Supplementation with a slow-release nitrogen ingredient associated or not with monensin on performance, metabolism, and meat quality of finishing beef cattle fed high starch diets

Abstract

This study aimed to assess the effects of a time-released nitrogen (N) supplement (Timafeed Boost®, Roullier Group, Saint-Malo, France) in association or not with monensin on the performance, metabolism, and meat quality of finishing steers. To investigate these outcomes, one hundred and twelve Nellore steers (380 kg ± 16.2) were used in a 2 × 2 factorial arrangement. Steers were allocated in 28 pens (four animals per pen) and the following treatments were randomly assigned to the experimental units: (1) Control (CON, n = 7) - finishing diet without additives; (2) Monensin-enriched diet (MON, n = 7) - monensin (Rumensin®, Elanco Animal Health, Greenfield, IN) provided at level of 30 mg per kg of dry matter (DM); (3) Gradual-N-release enriched diet (GRN, n = 7) - gradual-N-release supplement (Timafeed Boost®, Roullier Group, Saint-Malo, FR) provided at dose of 250 g per animal per day; or (4) Monensin + Gradual-N-release diet (MON + GRN, n = 7) - monensin (30 mg per kg of DM) associated to gradual-N-release product (250 g per animal per day). The experimental period comprised 102 days, being the first 15 days designated for the diet adaptation. The average daily gain (ADG) over the experimental period was reduced for steers fed GRN + MON (MON × GRN: P = 0.02) compared to those fed only GRN. Steers fed MON had greater DMI during the finishing phase than the other treatments (MON × GRN: P ≤ 0.03). Overall, steers fed CON diet had a greater day-by-day dry matter intake (DMI) variation than other treatments (MON × GRN: P ≤ 0.05). The GRN inclusion in the diet improved the feed efficiency in 5.7% (P = 0.04). Steers fed diets without GRN inclusion tended to had 17.8% additional blood urea concentration (P = 0.06). D-lactato and glucose levels were similar between treatments (P ≥ 0.21). The GRN use tended to increase (P = 0.09) the DM digestibility in ~5.6%. The microbial crude protein was reduced by MON + GRN association (MON × GRN: P = 0.02). The hot carcass weight was greater for GRN group compared to others (MON × GRN: P = 0.02). The use of GRN in the diet increased (P ≤ 0.04) the total and daily carcass gain, carcass yield and biological efficiency. In summary, these data indicate that the associated use of monensin with GRN should be avoided in finishing diets. The GRN technology showed be a promising technology to be used to boost muscle hypertrophy and carcass production of beef cattle.