Influence of forage level and corn processing method on feeding behavior of Nellore bulls

Abstract Text: The objective of this study was to investigate the influence of neutral detergent fiber from forage (NDFf) levels and corn processing methods (CPM) on feeding behavior of finishing Bos indicus cattle fed high-concentrate corn-based diets. Forty Nellore bulls (388.1 ± 25.8 kg) were used in a randomized complete block design in a 4 x 2 factorial arrangement. Four levels of NDFf (3, 8, 13, and 18% sugarcane silage DM basis) were evaluated for two CPM: high moisture corn (HMC) and finely ground dry corn (FGC). Animals were fed ad libitum for 81 d, with diets delivered twice daily in individual pens. Sugarcane silage contained 64.0% NDF and 10.8 mm of mean particle size, all diets had 8% of whole linted cottonseed and the geometric particle sizes were 1.30 and 5.84 mm for FGC and HMC, respectively. Feeding behavior was evaluated twice (24 h each period) with fixed intervals of five min. Activities evaluated were eating, drinking, ruminating (R), chewing (C) and idling (min/d). Intake (IN), rumination (RU) and total chewing rate (TCR) were calculated (min/kg of DM). Number of meals (NM), interval between meals (IR) and meal duration (MD) were estimated (min). The first derivative was solved of a 2^nd order polynomial to determine optimal NDFf level. Animals fed HMC had 12.6% lower DMI (P<0.01) and 6.1% lower ME intake (MEI; P=0.04) compared to those fed FGC, but the IN was 21.6% greater for HMC than FGC (P<0.01). There was a quadratic effect of NDFf on DMI (P<0.01), MEI (P<0.01) and IN (P<0.01), with 10.8, 11.4 and 10.0% NDFf yielding the highest intakes, respectively. These NDFf levels to achieve maximum DMI and MEI are greater than recommendations in literature. Interactions between CPM and NDFf were observed for R (P<0.01) and C (P<0.01), however, when the RU and TCR were calculated, linear effects of NDFf were found for both. Increasing NDFf level increases the RU (P<0.01) and TCR (P<0.01). The HMC increases NM (P<0.01) and decreases IR (P<0.01) and MD (P<0.01) when compared to FGC. Increasing NDFf level increased linearly the MD (P<0.01). In conclusion, zebu cattle required around 11% NDFf to maximize DMI and MEI. The HMC increased the NM (min) and the IN (min/kg of DM).

Keywords: behavior, feedlot, zebu