Different materials used as bedding may affect the growth of different microorganisms. Straw is generally the most recommended bedding. There is less rapid development of pathogenic microorganisms with chopped oats straw and cedar sawdust than with newsprint4. Chopped straw, however, is more favourable to Klebsiella than sawdust16. Sawdust and shavings, particularly if heated, encourage the rapid development of coliforms in general and are often responsible for "epidemics" of coliform mastitis36.