Effects of DL-malate on ruminal metabolism and performance of cattle fed ahigh-concentrate diet

To determine the effects of DL-malate on ruminal metabolism, four steers eq uipped with ruminal cannulas were fed an 80% rolled grain (75%, corn:25% wh eat) diet twice daily with a DMI equal to 2.0% of BW (485 +/- 24.8 kg). DL- Malate was infused into the rumen on two consecutive days in 500 mt of phos phate buffer to provide 0, 27, 54, or 80 g of DL-malate/d. Ruminal pH linea rly increased (P < .01) with DL-malate concentration and was greater (P < . 01) for DL-malate than for the control steers (6.01 vs 5.77). DL-Malate tre atment linearly decreased (P < .10) total VFA and tended to linearly increa se (P = .10) acetate concentration. Propionate, butyrate, and L-lactate con centrations and acetate:propionate ratio were not affected (P > .10) by DL- malate. Three finishing studies were conducted to determine the effects of feeding DL-malate on growth rate and feed efficiency. In a 98-d experiment, 33 crossbred steers were randomly allotted in a Calan gate feeding system to three DL-malate levels (0, 40, and 80 g/d). Steers (initial weight = 367 +/- 4.5 kg) were fed a lolled corn-based diet twice daily. After 84 d on f eed, gain efficiency (gain:feed) tended to improve with more DL-malate (lin ear, P < .10) and was 8.1% greater (P < .05) for DL-malate than for the con trol. The ADG Linearly increased (P < .05) with more DL-malate and was 8.6% greater(P = .10) for DL-malate than for the control. After 98-d on feed, A DG was linearly increased (P = .09) by DL-malate, and the greatest increase occurred with 80 g of DL-malate. In the second performance study, 27 Angus steers were randomly allotted in a Calan gate feeding system to three DL-m alate concentrations (0, 60, and 120 g/d). Steers (initial weight = 432 +/- 4.6 kg) were fed diets used in the first finishing study twice daily, but DL-malate was included during the 10-d step-up period. During the 10-d step -up period, feed efficiency and ADG linearly increased (P = .01) with more DL-malate. DL-Malate had little effect on steer and heifer performance or p lasma constituents in a 113-d finishing study. Collectively, these results suggest that feeding DL-malate to cattle consuming high-grain diets allevia tes subclinical acidosis, and it improved animal performance in two finishi ng studies.