Blood parameter of Nellore steers submitted to different levels of feed intake

Abstract

Blood parameters of 18 Nellore steers submitted to high concentrate diet in two sequential feeding regimes (Phase 1: restriction and Phase 2: ad libitum feed) were evaluated. In the first phase, steers were fed during 56 days in three intake levels of dry matter (ad libitum, 75 g dry matter (DM)/kg metabolic body weight (BW0.75) or 60 g DM/kg BW0.75. In the second phase, from the 57th day of confinement, animals fed 60 g DM/kg BW0.75 and 75 g DM/kg BW0.75 received feed ad libitum until the 136th day. In the 8th, 27th, 55th (first phase), 71st, 84th, 112th and 132nd (second phase day of experimental period, blood samples were collected and insulin-like growth factor I (IGF-I), triiodothyronine (T3), thyroxine (T4), glucose, plasma ureic nitrogen (PUN) and total protein (TP) were determined. In the first phase IGF-I, T4, glucose and total protein concentration was not different among treatments (P>0.05) and there was no interaction between treatment and time (P>0.05). There was an interaction among treatments and time on T3 and plasma ureic nitrogen (P 0.05). For plasma ureic nitrogen concentration there was an interaction among treatments and time (P=0.02). Lower levels of diet intake can be used to improve animal performance in feedlot.