Short-term heat shock proteins 70 and 90 mRNA expression profile and its relation to thermo-physiological parameters in goats exposed to heat stress.

To follow the inheritance potential for heat tolerance after a crossing program in goats, 24 kids from four groups of goat kids (6 kids in each) from Aradi (A) and Damascus (D), their crossbred first-generation F1 (½D½A) and second-generation F2 (¾D»A), were exposed to acute elevated environmental temperature in controlled climatic chambers. Rectal temperature (RT), respiratory rate (RR), heat tolerance coefficient (HTC), adaptability coefficient (AC), and mRNA expression of heat shock proteins 70 and 90 ((HSP70 and HASP90, respectively), using real-time PCR were estimated. Results showed that Aradi breed goats had the highest level of expression for heat shock proteins 70 and 90, followed by F1, F2, and Damascus (P ≤ 0.01). Crossbreeds and Damascus showed the highest RT, while Aradi breed showed the lowest value (P ≤ 0.01). Aradi and crossbreeds showed the highest RR, while Damascus showed the lowest RR (P ≤ 0.05). Aradi and F1 showed the highest HTC (P ≤ 0.05), while there was no significant difference between pure breeds and crossbreeds in AC. A significant positive phenotypic correlation (0.81) was observed between HSP70 and HSP90. In addition, RR showed moderate positive correlation with both HSP70 and HSP90. It could be concluded that Aradi breed had putative heat tolerance in comparison to its crossbred progeny from the Damascus breed. The crossbreeding may result in some loss of heat tolerance potential, but the crossbreeds still better adapted to high environmental temperature than the Damascus breed.

Evaluation of genetic diversity of Saudi native chicken populations using microsatellite markers.

The present study was conducted to evaluate the genetic diversity and relationships of 5 Saudi native chicken populations and a White Leghorn (L) strain as an exotic breed, using 25 microsatellite markers. According to morphological appearance and plumage color and pattern, they were classified into black (BL), black-barred (BR), dark brown (DB), light brown (LB), and gray (G) breeds. Twenty-five microsatellite markers were chosen based on the degree of polymorphism reported in the previous literature. The results revealed that all studied markers exhibited a varied percentage of polymorphism among native chicken populations. However, there were 81 polymorphic loci out of 109 loci. Based on cluster analysis, 3 main clusters of chicken populations were identified. Two clusters comprised native chicken breeds, while the L strain set the third one. Higher similarity was found between either black and gray populations (BL and G) or brown populations (LB and DB). They had a closer relationship to each other. Genetic distance between each couple was 0.11 and 0.12, respectively. The productive results revealed that the black breed had significantly (P < 0.0001) lighter body weight at sexual maturity compared to the other breeds. There was no significant difference between light and dark brown breeds for most productive traits. The genetic diversity we found among Saudi chicken populations may be of interest for improving productive performance and adaptability.

Quantitative trait loci underlying milk production traits in sheep.

Improvement of milk production traits in dairy sheep is required to increase the competitiveness of the industry and to maintain the production of high quality cheese in regions of Mediterranean countries with less favourable conditions. Additional improvement over classical selection could be reached if genes with significant effects on the relevant traits were specifically targeted by selection. However, so far, few studies have been undertaken to detect quantitative trait loci (QTL) in dairy sheep. In this study, we present a complete genome scan performed in a commercial population of Spanish Churra sheep to identify chromosomal regions associated with phenotypic variation observed in milk production traits. Eleven half-sib families, including a total of 1213 ewes, were analysed following a daughter design. Genome-wise multi-marker regression analysis revealed a genome-wise significant QTL for milk protein percentage on chromosome 3. Eight other regions, localized on chromosomes 1, 2, 20, 23 and 25, showed suggestive significant linkage associations with some of the analysed traits. To our knowledge, this study represents the first complete genome scan for milk production traits reported in dairy sheep. The experiment described here shows that analysis of commercial dairy sheep populations has the potential to increase our understanding of the genetic determinants of complex production-related traits.

Quantitative trait loci underlying udder morphology traits in dairy sheep.

A genome scan was conducted on the basis of the daughter design to detect quantitative trait loci (QTL) influencing udder morphology traits in Spanish Churra dairy sheep. A total of 739 ewes belonging to 11 half-sib families were genotyped for 182 microsatellite markers covering 3,248.2 cM (Kosambi) of the ovine autosomal genome. Phenotypic traits included scores for 5 linear udder traits: udder depth, udder attachment, teat placement, teat size, and udder shape. Quantitative measurements for the QTL analysis were calculated for each trait from evaluation scores using within-family yield deviations corrected for fixed environmental effects. Joint analysis of all families using Haley-Knott regression identified 5 regions that exceeded the 5% chromosome-wise significance threshold on chromosomes 7, 14, 15, 20, and 26. Based on the across-family results, a within-family analysis was carried out to identify families segregated according to the QTL and to estimate the QTL effect. The allelic substitution effect for individual families ranged from 0.47 to 1.7 phenotypic standard deviation units for udder shape on chromosome 15 and udder depth on chromosome 14, respectively. These QTL regions provide a starting point for further research aimed at the characterization of genetic variability involved in udder traits in Churra sheep. This paper presents the first report of a sheep genome scan for udder-related traits in a dairy sheep outbred population.

A male linkage map constructed for QTL mapping in Spanish Churra sheep.

A male ovine linkage map has been constructed on the basis of 11 half-sib families of a commercial population of Spanish Churra sheep as part of a genome scan for quantitative trait loci mapping. A total of 1421 daughters and their sires were genotyped for 182 microsatellite markers evenly distributed along the ovine autosomes. A total of 259,192 genotypes were obtained, generating an average of 669 informative meioses per marker. An autosomal genome length of 3262 cM was estimated for the Churra population with a mean marker interval of 17.86 cM. Our map represents an approximate 90% coverage of the autosomal ovine genome and constitutes a useful tool for the genetic dissection of complex traits in this breed. General agreement was found between the Churra map and other published maps for sheep, despite certain length discrepancies.

Short communication: detection of quantitative trait loci influencing somatic cell score in Spanish Churra sheep.

Eleven half-sib ovine families, including 1,421 Spanish Churra ewes, were analyzed for 181 microsatellite markers spanning the entire autosomic ovine genome. Using a multimarker regression method, a daughter experimental design was used to identify putative quantitative trait loci (QTL) affecting the somatic cell score (SCS). Chromosome-wise significance thresholds were set empirically by permuting the phenotypic data. Marker order and genetic distances of the autosomic linkage map built for this commercial population were in accordance with the published ovine linkage map. An across-family association analysis revealed a region on chromosome 20 suggestive of evidence for a QTL. Segregation of the QTL into 2 families was inferred from the within-family analysis, and differences in the position of the suggested QTL were found between the 2 half-sib groups. This could be the result of incomplete information associated with the markers for the significant families. The location of the major histocompatibility complex in proximity to the across-family effect suggests this region may harbor a segregating QTL for the SCS in the Churra population. Studies in dairy cattle examining the SCS have reported linkage associations on corresponding bovine orthologous regions, supporting the validity of our findings.