This study evaluatedbody fat, protein and energy contents and nutritional requirements for bodyweight (BW) gain of lambs in tropical semiarid conditions. Thirty-two castratedSanta Inês 3-to-4-month old lambs (initial BW: 15.8 kg ± 1.4 kg)were used. Eight lambs were initially slaughtered to serve as the referencefor initial body weight composition. The remaining 24 animals were placed ina randomized block with three treatments and eight replications. Each one ofthe eight experimental blocks consisted initially of three 15 kg lambs to whichtreatments (daily supplement levels: 0.0, 1.0, and 1.5% of body weight of acorn, soybean and minerals concentrate mixture adjusted for a daily 200 g BWgain at 1.5% level) were randomly assigned. As one of the lambs reached 30 kgall three were slaughtered. Body composition (per kg of empty body weight -EBW), ranged from 171.59 to 145.84 g protein, from 0.53 to 319.00 g fat, andfrom 2,06 to 3,90 Mcal energy, for lambs from 15 to 30 kg EBW, respectively.Net requirements for 200 g BW gain/day ranged from 25.99 to 22.09 g proteinand from 0.311 to 0.591 Mcal energy for lambs from 15 to 30 kg EBW, respectively.Santa Inês lambs browsing in tropical semiarid regions require more proteinand less energy than lambs raised in temperate regions or kept in feedlots intropical areas, as reported in the literature.
