Record ID: 1464353
Full text PDF: http://hdl.handle.net/10413/11669


Abstract

The goal of the study was to examine the use of pods from tree legumes as supplements to poor quality roughage-based diets. Trials were carried out to address issues related to the nutrient content of the pods and their limitations as supplements due to the presence of anti-nutritional factors. In the first trial (Chapter 3), the chemical, mineral and amino acid compositions of pods from six tree species were examined. The rumen degradation of the dry matter, nitrogen and cell wall constituents of the pods were evaluated, using the nylon bag technique. In trial 2 (Chapter 4), different rumen ecologies were created in fistulated sheep by feeding pasture hay in combination with different pod meals and alfalfa (50:50), in order to examine the effects of anti-nutritional factors (present in the pods) on the degradation of dry matter and fibre constituents by ruminal microorganisms. Trial 3 (Chapter 5) further examined the effects of anti-nutritional factors on the production of volatile fatty acids (VFAs) and on the activities of microbial enzymes in the rumen. In trial 4 (Chapter 6), ensilage was examined as a means of detoxification of cyanogenic glycosides in the pods of Acacia sieberiana and molasses as well urea were evaluated as preservatives that could improve the aerobic stability of the silage produced from the pods of A. sieberiana. In trial 5 (Chapter 7), the silage and four other feeds (3 pod meals and alfalfa) were used in a choice feeding trial to study the effect of anti-nutritional factors on the palatability and intake of the feeds by goats and sheep, using hay as the standard feed for comparison. Trial 6 (Chapter 8), evaluated the use of the silage with or without wheat bran as supplements to a roughage basal diet fed to lambs. Intake, digestibility of dry matter, organic matter, cell wall constituents, nitrogen retention and weight gain were considered as indices for examining the potential of the supplements. Chapter 9 presents a general discussion on the attributes and limitations of pods as supplements. It also leads to a conclusion on the importance of browse in tropics and raises the need for further research on this class of feeds. The results of the work show that pods from tree legumes are rich in nitrogen and minerals and may provide sufficient ammonia (71-85 mg/l of rumen fluid) in the rumen that could enhance the growth and/or activity of rumen microorganisms. The maintenance of rumen pH by the pod meals at a range of 6.2-6.4 gives an additional advantage over other supplements that contain high concentrations of soluble carbohydrates because cellulolytic activity by rumen microbes is said to be optimal around this pH range. The importance of pods as supplements was however, reduced by the presence of anti-nutritional factors (especially condensed tannins) which had a very high concentration (28%QE) in the pods of Acacia sieberiana. The results of the feeding trial showed a positive correlation with the intake of the basal diet and weight gain when pods meals were included in the diet at…