Nutritive values and anthelmintic activity of tanniniferous forages: Prospects of feeding management strategy to control Haemonchus contortus in Arsi-Bale goats in Ethiopia
In traditional grazing systems in Ethiopia shortage of nutrition and gastrointestinal parasites are serious constraints to small ruminant production resulting in reduced growth and death of animals. Smallholders are not able to use commercial anthelmintic drugs mainly due to high costs but also because of a lack of availability. Alternative control measures are thus needed. Tannins are known to have anthelmintic effects. Tanniniferous Sesbania sesban (acc. 15019) and Desmodium intortum (Greenleaf) are short-lived perennial forages used as fodder for ruminants in Ethiopia. The present work aimed to evaluate the nutritive values of morphological fractions of these tannin-containing forages, to assess the nutritional impact of tannins on feeding value, and to determine whether the proanthocyanidin (condensed tannin)-containing forage legumes could be integrated into a feeding management strategy as a means of Haemonchus contortus control in goats.
Significant (P<0.05) variations were observed between the different morphological fractions of the two forages species in terms of their chemical compositions, degradability, in vitro digestibility and gas production values (Paper I). Moreover, in the view of the optimal nutrient contents, supplementation with whole or fractionated forage parts of both sesbania and desmodium can improve the nutritional status of ruminants fed low quality roughages. The forages fractions combine qualities of high nutrient and good digestibility that make them relevant for use as supplement to low quality roughages, especially on smallholder farms.
The second study revealed that CTs from sesbania and desmodium had no adverse effect on intake, digestibility, rumen ammonia-N concentration, N metabolism and body weight change of the animals. However, parasite infected goats either gained marginally or lost weight (P<0.05) compared with healthy animals across all treatments suggesting that supplementing sesbania or desmodium at this level did not provide the kids with sufficient level of tannins to counter the negative impact of parasitism on weight gain.
The third study showed that proanthocyanidin extracts from the legume forages inhibited larval migration in vitro in a dose dependent manner, and at concentrations from 1000 μg/ml condensed tannin extracted from D. intortum caused a significantly higher inhibition of larval migration than did the corresponding concentrations of the S. sesban extract (P<0.01). Prolonged feeding of tanniniferous forage legumes showed that animals receiving desmodium had the lowest total worm burden, the lowest female to male parasite ratio, the lowest number of eggs in the uterus of each female worm and the lowest per capita fecundity (P<0.01), thus clearly illustrating the prospects of a feeding management strategy to control Haemonchus contortus in goats. A prophylactic procedure is suggested.
