3.3 | Diet characterization
Plant sequences from the samples were gathered into 56 taxa based on the
lowest taxonomic classification (genus or species level) that could be
determined confidently from GenBank and EMBL. The most abundant
sequences in the pool of potential food items were those related toLespedeza sp. (30.78%). Next were those related toArtemisia sp. (16.27%), Chenopodium sp. (14.44%), andCorispermum sp. (11.83%). In total, 26–44 diet items derived
from different taxa (mean = 35) were present in the diets of lambs.
PCoA via the Binary-Jaccard algorithm of diet communities revealed that
diets segregated mainly by preference for a handful of plant species
(Figure 1c). For all the diet item plant communities, a slightly higher
dependency on grazing type than
grazing period was the most
important driving factor contributing to the variation in diet
composition, explaining 18.25% of the variation. The second most
important distinction in diet composition was the different
compositional herbage species changing with the growing season. ANOVA
results indicated that there was significant interaction between the
grazing modes and sampling period (R2 = 0.50, P= 0.001). The predominant diet items in all samples are summarized and
shown in the heatmap (Figure 1d). In general, the dominant genera in
different grazing types and within the same modes in different periods
had numerous differences.
The top 20 taxa accounting for 97.96% of the total sequence reads were
used to investigate the diet composition of Tan sheep. Overall,Lespedeza sp ., Artemisia sp ., Chenopodium sp ., andCorispermum sp . were found to be the most predominant herbage
groups, being present in 100% of samples (FOO) and comprising 73.30%
of the total of diet DNA sequences (RRA) (30.81%, 16.29%, 14.40%, and
11.80%, respectively). Phellodendron amurense , Medicago
sativa , Salsola sp ., Bassia scoparia , Euphorbia
humifusa , Eragrostis sp ., Ixeris tamagawaensis ,Setaria italica , and Cenchrus flaccidus were also present
in 100% of the samples, comprising 3.94%, 3.32%, 3.14%, 2.51%,
2.05%, 1.47%, 1.23%, 0.78%, and 0.61% of RRA, respectively. Other
plant taxa included Sibbaldianthe bifurca at 95.83% (1.05% RRA)
and Arnebia euchroma at 91.67% (1.59% RRA). Oxytropis
halleri , Chloris pilosa , Convolvulus sp .,Astragalus peterae , and Caragana korshinskii were present
at 83.33%, 33.33%, 91.67%, 75.00%, and 91.67% FOO, respectively
(< 1% RRA; Table 3, Figure 2).
The multiple RRA measurements were averaged for each type-stage
combination. As shown in Figure 3, the stacked bar charts indicate that
the prevalent genera in the grazing group were
basically the same as those in the
time-limited grazing group, dominated by species such asLespedeza sp. , Artemisia sp. , Chenopodium
sp. , Corispermum sp. , and Phellodendron amurense , whereas
the proportions quite different (P < 0.05, Figure 3 and
Table 3).