Epidemiologic Aspects of a Foot- and-Mouth Disease Epidemic in Cattle in Ecuador
A case-control study was conducted to identify herd-level risk factors associated with foot-and-mouth disease (FMD) in Ecuador. Case herds were those with presence of cattle with clinical signs of FMD and that tested positive for FMD virus during the epidemic of 2002 (n = 39). Control farms (n = 78) were selected randomly from a list of farms without a history of FMD. All study farms were visited, and managers were interviewed to complete an epidemiologic questionnaire. Feedlot operations, purchase of livestock at markets, and close proximity to markets or slaughter facilities were identified as risk factors for FMD (P ≤ 0.01). In addition to systematic vaccination of the national herd, we recommend allocation of funds for ring-vaccination of cattle herds in close proximity to markets or slaughter facilities, and to enforce movement of vaccinated-cattle only to help control and prevent new epidemics of FMD.
Modeling alternative mitigation strategies for a hypothetical outbreak of foot-and-mouth disease in the United States.
Alternative mitigation strategies were compared during hypothetical outbreaks of foot-and-mouth disease (FMD) in the USA using a computer-simulation model. The epidemiologic and economic consequences were compared during these simulated outbreaks. Three vaccination and four slaughter strategies were studied along with two speeds of FMD virus spread among three susceptible populations of animals. The populations represented typical animal demographics in the United States. The best strategy depended on the speed of spread of FMD virus and the demographics of the susceptible population. Slaughter of herds in contact with known contagious herds was less costly than slaughtering only contagious herds. Slaughtering in 3 km rings around contagious herds was consistently more costly than other slaughter strategies. Ring vaccination in 10 km rings was judged more costly than slaughter alone in most situations. Although early ring vaccination resulted in lower government costs and duration in fast-spread scenarios, it was more costly when vaccinated animals were slaughtered with indemnity and other related slaughter costs.
Application of resource allocation optimisation to provide profitable options for dairy production systems
A linear program (LP) model analysed resource use on a 100 ha dairy farm. A single optimum-profit combination was established for resources which were either optimised or constrained. It was found that, with a fixed herd of 320 milking cows, when production increased from 305 kg milksolids per cow (kg MS/cow) to 415 kg MS/cow, cash profit increased by 65%. This required additional supplements. If, however, feed demand and supply were optimised at 415 kg MS/cow, the LP reduced milking cow number rather than buy in feed to meet the increased feed demand from higher production per cow. At all production levels chosen between 305 and 415 kgMS/cow, it was most economic to dry off and cull cows early in dry summers to optimise feed demand vs. feed grown; use nitrogen (N) fertiliser to avoid a feed deficit only when response rates of better than 10 kgDM to 1 kg N could be expected; not use N for growing supplements to harvest. Pasture cover, within defined constraint levels, provided a buffer for feed demand and supply fluctuations. The study highlights the importance of assessing production, income and cost in an integrated framework to identify the point at which individual resources become limiting.