Feeding behaviour of feedlot lambs offered different amounts of concentrate with or without protected fat

This study was carried out to evaluate the effect of different levels of concentrate associated or not with protected fat (calcium salts of fatty acids from soybean oil) in the diet on the feeding behaviour of feedlot lambs. Sixty-four 4 -month -old, non -castrated Santa Ines male lambs (20.07 +/- 0.25 kg BW) were distributed in a randomized complete block design, in a 4 x 2 factorial arrangement [four concentrate:roughage levels (C:R level - 400:600; 500:500; 600:400 and 700:300 g/kg, dry matter basis (DM)) and two inclusion levels of protected fat (0 and 35 g/kg, dry matter basis)]. An interaction effect between the concentrate levels and the inclusion of protected fat was detected for DM intake (g/day) (P = 0.020). The intake of neutral detergent fiber (NDF) decreased as the level of concentrate increased (P < 0.001), whereas it increased without the inclusion of protected fat (P = 0.003). The time spent in feeding (P < 0.05) and rumination (P < 0.001) decreased with increasing amounts of concentrate, whereas the time spent idling increased linearly (P < 0.001). The feeding efficiency (g DM/h) for DM increased (P = 0.019), and for NDF (g NDF/h) decreased (P < 0.001). Including protected fat increased feeding (g DM/h and g NDF/h) and rumination (g DM/h and g NDF/h) efficiencies (P = 0.015 and P = 0.023, respectively). The number of chews per day (P = 0.004) and number of cud chewed per day (P = 0.015) were linearly decreased as a function of the concentrate level. The DM (g) chewed per cud increased (P < 0.001) with higher levels of concentrate. The concentrate level of 700 g/kg DM increased the feedlot lambs' feeding and rumination efficiencies. Amounts higher than 35.0 g/kg DM of protected fat is not recommended considering the feeding behaviour results; mainly, DM intake and DM feeding efficiency. Nevertheless, studies based on performance and carcass yield are recommended.