Seasonality of goat diet and plant acceptabilities in the coastal scrub of Baja California, Mexico

Abstract

The feeding behavior of goats browsing in the coastal scrub of Baja California was studied for 2 years in order to characterize typical feeding periods in this highly variable climatic environment. As seasons may vary widely in dates, feeding periods were determined on the basis of the monthly variations in consumption of plants forming major components of the diet by means of a principal component analysis. Diet composition was determined using the bite-count method. Monthly observations of diet were distributed within three components, which explained 75.5% of the variation in the data. Three couples of positively correlated forages were found: (1) herbs and Lotus scoparius ( P<0.05); (2) Eriogonum fasciculatum and Viguiera laciniata ( P<0.01); and (3) Artemisia californica and Eriogonum wrightii ( P<0.01), which characterized three distinct feeding periods: wet, transition and dry. Seasonal acceptability indices of principal feeds were then calculated to show the variations of dietary preferences of goats during these three feeding periods. Shrubs contributed 48.1, 67.5 and 75.5% to diet during wet, transition and dry period, respectively. During the wet period, goats exhibited strong feed selectivity with only a legume shrub and herbs representing more than 65% of the diet. During the transition and dry periods, the decrease in the availability of the most preferred feeds, and specific plant phenological responses, induced goats to diversify their diet. Multivariate analyses of dietary data seem to be particularly useful on data collected from arid regions, where climate is highly unpredictable, in order give an overview of the variations of diet selection of range ruminants during climatically heterogeneous annual cycles.