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英文文献：Nevada Ranchers Attitudes Toward the Trichomoniasis Vaccine
英文文献作者：Salaghe, Florina,Harris, Thomas R.
英文文献摘要：
Nevada Ranchers Attitudes Towards the Trichomoniasis Vaccine - Survey Results - Past surveys of Nevada ranchers have showed that cattle producers have not adopted the necessary management practices designed to limit the incidence of Trichomonaisis (Trich), a “venereal disease of beef herds caused by the protozoan Tritrichomoniasis Foetus” (Bhattacharyya et al.,1997). This disease is very common in the Western United States and Florida because of free range commingling of herds on large tracts of public land. Trich is contracted during breeding (from bulls to cows and viceversa) and it does not have any obvious signs, making it difficult to identify and isolate the infected animals in order to prevent spread. When a bull is infected, it will be infected for life and there are no vaccines or treatments available to the cattle producers. There are however tests that can help identify the infected bulls. Tests are not available for cows. A T. foetus vaccine was developed by the University of Nevada in cooperation with Ford Dodge Laboratories and the USDA granted a conditional license to market the vaccine in 1989. This vaccine is only effective for cows and it helps limit the disease and the loss of cattle crop. Although the vaccine has been available for over twenty years, the rates of adoption are still lagging, while the disease incidence in the state is increasing, raising concerns of industry leaders and local authorities. In order to gather information on the factors and characteristics that influence the decision making process, a survey of Nevada cattle producers was conducted during 2012 and 2013. In this study we investigate the data collected and develop an adoption model to see how ranch specific factors, familiarity with the treatment, individual characteristics and attitudes toward risk influence the probability of adopting the vaccine. The goal of this paper is to find what influences their decision on whether to vaccinate or not, and what are the policy issues that need to be addressed in order to enhance its adoption or the adoption of alternative public land management practices. We incorporate subjective risk attitudes and estimate the probabilities of adoption for three different groups of respondents: users, potential users and nonusers. The importance of our analysis stems from the large economic impact that the disease has on the profitability of ranchers, as it reduces calf crops and increases culling. Since our dependent variable is categorical and has a natural ordering, we start by estimating an ordinal logistic regression. The most common critique of this model is that it often violates the implicit parallel line assumption and gives biased parameter estimates. In order to address this concern we estimate two additional, less restrictive models: an unconstrained generalized ordered logit model with alternative variant coefficients, and a partially constrained generalized ordered model where three of the parameters are unconstrained. The vector of parameters estimated using the partially constrained and the unconstrained generalized ordered model, can be interpreted as coefficients from binary logit models where we collapse the categories of our dependent variable into two groups. Allowing for the risk aversion coefficient to vary by alternative gives a better picture of what exogenous changes can be used to influence the management practices of different categories of adopters. For example, it shows that being risk averse pushes respondents away from being in extreme categories (Users and Nonusers). Ranchers are more likely to at least consider adopting the vaccine in the future conditional on the degree of risk aversion. The biggest effect of risk attitudes is to make nonusers move to the potential users category and consider future adoption of the technology. We find that the most effective variable that can push people from being potential users to adopting the vaccine is the familiarity with the disease treatment. So if ranchers have not adopted the vaccine yet but are considering doing it in the future, more information on the treatment might persuade them to move towards adoption. According to our survey results, the targeted channels of information should be specialty magazines and veterinarians. The majority of the respondents list these two as their primary sources of information together with “other ranchers” in the area. Since the primary reason that respondents list for not vaccinating their herd is the believe of not having a Trich problem and not enough information on the vaccine, policy makers should focus their attention on diffusing information about the T. foetus vaccine and increasing awareness of the risk of contracting the disease. Information on the incidence of the disease in the area might help ranchers more accurately assess the risk of not adopting the necessary management practices. Another policy implication that might be of interest is that the rates of adoption might be improved by making some of the management practices, such as testing of bulls mandatory. We have seen that people that transport cattle out of state are more likely to vaccinate and one of the reasons for doing so might be that some of the neighboring states have made testing mandatory.
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