Free-choice consumption of mineral lick blocks by fattening lambs fed ad libitum alfalfa hay and concentrates with different trace mineral content

Abstract

The objective of this study was to evaluate the ability of lambs to regulate intake of mineral lick blocks (MLBs) with different trace mineral content when alfalfa hay and concentrates, also with a different trace mineral content, were available to lambs for ad libitum consumption. Twelve 4-month-old purebred Karagouniko lambs were divided into three groups, pen housed individually, and fed unchopped alfalfa hay and concentrates ad libitum. The three concentrates used consisted of a basal concentrate food supplemented (TM+) or not (TM−) with trace elements and a vitamin premix. This basal food of the third group (3TM) was supplemented with a premix in which the trace minerals added were three times the amount of the control group, TM+. The experiment lasted 66 days. The first 31 days were used as an adaptation period, and from the 32nd day two different MLBs were put in each pen. One of the MLBs was white in colour while the other was light pink and had a three-fold greater trace mineral content compared to the white one. Two weeks following the introduction of the MLBs (adaptation period), the behaviour of lambs was video recorded for 48 h per week for 3 weeks. Food and water intake and MLB consumption were recorded regularly and the Cu and Zn concentrations were determined in the blood plasma and the liver of the lambs. The average daily MLB intake, the number of visits to the MLBs, and the time spent by the lambs licking the MLBs were higher for the group TM− and lower for the 3TM group. However, the daily mineral intake from the ingested MLB represented only a very small proportion of the total mineral intake of the animals. The differences among the groups in plasma and liver Cu and Zn concentrations represented the quantities ingested via the diet rather the MLBs. In conclusion, the results of this experiment did not show clearly that the lambs could regulate the intake of MLB because they failed to exhibit a ‘mineral wisdom’ related to their physiological needs and mineral status.