Detection of winter tick, Dermacentor albipictus, infestations using near infrared reflectance spectroscopy of bovine feces.

The objective of this study was to determine whether artificial infestations of D. albipictus could be detected in cattle using near infrared reflectance spectroscopy of bovine feces (fNIRS) and if detection capability was sensitive to size of tick infestation and phase of on-host stage-specific tick development. Fecal samples were collected daily from six non-infested then later tick-infested Bos taurus yearling heifers who each served as their own control. Cattle with D. albipictus infestations arising from as few as 1000 larvae were identified by fecal chemistry changes using fNIRS technology. In two separate trials, three animal pairs were infested with one of three treatment levels (low: ∼ 1000, medium: ∼ 4000, and high: ∼ 8000) of D. albipictus larvae in a repeated measures experimental design. Trial 1 consisted of tick naïve cattle while Trial 2 consisted of prior tick exposed cattle. Date of drop and daily sum of engorged female ticks were tabulated to characterize each infestation. Cluster, common factor, principal component and MANOVA analyses were used to define and assess fecal spectra changes associated with experimental stages of infestation. Cluster analyses found significant differences in fecal samples for heifer pairs in each treatment level group (low, medium, and high) in Trial 1 and then in Trial 2 from two pre-infestation control periods (outside and inside), three stages of tick development (larval feeding, nymphal feeding, adult feeding), and post-tick recovery periods. Five shifts in fecal chemistry of non-infested and tick-infested periods were identified by six clusters of NIRS fecal spectra measured between 576 and 1126 nm. The PCA's resulted in 97.56% and 97.77% for Trials 1 and 2 respectively of the total variation in the 1050 frequencies being explained by the first three principal components (P1, P2, P3). Results from the MANOVA and the Wilk's Lambda test for both trials showed highly significant evidence (p-values < 0.0001) of a difference in the means of the three principal components across the six Stages. There was significant evidence in Trial 1 (p-values = 0.0067) and Trial 2 (p-values < 0.0001) of a difference between the means of the three principal components across the three levels of tick infestation. These significant pair-wise comparisons reflect developmental phases of tick attachment and blood-feeding that define periods of increasing, peak and declining stress identified in five fecal chemistry shifts defined by six fecal spectral clusters.

The impacts of wildfires of different burn severities on vegetation structure across the western United States rangelands.

Large wildfires have increased in western US rangelands over the last three decades. There is limited information on the impacts of wildfires with different severities on the vegetation in these rangelands. This study assessed the impacts of large wildfires on rangeland fractional cover including annual forbs and grasses (AFG), perennial forbs and grasses (PFG), shrubs (SHR) and trees (TREE) across the western US, and explored relationships between changes in fractional cover and prefire soil moisture conditions. The Expectation Maximization (EM) algorithm was used to group wildfires into nine clusters based on the prefire rangeland fractional cover extracted from the Rangeland Analysis Platform. The Standardized Precipitation Evapotranspiration Index (SPEI) with various lag scales from the Gridded Surface Meteorological (GRIDMET) dataset was used to represent antecedent soil moisture conditions. The results showed generally that fractional cover decreased most for AFG and PFG during the fire year, one year postfire for SHR, and two years postfire for TREE. High severity wildfires led to the greatest decrease in cover for all plant functional types, while low severity wildfires caused the least decrease in the functional type cover in most cases, though some variations existed. Furthermore, the impacts of wildfires on vegetation cover were greater in woody (SHR and TREE) types than in herbaceous (AFG and PFG) types. Significant negative correlation existed between percent changes in AFG and PFG cover and SPEI indicating higher prefire soil moisture conditions likely increased fine fuel loads and led to a larger decrease in AFG and PFG cover following wildfires. Significant positive correlation existed between percent changes in SHR and TREE cover and SPEI indicating drier prefire conditions resulted in larger decreases in SHR and TREE cover following wildfires. These findings help better understand the impacts of wildfires on rangelands and provide insights for rangeland management.

Continental-Scale Patterns Reveal Potential for Warming-Induced Shifts in Cattle Diet.

In North America, it has been shown that cattle in warmer, drier grasslands have lower quality diets than those cattle grazing cooler, wetter grasslands, which suggests warming will increase nutritional stress and reduce weight gain. Yet, little is known about how the plant species that comprise cattle diets change across these gradients and whether these shifts in dietary quality coincide with shifts in dietary composition, i.e. the relative abundance of different plant species consumed by cattle. To quantify geographic patterns in dietary composition, we analyzed the dietary composition and dietary quality of unsupplemented cattle from 289 sites across the central US by sequence-based analyses of plant DNA isolated from cattle fecal samples. Overall, assuming that the percentage of reads for a species in a sample corresponds to the percentage of protein derived from the species, only 45% of the protein intake for cattle was derived from grasses. Within the Great Plains, northern cattle relied more on grasses than southern cattle, which derived a greater proportion of their protein from herbaceous and woody eudicots. Eastern cattle were also more likely to consume a unique assemblage of plant species than western cattle. High dietary protein was not strongly tied to consumption of any specific plant species, which suggests that efforts to promote individual plant species may not easily remedy protein deficiencies. A few plant species were consistently associated with lower quality diets. For example, the diets of cattle with high amounts of Elymus or Hesperostipa were more likely to have lower crude protein concentrations than diets with less of these grasses. Overall, our analyses suggest that climatic warming will increase the reliance of cattle on eudicots as protein concentrations of grasses decline. Monitoring cattle diet with this DNA-based sequencing approach can be an effective tool for quantifying cattle diet to better increase animal performance and guide mitigation strategies to changing climates.