Zinc in pig nutrition : the essential trace element and potential adverse effect on environment

Abstract

Zinc is an essential trace element which plays a rolein many biological functions. Loss of appetite, diarrhoea,growth retardation or parakeratosis are symptomsof zinc deficiency that occur in pigs fed non zincsupplemented diets. Due to a lack of knowledge of boththe actual zinc requirements of pigs and the factorsthat affect its availability in pigs, this element is oftenoversupplied in pig feeding. Such a practice has adirect adverse effect on the environment, particularlyin areas of intensive pig farming. To overcome this problemand avoid any wastage of dietary zinc, the supplyshould be better adjusted to the requirements and zincavailability should be improved as much as possible.Relying on a literature review, pig zinc requirementswere estimated according to body weight. The additionof phytase improves zinc bioavailability and 1000 unitsof microbial phytase /kg of diet were estimated to beequivalent to the addition of 24 and 19 mg /kg zincadded as zinc sulphate in the diets of piglets weighing15 kg and 25 kg, respectively. Such estimates are worthbeing validated experimentally. Moreover, the actualimpact of other dietary components on zinc availabilityremains to be assessed.