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There is, for dairy cows, a competition between two functions: lactation and reproduction. But, poor reproductive performances are associated with economic losses, disturbance of the work plan, and a mental workload for farmers. In addition, recent studies (Cutullic et al., 2009, 2011, 2012) have proven that milk yield and body condition had proper effects on the different reproductive stages (i.e. cyclicity, ovulation, fertility). These studies also showed the impacts of breeds x feeding systems interactions on reproductive performances. A model to predict reproductive outcomes have been developed by Brun-Lafleur et al (2013). However, a large variability of observed reproductive performances as compared to estimated ones is observed.

These show the lack of knowledge concerning phenotypic and genetic characteristics of dairy cows that have better reproductive performances than expected. And globally, which cows are robust in each system.

To address this question the experimental design of the Pin-au-Haras (monitored by Luc Delaby) is used.

For the past 8 years, 36 Normandes and 36 Holstein cows were equally distributed in 2 feeding groups (one with a restrictive diet, the other with a diet that enable the animal to express their potential, both grass-based), in a compact calving system.

• The first step of the PhD project will focus on characterizing the individual production and reproduction traits of the animals to identify the characteristics of robust animals, in different production systems.
• Then, the association of these traits with genetic characteristics will be performed.
• In the meantime, and additional experiment on 2 years with a similar design enriched with fine phenotyping (progesterone and/or oestradiol, energy or hormones metabolites determination in high-flow, automated oestrus detection…) will enable to test hypothesis built on previous results.
• Finally, the model will be completed in order to get a better prediction of the reproductive performances of dairy cows in various production systems.

Nicolas Bédère has been working on this subject of thesis since the 1st november of 2013 for 3 years. He is supervised by Catherine Disenhaus and Luc Delaby in the team dairy systems.

Contact

Catherine Disenhaus, disenhaus[at]agrocampus-ouest.fr (supervisor)
Nicolas Bédère, nicolas.bedere[at]rennes.inra.fr (Phd student)

Bibliographie

Brun-Lafleur, L., Cutullic, E., Faverdin, P., Delaby, L., Disenhaus, C., 2013. An individual reproduction model sensitive to milk yield and body condition in Holstein dairy cows. Animal 7, 1332–43.
Cutullic, E., Delaby, L., Causeur, D., Michel, G., Disenhaus, C., 2009. Hierarchy of factors affecting behavioural signs used for oestrus detection of Holstein and Normande dairy cows in a seasonal calving system. Anim. Reprod. Sci. 113, 22–37.
Cutullic, E., Delaby, L., Gallard, Y., Disenhaus, C., 2011. Dairy cows’ reproductive response to feeding level differs according to the reproductive stage and the breed. Animal 5, 731–40.
Cutullic, E., Delaby, L., Gallard, Y., Disenhaus, C., 2012. Towards a better understanding of the respective effects of milk yield and body condition dynamics on reproduction in Holstein dairy cows. Animal 6, 476–87.