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Antimicrobial drugs are fed to hogs at subtherapeutic levels to prevent disease and promote growth. However, there is concern that the presence of antimicrobial drugs in hog feed is a factor promoting the development of antimicrobial drug‐resistant bacteria. This study uses a treatment‐effects sample‐selection model to examine the impact that feeding antibiotics has on the productivity of U.S. hog operations. No relationship was found between productivity and antibiotics fed during finishing, but productivity was significantly improved when antibiotics were fed to nursery pigs. Restrictions on feeding antimicrobial drugs during the nursery phase would likely impose significant economic costs on U.S. hog producers.

A multipe¡ hedging model is developed that is simpler than other multiperiod models in the literature. The model permits periodic adjustment of the hedge while minimizing the producer's profit variance. Minimum risk hedge ratios are calculated for steers, cows, hogs, com, and soybeans using the full model with hedge adjustments every two months. These ratios are compared to those using the model without periodic hedge adjustments and to a simple single-period model. The results suggest that simple models may work well for simple hedges, while the full model is best for more complex hedging situations such as cross hedges.Key words: futures markets, hedge ratio, hedging, minimum ¡ multiperiod model.Our purpose in this paper is to develop a multiperiod hedging model in which the hedge can be updated each period. Other multiperiod hedging models (e.g., Anderson and Danthine, Karp) have substantial data requirements which limit their use as viable hedging tools. Our aim is to develop a simpler model that will have practical application. The model is used to calculate minimum risk hedge ratios for steers, cows, hogs, com, and soybeans, and these ratios are compared with hedge ratios based on a multiperiod model in which the hedge cannot be adjusted each period. Simple minimum risk hedge ratios also ate computed for each commodity and compared with the other ratios.

We estimate a CBS system model of U.S. derived demand for meat. We use this model (1) to examine relationships between three quality categories of beef and three other meats and (2) to simulate how taste shifts have affected demands for meats over time. We extend previous studies by disaggregating wholesale beef production into three quality categories: (1) USDA Choice grade or higher, (2) USDA Select or lower, and (3) cow and bull beef. Innovative features of our empirical model include a breakout of 'table cuts' into Choice and Select and the use of a hedonic characterization of the two breakouts to value "Choice-ness" and "beef-ness." Our model demonstrates important shifts in separate demands for Choice and Select beef. We show that, separately, the demand for Choice-grade beef declined in the 1980s and 1990s and the demand for Select beef increased, a departure from the relatively stable demand characterizations of more aggregated measures of combined Choice and Select beef. Copyright 2007 International Association of Agricultural Economists.

Bioeconomics, Infectious disease, Ecosystem management, White-tailed deer, Optimal control,