Feeding Behavior and Particle Sorting of Nellore Cattle Submitted to Either Nutritional Restriction or Intake of Concentrate Feedstuffs Prior to Adaptation Period

The study, conducted at São Paulo State University feedlot, Dracena campus, Brazil, was designed to evaluate the effects of either nutritional restriction or intake of concentrate feedstuffs before beginning the adaptation period on feeding behavior and selective consumption of Nellore cattle. The experiment was designed as a completely randomized block, replicated 8 times (4 animals/pen), in which 96 22-mo-old yearling Nellore bulls (365.5 ± 39.2 kg) were fed in 24 pens according to the treatments: Restriction (Tifton hay fed at 1.4% of BW + mineral supplement); Control (Tifton hay fed ad libitum + mineral supplement) and Concentrate (Tifton hay fed ad libitum + 0.5% of BW of a mix of concentrate feedstuffs and mineral supplement). This study lasted 144-d, divided into 2 periods: 32-d of pre-adaptation, in which cattle were submitted to the treatments previously described, and 112-d of feeding high-concentrate diets, where cattle were fed the same diets. The adaptation program consisted of ad libitum feeding of two diets over adaptation period with concentrate level increasing from 72% to 86% of diet DM. The finishing diet contained: 73.5% cracked corn grain, 14.0% sugarcane bagasse, 9.0% cottonseed meal, 1.5% supplement, 1.2% urea and 0.8% limestone (DM basis). Cattle were fed ad libitum three times daily throughout the study. Visual appraisal was made on day 102 of the period of feeding high-concentrate diets, every five minutes during 24 hours. Samples of diets and orts were collected for determination of particle sorting by using the Penn State Particle Separator [>19 mm (long), >8 mm (medium), >1.18 mm (short), and <1.18 mm (fine)]. No significant (P > 0.10) treatment effect was observed for time spent resting, ruminating, and eating, as well as for meal length and DMI. However, cattle submitted to either nutritional restriction or intake of concentrate had similar (P < 0.10) meals per day (Restriction= 13.38^ab, Control= 14.83^a, Concentrate= 11.98^b), DMI per meal in kg (Restriction= 0.82^a, Control= 0.70^b, Concentrate= 0.87^a), and intake of short (Restriction= 1.02^b, Control= 1.03^a, Concentrate= 1.02^b) and fine particles (Restriction= 0.97^a, Control= 0.96^b, Concentrate= 0.97^a). Nevertheless, cattle submitted to intake of concentrate had greater intake (P < 0.10) of long (Restriction= 0.77^b, Control= 0.94^ab, Concentrate= 1.02^a) and medium particles (Restriction= 0.98^b, Control= 1.08^a, Concentrate= 1.05^a) than animals submitted to nutritional restriction. Thus, cattle should not be submitted to nutritional restriction before the adaptation period to avoid sorting against long and medium particles.