Epidemiology of Mycoplasma bovis in Pennsylvania veal calves.

The objective of the study was to estimate the prevalence and incidence of Mycoplasma bovis, a common cause of pneumonia, in veal calves. Using simple random sampling, 252 calves from 4 veal herds located in central Pennsylvania were selected and longitudinally followed for monthly collection of nasal swabs. Bronchial swabs and lung lesions were collected at the slaughterhouse. Nasal, bronchial, and lung lesion swabs were cultured for bacterial respiratory pathogens. Ninety lung lesions were identified, of which 41.1, 1.1, 1.1, 7.8, and 4.4% were culture positive for M. bovis alone, Pasteurella multocida alone, Mannheimia haemolytica alone, M. bovis and P. multocida co-infection, and M. bovis and M. haemolytica co-infection, respectively. The data indicate that potential interventions, such as therapeutics, vaccines, or management control measures, would be most effective before 50 d of age based upon the cumulative incidence of colonization.

Elm Yellows Phytoplasma Lethal to Dutch Elm Disease-Resistant Ulmus americana Cultivars.

Ulmus americana (American elm) clonal cultivars Independence, New Harmony, and Valley Forge, together with the triploid putative hybrid cultivar Jefferson, were tested for reaction to the elm yellows (EY) phytoplasma. These cultivars all possess resistance to the fungal pathogen Ophiostoma novo-ulmi (1,4) but had not been screened for EY resistance or tolerance. Procedures and conditions of the test were similar to those used previously for assessing EY tolerance of Eurasian elm cultivars (3). In brief, 9 to 15 saplings of each cultivar and of U. americana raised from seed (susceptible controls), growing in a field plot at Ithaca, NY, were challenged by grafting their mainstems with bark patches from U. americana naturally affected by EY. Six to nine additional trees of each clone and of the seedling group were left untreated as controls. Inoculations were performed in July 1999, and trees were evaluated for symptoms in early September 2000. Multiple individuals in every inoculated group developed the syndrome typical of EY in U. americana: epinasty, foliar yellowing, yellow discoloration and necrosis of root and stem phloem, odor of methyl salicylate from moist discolored phloem on first exposure to air, defoliation or sudden permanent wilting, and death (2). The numbers of trees with these symptoms, of those inoculated, were: 9 of 9 Independence, 7 of 11 New Harmony, 10 of 14 Valley Forge, 3 of 13 Jefferson, and 12 of 15 trees grown from seed. Untreated controls remained asymptomatic, except for one tree of Valley Forge and two trees grown from seed that became infected naturally and had symptoms like those in the grafted trees. Based on these results, the elm cultivars named above are typical of U. americana in susceptibility to, and intolerance of, EY phytoplasmal infection. Effective EY resistance or tolerance in this species, although once thought to occur in rare individuals (2), remains undocumented. References: (1) J. L. Sherald et al. Can. J. For. Res. 24:647, 1994. (2) W. A. Sinclair. 2000. Page 121 in: The Elms. C. P. Dunn, ed. Kluwer Academic Publishers, Norwell, MA. (3) W. A. Sinclair et al. Plant Dis. 84:1266-1270, 2000. (4) A. M. Townsend. 2000. Page 271 in: The Elms. C. P. Dunn, ed. Kluwer Academic Publishers, Norwell, MA.

Responses of Six Eurasian Ulmus Cultivars to a North American Elm Yellows Phytoplasma.

Elms (genus Ulmus) of six clonal cultivars representing Eurasian species and hybrids were grafted when 2 to 3 years old with bark patches from U. rubra infected with an elm yellows phytoplasma or were left untreated as controls. The cultivars were U. glabra × minor 'Pioneer', U. minor × parvifolia 'Frontier', U. parvifolia 'Pathfinder', U. wilsoniana 'Prospector', and the complex hybrids 'Homestead' and 'Patriot'. Trees were evaluated for infection and symptoms 1 or 2 years after inoculation. Infection was detected via the 4',6-diamidino-2-phenylindol e·2HCl (DAPI) fluorescence test in 26 of 86 grafted trees representing five cultivars. Infection of selected trees was confirmed by polymerase chain reaction (PCR) amplification of a fragment of phytoplasmal rDNA, and the phytoplasma was identified by restriction fragment length polymorphism (RFLP) analysis of the amplified DNA using restriction enzymes AluI, RsaI, and TaqI. Elm yellows phytoplasma was also identified by nested PCR and RFLP analysis in two of seven inoculated, healthy-appearing, DAPI-negative trees and one noninoculated control tree. All RFLP profiles were identical to that of reference strain EY1. Phytoplasma-associated symptoms, observed in five cultivars, included suppressed growth, progressive size reduction of apical shoots and leaves, chlorosis, foliar reddening, witches'-brooms, and dieback. Phyto-plasma was not detected in cv. Homestead. Possible resistance of this cultivar to elm yellows phytoplasma was indicated by localized phloem necrosis in stems below inoculum patches.

A study of the factors that influence consumer attitudes toward beef products using the conjoint market analysis tool.

This study utilizes an analysis technique commonly used in marketing, the conjoint analysis method, to examine the relative utilities of a set of beef steak characteristics considered by a national sample of 1,432 US consumers, as well as additional localized samples representing undergraduate students at a business college and in an animal science department. The analyses indicate that among all respondents, region of origin is by far the most important characteristic; this is followed by animal breed, traceability, animal feed, and beef quality. Alternatively, the cost of cut, farm ownership, the use (or nonuse) of growth promoters, and whether the product is guaranteed tender were the least important factors. Results for animal science undergraduates are similar to the aggregate results, except that these students emphasized beef quality at the expense of traceability and the nonuse of growth promoters. Business students also emphasized region of origin but then emphasized traceability and cost. The ideal steak for the national sample is from a locally produced, choice Angus fed a mixture of grain and grass that is traceable to the farm of origin. If the product was not produced locally, respondents indicated that their preferred production states are, in order from most to least preferred, Iowa, Texas, Nebraska, and Kansas.