Suplementación parenteral con cobre y zinc en bovinos Brahman en crecimiento en la región sur occidental de Venezuela

in order to evaluate the effect of copper and zinc parenteral supplementation on average daily gain (adg), increases in body measurements and hematological values, growing brahman females (n = 33) and males (n = 34) were used, with body weight of 165 and 186 kg respectively, which were grouped into four sets of both sexes and assigned to four types of supplementation: 1) oral mineral supplementation (oms), 2) oms and copper injected (oms-cu), 3) oms and zinc injected (oms-zn), and 4) oms, copper and zinc injected (oms-cu-zn). the oral mineral supplement (50 g/animal/day) contained 500 ppm cu and 2,200 ppm zn. copper and zn were applied by subcutaneous injection at the beginning of the experiment in a single dose of 50 and 57.35 mg/100 kg of bw, respectively. every 28 days, body weight was recorded and blood samples were taken for hematocrit (hct) and hemoglobin (hb) analysis. wither height (wh), hip height (hh) and girth chest (gc) were measured at the beginning and end of the experiment. the experiment lasted 120 days between december and april. the animals were managed under rotational grazing in pastures of brachiaria decumbens and b. humidicola, with a stocking rate of 1.22 au/ha. average daily gain was not affected by treatments with an overall average value of 101.1 g/animal/day. the groups with no zn injected had a greater increase in wh (5.1 cm) than the other groups (p<0.05). the increases in hh and gc were not affected by treatments, with averages of 4.83 and 6.53 cm, respectively. it is concluded that parenteral mineral supplementation did not improve adg and increases in body measurements, under the experimental conditions described, when animals consume forages low in protein and slightly higher in fe and mn.