Abstract
Simple SummaryTo adequately manage ruminants in extensive grazing, it is important to have non-invasive techniques to evaluate their nutritional status. Some of these techniques are based on the use of fecal indicators, such as the concentration of nitrogen, phosphorus and 2,6-diaminopimelic acid. These indices have been used in some species of wild ungulates, but their use has been limited in domestic ruminants. Hence, this research proposes the evaluation of fecal indices, as predictors of intake of dry matter, nitrogen and phosphorus in sheep that graze on Mediterranean annual grasslands.The aim of the present study was to assess the reliability of fecal indices as predictors of nutrient intake in sheep under extensive grazing conditions. Fecal concentrations of 2,6-diaminopimelic acid (DAPAf), nitrogen (FN) and phosphorous (FP) were determined in four sheep kept in an extensive grazing system on annual Mediterranean grassland in the vegetative, reproductive and dry phenological stages. Metabolizable energy (MEI), crude protein (CPI) and phosphorus (PI) intake were calculated using the botanical composition, metabolizable energy, crude protein and phosphorus concentrations in each vegetal species making up the animal’s diet. Significant differences were observed in the nutrient intake for each phenological stage (p < 0.0001). The highest MEI, CPI and PI were observed during the vegetative stage (p < 0.0001). FN and FP were different in each phenological stage (p < 0.0001), with significant correlations observed between these variables (r = 0.916; p < 0.0001). Regressions among nutrient intake and fecal indices were significant, except in the cases of DAPAf and MEI, and DAPAf and CPI. Based on these results, fecal indices could be used to estimate nutrient intake in sheep under extensive grazing on annual Mediterranean grassland.
Highlights
Fecal indices as predictors of nutrient intake have been widely used to assess the nutritional status in ruminants [1]
Faecal nitrogen (FN) is a good indicator of protein intake [16,17], its usage is based on the fact that this compound reflects the amount of microbial biomass produced in conditions of high nitrogen availability at the ruminal level
The dry matter availability was different for each phenological stage (p ≤ 0.0001), and was found to be 60% higher in the dry season than in the vegetative season
Summary
Fecal indices as predictors of nutrient intake have been widely used to assess the nutritional status in ruminants [1] These studies have been carried out mostly in wild ungulates and aimed, through non-invasive techniques, to evaluate diet composition, such as protein [2], digestibility of dry matter [3], energy consumption [4] and the intake of minerals such as phosphorus [5] and calcium [6]. Higher FN indicates increased microbial protein production [18] This is similar with respect to the production of DAPAf, since the synthesis of this indigestible compound depends on the proliferation of Gram (-) bacteria in the rumen [19], which would benefit from a rich nutritional diet. This, in turn, is directly associated with a decrease in dry matter consumption [24]
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