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Improving lactation persistency, a strake for the dairy industry

During lactation, the milk production of a dairy cow follows a typical lactation curve: after calving, milk yield increases quickly to achieve peak lactation and then gradually decreases with advancing lactation until dry off. Lactation persistency can be defined as the rate at which the milk yield of a cow declines after peak lactation. It illustrates the ability of a cow to maintain high milk yield after this peak.
In the current economic, political, environmental and societal context of the dairy industry, improving lactation persistency of dairy cows can be interesting for both breeders and milk industry. Indeed, breeders could extend lactation, and therefore reduce nonproductive lifespan and the number of periods of early lactation when cows’ health and reproduction may be impaired. Furthermore, improving lactation persistency could stabilize annual milk production in terms of quantity and quality.

Is the rate of MEC exfoliation a determining factor for lactation persistency?

Milk is produced inside the mammary gland by specialized cells named Mammary Epithelial Cells (MEC). This type of cells exfoliates in milk during lactation. Our recent works have shown that a lower exfoliation could explain a better lactation persistency of ovariectomized dairy cows. Moreover, the lactogenic hormone prolactin could play a part in the regulation of the exfoliation process.
In this PhD thesis project, we suggest a new original criterion to characterize lactation persistency in dairy cows: MEC exfoliation estimation by measuring MEC concentration in milk. To do so, we have developed a method to purify milk mammary epithelial cells using magnetic beads coated with a specific anti-MEC antibody.

The first objective of this PhD thesis is to characterize MEC exfoliation process. In a first experiment, we will analyze MEC concentration in milk throughout milking. Then, the role of myoepithelial cell contraction in exfoliation process will be studied by injecting an oxytocin inhibitor in dairy cows.

The second objective is to test the rate of MEC exfoliation as an acceptable determining factor for lactation persistency. To do so, lactation persistency of dairy cows will be experimentally manipulated through variations in prolactin concentrations using a pharmacologic drug or feeding restriction.

The long-term purpose would be to propose a selection criterion for cow genetic selection based on their exfoliation rate in order to have cows with high lactation persistency and thus adapted to extended lactations. It could also help to define breeding practices that improve lactation persistency.

Lucile Hervé has been working on this subject of thesis since the 1st November of 2014 for 3 years. She is supervised by Hélène Quesnel and Marion Boutinaud in the lactation team.

Contacts

Marion Boutinaud : Marion.Boutinaud[at]rennes.inra.fr (PhD co-supervisor)
Hélène Quesnel : Helene.Quesnel[at]rennes.inra.fr (PhD supervisor)
Lucile Hervé : Lucile.Herve[at]rennes.inra.fr (PhD Student)