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International audience; The aim of this study was to observe the effect of feed restriction (FR) on milk concentrations of major proteins and microRNA in order to identify potential biomarkers of negative energy balance in cows. We hypothesized that the effects of FR on mammary gland metabolism are reflected in milk and its different fractions. Two FR trials were conducted at mid lactation to induce negative energy balance: a short duration and high intensity one (SH) and a long duration and moderate intensity one (LM). The SH experiment involved 8 Holstein cows. The LM experiment involved 19 Holstein cows either in control (n=9) or restriction conditions (n=10). FR lasted 6 and 29 days with a dry matter intake reduced by 64 and 20% of ad libitum intake, and induced a negative energy balance of-42 and-21 MJ/d, respectively for SH and LM experiments. Milk was sampled before, during (3 times for LM) and after the restriction periods. MicroRNA, extracted from whole milk, fat globules, milk isolated mammary epithelial cells and extracellular vesicles were sequenced and protein concentrations analyzed using LC-MS. Concentration of several major proteins decreased during FR: αS2-casein (LM and SH), αS1-casein (SH), κ-casein (LM), α-lactalbumin (LM), β-lactoglobulin (LM). Among 2896 microRNA detected in milk, the abundance of 159 microRNA was affected by FR, mostly in extracellular vesicles (n=83) and whole milk (n=85), few in fat globules (n=6), but none in mammary epithelial cells. Among these 159 microRNA, 15 varied in two compartments. These experiments showed that FR affects the abundance of proteins and microRNA in milk. It may reflect modifications of mammary gland metabolism. These results will be further explored by proteomic analysis and by RT-qPCR on more samples. These preliminary results are promising in the search for non-invasive biomarkers of negative energy balance in milk.

International audience; In the dairy cow, negative energy balance affects milk yield and composition as well as animal health. Studying the effects of negative energy balance on dairy cow milk production is thus essential. Feed restriction (FR) experiments attempting to reproduce negative energy balance by reducing the quantity or quality of the diet were conducted in order to better describe the animal physiology changes. The study of FR is also of interest since with climate change issues, cows may be increasingly faced with periods of drought leading to a shortage of forages. The aim of this article is to review the effects of FR during lactation in dairy cows to obtain a better understanding of metabolism changes and how it affects mammary gland activity and milk production and composition. A total of 41 papers studying FR in lactating cows were used to investigate physiological changes induced by these protocols. FR protocols affect the entire animal metabolism as indicated by changes in blood metabolites such as a decrease in glucose concentration and an increase in non-esterified fatty acid or β-hydroxybutyrate concentrations; hormonal regulations such as a decrease in insulin and insulin-like growth factor I or an increase in growth hormone concentrations. These variations indicated a mobilization of body reserve in most studies. FR also affects mammary gland activity through changes in gene expression and could affect mammary cell turnover through cell apoptosis, cell proliferation, and exfoliation of mammary epithelial cells into milk. Because of modifications of the mammary gland and general metabolism, FR decreases milk production and can affect milk composition with decreased lactose and protein concentrations and increased fat concentration. These effects, however, can vary widely depending on the type of restriction, its duration and intensity, or the stage of lactation in which it takes place. Finally, to avoid yield loss and metabolic disorders, it is important to identify reliable biomarkers to monitor energy balance.

Le 25 octobre 1415, la chevalerie francaise est decimee au cours de la bataille d’Azincourt. Le bilan est terrible et les consequences desastreuses pour le royaume de France. L’armee francaise, l’ost feodal compose en grande partie par les vassaux du roi Charles VI, est ecrasee par l’infanterie anglaise : les chevaliers sont cloues au sol par une intense pluie de fleches. Les archives conservees ne permettent pas d’avancer des chiffres exacts, mais on estime les pertes a environ 6 000 hommes ...