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Livestock farming has to face an increase of the demand of animal protein (milk and meat) especially in developing countries. On the other hand, it has to reduce its greenhouse gas, nitrate and ammonia emissions. A better efficiency of protein use is central for a more sustainable dairy production. A reduction of protein increases self-sufficiency and reduces nitrogen excretion, which impacts the environment such as eutrophication, acidification, due to ammonia and nitrate emissions (Van der Valt, 1988 ; Kay, 1969). A part of these emissions is linked to ruminal digestion by the microbial flora in dairy cows before intestinal digestion. To solve this problem, research has developed techniques to protect proteins and the most efficient technique was the tanning by formaldehyde, which is a reversible protection, found in 1975 (Vérité et al. 1977a et b). However, formaldehyde is a noxious molecule when used in firm therefore its utilization will be compromised in the years to come. This is why there is an interest for new techniques to protect proteins in feeds for cows to replace the tanning by formaldehyde.

One option which hasn’t been considered until now to replace the formaldehyde technique is the influence of physical characteristics of particle (size, density…) on the residence time of feeds in the rumen. A rapid escape from the rumen will increase the probability to preserve proteins. As the efficiency of these new techniques of protection is difficult to evaluate using classical methods of feed evaluation, there is a need of a new methodology to evaluate the value of feeds.

Towards new techniques of protein protection and new methodologies to estimate protein value

The objective of the thesis will be in the first place be to test the assumption that the physical characteristics (size, density…) of feeds particles play a role in the residence time of feeds in the rumen. Once these characteristics settled, they may be combined with one or several new techniques developed by feed industry to replace the tanning by formaldehyde. Concerning the new method of estimation of protein value of animal feed, it may be based on the response of milk protein synthesis and/or the amino acid blood rate of the cow after addition of the protected protein source in the diet of the cow.

The work will be divided in three parts:

• The study of the physical characteristics of food particles (size, density) that would allow a rapid passage out of the rumen to limit their degradation.
• The development of a new methodology for estimation of the protein value of feed. It will be based on the response of the production of milk protein with additional inputs of tested feed protein (integrating the variation of the response efficiency which makes this response is generally not linear).
• Develop in collaboration with the partner (AGRIAL – feed producer) a new protein material protection technology by combining different existing technologies and data obtained on ruminal transit rate. This test will also allow a final validation of the methodology implementation.

Florence Dufreneix is working on this subject of thesis since the 1^st january of 2016 for 3 years. She is supervised by Jean-Louis Peyraud and Philippe Faverdin in the team Dairy Systems.

Bibliographie

Kay R. N. B. Digestion of protein in the intestines of adult ruminants. Symposium proceedings, 1969, Vol 28, p 140-151. [Full text]
Van der Walt J. D., Meyer J. H. F. Proteins digestion in ruminants. South African Journal of animal science, 1988, Vol 18, No 1, p 30-41. [Full text]
Vérité R., Journet M., Flechet J., Lefaivre R., Marquis B., Vérité M. Utilisation des tourteaux traités au formol par les vaches laitières. II. – Effets sur la production laitière du traitement des tourteaux et du niveau d’apport azoté au début de lactation. Annales de zootechnologie, 1977a, Vol 26, No 2, p 183-205. [Full text]
Vérité R., Poncet C., Chabi S., Pion R. Utilisation des tourteaux traités au formol par les vaches laitières. I. Aspects digestifs. Annales de zootechnies, 1977b, Vol 26, No 2, p 167-181. [Full text]

Contact

Florence Dufreneix florence.dufreneix[at]rennes.inra.fr (PhD student)
Jean-Louis Peyraud jean-louis.peyraud[at]rennes.inra.fr (supervisor – Inra)
Philippe Faverdin philippe.faverdin[at]rennes.inra.fr (co-supervisor– Inra)
François Gautier f.gautier[at]agrial.com (co-supervisor – Agrial)