SPATIO-TEMPORAL VARIATIONS OF MACRO AND TRACE MINERAL CONTENTS IN SIX NATIVE PLANTS CONSUMED BY SMALL RUMINANTS AT NORTHEASTERN MEXICO

Abstract

During two consecutive years the Ca, K, Mg, Na, P, Cu, Fe, Mn and Zn contents were determined, seasonally, in foliar tissue of native trees (T) and shrubs (S) from northeastern Mexico such as Acacia rigidula (S), Bumelia celastrina (T), Croton cortesianus (S), Karwinskia humboldtiana (S), Leucophyllum frutescens (S) and Prosopis laevigata (T). Collections were carried out from August 2004 to May 2006 in a subtropical and semiarid region of the State of Nuevo Leon, Mexico at three county (Los Ramones, China and Linares) sites, which are grouped under a similar climatic pattern. Mineral concentrations were quantified using an atomic absorption spectrophotometer, with exception of P content that was estimated using a colorimeter. Mineral datawere statistically analyzed using one-way analysis of variance with a multi-factorial arrangement being years (2), sites (3), seasons (4), and plant species (6) the factors. All minerals in all plants were significantly different among years, sites and seasons; however, some interactions were not significant. In general, plants in Linares site had higher mineral content followed by Los Ramores and China; in addition, during the year two, all plants had higher mineral content; moreover, during summer all plants had higher mineral content followed by fall, spring and winter. Yearly and seasonal variations in plant minerals might have been related to seasonal water deficits, excessive irradiance levels during summer and extreme low temperatures in winter that could have affected leaf development and senescence. In spite of these differences, all plant species had suitable levels of Ca, Mg, K, Fe and Mn to satisfy grazing ruminant requirements. However, P, Na, Zn and Cu, showed marginal inadequate concentrations in prolonged periods throughout the year and it might have a negative impact on animal productivity.