The Centre of Animal Nutrition has many international contacts, all over the world. Many MSc-students and PhD-students come to Wageningen and Utrecht for their education and to become a scientist. Also many researchers like to spent a sabbatical with one of the partners of CAN. This large international network also offers the opportunity for researchers and PhD-students of CAN to spent a sabbatical or part of their PhD project abroad. Currently Tetske Hulshof is doing part of her PhD-project with prof. Paul Moughan and Dr Shane Rutherfurd at Massey University in New Zealand.
In research, there is a growing interest in quantifying the effect of heat processing for protein sources. Heat processing affects amino acids and especially decreases the amount of available lysine. Several analysis methods for available lysine are known and I am currently working to improve one of these at the Riddet Institute of Massey University (Palmerston North, New Zealand) as part of my PhD thesis.
My PhD project is about protein characteristics (i.e., measure of the feed ingredient or diet) that can accurately reflect in vivo protein quality for pigs and is part of the IPOP Customized Nutrition programme. For my study, we chose lysine as protein characteristic. Lysine is most affected by heat processing because it can react with sugars in the Maillard reaction or with other amino acids in cross-linking reactions and it is often the first limiting amino acid in diets for growing pigs.
Reactive lysine is lysine which has not reacted with sugars or amino acids, i.e., having a free ε-amino group, and is considered available for the animal. Reactive lysine can be analysed using a guanidination reaction in which a chemical compound (O-methylisourea) binds to the free ε-amino group. This will result in the conversion of lysine to homoarginine which is an amino acid that does not occur naturally in feed ingredients. The homoarginine can, thereafter, be measured using conventional amino acid analysis.
It was always thought that O-methylisourea binds specifically to free ε-amino groups of lysine. Results of my PhD-study, however, indicated that this might not be the case. As the method was developed at the Riddet Institute by prof. Paul Moughan and asc. prof. Shane Rutherfurd, it was a logical choice that I would study the specificity of the reaction and optimize the reaction conditions for amino acids with free α-amino groups here. I am already 2 months in New Zealand and will stay for another 4 months. During the week, I work at the Riddet Institute and during the weekends I travel around the North Island to experience the beautiful landscape and culture of New Zealand.