Duffield T F, Leslie K E, Sandals D, Lissemore K, McBride B W, Lumsden J H, Dick P, Bagg R
Department of Population Medicine, Ontario Veterinary College, University of Guelph, ON, Canada.
J Dairy Sci. 1999 Nov;82(11):2377-84. doi: 10.3168/jds.S0022-0302(99)75488-3.
Dry cows and pregnant heifers from 25 farms near Guelph, Ontario, Canada were enrolled in a large, double-blind, randomized clinical trial designed to evaluate the impact of monensin on energy metabolism, health, and production. A total of 503 cows was given monensin in controlled-release capsules, and 507 cows were administered placebo capsules 3 wk before expected calving date. The effects of treatment on health were evaluated using a logistic regression model. Treatment with monensin significantly reduced the incidence of abomasal displacement (OR = 0.41-0.84) and multiple illnesses (OR = 0.38-0.89). Monensin treatment tended to reduce the incidence of clinical ketosis (P = 0.11) and the risk of being culled (P = 0.09) in the first 94 d of lactation. Reproductive performance was analyzed with both a logistic regression model for conception rate and a survival analysis for days to first breeding and days from calving to conception. Treatment with monensin had no significant effect on any measure of reproductive performance.
