PSXIV-14 Effects of supplementation of Natural Zeolite on performance and carcass characteristics of feedlot beef cattle.

Abstract The use of additives with the capacity to modulate the rumen pH of feedlot cattle is important when feeding diets with a high amount of highly degradable starch. Hence, we hypothesized that the supplementation of Natural Zeolite (NZ) would improve performance of feedlot Bos indicus cattle receiving a finishing diet. On day -1, 256 Nellore bulls were assigned to a randomized completed block design, according to initial BW (344 ± 15.82 kg; 8 bulls/pen; 8 pen/treatment). The treatments consisted of: (1) CON= high moisture corn silage- based diet without NZ; (2) 1NZ = CON diet plus 1% NZ (DM), (3) 2NZ = CON diet plus 2% NZ, and (4) 3NZ = CON diet plus 3% NZ. The inclusion of NZ was carried out in the diet by removing high moisture corn silage. There were 3 adapting diets and the finishing diet (45 to 48% high moisture corn silage, 20% corn silage, 30% dry distiller’s grains with solubles and 2% minerals and vitamins mixture) that was offered throughout the experimental period (112 days). Cattle were fed twice a day and orts were removed 3 times a week, weighed, sampled and discarded. Feed and orts samples were dried at 105 °C for 24 h to determine dry matter (DM) and calculate DMI. The pen average daily gain (ADG) and DMI were used to calculate feed efficiency (FE). At the end of the feeding trial, animals were weighed (after 16 h of feed and water deprivation) and final shrunk body weight (FSBW) was calculated, evaluated for subcutaneous fat thickness (SFT) and the rib eye area (REA) obtained by means of an ultrasound image from the transverse direction of the Longissimus muscle between the 12th and 13th ribs. After slaughter, hot carcass weight (HCW) and dressing percentage were determined. Data were analyzed using the MIXED procedure of SAS. The inclusion of NZ did not affect the DMI (9.11 ± 0.12; P = 0.64), ADG (1.43 ± 0.03; P = 0.12), FE (0.158 ± 0.01; P = 0.36) and final BW (504.55 ± 3.18; P = 0.14). There was no effect of glauconite inclusion level on carcass characteristics, except for SFT, which obtained a cubic effect (CON = 5.05; 1NZ = 5.55; 2NZ = 5.06; 3NZ = 5.4; P= 0.04). In summary, NZ supplementation did not affect animal performance, but benefit the subcutaneous fat thickness of feedlot Bos indicus bulls.