Calibration to American options: numerical investigation of the de-Americanization method.

American options are the reference instruments for the model calibration of a large and important class of single stocks. For this task, a fast and accurate pricing algorithm is indispensable. The literature mainly discusses pricing methods for American options that are based on Monte Carlo, tree and partial differential equation methods. We present an alternative approach that has become popular under the name de-Americanization in the financial industry. The method is easy to implement and enjoys fast run-times (compared to a direct calibration to American options). Since it is based on ad hoc simplifications, however, theoretical results guaranteeing reliability are not available. To quantify the resulting methodological risk, we empirically test the performance of the de-Americanization method for calibration. We classify the scenarios in which de-Americanization performs very well. However, we also identify the cases where de-Americanization oversimplifies and can result in large errors.

Comparison of two strategies for systemic antibiotic treatment of dairy cows with retained fetal membranes: preventive vs. selective treatment.

The objective of this study was to evaluate the efficacy of a blanket systemic preventive treatment (PT) of cows having retained fetal membranes (RFM) with 1 mg/kg of ceftiofur administered the first day after calving regardless of their body temperature. This strategy was compared with a selective treatment (ST) strategy in which only cows having RFM and a rectal temperature > or = 39.5 degrees C within 10 d postpartum received ceftiofur. Cows that retained their fetal membranes for at least 24 h after calving were allocated to 2 groups. Rectal temperature was measured daily for 10 d postpartum. Sixty PT cows having RFM received a daily ceftiofur (1 mg/kg of body weight) treatment, administered subcutaneously during the first 3 d after diagnosis of RFM. If rectal temperature was > or = 39.5 degrees C after 3 daily treatments, cows received ceftiofur for 2 more days. Therapy in 53 ST cows was based on selective administration of ceftiofur to cows having fever during the first 10 d postpartum. Treatment was conducted for 3 to 5 consecutive days as described for PT cows, beginning on the first day of fever. In both groups, manual removal of the placenta was not attempted and antibiotic drugs were not administered into the uterus. For every cow having RFM enrolled in PT or ST, 1 cow without RFM that had calved on the same day was enrolled in a healthy control group (n = 113). All cows received two 25-mg doses of PGF(2alpha): 1 dose between 18 and 24 d and 1 dose between 32 and 38 d postpartum. The PT did not reduce the proportion of cows experiencing fever during 10 d postpartum compared with ST cows (71.7 vs. 69.8%). Results were compared using logistic regression models and survival analyses. The artificial insemination submission rate between 42 and 62 d postpartum was greater in PT (41.2 vs. 20.8 vs. 24.5%), but total conception rate was less in ST and control cows, respectively (25.0 vs. 38.9 vs. 36.2%). In this trial, a preventive systemic antibiotic treatment of all cows having RFM was not superior to a selective antibiotic treatment of cows only in case of fever.

Strategies to improve the therapy of retained fetal membranes in dairy cows.

In this field trial, a protocol for the treatment of retained fetal membranes (RFM) without any intrauterine therapy was compared with 3 protocols based on the intrauterine use of antibiotic pills (AP), the manual removal (MR) of the fetal membranes, or the combination of both (PR). The study was conducted on 5 commercial dairy farms in Germany. Cows with RFM for at least 24 h after calving were assigned to 1 of 4 treatment groups. Cows of all groups with a rectal temperature >or= 39.5 degrees C received a systemic antibiotic treatment with ceftiofur (1 mg/kg per d) for 3 to 5 consecutive days. In case of continued fever after 5 treatments, cows received a different antibiotic as an escape therapy. In the reference group (REF; n = 131), cows did not receive any additional treatment. All cows in group AP (n = 119) received intrauterine treatment with antibiotic pills consisting of 1,000 mg of ampicillin and 1,000 mg of cloxacillin for 3 consecutive days. In group MR (n = 121), an attempt was made to remove the fetal membranes manually, but uterine pills were not administered. In group PR (n = 130), an attempt was made to remove the fetal membranes manually and all cows received a local antibiotic treatment as in group AP. All cows received 2 doses of 25 mg of PGF(2alpha): one dose between 18 and 24 d and another between 32 and 38 d postpartum. Statistical analyses were performed using binary logistic regression models and survival analyses with group REF as reference. Of all animals, 79.8% had a body temperature of >or= 39.5 degrees C at least once within 10 d postpartum and were treated with ceftiofur. Occurrence of fever within 10 d postpartum was significantly lower in groups AP and PR compared with reference group REF, but was not different between groups MR and REF. Risk of receiving an escape therapy in case of fever after 5 treatments with ceftiofur did not differ among groups. Reproductive performance measures did not differ significantly between group REF and any of the comparison groups. Compared with a treatment protocol based only on systemic treatment with antibiotics for cows with a fever, neither intrauterine antibiotics nor manual removal of fetal membranes alone or in combination reduced proportions of cows needing an escape therapy nor did those treatments improve reproductive measures in the current lactation. Systemic treatment alone based on elevated rectal temperature was effective and reduced use of antibiotics compared with therapies that included intrauterine antibiotics.