Multiple genotypically unique strains of the tick-borne pathogen Anaplasma marginale occur and are transmitted within regions where the organism is endemic. In this study, we tested the hypothesis ...that specific A. marginale strains are preferentially transmitted. The study herd of cattle (n = 261) had an infection prevalence of 29% as determined by competitive inhibition enzyme-linked immunosorbent assay and PCR, with complete concordance between results of the two assays. Genotyping revealed the presence of 11 unique strains within the herd. Although the majority of the individuals (70 of 75) were infected with only a single A. marginale strain, five animals each carried two strains with markedly distinct genotypes, indicating that superinfection does occur with distinct A. marginale strains, as has been reported with A. marginale and A. marginale subsp. centrale strains. Identification of strains in animals born into and infected within the herd during the period from 1998 to 2003 revealed no significant difference from the overall strain prevalence in the herd, results that do not support the occurrence of preferential strain transmission within a population of persistently infected animals and are most consistent with pathogen strain transmission being stochastic.
Abstract
Shiga toxin-producing E. coli (STEC) belonging to serogroups O26, O45, O111, O103, O121, O145, and O157, called ‘top-7’, are major foodborne pathogens. Cattle are a major reservoir, in which ...STEC colonize the hindgut and are shed in the feces, which is a major source of contamination of food. Our objective was to evaluate the impact of a proprietary yeast-based synbiotic product (prebiotic and probiotic; Alltech, Inc., Nicholasville, KY) on fecal shedding of top-7 STEC in feedlot cattle. Twenty existing pens, housing 40–112 steers per pen, with an estimated 60 to 90 days to slaughter, were randomly assigned to a control group or a treatment group that received 22 g of the synbiotic product per steer per day, as a top dress, in a finishing diet. Twenty pen-floor fecal samples were collected from each pen on days 0, 21, 42, and 54. Fecal samples were enriched and subjected to a multiplex PCR assay targeting serogroup-specific genes for the top-7 STEC and three major virulence genes, stx1 (Shiga toxin 1), stx2 (Shiga toxin 2), and eae (intimin). Bivariate descriptive statistics for the major serogroups and virulence genes were assessed prior to multivariable analysis using mixed effects logistic regression. The overall prevalence of the top-7 serogroups were 44.5% of O26, 41.3% of O157, 15.1% of O103, 13.7% of O45, 7.8% of O121, and 0.6% of O111. The overall prevalence of stx1, stx2, and eae were 43.9%, 70.8%, and 49%, respectively. E. coli O26, O157, and O45 had a significant treatment and sampling day interaction (P < 0.0001). On d 42, fecal samples from treated group had lower prevalence (P < 0.01) of O26, O103, and O45 compared to the control group. In conclusion, the in-feed administration of the synbiotic product appears to reduce fecal shedding of certain top-7 STEC serogroups in the feedlot cattle.
Scope of study. Studies were conducted to determine if feeding different levels of supplemental energy would affect the onset of puberty in heifers. Treatments consisted of feeding a 40% supplement, ...two levels of a 20% supplement or feeding a 40% treatment then a high concentrate diet before breeding. Onset of puberty, body weight and body condition score were measured. Also, a study was conducted to determine the effects of protein and energy supplementation on cowherd performance. Cows were fed isonitrogenous amounts of a 40% or 20% crude protein supplement prepartum; and postpartum cows were fed 40% or 20% supplement or were fed the 40% supplement at double the daily supplemental crude protein intake. Cow weight and body condition score, milk production and calf weight were measured. A subsample of cows were used to determine the effect of supplementation and physiological status on low-quality hay intake and digestibility. Findings and conclusions. Age of puberty was similar for heifers fed 40% and 20% supplements. Heifers fed the greater amount of 20% supplement had greater average daily gains and pubertal weights than heifers fed 40% and the low level of 20% supplement. Feeding high concentrate hastened onset of puberty and increased the number of heifers reaching puberty before the breeding season. Feeding the 40% supplement, exclusively, reduced pregnancy rates compared to other treatments. Prepartum cow weight, body condition score and pregnancy rate were greater for cows fed 20% versus those fed 40% supplements. Weight gains, body condition score and milk production were similar for all supplements fed after calving. Hay intake and digestibility were lower for cows fed 20% than 40% supplements. Feeding a high level of 40% or a 20% supplement had similar effects on hay utilization.
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