The aim of this study was to investigate the associations between variability in the myostatin, α^A-globin and lactate dehydrogenase B genes and racing performance in homing pigeons. The study included 123 animals (60 females and 63 males) participating in racing competitions. The data set used in this study consisted of scores from 17 short (≤ 400 km) and 11 long races (≥ 500 km) (2589 race records in total). Our study is the first study to analyse the associations between polymorphisms in the myostatin, α^A-globin and lactate dehydrogenase B genes and racing performance in pigeons. However, no associations were found between the SNPs analysed and the studied traits.

ABSTRACT:Myostatin is considered to be one of the most powerful negative regulators of muscle growth. The lack of a functional myostatin (MSTN) or its mutation can result in uncommon musculature like "double-muscling" in Belgian Blue cattle. Recent studies on MSTN variability indicate its relationship with racing performance in dogs and racehorses. Considering the high homology of MSTN among the vertebrates, there are grounds to suppose that the same correlation will occur in pigeons. The aim of this study was to analyse MSTN variability in several pigeon breeds raised for different purposes. The PCR-RFLP method was used for genotyping the C → T silent substitution in exon 3 of the MSTN gene. A total of 376 domestic pigeons (Columba livia var. domestica) were genotyped. The differences in genotype frequencies (P < 0.01) and allele frequencies (P < 0.01), between the studied groups were observed. Minor allele (MSTN T ) frequency was the highest in the group of utility pigeons (0.291), which are characterised by abundant muscle mass and higher body mass-to-muscle mass ratio. Further studies should be performed in order to determine the impact of the SNP analysed in the present paper on the amount of functional myostatin in muscles.

In the work presented, an analysis of the genetic values of conformation traits and their relations with the genetic value of dairy traits based on dairy performance (milk, fat and protein yield) and conformation data, was performed. Data were obtained for Polish Holstein-Friesian cows of the Black-and-White variety, maintained in 21 herds in the region of Wielkopolska (central Poland) and born between 2001 and 2004. The genetic values for the data analysed were estimated using the BLUP (best linear unbiased prediction) method and a mixed model. For the traits analysed, a genetic trend as well as genetic correlations between the dairy and conformation traits were estimated. The population analysed was divided depending on the year of birth and production level. The results obtained show a systematic increase in the traits analysed (positive genetic trends) both for dairy and conformation traits (with the exception of temperament). The highest genetic correlations between dairy and conformation traits were obtained for the udder, temperament and dairy type, while the lowest were obtained for height at sacrum and calibre. The analysis of the genetic value of conformation traits in cows of different dairy production genetic values indicated that the highest results were obtained for the group of animals with the highest genetic dairy production value. In turn, the analysis of the genetic value of traits of cows born in different years did not show statistically significant differences, with the exception of height in the youngest group.

The objective of this work was to study the reasons for culling one-day old broiler chicks and to examine the relationship between the age and line of the hens and the culled chick’s body mass. Hatching eggs and day-old chicks were collected from a commercial flock of the Cobb 500 and Ross 308 broiler lines. The eggs were collected when the hens were 32, 42 and 52 weeks old. The reasons for culling the chicks were assessed immediately after the chicks had been removed from the hatcheries. The four main groups of defects were distinguished, depending on the part of the chick’s body. A fifth group covered general developmental defects. Within each group, the structural defects were identified in detail. The statistical analysis was performed in the R project. Amongst 57 600 chicks evaluated, 1042 malformations disqualifying them from further rearing were found in 666. The most frequent developmental defects were associated with the structure of the abdominal wall and umbilical cord: these were found in 155 chicks from the Ross 308 line and in 107 from the Cobb 500 line. In turn, umbilical defects occurred in 95 and 104 chicks from the Ross 308 and Cobb 500 lines, respectively. Abdominal defects were the most common in 107 chicks from the 42-week-old layers and in 89 chicks from the 52-week-old layers. There were also correlations between the age of the parent flock and the following defects: glued down, lack of down on the wings, contorted hips, wry neck and spine, and lack of a wake-up reflex. The average body weights of the Ross 308 and Cobb 500 chicks were 44.00 g and 43.13 g, respectively, but these differences were not statistically significant. However, the age of the broiler breeders (42 or 52 weeks) did affect the chick’s body weight (P ≤ 0.05). The lightest chicks (40.75 g) came from the Ross 308 line (age 42 weeks) and were nearly 4 g lighter than all the other groups. Most relationships between the lines of the layer hens at a particular age and the occurrence of malformations in the chicks were found in the hens aged 32 weeks, which may indicate the need for changes in the management of the eggs from the youngest layers belonging to the different lines.

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