Kelly Nichols receives Pieter Walstra Award

The thesis has greatly advanced the understanding of energy and protein metabolism in dairy cattle. Six of the chapters in Nichols’ thesis have already been published in the leading Journal of Dairy Science. Findings of this research have directed practical strategies to increase the transfer of dietary protein into milk protein and reduce nitrogen excretion. The research thereby contributes significantly towards sustainable dairy production by offering nutritional strategies that reduce ammonia emissions to the environment.

Nutritional interventions

A particularly impactful and innovative aspect of Nichols’ thesis is her study of nutritional interventions at the whole-body and mammary gland level of lactating dairy cattle over 3 experiments. This approach allowed the fundamental discoveries of energy and protein metabolism at the tissue and cellular level to be applied at the whole animal level, and was translated into advice for nutritionists and farmers with respect to inclusion of energy and protein components in dairy rations.

A key finding with critical importance to practice is that remarkably high milk nitrogen efficiency and low nitrogen excretion, and hence low ammonia emissions, can be achieved by formulating dietary protein to supply a mixture of specific essential amino acids.

Amino acids

Furthermore, the type of energy source in the diet will affect amino acid partitioning between body storage, milk synthesis, and excretion. The work presented in this thesis shows clearly that the supply of a single amino acid does not necessarily limit milk protein synthesis, and suggests that this widely-held view should be abandoned in practice.

Instead, attention should be paid to the profile of specific amino acid groups and the type of energy in dairy rations when aiming to achieve improvements in nitrogen use efficiency, as both these factors impact the mammary gland response to variation in nutrient supply.

Pieter Walstra Award

The Pieter Walstra Award has been installed in 2011 by the Dutch Dairy Organisation (NZO) to honour the unique contribution of Prof. dr. Pieter Walstra to the area of dairy science and technology. The award is handed out every two years.

The jury finds Nichols’ PhD thesis not only of very high scientific quality, but also particularly relevant given the current discussion about nitrogen in agriculture. The thesis has clear practical implications for the whole dairy chain.

Kelly Nichols received her PhD from Wageningen University in April 2019. The research was funded within the Feed4Foodure research programme. Nichols now works as research scientist for the Animal Nutrition Group.