Carcass traits of feedlot Nellore bullocks fed with two different types of ruminally protected fat

The objective of the study was to evaluate two different sources of ruminally protected fat on feedlot performance of Nellore bullocks. It was used 53 intact Nellore males with 315 ? 5.9 kg of initial body weight (IBW) and 20 months old. Six animals were random selected and harvested at the first day of study for carcass gain calculation while 47 animals were allocated in individual pens for feedlot performance evaluation. Trial design was randomized blocks (based on IBW) divided in three treatments: Control - no addition of fat (CON, n=16), Nutrigordura(R) - ruminally protected soybean oil (NUT, n=16) and a blend of ruminally protected vegetable oils containing both saturated and unsaturated sources (BRP, n=15). Animals were fed for 140 d with a 88% concentrate diet (14.2 % of CP and 2.74 of Mcal/ kg of DM, for NUT and BRP; 14.4 % of CP and 2.63 Mcal/ kg of DM for CON) composed of grounded corn, citrus pulp, peanut meal, trace minerals supplement and sugar cane bagasse. Diets of NUT and BRP treatments were isoproteic and isoenergetic with the same inclusion of protected fat (3.36% of DM). Animals were fed twice daily with total mixed ration management. Animals were considered as experimental unit and variables were analyzed using ANOVA (P<=0.10; PROC MIXED of SAS), and means were compared by contrasts (C1 = CON vs NUT+BRP; and C2 = NUT vs BRP). There were no differences (P>0.10) between contrasts for carcass depth and lengh, topside (TS) size, hindquarter and forequarter proportions in relation to cold carcass weight (CCW). However, it was observed differences for TS perimeter (C1; P=0.04) and short ribs (SR) proportion in relation to CCW (C1; P<0.01). Subcutaneous Fat Thickness (SFT) was greater for animals that received fat (3.2 mm CON vs. 4.4 mm for NUT and BRP; P=0.01). In addition, CCW presented difference between contrasts (C1: P<0.01, C2: P=0.03), in which BRP was greater than NUT and both fats were higher than CON. Complementarily, CCW of BRF was 13 kg heavier than NUT. Additionally, Ribeye Area (REA), presented differences in both contrasts (C1: P=0.04, C2: P=0.08), whereas BRP was 5 cm² larger than NUT. In conclusion, BRF produced heavier carcasses, with greater BFT and REA, in comparison to NUT and CON.