201. Performance of Beef and Dairy-origin Male Cattle During Growing and Finishing Phases.

Abstract This study evaluated performance of cattle from different genetic backgrounds during growing and finishing phases. Ninety-six animals (initial BW = 194 ± 2.4 kg) were assigned to four genetic groups representing Brazilian beef systems: Angus × Nellore castrated (ANG), dairy crossbred non-castrated (DOC), Holstein castrated (HOL), and Nellore non-castrated (NEL), in a randomized complete block design. Animals were housed in pens (three per pen; experimental unit) and fed diets transitioning from forage-based growing to high-concentrate finishing. The experimental period included growing phase 1 (GRW1; 85 d), growing phase 2 (GRW2; 118 d), and finishing (FIN; 96 d). At the end of GRW2, 32 animals were slaughtered and the remainder continued to FIN. Variables evaluated were body weight (BW), average daily gain (ADG), dry matter intake (DMI), and feed efficiency (FE). Data were analyzed using mixed models, with treatment as fixed effect and block as random effect. Initial BW at each phase was used as a covariate, and initial BW of the experiment was used for overall analyses. BW differed among treatments during GRW1, with DOC and NEL heavier (313 and 311 kg) than ANG and HOL (269 and 280 kg; P < 0.01). No differences were detected in GRW2 (mean = 413 kg; P = 0.27), and final BW tended to differ in FIN (ANG = 532, HOL = 542, ML = 514, NEL = 537 kg; P = 0.09). ADG followed a similar pattern, with higher gains for DOC and NEL in GRW1 (1.34 and 1.35 kg/day) compared with ANG and HOL (0.90 and 1.01 kg/day; P < 0.01), with no differences thereafter (P ≥ 0.11). DMI differed among treatments, mainly in GRW2 and FIN. HOL had the greatest intake (9.58 and 9.42 kg/day), whereas DOC and NEL had lower intake (7.89–7.97 and 7.26 kg/day; P < 0.01). Overall DMI was greater for HOL (8.63 kg/day) compared with ANG (7.44), ML (7.28), and NEL (7.30; P < 0.01). Expressed as %BW, DOC showed the highest intake in GRW1 (2.72%; P < 0.01). FE was affected by genetic group. DOC and NEL were more efficient in GRW1 (0.205 and 0.217) than ANG and HOL (0.159 and 0.168; P < 0.01). In GRW2, NEL remained the most efficient (0.151), whereas HOL showed the lowest FE (0.113; P < 0.01). Overall, NEL and DOC had greater FE (0.165 and 0.156), while HOL was the least efficient (0.134; P < 0.01). In summary, NEL and DOC showed greater efficiency with comparable performance, whereas HOL had higher intake but lower efficiency, supporting the use of dairy crossbred males in beef systems.