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The aim of the present study was to investigate the effects of milk composition changes on the in vitro growth of bovine mastitis pathogens. Nutritional requirements of three major bovine mastitis pathogens Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Streptococcus uberis (S. uberis) were investigated in vitro. We used ultra-high temperature (UHT) treated milk with different contents of fat, protein, and carbohydrates to test the influence of the availability of various milk constituents on pathogen growth characteristics. Additionally, the bacterial growth was investigated under experimentally modified nutrient availability by dilution and subsequent supplementation with individual nutrients (carbohydrates, different nitrogen sources, minerals, and different types of B vitamins) either to milk or to a conventional medium (thioglycolate broth, TB). Varying contents of fat, protein or lactose did not affect bacterial growth with the exception of growth of S. uberis being promoted in protein-enriched milk. The addition of nutrients to diluted whole milk and TB partly revealed different effects, indicating that there are media-specific growth limiting factors after dilution. Supplementation of minerals to diluted milk did not affect growth rates of all studied bacteria. Bacterial growth in diluted whole milk was decreased by the addition of high concentrations of amino acids in S. aureus, and by urea and additional B vitamins in E. coli and S. aureus. The growth rate of S. uberis was increased by the addition of B vitamins to diluted whole milk. The present results demonstrate that growth-limiting nutrients differ among pathogen types. Because reduced bacterial growth was only shown in diluted milk or TB, it is unlikely that alterations in nutrient availability occurring as a consequence of physiological changes of milk composition in the cow's udder would directly affect the susceptibility or course of bovine mastitis.
The Laboratoire des Sciences du Climat et de l'Environnement (LSCE) research program on prehistoric art conducts chronological studies of parietal representations with their associated archaeological context. This multidisciplinary approach provides chronological arguments about the creation period of parietal representations. This article presents chronological investigations carried out in several decorated caves in France (La Grande Grotte, Labastide, Lascaux, La Tête-du-Lion, Villars) and Spain (La Garma, Nerja, La Pileta, Urdiales). Several types of organic materials, collected from different areas of the caves close to the walls and in connection with parietal art, were dated to determine the periods of human presence in the cave, a presence that may have been related to artistic activities. These new radiocarbon results range from 33,000–29,000 (La Grande Grotte) to 16,000–14,000 cal BP (Urdiales).
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