THE EFFECT OF MONENSIN ON LACTATION DAIRY COWS: A DOSE RESPONSE EVALUATION

Monensin (Rumensin®) was fed at doses of 0, 8, 16, or 24 ppm to 966 dairy cows in nine different geographical locations in the USA and Canada. A dose response analysis was conducted on the primary variable, milk production efficiency, to determine the most appropriate dose response function, establish a minimum effective dose, and, when possible, determine a maximum effective dose. Linear mixed models (SAS® Proc Mixed v6.12) were fit to the data. Linear contrasts comparing the non-zero doses of monensin to the control were done to initially determine a minimum effective dose from the 3 non-zero design points. In addition, eight predefined linear contrasts were used to initially determine the general linear-plateau shape of a dose response function for each primary variable. A weighted regression analysis of the least squares means and corresponding standard errors was used when it was necessary to discriminate between the competing linear-plateau functions. A non-overlapping confidence interval process was followed, if it was deemed appropriate, to establish a minimum effective dose for a nondesign point. In cases where the dose response function had a plateau, the dose where the plateau began was classified as the “maximum effective dose” (minimum dose for maximum effect). In cases where the dose response function did not have a plateau, the maximum effective dose was the largest dose used in the study if the response rate was significant

EVALUATING CLINICAL MASTITIS IN DAIRY CATTLE FED MONENSIN

The effect of Monensin on clinical mastitis in dairy cattle was evaluated from data collected at nine geographical clinical field trials using 966 Holstein cows and heifers in the United States and Canada. At each site, a randomized complete block design was conducted. Monensin (Rumensin®) was fed at concentrations of 0, 8, 16, or 24 ppm in a total mixed ration beginning 21 days before first calving for all nine sites, up to 7 days after second calving for six sites, and 203 days after second calving for three sites. Quarter milk samples were taken and cultured to determine the causative pathogen for each mastitis case and if clinical signs were observed the disease data were grouped according to etiology and analyses conducted. Analyses were conducted for all clinical mastitis cases as well as for a breakdown of the clinical mastitis cases into microorganism group levels. A generalized linear mixed model and a linear mixed model were used to determine if there were significant differences in clinical mastitis between the non-zero concentrations of Monensin and controls. Response variables for the clinical mastitis cases that were analyzed using a generalized linear mixed model were Animal rate, Quarter rate, Observation rate, and Incident rate. An additional response variable, Average case duration, was analyzed using a linear mixed model. Inferences from the analyses indicate that Monensin does not influence the susceptibility of dairy cattle to clinical mastitis

EVALUATING THE EFFECTS OF MONENSIN OVERDOSE IN DAIRY CATTLE

Monensin is approved as a feed additive by the FDA Center for Veterinary Medicine to increase milk production efficiency in lactating dairy cattle. To assess the effects of a gross error in mixing monensin into cattle feed, a 10-fold overdose was given for three consecutive days to naïve cows as well as cows previously dosed with monensin within the label range. Cows were evaluated during the overdose and for a subsequent 4 week observation period. Physiological variables were analyzed, including dry matter intake, body weight, body condition score, and serum chemistry profile. Production variables were analyzed, including milk yield and milk composition. Cows were blocked according to pre-treatment milk output, days in milk, and body condition. Results were analyzed using linear mixed model methodology with a baseline covariate. The study provided information for the veterinarian and the dairy farmer for determining whether an overdose may have occurred, for assessing the prognosis, and for deciding whether to continue feeding monensin immediately following an overdose

A Framework for Evaluating Biomarkers for Early Detection: Validation of Biomarker Panels for Ovarian Cancer

A panel of biomarkers may improve predictive performance over individual markers. Although many biomarker panels have been described for ovarian cancer, few studies used pre-diagnostic samples to assess the potential of the panels for early detection. We conducted a multi-site systematic evaluation of biomarker panels using pre-diagnostic serum samples from the Prostate, Lung, Colorectal, and Ovarian Cancer (PLCO) screening trial