Projects / Programmes
Fine genetic mapping of abdominal fatness and bone strength quantitative trait loci (QTL) and application of these QTLs in commercial chicken populations.
| Code |
Science |
Field |
Subfield |
| 4.02.00 |
Biotechnical sciences |
Animal production |
|
| Code |
Science |
Field |
| B400 |
Biomedical sciences |
Zootechny, animal husbandry, breeding |
chickens, abdominal fat, bone strength, mapping of quantitative trait loci
Researchers (9)
Organisations (1)
Abstract
Commercial selection of meat-type chickens has become complex as it must take into consideration a great number of objectives, all related to reduction of costs, the improvement of animal welfare status and quality of the final product. Historically, selection for growth in broilers has altered the growth pattern so that birds reach the slaughter weight at younger ages. The success of intense genetic selection has been accompanied by a number of negative consequences, including increased abdominal fatness and increased incidence of leg weakness. Excessive fat is a well known problem in poultry. It depresses feed efficiency, has no commercial value, and poses a major health risk to consumers. Bone problems affect mortality on the farm and condemnations within processing plant and thus raise both welfare and economic concerns. Growth, as well as fitness traits (abdominal fatness, bone strength), are controlled by many genes with large effects (quantitative trait loci, QTL). Since growth and fitness traits are negatively correlated it is difficult to improve fitness and simultaneously increase growth rate and meat yield by traditional, direct phenotypic selection. In addition, performing fitness traits phenotypic measurements is often laborious and expensive. Thus selecting individuals with additional information about their genotype for markers associated with QTLs (MAS - marker-assisted selection) is preferred. Because the negative genetic correlation between growth and fitness is not absolute, it is possible to select for genotypes with high fitness characteristics and high yield using marker-assisted selection. The objective of this research is to identify genetic markers for marker-assisted selection for improved leg bone strength and decreased abdominal fatness in chickens. We previously identified some QTLs affecting abdominal fatness and feet bone weight. Narrowing down of the QTL regions using additional markers is helpful for further selection of the candidate genes and finally the actual genes. The research is based on the hypothesis that polymorphisms associated with candidate genes, may be used for marker assisted selection. The project will use QTL to identify candidate genes and test their validity in Slovene commercial populations of chickens.
Significance for science
The broiler breeders' main requirement has always been quick growth, which means the highest body mass at a certain age and the lowest number of fattening days for a desired market weight, respectively. This aim has been realised by group (individual) selection, which principle was the selection of best animals to high body weight at a fixed age for later reproduction. The use of big populations and high heritability to body weight at fixed age enabled quick and stable development. Unfortunately higher gains achieved by energy rich feeding mixtures resulted in fat chickens with frequent leg damages. Such conditions contribute to high percentage of languished animals and therefore lower quality of carcasses. The reasons for leg deformations are complex and involve the technology of breeding, nutrition regime and various infections as well as genetics. The symptoms include general weakness of feet (chickens crouch or sit) and deformed bones in one or both legs (animals cannot stand or move and they lie on sides). Between the above extremes there are a number of damages that can be hardly distincted.
Better skeletal integrity and lower fat content in animals can be achieved only if we find markers connected to these traits. In our research we evaluated the traits like amounts of abdominal fat, diameter, weight and length of thighbone and shinbone, their fracture strength and foot weight. A few reports were found in literature concerning the fracture strength of bones in broilers over their growth and development. We found out a significant correlation between weight and fracture strength which indicates that bone weight is an important indicator of fracture strength. Therefore, any nutritional, environmental, or genetic factors that contribute to the bone weight improve their fracture strength, skeletal integrity and diminish various damages (fractures, breakings, crushing etc.). In our research two chromosome regions with significant impact on foot weight were determined. It concerns a product that gains in importance in the East Asian markets where heavier foots achieve better prices. We discovered a region on the chromosome 11 that influenced the amount of abdominal fat and, even more, no reports exist yet. It should be mentioned that we were the first to confirm the suitability of FSIL model of crossing in poultry which can be used for discovery of quantitative loci.
Significance for the country
The results of the project can mainly contribute to the development of Slovenia.
- The presentation of our own original scientific results at international conferences and in international scientific journals will add to the impact of Slovenian research work.
- The inclusion of undergraduate students into research work significantly contributes to the level of teaching process and help to enhance its contents.
- The integration of fracture strength and abdominal fat to traits considered in the selection of broilers is important because the studied traits have a direct effect on economics of rearing as well as an expected positive social and economic effect. Besides economics, the positive effects are demonstrated in the well being and health of animals that are expressed in security and quality of animal products.
- A special emphasis should be given to continual international cooperation with best researchers from Roslin Institute of Scotland.
Most important scientific results
Annual report
2008,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2008,
final report,
complete report on dLib.si
