Resistance to gastrointestinal parasite infection in Djallonké sheep

Abstract

Gastrointestinal parasitism places serious constraints on small ruminant production. The situation has been exacerbated by development of drug resistance in many parasite populations, leading to interest in identification of animals with genetically mediated resistance or tolerance to nematode infections. This study assessed the response to natural infection with gastrointestinal nematodes (GIN) in Djallonké sheep during the rainy season in the Sudan-Guinea Savannah region of Burkina Faso. Haemonchus contortus is the most prevalent GIN at this site and time. Djallonké lambs ( n = 434) were sampled from 40 households and evaluated at a common location in southern Burkina Faso. Lambs were dewormed with levamisole at 2 to 6 months of age and returned to infected pastures. Fecal egg counts (FEC), packed cell volumes (PCV), and FAffa Malan CHArt (FAMACHA © ) scores were determined 28 and 35 days after deworming. Lamb mortality was monitored throughout the experiment. Least-squares means for BW increased from 13.8 ± 0.2 kg at 28 days to 14.0 ± 0.2 kg at 35 days ( P < 0.01). Simple means and medians for FEC were 615 and 100, respectively, at 28 days and 850 and 175, respectively, at 35 days. The FEC exhibited strong right skewness. Following logarithmic transformation and back-transformation of resulting least-squares means to the original scale, FEC were higher ( P < 0.01) for males (208 ± 27) than females (122 ± 10). Least-squares means for PCV decreased ( P < 0.001) from 28 (36.3 ± 0.5%) to 35 days (33.7 ± 0.5%), and were higher ( P < 0.01) for females (36.0 ± 0.4%) than males (33.9 ± 0.7%). Correlations (r) between repeated measurements of BW, FEC, PCV and FAMACHA scores at 28 and 35 days were all positive ( P < 0.001). The correlation between FAMACHA scores and PCV was negative at 28 ( r = − 0.14) and 35 days ( r = − 0.18) ( P < 0.001). This study revealed that BW was an easily measured predictor of the ability of the lamb to resist infection with GIN and maintain PCV, and confirmed that FAMACHA scores are useful indicators of differences in FEC. Approximately 40% of female and 30% of male lambs did not show detectable levels of infection (i.e. FEC = 0) under field conditions. The great variability that was observed in FEC and PCV suggests potential to use Djallonké sheep in breeding programs to enhance resistance to GIN.

Identification of genomic regions and candidate genes of functional importance for gastrointestinal parasite resistance traits in Djallonké sheep of Burkina Faso

“…Performance data were obtained from a trial designed to assess environmental factors affecting gastrointestinal parasite resistance in Djallonké sheep of Burkina Faso. Morphological and genetic description of this sheep population can be found in Traoré et al (2008) and Álvarez et al (2009, 2012). Data were obtained from (a) a field trial, involving 434 lambs, carried out in the surroundings of Mangodara (Comoé province) located in the southern Sudan to Guinea savannah region of Burkina Faso during the rainy season 2014 (Traoré et al, 2017) and from (b) 19 lambs sampled in Dédougou (Mouhoun province), southwestern Burkina Faso, and submitted simultaneously to the same protocol at the facilities of the Kamboinsé station of the INERA (Álvarez et al, 2018) near Ouagadougou (central Sudan to Sahel savannah region of Burkina Faso).…”

Ancient Homozygosity Segments in West African Djallonké Sheep Inform on the Genomic Impact of Livestock Adaptation to the Environment

“…The model implemented in ZooROH assumes random mating and deviations from panmixia may bias results. However, the Djallonké sheep breeding scenario fits well to this assumption: unsupervised matings are the rule, no selection programs exist, and a strong gene flow exists between neighboring populations [4,5,7,[18][19][20].…”

“…Data, comprising 184 DNA samples from Djallonké lambs (64 males and 120 females) were previously analyzed using microsatellites and Single Nucleoride Polimorphism (SNP) data [7,18]. Samples were obtained during a field trial for the assessment of gastrointestinal parasite resistance [18][19][20] and DNA extracted using standard procedures [21] (see previous references for full details of sampling). Briefly, 166 individuals were sampled in Mangodara (latitude 9 • 53 59.99 N; longitude 4 • 20 59.99 W; Comoé province) and the other 18 (9 males and 9 females) in Dédougou (latitude 12 • 27 48.17 N; longitude 3 • 27 38.7 W; Mouhoun province).…”

Genomic scan of selective sweeps in Djallonké (West African Dwarf) sheep shed light on adaptation to harsh environments

“…Morphological and genetic description of both the Djallonké and the Burkina-Sahel sheep populations of Burkina Faso is available in the literature 21,22,30 . The management of the Djallonké sheep of Burkina Faso has been described as well 31 . Sheep breeding in Burkina Faso is based on small-holders and carried out in extensive conditions with no supplementation.…”