Haemonchotolerance in West African Dwarf goats: contribution to sustainable, anthelmintics-free helminth control in traditionally managed Nigerian dwarf goats.
Bottom Line: Here, we summarise the history of this breed and explain its economic importance in rural West Africa.If haemonchotolerance can be shown to be genetically controlled, it should be possible to exploit the underlying genes to improve GIN resistance among productive fibre and milk producing breeds of goats, most of which are highly susceptible to nematode infections.Either introgression of resistance alleles into susceptible breeds by conventional breeding, or transgenesis could be used to develop novel parasite-resistant, but highly productive breeds, or to improve the resistance of existing breeds, benefitting the local West African rural economy as well as global caprine livestock agriculture.
Affiliation: Faculty of Veterinary Medicine, University of Nigeria, Nsukka, Nigeria.Show MeSH
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Mentions: The second characteristic feature of haemonchotolerance demonstrated in naturally and experimentally acquired infections was the marked individual variability in faecal egg counts (FECs), which allowed identification and segregation of goats from both the humid and savannah zones into strong (Low FEC) and relatively weak (High FEC) responder phenotypes (Fig. 4). In naturally acquired infections, the former phenotype, with FECs of only 0–50 eggs per gram (epg) of faeces, were the strong haemonchotolerant phenotype and constituted approximately 76 and 80–85%, respectively, of the population of all goats examined during the rainy season in the two zones (Fig. 3) when goats from these climatic zones of Nigeria are usually exposed to the highest levels of infection . The above dichotomy in FEC phenotypes of WAD goats, namely high (HFEC) and low (LFEC) phenotypes, was the simplest and most reliable means of identification of strong and weak haemonchotolerance in naturally and experimentally infected goats. There was a strong positive correlation between FEC and Wb (Fig. 5) in the latter studies [14, 16], which makes the former a valuable phenotypic marker of haemonchotolerance in Nigerian WADs. Wide variations in FEC between and within breeds have been reported in sheep [30, 31, 43, 50, 52] and goats [20, 37, 40, 47] from different parts of the world, although the variability is generally wider in the former than in the latter, and so is not peculiar to Nigerian WAD goats. However, Nigerian WAD goats are unique in the range of variability in FEC, the exceptionally strong degree of resistance demonstrated even by 7–9-month-old kids, particularly in H. contortus infections, evidenced by the extremely low FEC and Wb following heavy primary and challenge infections, and the preponderance of the resistant phenotype in WAD goat populations from the southern humid to the northern savannah zones of the country.Figure 4.
Affiliation: Faculty of Veterinary Medicine, University of Nigeria, Nsukka, Nigeria.