The present studywas conducted to determine the body composition and the mineral requirementsfor growth of wool and hair lambs. A total of 34 castrated lambs with an initialbody weight (BW) of 19.9±0.8 kg were used; 17 of these lambs were ofthe genotype Ideal × Ile de France and 17 were Santa Inês. Ten lambs(5 of each genotype) were slaughtered at the beginning of the experiment toestablish their initial body composition. The remaining lambs were assignedto one of three diets (40% roughage and 60% concentrate, 60% roughage and 40%concentrate, or 80% roughage and 20% concentrate) in a 2 × 3 factorialarrangement of treatments. All of the diets were provided ad libitum.When the group under 40% roughage and 60% concentrate reached 35 kg BW, allof the animals were slaughtered. Linear regressions were used to determine therelationship between the shrunk BW and the empty body weight (EBW) for eachgenotype. These equations were compared and revealed differences between thegenotypes. The allometric equations were calculated using the relationship betweenthe amount of minerals and the EBW. The equations of a given mineral for eachgenotype were compared to verify if they were statistically different. The equationsfor calcium, phosphorus, magnesium and sodium differed between genotypes. Thesame equations were used to estimate the major body mineral composition perkilogram of EBW. The net requirement for gain of the fleece-free Ideal ×Ile de France lambs ranged from 7.77 to 6.80 g Ca, 4.54 to 4.14 g P, 0.30 to0.27 g Mg, 1.18 to 1.07 g K and 0.84 to 0.76 g Na per kg BW gain, and the requirementsof the Santa Inês animals ranged from 9.57 to 8.37 g Ca, 5.39 to 4.91g P, 0.36 to 0.33 g Mg, 1.18 to 1.07 g K and 0.90 to 0.81 g Na per kg BW gainfor the lambs weighting 20 to 35 kg. Santa Inês lambs showed higher requirementsfor Ca, P, Mg and Na.
