The idea that the rate of production of new infections, of directly transmitted microparasites, is a reflection of an interaction between the number of infectious hosts and the number of susceptible hosts in a population is central to our understanding of dynamical processes in epidemiology. Empirical support for the idea has been seriously lacking, especially for endemic infections in natural hosts, but is provided here for cowpox virus infection in bank voles (Clethrionomys glareolus), using alternative descriptions of transmission dynamics: true and pseudo mass action. The former appears, overall, to give a better description of the dynamics. Transmission rates differ in two natural populations, but both support previously untested theories on the allometric scaling of transmission rates.

Despite the heavy reliance of the New Zealand beef industry on animals produced from the dairy industry (predominantly Friesian and Friesian cross), there is a widespread belief that beef of dairy origin is inferior to beef produced from traditional 'British' breeds. This belief is not supported by the scientific literature. There is a large body of work that suggests there is no difference between dairy and traditional British beef breeds in growth potential, lean meat yield, yield of prime cuts, and the quality of meat produced when grazed under similar conditions and slaughtered at the same chronological age or the same level of maturity (fatness). The current New Zealand payment schedule based on carcass weight, fatness and muscularity, undervalues dairy carcasses for having a different pattern of fat distribution (i.e. less subcutaneous fat) and a different muscle shape (poorer conformation score). In New Zealand, the key commercial driver for using traditional beefbred cattle appears to be their ability to achieve the 3 mm minimum fat depth and therefore a prime-graded carcass at a lighter carcass weight and with a younger animal compared to dairy-bred cattle. ARTICLE HISTORY