Wageningen Animal Breeding & Genomics is proud to announce the graduations and upcoming PhD defences of our PhD candidates.
The public PhD defences and graduations of Wageningen University are in the Aula and can be (re)viewed online at WURtv.
On Friday December 15 at 14:30 Zih-Hua Fang will defend her thesis entitled: 'The genetic backgrounds of bovine 𝛼𝑠1- and 𝛼𝑠2-casein phosphorylation'. Defence in France.
Summary: Phosphorylation of caseins is a crucial post-translational modification that allows caseins to interact with calcium phosphate to form casein micelles. This thesis investigated the genetic background of the phosphorylation of 𝛼𝑠1- and 𝛼𝑠2-casein. For this purpose, phosphorylation levels in French Montbéliarde and Dutch Holstein Friesian cows were studied. This study shows that genetic factors contribute substantially to differences in 𝛼𝑠1- and 𝛼𝑠2-casein phosphorylation: intra-herd heritability’s for various casein phosphorylation traits range from 0.07 to 0.89. A genome wide association study identified 10 chromosomal regions that were associated with relative concentrations of 𝛼𝑠-casein phosphorylation isoforms. Some of the identified regions are associated with milk protein synthesis whereas others with phosphorous secretion in milk. The results suggest two systems that regulate the phosphorylation of 𝛼𝑠1- and 𝛼𝑠2-casein. Differences between cows in 𝛼𝑠-casein phosphorylation affect the technological properties of milk and, therefore, this study is highly relevant for manufacturing of dairy products.
On Tuesday December 19 at 9:15 Qianqian Zhang will defend her thesis entitled: "Exploiting whole genome sequence variants in cattle breeding'. Defence in Denmark.
On Friday Januari 19 at 16:00 Tom Berghof will defend his thesis entitled: 'Selective breeding on natural antibodies in chickens'.
Summary: Diseases have a considerable impact on animal welfare, production efficiency and profitability. Improving general disease resistance is therefore of great interest. This might be achieved by selective breeding. Natural antibodies are associated with survival in layer chickens. However the genetic background of these antibodies, and the possibility to breed for them has not been studied. This PhD thesis investigated the genetic background of natural antibodies in layer chickens. A QTL with a major effect on natural antibodies was identified: based on sequence data, it was concluded that Toll-like receptor 1A is the most likely candidate gene. In addition, chickens were successfully selected for high and low levels of natural antibodies. Chickens selected for high levels of natural antibodies showed an increased disease resistance against avian pathogenic E. coli at young age compared to chickens selected for low levels of natural antibodies. Results from this thesis suggest promising opportunities to improve general disease resistance through selective breeding on natural antibodies in chickens.
On Friday Februari 23 at 16:00 Sonia Eynard will defend her thesis entitled: 'Using genomic information to conserve genetic diversity in livestock'.
Summary: The conservation of genetic diversity in livestock has gained attention over the past decades because of the presumed negative impact that past artificial selection had on genetic diversity. Yet, genetic diversity is necessary to enable livestock breeds to respond in the long-term to changes in breeding goals and external factors such as climate. With the availability of dense genotypes and even of whole genome sequence come opportunities to quantify the impact of selection on genetic diversity and to develop new tools to mitigate this impact. In this thesis I describe how genomic information can be useful for long-term selection decisions and quantification of loss of genetic diversity to better safeguard breeds’ potential for the future. Moreover, methods to simultaneously maximise selection response and conservation of genetic diversity were investigated, along with the potential of the material stored in the gene bank for long-term selection decisions, especially for small breeds.
Sabine van Engelen
On Wednesday March 28 at 16:00 Sabine van Engelen will defend her thesis entitled: 'Exploring genetic variation in methane emission by dairy cows'.
Summary: Each individual dairy cow emits between 60 and 160 kg of methane (CH4), a harmful greenhouse gas, per year. Methane emission could be reduced by selective breeding which utilizes the influence of the genetics of the host on CH4 production. The main aim of this thesis is to answer the question whether there is genetic variation in CH4 emission by dairy cows. In order to quantify the genetic variation in CH4 emission, 3 different indicators were used: 1) indicator based on milk fat composition; 2) indicator based on CH4 and CO2 concentrations measured in the breath of the cow; 3) indicator based on milk mid-infrared spectra. These three indicators showed heritable variation ranging between 3 to 12% for milk mid-infrared predicted CH4 emission and 12 to 44% for milk fat predicted CH4 emission.