John Fetrow

A field evaluation of oxibendazole in horses infected with benzimidazole resistant small strongyles

Summary Horses with a history of frequent benzimidazole (BZD) treatment were used in a trial to assess the effectiveness of oxibendazole (OBZ). Initial investigations established that these animals were infected with small strongyles resistant to thiabendazole (TBZ), mebendazole (MBZ), cambendazole (CBZ), oxfendazole (OXF) and fenbendazole (FBZ). The herd was subsequently divided into four groups and received TBZ, CBZ, OBZ, or no treatment. OBZ effectly reduced fecal egg counts. Similar reductions were not observed with TBZ or CBZ.

Influence of Inoculum Volume in Diagnosis of Environmental Mastitis from Clinical Quarters

Diagnosis of acute clinical mastitis is often difficult because milk samples from such cases commonly produce no detectable growth. As many as one-third of milk samples from acute mastitis cases have produced no detectable organisms when cultured using standard procedures. One method used to improve diagnosis of mastitis is the plating of larger volumes of milk inoculum.4,8,12 The purpose of this study was to determine if plating a volume of milk inoculum larger than the standard 0.01 ml from clinical mastitis cases would produce an increase in the number of cases in which a bacterial cause was diagnosed. In Experiment 1 (comparison of 0.05 vs. 0.01 ml of inoculum), 234 samples were obtained prior to treatment from 201 cows with clinical mastitis on 5 North Carolina dairies from January 1987 to January 1988. In Experiment 2 (comparison of 0.10 vs. 0.01 ml of inoculum), an additional 127 milk samples were obtained by similar methods from the same dairies during 1988. The dairies included 3 Holstein herds maintained by the North Carolina Department of Agriculture (139, 193, and 144 milking cows, respectively) and 2 herds maintained by North Carolina State University (137 milking Jerseys and 140 Holsteins, respectively). Herds studied were free of Streptococcus agalactiae, and bulk-tank milk samples were examined at intervals not >60 days. Mycoplasma spp. isolations had not been made from any bulktank milk sample examined. Clinical mastitis was defined as the presence of grossly detectable abnormalities of the milk or the mammary gland. Milkers detected mastitis in the parlor during udder preparation. If abnormalities were detected, milkers were instructed to prepare affected quarters aseptically using recommended techniques’ and to collect milk samples into sterile glass vials. Samples were frozen at -20 C immediately after collection and were submitted to the laboratory at intervals not >2 weeks. Samples were handled in this manner for convenience and to approximate conditions under which samples are handled in actual field diagnosis of mastitis. Standard microbiology techniques were used in isolation and identification of microorganisms from milk samples. 1,3 For each sample in Experiment 1, 0.01and 0.05-ml samples were inoculated onto halves of trypticase soy agar with 5%

Application of portfolio theory in decision-tree analysis

A general application of portfolio analysis for herd decision tree analysis is described. In the herd environment, this methodology offers a means of employing population-based decision strategies that can help the producer control economic variation in expected return from a given set of decision options. An economic decision tree model regarding the use of prostaglandin in dairy cows with undetected estrus was used to determine the expected return of the decisions to use prostaglandin and breed on a timed basis, use prostaglandin and then breed on sign of estrus, or breed on signs of estrus. The risk attributes of these decision alternatives were calculated from the decision tree, and portfolio theory was used to find the efficient decision combinations (portfolios with the highest return for a given variance). The resulting combinations of decisions could be used to control return variation.