Estudo das deficiências minerais em vacas em lactação da bacia leiteira do município de Rondon do Pará, estado do Pará

Abstract

We conducted a study of mineral deficiencies in lactating cows from dairy herds belonging to 13 properties of the milk basin of Rondon do Pará, in the state of Pará. We determined the levels of phosphorus (P), specific gravity and percentage of ash in the bone and levels of copper (Cu), cobalt (Co), selenium (Se), zinc (Zn), iron (Fe) and manganese (Mn) in the liver of 47 dairy cows in lactation 2. These samples were collected by means of biopsies performed in the top third of the 12th rib on the right side and the caudal edge of the caudate lobe of the liver, respectively. The herds were composed of crossbred (Holstein x Zebu), kept in extensive production system on Brachiaria brizantha cv Marandu and received mineral supplementation. The mineral mixture in 12 properties were commercial type, called "full" and the owners added a quantity of salt above the manufacturer's recommendations in ten properties. In addition, the mineral mixtures were provided in troughs without covering in seven properties and in other eight, the providing of the mineral mix was not performed daily. In 11 properties there were clinical histories consistent with mineral deficiencies in livestock and placenta retention and osteophagia were the most frequently reported ones. The results of chemical analysis showed deficiency in P in five properties, in Co in two properties, in Se in eight properties, in Zn in eight properties. It is concluded that the deficiency of P, Se and Zn occurs in a greater proportion and the deficiency of Co occurs in a lesser proportion and the mineral supplementation performed in the properties do not supply the daily demands of P, Se and Co, based on the estimated daily consumption of 30 g of NaCl per animal and the troughs little adequate or inadequate for proper supplementation, as well as inconstant supply of mineral mixtures contribute to the deficiency of one or more minerals.