The aim of this study was to investigate the associations between variability in the myostatin, α<sup>A</sup>-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<sup>A</sup>-globin and lactate dehydrogenase B genes and racing performance in pigeons. However, no associations were found between the SNPs analysed and the studied traits.
The mating system of small populations, isolated as a result of habitat fragmentation, is a key factor in their survival. As such populations are at risk of losing their genetic variation, reduction of their evolutionary potential is a distinct possibility. A flexible mating system may therefore provide a means of maintaining genetic variation. The mating system of the edible dormouse (Glis glis), a small arboreal rodent endangered by the fragmentation of its habitats, is not well understood. To date, only one study has provided evidence of multiple paternity in dormice. We present the results of a four‐year study of eight isolated dormouse populations. Using 138 individuals and 10 polymorphic autosomal microsatellite loci, we examined the prevalence of multiple paternity in these populations. In addition, we investigated the frequency of communal nesting and the genetic relationships between the females and juveniles occupying a single nest box. We found a high prevalence of multiple paternity (70% of the litters were multiple‐sired), a weak genetic relationship between the juveniles and the accompanying females (in 81% of cases the female residing with juveniles in a nest box was not their biological mother) and a 10.5% frequency of communal nesting in all nests. Given the low genetic variability of dormice, the multiple paternity and promiscuity observed in this species can help to maintain its genetic diversity.
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.
The study estimated phenotypic correlations between reproductive traits in sows classified as maternal (Polish Large White, Polish Landrace, and Yorkshire) and paternal (Duroc, Berkshire, and Hampshire) components, kept on farms located in Poland and in the United States. Altogether, it used data on 736 litters from 196 sows to analyse traits related to litter and reproductive cycle length. The former included litter size, the numbers and the percentages of piglets born alive, stillborn, and weaned; the latter included gestation length, lactation length, and the lengths of weaning-to-conception, farrowing-to-conception, and farrowing intervals. The strongest positive correlations between the litter-related traits were those between litter size and the number of piglets born alive (0.90), the number and the percentage of piglets born alive (0.88), the numbers of piglets born alive and weaned (0.78), and litter size and the number of weaned piglets (0.68); the strongest negative correlations were between the percentage of piglets born alive and the percentage (−0.95) and the number (−0.82) of stillborn piglets. Among the traits related to reproductive cycle length, the strongest positive correlations were those between the length of weaning-to-conception interval and the lengths of farrowing-to-conception (0.96) and farrowing (0.97) intervals, and between the length of farrowing-to-conception interval and farrowing interval (0.98). Gestation length and lactation length were weakly negatively correlated (−0.25). Correlation coefficients between the traits related to litter size from one side and reproductive cycle length from the other were low and mostly statistically non-significant, suggesting that using phenotypic correlations can help improve economically important reproductive traits, but only within the two above-mentioned groups of traits.
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