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.

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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<0.05), except on spring season born bulls.

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Aim. The aim of the study was to explain the difference of pH values in heifer and bull meat and to carry out an analysis of the effect of age in groups of both sexes. Methods. The study contains data on 2,469 beef breed and their crossbreed cattle fattened on farms in Latvia and Lithuania, slaughtered in a certifi ed Lithuanian slaughterhouse ʻAgaras’ in 2018. For the assessment of the effect of sex, the beef cattle were divided into 2 study groups: 1,266 bulls and 1,203 heifers. 3 study groups were created for analysis of the effect of age: 12 – 17 months; 18 – 23 months; 24 and more months. Analysis of the data acquired was based on the indicators of descriptive statistics. T–test and Pearson correlation analysis were used. Results. The average pH in the meat of bulls was 5.87 ± 0.011, but in the meat obtained from heifers – 5.66 ± 0.005 (p ≤ 0.05). Within the desired pH value from 5.4 to 5.8, the group of bulls comprised 65 % of carcasses and the group of heifers – 86 % of carcasses. In the group of bulls, 35 % of carcasses had an increased pH in the meat (pH –≥ 5.9), while in the heifers’group – 13%. For a small part of the carcasses in both study groups, too low pH was found in meat (pH ≤ 5.3), with 1% in the group of bulls and 0.4% in the group of heifers. An analysis of the effect of age found no signifi cant differences in pH values between bulls of different ages. In the heifers’study group, the highest pH in meat was found in the group above 24 months of age, pH–5.69. Correlation analysis between the meat pH and the slaughter results showed a weak or non–existent relationship. In the overall study group, stronger correlation was observed between pH and fat score (r = –0.21, p < 0.05). Conclusions. The results indicate that meat from heifers is better quality in terms of desired pH. Meat with the desired pH can be used in the production of high-quality products that provide higher profi ts.