Introduction

There are currently 5 million goats in the USA, with potential to produce mohair, meat, and cashmere worth $550 million/year. Recently, interest in goat meat has risen, fueled by the increasing demand by ethnic populations within the USA. Despite the spiraling number of goats slaughtered in the USA, the demand for goat meat is much greater than the domestic supply. Thus, considerable goat meat is imported from Australia and New Zealand. In 1990, the USA imported 1,362 metric tons of chilled or frozen goat meat, at a value of $1.86 million. By 1992, imports rose by 70% to 2,362 metric tons, with a value of $3.6 million.

The domestic shortfall in goat production can be addressed by either increasing the number of goats or improving production of the existing population (Poore, 1993). In regard to the latter mode, internal and external parasites seriously limit both per head productivity and the density at which goats can be raised on farms. In ruminants, high internal nematode burdens suppress live weight gain, reproductive efficiency, milk and wool production (Blackburn et al., 1991) and sometimes even result in death (Rahman and Collins, 1990). In the Australian and New Zealand sheep industries, the annual economic loss attributed to nematodes is estimated at $400 (Gray, 1987) and $270 million (Parker, 1991), respectively, despite an anthelmintic expenditure of $50 million by Australian farmers (Gray, 1987). Similar estimates are not readily available for the USA small ruminant industry, but it is believed that economic losses are of similar magnitude (SR-CRSP, 1991).

Conventional methods to control internal parasites include anthelmintic drenching, pasture spelling, crop rotation, and integrated grazing systems using stock with low internal parasite susceptibility. Anthelmintic use, by far the least complex of control options, is currently the preferred method for internal parasite management (Jackson, 1991; Zajac and Moore, 1993). Unfortunately, after many years of heavy reliance on anthelmintics for internal parasite control, parasite resistance has emerged. Anthelmintic resistance has been documented across the world, including Africa (Maingi, 1991), Asia (Dorny et al., 1993), and North America (DeVaney et al., 1992). Anthelmintic resistance of internal parasite populations exists for all current drug families including benzimidazole (McKenna, 1990), levamisole (Verady et al., 1993), ivermectin (DeVaney et al., 1992), and tomorantel (Anderson et al., 1988). In some studies, internal parasite populations have multiple resistances. To avoid anthelmintic resistance, goat producers must reduce reliance on anthelmintics and seek alternative, sustainable methods for internal nematode control.

Medicinal plants such as Hagenia abyssinica (Kosso) and Glinus lotoides (Hirta) contain substances with nematocidal activity (Abegaz and Dagne, 1978). The ability to control nematode infestation in humans through use of plants with anthelmintic properties has been recognized and is widely used in countries such as Ethiopia (Abegaz and Dagne, 1978; Sofowora, 1982). However, potential use of these plants as anthelmintics and optimal dosing regimes for ruminants have yet to be identified. Thus, the objective of this research was to examine the anthelmintic activity of Hagenia abyssinica (Kosso) in growing Alpine goats.

Material and Methods

Fresh fecal samples were collected from Alpine goats not previously drenched with anthelmintics for one month prior to the experiment. Goats with fecal egg count burdens in excess of 1,000 eggs/gram of feces (for a total of at least 42 goats) had three consecutive daily pretreatment fecal samples collected for egg concentration determination using a McMaster chamber. Fecal eggs were categorized by type. Goats were blocked according to worm infestation, and plant extracts were administered once orally. Control goats were administered solvent or basal solution, and the three nonzero dose levels were 20, 40 and 60 g dry matter of Kosso. Fecal egg count were taken at 24, 48, 72, and 96 hours postdosing to determine the reduction in fecal egg counts. Count data was transformed using log(count+10) and packed cell volume was transformed using arcsin function. Repeated measures were analyzed using PROC MIXED of SAS. Otherwise, PROC GLM was used.

Results and Discussion

Heterogeneity of slope was similar among variables except for the number of trichuris eggs (Table 1), indicating that for all variables except trichuris eggs treatment effects were similar among the different days of sampling. The only variable affected by oral dosing with Kosso was the number of cestode eggs, being decreased. The appearance of cestodes in feces occurred soon after dosing, starting only 1 day later. Different levels of Kosso were given to discern a minimal level of Kosso necessary for anthelmintic effects. However, the results obtained suggest need for further study of Kosso levels, since cestode egg levels were similar among nonzero levels and numerically the number was greater for the 60 vs 20 and 40 g doses.

Conclusions

Kosso appears to hold promise as an anthelmintic for cestode control in goats. However, further research is needed to determine optimal levels of Kosso, as well as to identify mode of action and specific fraction(s) of Kosso with anthelmintic activity. Furthermore, there should be experimentation with other plants possibly possessing anthelmintic activities, such as Glinus lotoides (Hirta). Such work might one day yield low-cost and sustainable methods of internal parasite control for use in goat production systems.

Acknowledgement

This research was supported by USDA/FAS/ICD/RSED Project Number 58-3148-0914.

References

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Table 1. Effects of level of oral administration of Hagenia abyssinica (Kosso) on measures of internal parasitism in growing Alpine goats

Figure 1. Eggs per gram of feces for cestodes.

Figure 2. Eggs per gram of feces for strongyles.

Figure 3. Eggs per gram of feces for trichuris.

Figure 4. Oocystes per gram of feces for eimeria.

Citation:

Abebe, G., L.J. Dawson, G. Detweiler, T.A. Gipson and T. Sahlu. 2000. Hagenia abyssinica (Kosso) for internal parasite control in goats. In: R.C. Merkel, G. Abebe and A.L. Goetsch (eds.). The Opportunities and Challenges of Enhancing Goat Production in East Africa. Proceedings of a conference held at Debub University, Awassa, Ethiopia from November 10 to 12, 2000. E (Kika) de la Garza Institute for Goat Research, Langston University, Langston, OK pp. 190-195.