Ruminant Nutrition: Feed Additives

Feed additives are largely used in beef cattle diets to improve performance and reduce risks of nutritional disorder diseases like acidosis and timpanism. However, some countries tend to ban the use of ionophore in animal nutrition due to the risk of resistance of some microorganisms. Therefore, alternatives to non-antibiotic additives must be studied. The objective of this work was to investigate the effects of different feed additives on performance and carcass traits of beef cattle. Twenty 2 Nellore bulls (initial BW 353 ± 20.9 kg) and 22 steers (initial BW 320 ± 1.5 kg; 21mo old) were fed high concentrate diet (85% of concentrate and 15% of sugarcane bagasse as roughage source). The animals were allotted in 4 pens equipped with calan gate system and randomly assigned within sex (block) to one of the 4 treatments: Monensin at 30 mg/kg DM (MON); Virginiamycin at 30 mg/kg DM (VIR); combination to MON (15 mg/kg DM) plus VIR (15 mg/kg DM) (MPV); Blend of Castor Oil Acid and Cashew Oil fed at 500 mg/kg DM (COC). Feed and orts were computed daily for each animal for DMI and feed efficiency calculations. Animals were weighed (BW) and ultrasound scanned at the first day of the feedlot and each 28 d. Ultrasound measurements taken were Longissimus muscle area (ULMA) and backfat thickness (UBFT) between 12th and 13th ribs. After 112 d on feed, cattle were slaughtered and hot carcass weight (HCW), kidney, pelvic and inguinal fat (KPIF) and dressing percentage (DP) calculated. Dry matter intake for treatment MON was smaller (9.7kg/day; P = 0.04) when compared with COC (11.1kg/day) with no differences of VIRG and MPV (10.1 and 10.4kg/day, respectively). There was no effect of treatments on ADG (1.60 ± 0.26 kg), feed efficiency (0.156 ± 0.02 kg ADG/kg DMI), final BW (510 ± 47 kg), HCW (307 ± 27.2 kg), dressing percentage (60.0 ± 1.78%), UBFT (5.9 ± 2.1 mm) and KPIF (3.12 ± 1.62%) at slaughter. Longissimus muscle area was higher for MPV (80.9cm2; P = 0.008) than COC (74.4cm2) and VIR (74.4cm2). The additives studied can replace ionophores to beef cattle fed high concentrate diet, without affecting animal performance and most of carcass traits.