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Sheep and goat browsing a tropical deciduous forest during the rainy season: why does similar plant species consumption results in different nutrient intake?
During the rainy season, the tropical deciduous forest (TDF) supposedly represents an abundance of biomass for sheep and goats. Nevertheless, quantitative estimations of feed intake during the rainy season are lacking. This study investigated the feeding behaviour of sheep and goats in a TDF in Mexico and quantified their nutrient intake during the rainy season. Plant species (PS) consumed, size and weight of bites, and nutritional quality were determined by continuous bite monitoring through direct observation. Adult ewes (n = 3) and goats (n = 3) were observed in their grazing circuits (4 h/day) for 12 days during the rainy season. Sheep and goats consumed 61 PS and performed a similar median number of bites (1751 vs. 2053 bites/day, respectively; P > 0.05). Although they shared 52.5% of the PS harvested, only seven PS contributed most of the dry matter intake (DMI) for sheep (96.7%) or goats (90.5%). Sheep consumed more grass than goats (79.8% vs. 48.3% of their DMI, respectively), while goats ate more shrubs than sheep (30.0% vs. 7.6% of their DMI, respectively). The diet ingested by goats included more polyphenols (P < 0.05) and a higher frequency of larger and heavier bites than sheep (P < 0.05). Sheep reached 61.3% and 57.7% of their metabolizable energy and crude protein maintenance requirements. Similarly, goats covered 63.3% of their metabolizable energy and 108.2% of crude protein requirement. Although the main ration of sheep and goats was composed of similar PS, their different harvesting behaviour resulted in different macronutrient consumption.
AN16512 Accepted 18 September 2017
© CSIRO 2017