Characterization of the daily behavior of grazing Girolando heifers in integrated livestock systems.

摘要: Tree shade in pasture system should be an alternative to reduce the impact of warm climate and heat stress on dairy cattle herd. This study aimed to access grazing behavior of Girolando heifers in integrated crop, livestock (ICLS) and forestry (ICLFS) systems throughout a 24-hour day. Trial was carried out at Experimental Field of Embrapa Rondônia in Porto Velho from September to November of 2015. Eight 25±6.8 month-old Girolando (¾Holstein× ¼Gir) heifers with 268±83 kg of live weight (LW) were distributed in a 2x2-crossover trial (two systems x two 30-day evaluation periods). Both systems had pastures cultivated with xaraés palisadegrass under intermittent stocking (2.5 animal unit ha-1). The ICLFS was shaded by seven tiers of eucalyptus trees planted in four lines with 3x3 m of plant distance with 65% of crown cover. For assessing heifer behaviors, audio data was collected during 48 hour of each evaluation period with MP3 recorders. Bioacustic analysis was performed using Audacity® software for identification of times spent with grazing, rumination, resting and water drinking. Data for estimation of Temperature-Humidity Index (THI) during the experimental period was taken from a weather station located 500 m from the experimental area. Variance analysis was performed by MIXED procedure of SAS. Means were compared between treatments (ICLS and ICLFS) during 00: 00h to 23: 00h by F test at 5% of significance level. The means of THI range from 72 to 80 throughout a 24-hour day, which mean mild to moderate stress thresholds. Regardless the system, grazing was higher in the beginning of morning (from 06: 00h to 08: 00h …