PSXII-34 Narasin improves performance of grazing Nellore yearling bulls receiving protein supplement

Abstract

The objective of this trial was to determine the effect of narasin inclusion into a protein supplement on the performance of grazing yearling bulls. One hundred and fifty Nellore yearling bulls were blocked by initial BW (332 ± 3.4 kg) and assigned to 30 paddocks (15 paddocks/treatment). Sixty paddocks of Brachiaria brizantha with 1 ha each were used, whereas each paddock was continuously grazed by 28 d, followed by a resting period of 28 d. Paddocks were rotated among treatments every 28 d to minimize possible paddock variation. The experimental period lasted 112 d, divided into 4 periods of 28 d each. The treatments were: 1) negative control (no narasin: 0N), and 2) 13 ppm of narasin/d (13N; Zimprova®; Elanco, São Paulo, Brazil). Narasin was added to the protein supplement by adjusting its concentration in each 28-d period, according to the supplement intake (SI) during the previous period. The SI was evaluated on a weekly basis. Forage mass in the paddocks was measured by choosing two points upon entry and exit of the lot from each pasture. All data were analyzed using the PROC MIXED procedure of SAS. The ADG and SI were analyzed as repeated measures over time. There was no treatment × period interaction for ADG (P = 0.06) and SI (P = 0.66). Narasin inclusion into the protein supplement did not affect SI (0N = 435.5, 13N = 431.3 g/d; SEM = 12.2; P = 0.74), increased the ADG (0N = 0.240, 13N = 0.284 kg; SEM = 0.017; P < 0.01) and the final BW of the yearling bulls (0N = 357.7, 13N = 363.0 kg; SEM = 3.43; P < 0.01). In conclusion, narasin inclusion into protein supplement improved the performance of grazing yearling bulls.

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

“…Daily supplementation of narasin increased ruminal propionate and SCFA concentration and reduced Ac:Prop ratio in beef cattle fed forage-based diets ( Miszura et al, 2019 ; Polizel et al, 2020 ; Limede et al, 2021 ). Additionally, daily supplementation of narasin into low-consumption mineral and protein supplements benefited performance in grazing cattle ( 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. In fact, even after the removal of ionophores from the diet, there is still a residual effect on ruminal environment and fermentation parameters of steers consuming forage-based diets ( Bell et al, 2017 ).…”

“…Narasin is an ionophore that improves performance of grazing beef cattle without affecting mineral ( Silva et al, 2015 ) or protein supplement intake ( Polizel et al, 2019 ). 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 ).…”

“…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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“…Some studies were carried out with the objective of evaluating the effects of narasin in diets containing high forage content. Polizel et al (2019) evaluating the ruminal fermentation parameters of cattle fed high roughage diets receiving control (no narasin), 13 mg/kg DM and 20 mg/kg DM of narasin, observed that narasin doses increased the molar proportion of propionate, decreased acetate, and consequently altered the acetate:propionate ratio. These changes in rumen fermentation parameters were obtained when narasin was supplied once a day (every 24 hours).…”

“…There was no interaction between treatment and period for ADG and DMI, however, the inclusion of narasin in mineral salt did not affect DMI and increased ADG and final body weight. Polizel et al (2019) evaluated the effect of narasin on protein supplementation on the performance of Brachiaria brizantha grazing bulls. The experimental treatments were control (no additive inclusion) and the inclusion of 13 ppm narasin.…”