The objectives of this experiment were to determine the apparent absorption, to estimate the endogenous fecal losses and the true absorption of Mg and to determine the ad libitum drinking water ingestion and the Mg serum concentration for Anglonubian (AN) and Saanen (SN) goat breeds. Twelve kids, six of each breed, with average 19.8 kg LW, were used. Semipurified diets (low Mg content) based on cracked rice, corn gluten meal and cellulose were supplemented with MgO to obtain the levels of .05 (without supplementation), .20 and .35% of Mg (% DM). The levels of Mg affected the coefficient of apparent absorption of Mg and Ca, with average values of 57.8, 73.9, and 73.2% for Mg and 55.7, 39.6 and 49.5% for Ca for diets with .05, .20, and .35% Mg, respectively. However, there was no effect of the dietary Mg level on the coefficient of apparent absorption of P, Na and K. An interaction between Mg level and breeds was observed for the real absorption of Mg. The mean for AN breed, on the level .05% Mg was 61.0% and for the levels 0.20 and 0.35% Mg, 77.2 and 73.2%, respectively. However, for SN breed the means were 73.3, 75.5 and 76.0%, for the same levels, without differences. The digestibility of dry matter, crude protein, and nitrogen free extract decreased with the crescent dietary Mg level. The fecal (7.0, 20.8 and 34.4 mg/kg LW0.75.d) and urinary (3.9, 30.8 and 44.6 mg/kg LW0.75.d) Mg excretion increased with the crescent dietary Mg level. There was also influence of the dietary Mg level on the blood serum Mg concentration (1.74, 2.23 and 2.80 mg/dL for .05, .20, and .35% Mg, respectively).
absorption; Anglonubian; goats; requirement; water ingestion; magnesium; endogenous loss; Saanen
