Submitted to: Applied Animal Behaviour Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/1997
Publication Date: N/A
Citation: Interpretive Summary: While portable computers allow us to gather great volumes of data in the field, scientists are still faced with choosing variables that will suitably answer their questions. We examined-several different methods used to describe forage selection by goats to determine which method would most easily describe their forage preferences. Behaviors or activities that were monitored included counts or measures of: total number of visits to plants, total bites, bites per visit, total grazing time, time per visit, bite rate, and counts and measures of plants grazed or regrazed in grass pastures and on native sagebrush rangelands. Although tedious to acquire, bite count methods have been a long used standard, and we compared our other measures with this variable. In grass pastures, where all plants were of similar size and shape, many of the measures gave adequate rankings of forage acceptability. On native rangeland, however, where forages ranged from small flowering plants to shrubs and trees, total grazing time was the only measure consistently yielding the same forage rankings as total bites. Grazing time is more easily measured than the more attention demanding counting of individual bites, and researchers can probably obtain satisfactory rankings of livestock preferences with less effort by monitoring the time animals spend grazing each forage.
Technical Abstract: Portable computers presently allow documentation of real-time grazing behavior under field conditions. The objective of this research was to examine relationships among variables describing grazing behavior and forage utilization by goats to identify the most easily monitored activity capable of accurately ranking their relative preferences. Relationships were investigated in grassy paddocks and on native shrub/steppe rangeland. "Total bites" was considered the most accurate depiction of actual diet. In grassy paddocks, with 8 different forages available, total visits, total bites, total time, number of plants grazed, number of plants regrazed, and number of regrazing events were highly correlated (r is greater than or equal to 0.94) during both the boot and dormant stages of phenology. Utilization data were poorly correlated (mean r = 0.67) with more direct measures of the goats' diets. Correlations were much weaker in shrub/steppe vegetation where a variety of life forms were available (mean r = 0.45), and only total time versus total bites and bites/visit versus time/visit) exhibited correlations greater than or equal to 0.94. Total time was the only variable consistently correlated with total bites in both the grassy paddock and shrub/steppe pastures. We suggest adequate rankings of relative forage preference of goats can be obtained by measuring the grazing time expended with each forage.