Effects of supplement type and narasin inclusion on supplement intake by Bos indicus beef bulls grazing a warm-season forage

Abstract

This study aimed to evaluate the effects of supplement type and narasin inclusion on the frequency and supplement intake of grazing Bos indicus beef bulls. Four hundred animals were ranked by initial BW (383 ± 35 kg) and allocated into one of four paddocks of Brachiaria brizantha cv. Marandú (100 animals/paddock). Paddocks were randomly assigned to receive either a mineral salt (MIN) or a protein-energetic supplement (PREN) containing or not narasin (N) for a 90-d period. An individual electronic data capture system with 11 feed bunks was used to individually measure supplement intake and meal frequency in each paddock. The evaluations and analysis of individual intake, frequency of visits to the feeder, and intake per visit (I/V) were performed every 15 d and classified as periods (PR1 through PR6). All data were analyzed as a 2 × 2 factorial design with the PROC MIXED procedure of SAS. A supplement type × N × PR interaction was observed (P < 0.0001) for daily supplement intake. No differences were observed between MIN, whereas PREN had a greater (P ≤ 0.03) supplement intake on PR1 and PR3, but a reduced supplement intake on PR6 compared with PREN + N (P = 0.02). Moreover, no supplement type × N interaction (P = 0.47) or N (P = 0.44) effects were observed for daily supplement intake in the present study. A supplement type × N × PR interaction was detected (P < 0.0001) for the frequency of visits in the feeders. Throughout the experimental period, animals from the MIN + N had a greater (P ≤ 0.02) frequency of visits compared with MIN cohorts. A supplement effect was detected for I/V (P = 0.02), whereas neither a narasin effect (P = 0.74) nor interactions (P ≥ 0.16) were observed. Animals offered PREN had a greater I/V when compared with MIN cohorts (145 vs. 846 g/d for MIN and PREN, respectively; SEM = 16.1). When these data are reported as percentage of days visiting the feeder within each PR, MIN and MIN + N animals visited the feeder for 25.8% and 35.9% of the days, respectively. Conversely, no differences were observed (P = 0.65) in the overall mean visits per PR between PREN and PREN + N (12.8 vs. 12.3 d for PREN and PREN + N, respectively; SEM = 0.195). As percentage of days visiting the feeder, PREN and PREN + N visited the feeder for 85.1% and 81.9% of the days, respectively. In summary, narasin inclusion did not reduce supplement intake, regardless of supplement type, but increased the frequency of visits to the feeder for the MIN treatment.

Effects of narasin supplementation on dry matter intake and rumen fermentation characteristics of Bos indicus steers fed a high-forage diet

“…The lack of effects on forage and mineral DMI observed herein is in agreement with Silva et al (2015) , who reported that inclusion of narasin (13 ppm) into a mineral mixture did not impact mineral and forage DMI. Moreover, Cappellozza et al (2019) also demonstrated that supplementation with 13 ppm of narasin did not impact the intake of mineral salt and a low-intake, protein-energy supplement (1.7 g/kg BW) in grazing B. indicus bulls. Nonetheless, increasing the narasin dose by approximately 50% did not impact concentrate, forage, and total DMI, but tended to decrease mineral supplement intake compared to animals consuming the recommended label dosage (13 ppm).…”

Effects of narasin supplementation frequency on intake, ruminal fermentation parameters, and nutrient digestibility of Bos indicus Nellore steers fed with forage-based diets

“…Low-consumption supplements are the most feasible and simple alternative in grazing systems and often serve as carriers for feed additives ( McDowell, 1996 ; Bretschneider et al, 2008 ). Although ionophores have been shown to enhance productivity of beef cattle fed forage-based diets ( Bretschneider et al, 2008 ), their use is limited, given reduced supplement intake, increased intake variability across animals and over time, and labor required for their utilization in grazing systems ( Davenport et al, 1989 ; Bretschneider et al, 2008 ; Cappellozza et al, 2019 ). Furthermore, the infrequent supplement intake by grazing animals ( Cappellozza et al, 2019 ) might impact the effects of a feed additive on rumen metabolism and growth performance ( Bretschneider et al, 2008 ).…”

“…Although ionophores have been shown to enhance productivity of beef cattle fed forage-based diets ( Bretschneider et al, 2008 ), their use is limited, given reduced supplement intake, increased intake variability across animals and over time, and labor required for their utilization in grazing systems ( Davenport et al, 1989 ; Bretschneider et al, 2008 ; Cappellozza et al, 2019 ). Furthermore, the infrequent supplement intake by grazing animals ( Cappellozza et al, 2019 ) might impact the effects of a feed additive on rumen metabolism and growth performance ( Bretschneider et al, 2008 ). Large meal size may also increase the probability of feed additive toxicity in grazing animals, if the bunk space is not appropriate to avoid overconsumption ( Horn, 2006 ).…”

“…Daily supplementation of narasin to beef cattle fed forage-based diets increased concentration of ruminal propionate and total short-chain fatty acids (SCFA) and reduced acetate:propionate (Ac:Prop) ratio ( Miszura et al, 2019 ; Polizel et al, 2020 ; Limede et al, 2021 ). Also, supplementing narasin daily into low-consumption mineral and protein supplements increased animal performance ( Polizel et al, 2017 , 2018 , 2019 ), given these supplements are often consumed erratically by animals ( Cappellozza et al, 2019 ), denoting a possible lasting effect of this molecule on ruminal metabolism. Accordingly, Pasqualino et al (2020) reported an increased rumen propionate concentration even after 4 days of narasin withdrawal, suggesting a lasting residual effect of narasin on rumen fermentation routes.…”

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“…Evaluating supplement intake by grazing beef bulls, Cappellozza et al (2019) did not found reduce supplement intake by narasin inclusion. Besides that, the authors found an increased the frequency of visits to the feeder for mineral salt containing narasin.…”