PSVIII-17 Effects of managing mature beef bulls on divergent planes of nutrition on eating and activity behavior characteristics.

Abstract Fifteen mature Angus-based beef bulls (847.2 ± 23.6 kg initial body weight [BW]) were used in a 112-d experiment to evaluate the effects of divergent planes of nutrition on behavior activity characteristics. Bulls were ranked by BW and randomly assigned to one of two dietary treatments: 1) managed on a positive plane of nutrition (POS, n = 7) or 2) managed on a negative plane of nutrition (NEG, n = 8). All bulls were fed a common total mixed ration delivered into Insentec feeders and adjusted biweekly to achieve targeted weight gain or loss of approximately 12.5% of original BW. Activity data were captured by an ear tag accelerometer system (CowManager), with every minute of every day characterized as eating, ruminating, not active, active, or highly active. To monitor behavioral changes over the course of the experiment, data were classified into four periods representing days 0 to 27 (Period 1), 28 to 55 (Period 2), 56 to 83 (Period 3), and 84 to 112 (Period 4). Data were analyzed as repeated measures in time using the MIXED procedure of SAS with bull as the experimental unit. To achieve targeted weight divergence POS bulls (12.7 ± 1.10 kg/d) had greater dry matter intake (P = 0.0003) than NEG bulls (5.3 ± 1.03 kg/d), resulting in greater (P < 0.001) body weight gain for POS (1.21 ± 0.05 kg/d) compared with NEG (-1.20 ± 0.05 kg/d). Eating activity was influenced by a treatment × period interaction (P = 0.04), with NEG bulls spending more time with eating behavior (P < 0.05) compared with POS bulls during periods 1, 2, and 3, and no difference observed during period 4. Not active behavior was also influenced by a treatment × period interaction (P = 0.05), with no differences present during period 1, but NEG bulls spent more time not active (P < 0.05) compared with POS bulls during periods 2, 3, and 4. No treatment × period interactions were present for ruminating, active, and highly active behaviors (P > 0.14). Also, no treatment effect was observed (P = 0.36) on ruminating. Active and highly active behaviors were strongly impacted (P < 0.0001) by treatment, where POS were more active (283.8 ± 9.03 min/d) and highly active (117.6 ± 3.29 min/d) versus NEG bulls (176.8 ± 8.25 and 84.3 ± 3.00 min/d, respectively). These data indicate that though POS bulls had greater DMI from feed bunks, NEG bulls had greater activity classified as eating, perhaps indicating more time seeking food from pen floors and bedding after initial allotment to bunk was consumed. Moreover, the additional energy consumed by POS bulls allowed them to be more active and highly active compared with bulls offered less feed.