Biochemical indicators of nutritional status and its relation with feed intake in lactating cows fed on natural pastures of the plain of Mendoza

In the livestock production in arid and semiarid systems the rangelands are used for cow-calf operations. It is difficult to estimate the quality of the ingested forage and often management decisions must be taken without suitable information. In this paper biochemical parameters were analyzed in the lactation period of Aberdeen Angus cows feeding in rangelands in the dry season (April to September) and in the first month of the wet season (October). These parameters were related to ingestion estimators based on the botanical composition of the diets and the available forage. It was found that the behavior of the biochemical parameters was related to the forage ingested and the botanical composition of diets during the dry season or in the mentioned month of the wet season. Relations were found between the tested metabolites that permit an estimate of the nutritional state of the cows of the rangelands on the plains of Mendoza. The most representative indicators of the nutritional condition that also had high sensitivity were selected: Ur/Cr and Ur/Lec and it was found that the relationship Ur/Cr was highly sensitive and that other indicators were as well significant.