Factors of variation of the milk composition on the Reunion Island

In order to characterise the incidence of livestock farming practices and rations distributed to the animals on milk quality, surveys and feeding controls were carried out quarterly on twenty-nine dairy farms during 14 months (2002-2003). Herds milk samples were collected and analysed for chemical composition (fat, protein, urea, lactose, and mineral contents) and for hygienic quality (total bacteria, butyric spore and somatic cell counts). The 116 milk sample data were analysed to build a five-class milk quality typology. This typology was then confronted to the management practices. The main factors influencing the variability of herd milk were the season, and the level and nature of feeding. The milks highest in fat and proteins contents were produced in the winter, particularly when the animals were fed temperate forages. Regarding hygienic quality, the best results were obtained in the winter and spring, in areas with low rainfall. None of the five milk classes combined on a same period high fat and protein contents, and low levels of butyric spore and somatic cell counts. An important margin of progress in mastering these main quality parameters appeared. This could be realised by adapting feeding practices and/or herd management techniques that were identified in the study.