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Body content and net and dietary requirements of macrominerals (Ca, P, Mg, Na and K) of crossbred Holstein-Gyr steers during compensatory growth

Thirty-nine crossbreed Holstein-Gyr steers were used aiming to evaluate the influence of compensatory growth on body content and on net and dietary requirements of calcium, phosphorus, magnesium, sodium, and potassium of bovines. Thirty animals were submitted to a high pasture stocking rate, while nine had free access to the pasture (continuous growth group), during 114 days. After that, six animals from the first group and three from the second group were slaughtered, and the remaining animals were feedlot confined. From the animals of the first group, twelve animals were full fed (compensatory growth group) and twelve animals were fed 15% above the maintenance level (maintenance group), while the six animals from continuous gain group were full fed the same diet. Regression equations of log kg body contents of each mineral as a function of log empty-body weight (EBW) were fitted. The macrominerals requirements did not differ regarding to the treatments, and the net requirements for 1 kg of EBW gain ranged from 10.04 to 12.38 g for calcium; 9.33 to 9.41 g for phosphorus; 0.50 to 0.38 g for magnesium; 1.22 to 1.07 g for sodium; and 2.24 to 2.75 g for potassium, for steers with weights between 150 to 450 kg, respectively. The dietetic macrominerals requirements, for 1 kg of liveweight of gain, ranged from 15.88 to 25.68 g for calcium; 16.62 to 10.35 g for phosphorus; 5.12 to 9.82 g for magnesium; 2.25 to 4.35 g for sodium; and 18.23 to 49.18 for potassium.

bovine; body content; macrominerals; nutritional requirements


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