Using Fecal DNA Metabarcoding to Investigate Foraging Reveals the Effects of Specific Herbage on the Improved n-3 Fatty Acid (PUFA) Composition in the Longissimus Dorsi Muscle of Grazing Tan Sheep

Understanding the natural diet of grazing sheep can help fulfill their nutritional requirements and positively affect the quality of their meat. Emerging fecal DNA (fDNA) metabarcoding technology can provide more accurate estimates for the dietary composition of free-ranging animals. This study has shown that pasture feeding can promote deposition of n-3 polyunsaturated fatty acids (PUFAs) in Tan lambs' muscle and decrease the ratio of n-6/n-3 fatty acids (FAs), and thus, we investigated the dietary composition of grazing lambs using fDNA metabarcoding to assess the prevalence of medicinal herbage plants in their diet. Herein, based on the full-time natural pasture grazing and 4-h natural pasture grazing with indoor feeding patterns, the herbage taxa (Bassia scoparia, Euphorbia humifusa, Arnebia euchroma, and Salsola sp.) most correlated to n-3 PUFAs were highlighted to elucidate how diversification in dietary components was associated with the muscle FA profile of lambs. Our findings provide experimental evidence for future feeding research.

Trichuriasis in Human Patients from Côte d'Ivoire Caused by Novel Trichuris incognita Species with Low Sensitivity to Albendazole/Ivermectin Combination Treatment

Albendazole/ivermectin combination therapy is a promising alternative to benzimidazole monotherapy alone for Trichuris trichiura control. We used fecal DNA metabarcoding to genetically characterize Trichuris spp. populations in patient samples from Côte d'Ivoire showing lower (egg reduction rate <70%) albendazole/ivermectin sensitivity than those from Laos and Tanzania (egg reduction rates >98%). Internal transcribed spacer (ITS) 1 and ITS2 metabarcoding revealed the entire detected Côte d'Ivoire Trichuris population was phylogenetically distinct from T. trichiura found in Laos and Tanzania and was more closely related to T. suis. Mitochondrial genome sequencing of 8 adult Trichuris worms from Côte d'Ivoire confirmed their species-level differentiation. Sequences from human patients in Cameroon and Uganda and 3 captive nonhuman primates suggest this novel species, T. incognita, is distributed beyond Côte d'Ivoire and has zoonotic potential. Continued surveillance by using fecal DNA metabarcoding will be needed to determine Trichuris spp. geographic distribution and control strategies.

Sheep dietary preferences in targeted grazing: demographic, management, and weather effects in northern mixed-grass prairie

Diet selection and composition of sheep target grazing plains larkspur (Delphinium geyeri Greene) in northern mixed-grass prairie were evaluated during a drought year (2022). Thirteen Rambouillet ewes (3-to 6-year-old, body weight (BW) 76 kg ± 2.9), 14 Dorper ewes (3-to 6-year-old, BW 47 kg ± 1.8), and 123 Dorper ram lambs (<1 year-old, BW 25 kg ± 0.4) were used for targeted grazing. Over the 20-day first phase (mid-May to early June), sheep were subjected to three stock density treatments: (1) high, 40 animal units (AU)/ha, (2) moderate, 20 AU/ha, and (3) light, 13 AU/ha. In the second phase (21 d, early-to late-June), the same sheep grazed four 1.5 ha paddocks sequentially at a very light stock density of 7 AU/ha. Dietary composition was assessed through focal bite count observations at the plant functional group level for phase one only, and dietary composition was estimated through fecal DNA metabarcoding (f.DNA) at the plant species level for both phases. Results indicated a uniformly low preference for larkspur (< 1% in diets). There were no significant effects of breed or age on focal bite count observations of plant functional groups (grasses, forbs, and larkspur), nor were there significant effects of breed or age on f.DNA diet proportions of plant functional groups (p > 0.05). Stock density did influence focal bite count observations, with higher forb intake (p = 0.0004) and lower grass intake (p = 0.009) observed at the moderate density compared to the high density. In phase two, grass and larkspur intake decreased while forb intake increased according to f.DNA (p < 0.01). These findings suggest that moderate stock density, combined with an understanding of plant phenology, precipitation variability, and animal forage preferences can optimize vegetation and animal performance in adaptive targeted grazing management within this ecosystem.

Black-throated blue warblers (Setophaga caerulescens) exhibit diet flexibility and track seasonal changes in insect availability

Changes in leaf phenology from warming spring and autumn temperatures have lengthened the temperate zone growing "green" season and breeding window for migratory birds in North America. However, the fitness benefits of an extended breeding season will depend, in part, on whether species have sufficient dietary flexibility to accommodate seasonal changes in prey availability. We used fecal DNA metabarcoding to test the hypothesis that seasonal changes in the diets of the insectivorous, migratory black-throated blue warbler (Setophaga caerulescens) track changes in the availability of arthropod prey at the Hubbard Brook Experimental Forest, New Hampshire, USA. We examined changes across the breeding season and along an elevation gradient encompassing a 2-week difference in green season length. From 98 fecal samples, we identified 395 taxa from 17 arthropod orders; 242 were identified to species, with Cecrita guttivitta (saddled prominent moth), Theridion frondeum (eastern long-legged cobweaver), and Philodromus rufus (white-striped running crab spider) occurring at the highest frequency. We found significant differences in diet composition between survey periods and weak differences among elevation zones. Variance in diet composition was highest late in the season, and diet richness and diversity were highest early in the season. Diet composition was associated with changes in prey availability surveyed over the green season. However, several taxa occurred in diets more or less than expected relative to their frequency of occurrence from survey data, suggesting that prey selection or avoidance sometimes accompanies opportunistic foraging. This study demonstrates that black-throated blue warblers exhibit diet flexibility and track seasonal changes in prey availability, which has implications for migratory bird responses to climate-induced changes in insect communities with longer green seasons.