Abstract
Abstract: The objective of this work was to evaluate the effect of narasin inclusion in mineral and protein supplements on the performance and supplement intake of grazing beef yearlings. One hundred and fifty Nellore yearlings with 17.0±0.06 months of age and 219.7±1.62 kg initial body weight (BW) were allocated into 30 experimental units (EUs), with five animals each. The EUs were assigned to 16 paddocks, which were continuously stocked for 28 days, followed by 28 days of rest. A randomized complete block design was used. The experiment lasted 140 days, divided into five periods of 28 days each. The assessed treatments were: control mineral supplement (CON); CON + 1,800 (N1800) or 2,750 (N2750) mg narasin per kilogram of supplement; and protein mineral supplement (PROT) or PROT + 360 mg narasin per kilogram of supplement (PROT 360). The inclusion of narasin in the mineral supplement increased average daily gain (ADG) in the first period and decreased supplement intake in the first, second, and third periods, when compared with the CON treatment. The ADG and supplement intake were similar between the N1800 and N2750 treatments. Narasin has a positive effect on ADG up to 28 days of supplementation and controls mineral supplement intake, without compromising this gain.
Highlights
The use of ionophores in mineral mixtures is an economical and easy alternative for producers who are trying to improve cattle performance (Sartori et al, 2017)
Ionophores have been shown to improve the performance of beef cattle on pasture (Sartori et al, 2017; Polizel et al, 2018), their use is limited, likely due to the labor required for their administration in grazing conditions
Because of its ability to carry ions through cell membranes, this molecule can be used as a growth promoter in ruminant nutrition, selecting rumen bacteria and protozoa (Azzaz et al, 2015)
Summary
The use of ionophores in mineral mixtures is an economical and easy alternative for producers who are trying to improve cattle performance (Sartori et al, 2017). Ionophores have been shown to improve the performance of beef cattle on pasture (Sartori et al, 2017; Polizel et al, 2018), their use is limited, likely due to the labor required for their administration in grazing conditions. There are few promising studies assessing narasin as a growth promoter in ruminant diets, especially in the field, which could lead to beneficial responses in rumen parameters (Polizel et al, 2020) and animal performance (Polizel et al, 2020) when combined with high forage contents. According to Polizel et al (2018), the addition of narasin did not cause any reductions in mineral supplement intake, which is an indicative that the inclusion of narasin in mineral and protein supplements may improve yearling performance, without affecting supplement intake
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