This study was carried out in order to determine body composition in magnesium, potassium and sodium requirements for weight gain in Santa Inês lambs. Two experiments were conducted using 18 animals in each one: in the first experiment, animals with mean initial live weight of 25 kg were used; in the second, animals with initial live weight of 15 kg were used. Six animals were slaughtered at the beginning of each experiment, in order to determine the amount of each mineral retained in the animals' body, as check animals for comparative slaughter technique. The remaining twelve animals were divided in two groups: six animals were ad libitum fed and six animals were restrictedly fed. The animals ad libitum and restrictedly fed were slaughtered when the first reached 35 and 25 kg of live weight, in the first and in the second experiments, respectively. Their body composition was estimated through the prediction equations obtained from the regression of the logarithm of the amount of Mg, K, and Na in the empty body on the logarithm of the empty body weight. The net requirements for gain were obtained through derivation of the body composition prediction equation. Net requirements of Mg, K and Na for kg of live weight gain for lambs with 15 and 35 kg of live weight were, respectively: 0.47 and 0.41 g of Mg; 2.32 and 2.05 g of K; 1.33 and 0.55 g of Na.
Ovis aries; sheep; nutritional requirements; mineral nutrients
