Effects of pretransit diets and post-transit potassium levels for feeder calves.

Two trails were conducted to study effects of K addition to receiving diets and the effects of feeding either a 55% concentrate diet or hay before shipment on the health, performance and blood chemistry of transported calves. One-hundred seven steer calves were used in trial 1 and 160 steer calves in trial 2. Postshipment diets for trial 1 contained .9 or 1.4% K and for trial 2 were .7, 1.3, 2.2 or 3.1% K. The preshipment diets were fed 3 d before shipment and the receiving diets were fed for 2 wk after feedlot arrival. Performance data were collected for 28 and 49 d for trials 1 and 2, respectively. Feeding a 55% concentrate diet before shipment significantly reduced mortality of transported calves. Potassium additions to the diet after arrival improved performance of transported calves. Upon arrival at the feedlot, calves fed the 55% concentrate diet preshipment had lower (P less than .05) plasma urea-nitrogen (PUN) values than calves fed hay preshipment. Blood packed cell volume (PCV) increased (P less than .05) as the receiving diet K level increased from .7 to 2.2%. The K recommended for transported calves was calculated to be 24.7 g/100 kg of body weight for the first 2 wk after arrival, 20% more than the requirement for nontransported calves.