Potential nutritive value and tannin bioassay of selected Acacia species from Kenya

Abstract

Six Acacia forage species-A. brevispica, A. elatior, A. mellifera, A. nilotica, A. senegal and A. seyal -were analysed for their chemical composition, including phenolics and rumen fermentation characteristics. In vitro gas production technique was used to study the rumen fermentation characteristics and the effect of tannins present in the browse forages on in vitro fermentation by including polyethylene glycol (PEG-6000) in the incubation. The forages had high crude protein content (145.7-270.1 g kg −1 DM) and low to moderate content of neutral detergent fibre (220.2-442.8 g kg −1 DM). The forages had variable content of total extractable phenolics ranging from 18.4 to 384.2 g kg −1 DM and total extractable tannins ranging from 7.1 to 364.8 g kg −1 DM (tannic acid equivalent). Fractionation of the condensed tannin flavonoids showed that the delphinidin/cyanidin ratio ranged from not detected:100 to 71:29. The gas production potential ranged from 28.4 to 40.8 mL gas 0.2 g −1 DM. The rate of gas production was highest in A. elatior and lowest in A. nilotica. Addition of PEG-6000 increased gas production significantly (P < 0.05) in all species except A. mellifera. PEG-6000 addition did not have any significant effect on in vitro true dry matter and organic matter degradability but decreased the partitioning factor in all the species. Gas production and degradability parameters correlated positively with the CP content and negatively with the fibre and phenolics contents. Based on chemical composition, gas production and degradability, the forages have high potential nutritive value, especially as supplements to low-quality feeds in the tropics and particularly during the dry season. However, the presence of tannins in terms of high levels and biological antinutritive activity may limit the nutritive potential of some of the forages, such as A. seyal and A. nilotica.

Evaluation of nutritive value and palatability by goats and sheep of selected browse foliages from semiarid area of Kenya

“…This shows that the tannins in B. discolor are of the highest biological antinutritive activity among the browse foliages evaluated. In another study (Osuga et al . 2007), the tannins in B. discolor were found to have a high prevalence of prodelphinidin flavonoids, which are of high molecular weight and therefore interact more strongly with enzymes and other proteins than other tannins of low molecular weight (Kawamoto et al .…”

“…The significant differences ( P < 0.05) among the browse foliages for their in vitro gas production and fermentation characteristics are in agreement with previous studies on similar foliages from Kenya (Abdulrazak et al . 2000; Osuga et al . 2006, 2007).…”

“…Browse foliages have been reported to contain tannins with varying concentrations (Abdulrazak et al . 2000; Osuga et al . 2006, 2007).…”

Nutritive evaluation of foliage from fodder trees and shrubs characteristic of Algerian arid and semi-arid areas

“…The CP content of the browse species studied herein was always higher than the minimum level of 7-8% DM required for optimum rumen function and feed intake in ruminant livestock (Van Soest, 1994). Given the high CP content of the Acacia foliage, this fodder resource can be considered a suitable supplement for poor quality (low N content) natural pastures and crop residues such as straw and stover (Osuji and Odenyo, 1997;Osuga et al, 2007), even though tannins can considerably reduce the extent of protein degradation in the rumen (Makkar, 2003;Alam et al, 2007). The low-to moderate fibre content of Acacia foliage would also benefit voluntary intake and digestibility of poor quality roughage (Osuji and Odenyo, 1997).…”

Effect of supplementing Rhodes grass hay (Chloris gayana) with Berchemia discolor or Zizyphus mucronata on the performance of growing goats in Kenya

“…To tackle the situation, there is a need to explore ways of alleviating such losses, especially through the use of locally available feed resources which may be of high nutritive value. Hence, identification of nutritious feed resources is important so that farmers can be advised to harvest and keep such feeds in times of plenty (rainy season) for use during the lean periods (Osuga et al., 2007). Berchemia discolor and Z. mucronata are some of the browse species available in the tropics, which can be used for feeding ruminants.…”