Effect of mineral mixture on behavior patterns of Portuguese native heifers during Mediterranean spring and summer

Abstract

The aim of this study was to evaluate the effect of supplementation with protein enriched mineral salt in behavior and productive performance of heifers of native breeds during the Spring and Summer in a Mediterranean climate. The study was conducted between April and August, during 150 days. Two homogeneous groups of heifers (± 8 months of age) were formed and assigned in two treatments: without mineral salt (NS) and with mineral salt (WS). The animals were placed in two adjacent fences with approximately 4 ha each. The test was divided into two periods: P1 (from April to 15th June) and P2 (from 16th June to late August). In P1 animals ate only natural grassland, while in P2 animals were supplemented with hay of poor quality. Behavior observations were made using focal methodology every 5 minutes, from 7 a.m. to 8 p.m. Observed activities were: grazing, ruminating and leisure; and events: water intake and mineral salt intake (this last only in treatment WS). Grazing is the activity that takes longer throughout the day, followed by leisure and rumination. Supplementation with the mineral salt resulted in no change in the duration of activities. Environmental variables, i.e. the high summer temperatures were most responsible for changing behavior patterns, determining that food intake occurred preferentially during the cooler periods. The search for mineral salt increased significantly during the hottest period. The supply of mineral salt determined a significant increase in plasma concentrations of thyroxine (T4), which have contributed to a higher average weight gain.