Resumen

PINTO-SANTINI, Livia; GODOY, Susmira; CHICCO, Claudio  y  CHACON, Tony. High Levels of Dietary Iron and Molybdenum on Copper Nutrition in Cross Bred Cows. Rev. Cient. (Maracaibo) [online]. 2007, vol.17, n.6, pp.588-596. ISSN 0798-2259.

To evaluate the effect of high levels of iron (Fe) and molybdenum (Mo) on copper (Cu) nutrition, 20 dry cross bred cows, Bos Taurus x Bos indicus, of 394 kg BW, with no less than two calving, were assigned to the following treatments: (1) Control (C); 10 ppm Cu(2); Mo 10 ppm + 20ppm Cu (Mo); (3) 10ppm Cu+ 1000 ppm Fe (Fe); and (4) 10 ppmCu+ 1000 ppm Fe+ 20 ppm Mo ( MoFe). Cows were fed chopped forage ad libitum (Panicum maximum and Andropogun gayanus) and 1.5 kg concentrate feed (corn meal, 95% and urea, 5%) containing minerals in the proportions as previously indicated. Serum samples were taken every 28 days for Cu, Fe and cerulopasmine (Cp) activity. Liver sample, via biopsy, at the same time intervals, were also taken to measure Cu, Fe and Mo concentrations. The experiment lasted 192 days. Body weights were not affected by treatments: 385; 353; 396 and 382 kg, respectively for T, Cu, Fe,and MoFe. Copper serum concentration values (µg ml^-1) were 0.81, 0.67, 0.50 and 0.71, respectively for the same order, being Fe the lowest (P<0.05). Ceruloplasmine absorbancy values were not different among treatments. Liver copper concentration values were significantly different (P<0.05) among treatments, with higher value (mg KgMS^-1) for T (71.9) and lower for Mo (26.6), Fe (30.8) and MoFe (31.4). Liver iron concentration (mg kgMS^-1) values were not different among treatments, with values of 559.0, 513.3, 559.8, and 797.3 respectively for C, Mo, Fe and MoFe. Liver Mo take up (mg kgMS^-1) was greater (P<0.01) for Mo treatment (19.9) and MoFe (15.8) in relation to T (1.7) and Fe (1.9). Results indicate that high levels of Mo and Fe decreased liver copper, below critical levels. However, the reduction of liver copper was no associated with clinical sign of copper efficiency. Probably lower levels of liver copper are required to show changes in ceruloplasmine and blood serum concentrations as well as other biochemical changes at tissue level.

Palabras clave : Copper; iron; molybdenum; ruminants; antagonism; ceruloplasmine.