POLYMORPHISM OF THE PROLACTIN GENE AND ITS EFFECT ON FIBER TRAITS IN GOAT.

The prolactin gene (PRL) is a potential candidate gene for the goat cashmere traits in marker-assisted selection. Thus, the aim of this study was to detect PRL gene polymorphism and its association with fiber traits in 200 Raini cashmere goats native to the south-east of Iran. A 196-bp fragment encoding exon 5 within the goat PRL gene was amplified using PCR specific primers. The amplification products were subjected to the single stranded conformation polymorphism (SSCP) analysis. Three different SSCP banding patterns (CC, AC and AA) were observed in exon 5 of the caprine PRL gene. The pattern frequencies for CC, AC and AA were 0.39, 0.38 and 0.23 and frequencies of the A and C alleles were 0.42 and 0.58, respectively. The genotypic distributions did not deviate from the Hardy-Weinberg equilibrium (P> 0.05). The number of observed alleles, number of effective alleles, expected heterozygosity, observed heterozygosity, mean of heterozygosity, expected homozygosity, observed homozygosity, Nei's index and Shanon's index were 2.0, 1.9, 0.48, 0.38, 0.48, 0.51, 0.61, 0.48 and 0.68, respectively. Results of association between genotypes and fiber traits indicated that the CC genotype had the highest fiber length compared with the AA and AC genotypes (P < 0.05) while there was no significant association between the PRL gene genotypes and fiber diameter. These results imply that the PRL gene polymorphism can be used as a molecular marker to improve fiber production without a negative effect on fiber diameter.

Identification of point mutations in exon 2 of GDF9 gene in Kermani sheep.

Screening the fertile ewes from national herds to detect the major genes for prolificacy is an effective way to create the fertile flocks. Growth differentiation factor (GDF) 9 is a member of the transforming growth factor ß superfamily that is essential for folliculogenesis and female fertility. The aim of this study was to detect single nucleotide polymorphisms (SNPs) in exon 2 of GDF9 gene in Kermani sheep breed using PCR-SSCP. Genomic DNA was extracted from whole blood of collected samples using salting-out method. Whole exon 2 of GDF9 gene was amplified (634 bp and 647 bp fragments) using designed specific primers. The single stranded conformation polymorphism (SSCP) patterns of PCR products were studied using electrophoresis on acrylamide gel and silver-nitrate staining method. Finally, 4 banding patterns for the first primer pair and 4 banding patterns for the second primer pair were obtained. Also, indices of population genetic per SNP were calculated using Gen Alex 6.41 software. The sequencing results showed the presence of 3 mutations (SNP) (443, 477 and 721 positions) in the studied population.

Genome-scan analysis for genetic mapping of quantitative trait loci underlying birth weight and onset of puberty in doe kids (Capra hircus).

The objective of this study was to locate quantitative trait loci (QTL) causing variation in birth weight and age of puberty of doe kids in a population of Rayini cashmere goats. Four hundred and thirty kids from five half-sib families were genotyped for 116 microsatellite markers located on the caprine autosomes. The traits recorded were birth weight of the male and female kids, body weight at puberty, average daily gain from birth to age of puberty and age at puberty of the doe kids. QTL analysis was conducted using the least squares interval mapping approach. Linkage analysis indicated significant QTL for birth weight on Capra hircus chromosomes (CHI) 4, 5, 6, 18 and 21. Five QTL located on CHI 5, 14 and 29 were associated with age at puberty. Across-family analysis revealed evidence for overlapping QTL affecting birth weight (78 cM), body weight at puberty (72 cM), average daily gain from birth to age of puberty (72 cM) and age at puberty (76 cM) on CHI 5 and overlapping QTL controlling body weight at puberty and age at puberty on CHI 14 at 18-19 cM. The proportion of the phenotypic variance explained by the detected QTL ranged between 7.9% and 14.4%. Confirming some of the previously reported results for birth weight and growth QTL in goats, this study identified more QTL for these traits and is the first report of QTL for onset of puberty in doe kids.

Identification of QTL for live weight and growth rate using DNA markers on chromosome 3 in an F2 population of Japanese quail.

The Japanese quail (Coturnix japonica) is an important agricultural species and is an animal model for genetic researches. This study was conducted to identify quantitative trait loci (QTL) affecting live weight and growth rate on chromosome 3 in quail. Two strains of Japanese quail including wild and white were crossed reciprocally and F1 generation was created. The birds from F2 generation were measured for growth traits and all of 472 birds (8 pairs from the parental strains, 34 F1 birds and 422 F2 birds) were genotyped for microsatellite markers on chromosome 3. The results indicated chromosome wide significant QTL for hatching weight (P < 0.01) and weight at 1, 2, 3 and 4 weeks of age, average daily gain from hatch to 1, 1-2 and 3-4 weeks of age and Kleiber ratio (P < 0.05), an indirect criterion of feed efficiency. The highest QTL additive and imprinting effects (2.72 and 0.79 % of the trait variation in the F2 population, respectively) were related to hatching weight. The identified QTL for this trait (at 7 cM relative to the centromeric region of the chromosome) had significant interaction with sex and hatch (P < 0.01). The dominance effect of QTL was significant (P < 0.05) for bodyweight at one week of age accounting for 1.69 % of the trait variation in the F2 population.

Genetic mapping of quantitative trait loci for meat quality and muscle metabolic traits in cattle.

A whole-genome scan was carried out in New Zealand and Australia to detect quantitative trait loci (QTL) for live animal and carcass composition traits and meat quality attributes in cattle. Backcross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin backgrounds. The New Zealand cattle were reared and finished on pasture, whilst Australian cattle were reared on grass and finished on grain for at least 180 days. This paper reports on meat quality traits (tenderness measured as shear force at 4-5 ages on two muscles as well as associated traits of meat colour, pH and cooking loss) and a number of metabolic traits. For meat quality traits, 18 significant QTL (P < 0.05), located in nine linkage groups, were detected on a genome-wise basis, in combined-sire (seven QTL) or within-sire analyses (11 QTL). For metabolic traits, 11 significant QTL (P < 0.05), located in eight linkage groups, were detected on a genome-wise basis, in combined-sire (five QTL) or within-sire analyses (six QTL). BTA2 and BTA3 had QTL for both metabolic traits and meat quality traits. Six significant QTL for meat quality and metabolic traits were found at the proximal end of chromosome 2. BTA2 and BTA29 were the most common chromosomes harbouring QTL for meat quality traits; QTL for improved tenderness were associated with Limousin-derived and Jersey-derived alleles on these two chromosomes, respectively.

Quantitative trait loci for organ weights and adipose fat composition in Jersey and Limousin back-cross cattle finished on pasture or feedlot.

A QTL study of live animal and carcass traits in beef cattle was carried out in New Zealand and Australia. Back-cross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin backgrounds. This paper reports on weights of eight organs (heart, liver, lungs, kidneys, spleen, gastro-intestinal tract, fat, and rumen contents) and 12 fat composition traits (fatty acid (FA) percentages, saturated and monounsaturated FA subtotals, and fat melting point). The New Zealand cattle were reared and finished on pasture, whilst Australian cattle were reared on grass and finished on grain for at least 180 days. For organ weights and fat composition traits, 10 and 12 significant QTL locations (P<0.05), respectively, were detected on a genome-wide basis, in combined-sire or within-sire analyses. Seven QTL significant for organ weights were found at the proximal end of chromosome 2. This chromosome carries a variant myostatin allele (F94L), segregating from the Limousin ancestry, and this is a positional candidate for the QTL. Ten significant QTL for fat composition were found on chromosomes 19 and 26. Fatty acid synthase and stearoyl-CoA desaturase (SCD1), respectively, are positional candidate genes for these QTL. Two FA QTL found to be common to sire groups in both populations were for percentages of C14:0 and C14:1 (relative to all FAs) on chromosome 26, near the SCD1 candidate gene.

Quantitative trait loci for live animal and carcass composition traits in Jersey and Limousin back-cross cattle finished on pasture or feedlot.

A quantitative trait locus (QTL) study was carried out in two countries, recording live animal and carcass composition traits. Back-cross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin breed backgrounds. The New Zealand cattle were reared on pasture to carcass weights averaging 229 kg, whilst the Australian cattle were reared on grass and finished on grain (for at least 180 days) to carcass weights averaging 335 kg. From 11 live animal traits and 31 carcass composition traits respectively, 5 and 22 QTL were detected in combined-sire analyses, which were significant (P < 0.05) on a genome-wise basis. Fourteen significant traits for carcass composition QTL were on chromosome 2 and these were traits associated with muscling and fatness. This chromosome carried a variant myostatin allele (F94L), segregating from the Limousin ancestry. Despite very different cattle management systems between the two countries, the two populations had a large number of QTL in common. Of the 18 traits which were common to both countries, and which had significant QTL at the genome-wise level, eight were significant in both countries.

Effects of the myostatin F94L substitution on beef traits.

This study investigated the effects of a SNP in the myostatin gene (MSTN or growth differentiation factor 8, GDF8) on birth, growth, carcass, and beef quality traits in Australia (Aust.) and New Zealand (NZ). The SNP is a cytosine to adenine transversion in exon 1, causing an amino acid substitution of leucine for phenylalanine(94) (F94L). The experiment used crosses between the Jersey and Limousin breeds, with the design being a backcross using first-cross bulls of Jersey x Limousin or Limousin x Jersey breeding, mated to Jersey and Limousin cows. Progeny were genotyped for the myostatin SNP and phenotyped in Aust., with finishing on feedlot (366 calves, over 3 birth years) and in NZ with finishing on pasture (416 calves, over 2 birth years). The effect of the F94L allele (A allele) on birth and growth traits was not significant. The F94L allele in Limousin backcross calves was associated with an increase in meat weight (7.3 and 5.9% of the trait mean in Aust. and NZ, respectively, P < 0.001), and a reduction in fat depth (-13.9 and -18.7% of the trait means on live calves (600 d) and carcasses, respectively, Aust. only, P < 0.001), intramuscular fat content (-8.2% of the trait mean in Aust., P < 0.05; -7.1% in NZ, not significant), total carcass fat weight (-16.5 and -8.1% of the trait mean, Aust. and NZ; P < 0.001 and P < 0.05, respectively). Meat tenderness, pH, and cooking loss of the M. longissimus dorsi were not affected by the F94L variant. In the Jersey backcross calves, additive and dominance effects were confounded because the F94L allele was not segregating in the Jersey dams. The combined effects, however, were significant on LM area (4.4% in both Aust., P < 0.05, and NZ, P < 0.01), channel fat (-11.7%, NZ only, P < 0.01), rib fat depth (-11.2%, NZ only, P < 0.05), and carcass fat weight (-7.1%, NZ only, P < 0.05). The results provide strong evidence that this myostatin F94L variant provides an intermediate and more useful phenotype than the more severe double-muscling phenotype caused by knockout mutations in the myostatin gene.