SUPLEMENTAÇÃO NA FASE DE PRÉ-TERMINAÇÃO E TEMPO DE ADAPTAÇÃO AO CONFINAMENTO DE VACAS NELORE DE DESCARTE

Abstract

Adaptation to the feedlot system is important and should be done gradually to avoid metabolic disorders and performance fluctuations, since the animals have come from a forage-rich diet to one with a high proportion of concentrate. The objective was to evaluate the supplementation impact during the grazing period and the duration of dietary adaptation in the feedlot on performance and carcass quality of cull Nelore cows. The experiment was conducted at the Livestock Sector of the Comigo Technological Center (CTC), in Rio Verde, Goiás, Brazil, from May to August 2022. Before feedlot finishing, the animals were managed on Tifton-85 grass pasture (Cynodon dactylon) for 60 days. The experimental design used during the grazing period was completely randomized with two treatments (mineral supplement at 0.05% of body weight, and protein-energy supplement at 0.6% of body weight), with eight replicates per treatment. In the feedlot phase, the experimental design was also completely randomized, in a 2 x 2 factorial scheme, with two supplementations (mineral at 0.05% of body weight and protein-energy at 0.6% of body weight) and two adaptation periods (10 and 20 days). Thus, the treatments used were: 1) mineral supplement with a 10-day adaptation period; 2) mineral supplement with a 20-day adaptation period; 3) protein-energy supplement at 0.6% of body weight with a 10-day adaptation period; and 4) protein-energy supplement at 0.6% of body weight with a 20-day adaptation period. A total of 94 Nelore cows were used, all over 5 years old, non-pregnant, with an average initial body weight (BW) of 327 ± 54 kg. It was concluded that prior supplementation with protein-energy supplement resulted in greater initial and final weight gain in the feedlot, improved body condition score, higher slaughter weight and hot carcass weight, better carcass yield, and increased marbling in cull Nelore cows finished in feedlot conditions. Additionally, a 20-day adaptation period in the feedlot promoted higher feed intake and better fecal score.