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The aim was to evaluate the performance, feeding behavior and nutrient digestibility of lambs ranked according to residual feed intake (RFI) and residual intake and gain (RIG). A total of 102 male lambs (½ Dorper ½ Santa Inês; 70 d; 24.6 ± 3.71 kg) were used. The mean values of the RFI classes were -0.101, 0.0, and 0.091, and those of the RIG classes were 1.980, -0.032 and -2.369, for efficient, medium and inefficient lambs, respectively. Average daily gain was not correlated to RFI, but was correlated to RIG. Physiological parameters (i.e., respiratory frequency and heart rate), ruminal movement and rectal temperature were similar between efficient and inefficient lambs (i.e., for RFI and RIG; P > 0.05). Efficient RFI and RIG lambs spent less time ruminating and drinking water and more time eating (P < 0.05). Rumination time is a good feeding behavior marker to distinguish efficient and inefficient lambs (i.e., RFI and RIG). Inefficient feedlot lambs exhibited greater dry matter intake; this difference was not reflected in digestibility traits. These results may assist in the identification of more efficient animals to lower production costs and mitigate the environmental impact of lamb production systems. |
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