BackgroundSheep is important in the socio-economic lives of people around the world. It is estimated that more than half of our once common livestock breeds are now endangered. Since genetic characterization of Nigerian sheep is still lacking, we analyzed ten morphological traits on 402 animals and 15 microsatellite DNA markers in 384 animals of the 4 Nigerian sheep breeds to better understand genetic diversity for breeding management and germplasm conservation.ResultsMorphological traits of Uda and Balami were significantly (P < 0.05) higher than Yankasa, which were both higher than West African Dwarf (WAD) sheep. Stepwise discriminant analysis showed tail length, rump height, chest girth, ear length and chest depth as the most discriminating variables for classification. Mahalanobis distances show the least differentiation between Uda and Balami and the largest between WAD and Balami sheep. While 93.3% of WAD sheep were correctly assigned to their source genetic group, 63.9% of Yankasa, 61.2% of Balami and 45.2% of Uda were classified correctly by nearest neighbour discriminant analysis. The overall high Polymorphism Information Content (PIC) of all microsatellite markers ranged from 0.751 to 0.927 supporting their use in genetic characterization. Expected heterozygosity was high for all loci (0.783 to 0.93). Mean heterozygote deficiency across all populations (0.171 to 0.534) possibly indicate significant inbreeding (P < 0.05). Mean values for FST, FIT and FIS statistics across all loci were 0.088, 0.394 and 0.336 respectively. Yankasa and Balami are the most closely related breeds (DA = 0.184) while WAD and Balami are the farthest apart breeds (DA = 0.665), which is coincident with distance based on morphological analysis and population structure assessed by STRUCTURE.ConclusionsThese results suggest that within-breed genetic variation in Nigerian sheep is higher than between-breeds and may be a valuable tool for genetic improvement and conservation. The higher genetic variability in Yankasa suggests the presence of unique ancestral alleles reflecting the presence of certain functional genes which may result in better adaptability in more agro-ecological zones of Nigeria. These genetic characteristics are potentially useful in planning improvement and conservation strategies in Nigerian indigenous sheep.

Serum biochemical and haematological indices constitute important panels in the diagnosis, prognosis and treatment of livestock diseases via the investigations of myriads of parameters influencing these blood and serum biochemical indices. Serum biochemical indices, haematological indices and blood electrolytes are critical physiological indices which have health implications on the diagnosis, prognosis and treatment of livestock diseases especially in animals bred under different management systems. It is important to stress that cascades of parameters of both genetic and non-genetic origin greatly have direct and indirect health implications on serum biochemical indices and blood electrolytes in livestock animals and subsequently on their health/ production performances. Laboratory blood tests would be a vital tool to help detect any deviation from normal state of wellbeing in animals. Therefore, this review intends to provide base line information to establish certain haematological and serum biochemical indices as standard references which can be employed as alternative therapy for diagnosis, prognosis and treatment of cascades of diseases plaguing livestock animals bred under different management systems especially under the harsh condition of the tropics. Hence, it is important to establish standard values for the various blood and serum biochemical indices base on parameters of non-genetic origin; age, sex, physiological state, stress level, management systems, medication, health status, nutrition, hormone, climate, etc. and genetic parameters which include the breed and genotype of the animal among others obviously affect the blood and serum profile of healthy animal which subsequently influence their production performance and efficiency.

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The DQB1 locus is located in the major histocompatibility complex (MHC) class II region and involved in immune response. We identified 20 polymorphic sites in a 228 bp fragment of exon 2, one of the most critical regions of the MHC DQB1 gene, in 60 Nigerian goats. Four sites are located in the peptide binding region, and 10 amino acid substitutions are peculiar to Nigerian goats, compared with published sequences. A significantly higher ratio of nonsynonymous/synonymous substitutions (dN/dS) suggests that allelic sequence evolution is driven by balancing selection (P < 0.01). In silico functional analysis using PANTHER predicted that substitution P56R, with a subPSEC score of -4.00629 (Pdeleterious = 0.73229), is harmful to protein function. The phylogenetic tree from consensus sequences placed the two northern breeds closer to each other than either was to the southern goats. This first report of sequence diversity at the DQB1 locus for any African goat breed may be useful in the search for disease-resistant genotypes.

Trypanosomosis remains a major challenge to livestock production in much of tropical Sub-Saharan Africa, while diagnosis and treatment still depend on inefficient parasitological techniques. Endemic infections depend on animal reservoirs with subclinical parasitemia. We report molecular diagnosis of subclinical Trypanosoma vivax (T. vivax) infection using polymerase chain reaction (PCR) for the first time in Nigerian goats and associate parasite presence with gross physiological traits and serum metabolites in extensively managed Nigerian goats. PCR was used to amplify a 400 bp DNA fragment of the parasite genome in 205 goats across three geographical zones of the country. Results showed a high subclinical infection rate (SCIR) of 71.7% in the total goats examined. Overall SCIRs of 71%, 75.9% and 55.6% were recorded in West African Dwarf, Red Sokoto and Sahel goats respectively, while geographical SCIRs were 71.2% (Southwest), 75% (Northwest) and 70% (Northeast). T. vivax presence had significant (P < 0.05) effect on respiratory rate and is associated with higher creatinine levels in sera. Logistic regression analyses with Hosmer-Lemeshow goodness-of-fit showed that respiratory rate is the most important predictive trait for the presence of T. vivax infection (P < 0.05). Goats appear to be a viable reservoir for T. vivax infection of other livestock. Molecular diagnosis of subclinical trypanosomosis using PCR could be useful for large scale epidemiological studies, early diagnosis of subclinical infection and treatment of the disease in extensively managed tropical goats.