Effect of malate form (acid or disodium/calcium salt) supplementation on performance, ruminal parameters and blood metabolites of feedlot cattle

Heifers, 108, housed in 18 pens of 6/pen were used in a 141 d feedlot study. Six pens were randomly assigned to each of the following experimental diets: CON: control (no additive); MA: CON plus 1.08 kg/t of malic acid (0.98 g of malate/g product); and MAL: CON plus 2 kg/t of disodium/calcium malate (0.53 g of malate/g product). Both additives provided 1.1 g of malate/kg of concentrate (as mixed). Concentrate dry matter (DM) intake (kg/pen) and individual animal body weights (BW) were determined every 28 d. At 0, 84 and 141 d, ruminal fluid was obtained by ruminocentesis and blood samples were collected via tail venipuncture from 2 heifers/pen (12/diet). At slaughter, individual carcass weights were measured and carcass yield was determined. An in vitro study was also conducted to analyse ruminal fermentation of the 3 experimental diets. Batch cultures were inoculated with ruminal fluid from CON heifers incubated for 17 h at 39 °C, and main fermentation parameters were determined (i.e., pH, volatile fatty acids (VFA) and CH4 production, ammonia–N and lactate concentrations, and diet degradability). There were no differences among groups in BW, concentrate DM intake or BW gain at any time during the experiment. At slaughter, there were no differences in hot carcass weight and yield or carcass classification among groups. There were no effects of treatments on ruminal parameters (i.e., pH and concentrations of VFA and lactate), with the exception of NH3–N concentrations, which were higher (P<0.05) for MAL compared with CON and MA groups at 84 d of sampling. Blood metabolites (i.e., glucose, urea–N, lactate) were unaffected by treatments. In the in vitro study, there were no differences among diets in any parameter measured. Under the conditions of this study, supplementation with MA or MAL had no effect on animal performance, ruminal parameters or blood metabolites, and results did not depend on whether malate was administered as the free acid or as the disodium–calcium salt.