The myostatin (MSTN) gene region encompassing the 5'UTR and part of intron I was sequenced in animals of two herds of Latvian Darkhead sheep to extend data on the ovine MSTN gene polymorphism and to provide information useful for local breed conservation. Two and four polymorphic loci were revealed in the 5'UTR and intron I. Four and five local haplotypes were constructed, respectively. The genotyping data obtained and that previously reported for the same genomic region were combined in one dataset for the haplotype analysis. Recombination events were detected between loci (c.-40, c.-37) in the 5'UTR and (c.373+18, c.373+101) and (c.373+101, c.373+241) in intron I. Single-nucleotide polymorphisms at c.373+249 and c.373+323 appear to be involved in the strong linkage (p < 0.01). Linkage blocks (c.373+241, c.373+243) and (c.373+241, c.373+259) were revealed at nominal (p < 0.05) level of probability. Haplotype-specific patterns of the transcription factor binding sites predicted in silico were constructed to evaluate a putative functional significance of the particular alleles and haplotypes. A nucleotide at c.373+18 was shown to influence the pre-mRNA secondary structure. DNA curvature predicted in silico for allele c.373+101C was proven experimentally. A possible impact of the particular polymorphisms on the transcription and/or splicing efficiency is discussed.

Latvia has two local Bos taurus breeds—Latvian Brown (LBG) and Latvian Blue (LZG)—characterized by a good adaptation to the local climate, longevity, and high fat and protein contents in milk. Since these are desired traits in the dairy industry, this study investigated the genetic background of the LBG and LZG breeds and identified the genetic factors associated with mastitis. Blood and semen samples were acquired, and whole genome sequencing was then performed to acquire a genomic sequence with at least 35× or 10× coverage. The heterozygosity, nucleotide diversity, and LD analysis indicated that LBG and LZG cows have similar levels of genetic diversity compared to those of other breeds. An analysis of the population structure revealed that each breed clustered together, but the overall differentiation between the breeds was small. The highest genetic variance was observed in the LZG breed compared with the LBG breed. Our results show that SNP rs721295390 is associated with mastitis in the LBG breed, and SNPs rs383806754, chr29:43998719CG>C, and rs462030680 are associated with mastitis in the LZG breed. This study shows that local Latvian LBG and LZG breeds have a pronounced genetic differentiation, with each one suggesting its own mastitis-associated SNP profile.

Myostatin (MSTN), a member of the TGFβ superfamily, negatively affects skeletal muscle growth and controls muscle development at stages of pre-natal muscle growth. Marker-assisted selection with molecular markers of the MSTN gene can be used in animal husbandry for higher-quality and more economically profitable lambs. The study aims to identify multi-locus genotypes within the MSTN gene regions as molecular markers for fattening, feed efficiency, and carcass traits in Latvian sheep. This analysis was conducted on 76 intensively fattened male lambs representing six breeds in Latvia. Nine genotypes were identified based on four SNPs in the promoter and exon 1 regions, while six and four SNPs in introns 1 and 2 led to the formation of 14 and 10 genotypes, respectively. Six genotypes identified in the 3′UTR were significantly linked to traits such as birth weight, slaughter yield, muscle development, fat depth, average daily gain, dry matter intake, and feed efficiency. Genotypes of intron 1 were associated with slaughter yield, while genotypes of intron 2 were linked to fat depth, dry matter intake, and residual weight gain. The study concludes that MSTN gene SNPs can be used in selection to enhance sheep breeds in Latvia and improve economic outcomes for breeders.

The aim of this study was to explain the birth season effect on Hereford bulls fattening results. The research was made within the project ‘Baltic Grassland Beef’ framework in years 2015 and 2016. Data about 41 Herford purebred bull was used in the research, grown in different farms of Latvia. Bulls were slaughtered in certified slaughterhouse ‘Agaras’ (Lithuania). The average birth weight of the Hereford breed bulls was in border from 42.9 – 45.0 kg. The lowest birth weight was on spring season born bulls – 42.9 kg, but the highest on winter season born bulls - 45.0. Average realization age of bull’s, in the research groups, was on range from 567 days to 661 days. Bulls born on autumn and winter before slaughtering were significantly older, respectively 661 and 655 days with live weight of 519.9 kg un 542.1 kg. On spring born bulls with age 600 days reached the biggest live weight – 542.0 kg, respectively these group bulls average daily weight gain from birth to slaughter per day was the biggest among all the groups – 831.9 g. The highest slaughter weight showed on autumn and winter seasons born bulls, respectively 275.5 kg and 274.8 kg. In the research groups on different seasons born bulls conformation score was from points 2.4 to 2.6. All the bull’s carcass in the research groups were evaluated as 2nd and 3rd fat class. between the age before slaughter and average daily weight gain from birth to slaughter there is an important negative correlation (from r = -0.858 to = -0.977, p&lt;0.05), except on spring season born bulls.