Predicting cumulative risk of bovine respiratory disease complex (BRDC) using feedlot arrival data and daily morbidity and mortality counts

Although bovine respiratory disease complex (BRDC) is common in post-weaning cattle, BRDC prediction models are seldom analyzed. The objectives of this study were to assess the ability to predict cumulative cohort-level BRDC morbidity using on-arrival risk factors and to evaluate whether or not adding BRDC risk classification and daily BRDC morbidity and mortality data to the models enhanced their predictive ability. Retrospective cohort-level and individual animal health data were used to create mixed negative binomial regression (MNBR) models for predicting cumulative risk of BRDC morbidity. Logistic regression models were used to illustrate that the percentage of correctly (within |5%| of actual) classified cohorts increased across days, but the effect of day was modified by arrival weight, arrival month, and feedlot. Cattle arriving in April had the highest (77%) number of lots correctly classified at arrival and cattle arriving in December had the lowest (28%). Classification accuracy at arrival varied according to initial weight, ranging from 17% (< 182 kg) to 91% (> 409 kg). Predictive accuracy of the models improved from 64% at arrival to 74% at 8 days on feed (DOF) when risk code was known compared to 56% accuracy at arrival and 69% at 8 DOF when risk classification was not known. The results of this study demonstrate how the predictive ability of models can be improved by utilizing more refined data on the prior history of cohorts, thus making these models more useful to operators of commercial feedlots.     

Experimental evidence for species‐specific response to turbidity in imperilled fishes

相似文献   

Integrating multiple techniques to identify stock boundaries of common bottlenose dolphins (Tursiops truncatus)

相似文献   

Effects of chronically elevated nitrogen and sulfur deposition on sugar maple saplings: Nutrition,growth and physiology

At the Bear Brook Watershed in Maine (BBWM), we examined the effects of long-term experimentally elevated N and S deposition on foliar chemistry, growth, and photosynthetic capacity of sugar maple (Acer saccharum) saplings. The BBWM is a paired watershed system; one watershed has been acidified bimonthly with granular ammonium sulfate ((NH₄)₂SO₄) since 1989. The adjacent watershed is used as a reference. We observed a 56% increase in foliar Al and a 25% reduction in foliar Ca for sugar maple saplings on the treated watershed compared to reference. Foliar N (+15%), P (+10%), and K (+15%) were significantly elevated in treated saplings. Along with changes in foliar nutrients, there were significant differences in photosynthetic capacity.     

A comparison of riparian plant community response to herbivory by beavers (Castor canadensis) and ungulates in Canada's boreal mixed-wood forest

Herbivores, such as beavers (Castor canadensis) and ungulates, can dramatically alter the species composition and structure of riparian vegetation communities. We examined how four different levels of beaver presence and ungulate density influenced the structure and composition of riparian vegetation communities in the mixed-wood boreal region of east-central Alberta, Canada. Beavers, as central-place foragers, focus on similar species utilized by the six ungulate species in our study area. However, we found that vegetation responded differently relative to the percent cover and heights of emergent, shrub, herbaceous dicots, and tree species depending on the varying combinations of beaver presence and ungulate densities. There was an obvious negative effect of ungulate herbivory on shrub heights and cover; however, we were unable to find any significant effects on the overall composition and structure of vegetation communities that were exclusively related to beaver activities. In areas with no beavers and lower ungulate densities there was a positive growth response in preferred species (e.g., Salix spp., Prunus spp.), which clearly demonstrated the degree of combined influence that these herbivores have on riparian communities. In these areas, Salix spp. was four times shorter than in areas where beavers were not present and ungulate densities were lower. In addition percent cover was lowest for emergent vegetation and herbaceous dicots in areas with higher ungulate densities. Many studies focus on single-species effects on forage resources, yet our research shows that the study of combined effects of multiple herbivores can provide a new insight into these complex systems.     

Effects of mountain pine beetle (Dendroctonus ponderosae Hopkins) infestations on forest stand structure in the southern Canadian Rocky Mountains

Forests in the montane and lower subalpine ecoregions of the southern Canadian Rocky Mountains may have been more open and structurally diverse at the beginning of the 20th Century than today. Today, the area of mature Pinus contorta subsp. latifolia Dougl. forest that is conducive to mountain pine beetle (MPB, Dendroctonus ponderosae Hopkins) infestations, infrequent high severity fires, and herbivory appears to have increased in Banff and Kootenay National Parks. Based on a review of the literature, we hypothesised that MPB infestations increase forest stand structural diversity and tree species diversity. Stand structure parameters were investigated in mesic montane and lower subalpine stands approximately 15, 25, and 65 years after MPB outbreaks. Parameters measured were stand density (number of trees per ha), diameter at breast height, height class, species, age class distribution, and coarse woody debris mass. Influences of fire frequency, time since fire, and fire severity on these parameters were assessed to determine whether fire history had a confounding influence on stand structure. The Shannon–Wiener index indicated higher stand structural diversity 15 years but not 25 and 65 years after MPB infestations. MPB infestations led to general decreases within stands in the number of living trees, small diameter snags, and Pinus tree species and an increase within stands in the number of large diameter snags. Management that allows the occurrence of the natural fire regime of variable severity fires, in addition to some MPB infestations, would provide for more open and diverse stands. MPB infestations have some effects on stand structure that are similar to those of fire. Changes in stand structure resulting from recent declines in burning rates within Banff and Kootenay National Parks can be reversed to some extent by MPB infestations.     

Influence of fire intensity on structure and composition of jack pine stands in the boreal forest of Quebec: Live trees,understory vegetation and dead wood dynamics

North American jack pine (Pinus banksiana Lamb.) stands are generally characterized by an even-aged structure resulting from high intensity fires (HIF). However, non-lethal fires of moderate intensity (MIF), which leave behind surviving trees, have also been reported. The objectives of this study were two-fold: (1) assess the concurrent dynamics of live trees, understory vegetation and different types of coarse woody debris (CWD) during succession after HIF; and (2) document how MIF affects stand structure component dynamics compared to HIF. Stands affected by both HIF and MIF were selected. Tree characteristics and age structure, understory biomass, and CWD volume were assessed. Our results suggest that the structural succession of jack pine stands following HIF comprises three stages: young stands (<48 years), premature and mature stands (58–100 years) and old stands (>118 years). Canopy openness and jack pine density significantly decreased with time since HIF, while black spruce density and CWD volume significantly increased. The highest structural diversity was measured in the premature and mature stands. Compared to HIF, MIF increased mean jack pine basal area, decreased average stand density, delayed the replacement of jack pine by black spruce replacement in the canopy, decreased CWD volume, and significantly increased bryophytes mass. MIF increased the diversity of live trees and generally decreased CWD structural diversity. The study confirms the diversity of natural disturbance magnitude and successional processes thereby initiated. Thereafter, it appeared to be relevant for adjustment of disturbance emulating forest-management systems.     

Investigating the Research Practices of Agriculture Scholars: Findings From the University of Florida

ABSTRACT

The University of Florida (UF) George A. Smathers Libraries is one of 19 institutions that participated in an Ithaka S+R Research Support Services investigation of agricultural sciences. The authors conducted a qualitative analysis of research support services based on one-on-one semistructured interviews with 15 faculty of the UF Institute of Food and Agricultural Sciences in 2016. A number of core themes emerged from the analysis of research practices in the local study at UF. Core themes included finding appropriate literature, data management issues and tools, repositories for sharing research products, and research dissemination. This report summarizes a subset of these results, focusing on themes related to academic library services that support agricultural scholars research needs.