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Study adaptive responses of dairy animals

The traditional dairy production system is about to change bringing more uncertainty and this will impact on herd management practices. Thus dairy farmers need to have robust dairy cows, that can easily adapt to such diverse and fluctuating conditions. This requires the identification, and even the selection, of dairy cows that have the ability to perform well under such novel management conditions. The mammary gland by being responsible for the milk production plays a central role in this diversity. The characterization of its plasticity is a key element for the understanding of the robustness of the dairy cow.
To study the plasticity of the mammary gland, it is necessary to study this organ when its functioning is challenged. The once-daily milking is a relevant model of challenge because of its local action on the udder, the elevated response on the 2 components of the adaptation (capacities to resist the disturbance and to return to the initial state), and the strong variability of the response observed between dairy cows.

Effects and responses to the once-daily milking

The thesis has a double objective:

• to develop methods to characterize the plasticity of the mammary gland of dairy cows by using a multi-trait and temporal approach to take into account the effects of once-daily milking on milk production and composition and the response in the course of time
• to characterize and model the biological responses to identify, even classify factors (genetic or not) of the adaptive capacity of dairy cows.

The 1st phase of the thesis will consist in determining the part of the genetic contribution explaining the variability of response between cows (400 crossbred dairy cows Normande x Holstein; a 3-wk once-daily-milking challenge). The 2nd phase will aim at characterizing and modelling the plasticity of the mammary gland and at identifying predicting phenotypes. For that purpose, previous data will be combined to data issued from a trial describing the inter- and intra-lactation repeatability of the response to a once-daily-milking challenge carried out on one single day, and phenotyping cows on targeted criteria (intramammary pressure, inflammatory response; milk composition…).

An interdisciplinary approach

The thesis consists of a trial (2014) and a in silico work. It consists of an interdisciplinary approach of predictive biology combining the genetic analysis of data, the modelling of response curves, and the knowledge of physiology of lactation.

Clementine Charton is working on this thesis since november 2013, for 3 years.
She is supervised by Jocelyne Flament (lactation team, PEGASE unit) and Hélène Larroque (SAGA unit) in Toulouse.

Contact

Jocelyne Flament, UMR PEGASE (Jocelyne.Flament[at]agrocampus-ouest.fr)
Hélène Larroque, UR SAGA (helene.larroque[at]toulouse.inra.fr)