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Introduction: Elevated β‐amyloid is used to enroll individuals into preclinical Alzheimer's disease trials, but the screening process is inefficient and expensive. Novel enrichment methods are needed to improve efficiency of enrollment. Methods: Alzheimer's disease incidence rates and a polygenic hazard score were used to create a gene‐ and age‐defined ADAge. An ADAge cutpoint was chosen to optimally predict β‐amyloid positivity among clinically normal Alzheimer's Disease Neuroimaging Initiative participants and applied to an independent Alzheimer's Disease Research Center validation cohort. The impact of ADAge enrichment on screening costs was evaluated in the Anti‐Amyloid Treatment in Asymptomatic Alzheimer's Disease trial data. Results: In the validation cohort, the ADAge‐enriched sample had a higher proportion of individuals with elevated β‐amyloid (difference [95% CI] 0.19[0.07 to 0.33]) than the unenriched sample. ADAge enrichment lowered screening costs by $4.41 million (31.00%) in the real‐world clinical trial scenario. Discussion: ADAge enrichment provides for a more efficient and cost‐effective means to enroll clinically normal individuals with elevated β‐amyloid in clinical trials. [ABSTRACT FROM AUTHOR]

Background: Elevated β‐amyloid (Aβ) is used to enroll clinically normal (CN) individuals in preclinical Alzheimer's disease (AD) trials, but the screening process is inefficient and expensive. Novel enrichment methods are needed to improve efficiency of enrollment of these individuals while reducing costs. We hypothesized that by combining a polygenic hazard score (PHS) and age‐specific risk for AD we could predict elevated Aβ in CN individuals. Method: AD incidence rates and each participant's PHS were used to adjust the participant's chronological age based on protective or deleterious genetic factors, thus creating an ADAge. An individual's ADAge is defined as the chronological age at which there is equivalent AD risk in the population. Meng's test was used in the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort to assess whether the ADAge was more correlated with Aβ than was chronological age. An ADAge cutpoint was chosen to optimally predict Aβ positivity among 306 CN participants from the ADNI and applied to 1000 bootstrap samples of an independent validation cohort of 80 CN participants from the UC San Diego Shiley‐Marcos Alzheimer's Disease Research Center. The differences in means between samples enrolled by each strategy (ADAge enrichment vs no enrichment) were calculated to determine the efficiency of ADAge‐informed Aβ screening for preclinical AD trials as well as to determine the impact of ADAge enrichment on trial population demographics. The screening cost for enrolling 1000 Aβ+ CN participants in a clinical trial using each enrollment strategy was compared. Result: Compared to chronological age, ADAge was more correlated with Florbetapir SUVR in the ADNI cohort (p <.001). In the validation cohort, the ADAge‐enriched sample had a higher proportion of individuals with elevated Aβ (difference[95% CI] 0.19[0.07–0.33]) than the unenriched sample. The ADAge‐enriched sample was older than the unenriched sample (difference 3.00[0.94 – 5.22]). However, the samples were similar in the proportion of APOE ε4 carriers, the dementia rating scale score, and the proportion of female participants. ADAge enrichment lowered screening costs by $5.3 million (34%) in a clinical trial scenario. Conclusion: ADAge enrichment provides for a more efficient and cost‐effective means to enroll CN individuals with elevated Aβ in clinical trials. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to evaluate the Fieldscout CM 1000 NDVI and Yara N-Tester as easy-to-use and cost-effective tools for predicting foliar chlorophylls ( a, b and total) and crude protein ( CP) concentrations in herbage from three tropical grass species. Optical chlorophyll measurements were taken at three stages (4, 8 and 12 weeks) of regrowth maturity in Guinea grass ( Panicum maximum) and Mulato II ( Brachiaria hybrid) and at 6 and 12 weeks maturity in Paspalum spp ( Paspalum atratum). Grass samples were harvested subsequent to optical measurements for laboratory analysis to determine CP and solvent-extractable chlorophylls ( a, b and total) concentrations. Optical chlorophyll measurements and CP concentrations were highly correlated (Yara N-Tester: r2 = 0·77-0·89; Fieldscout CM 1000 NDVI: r2 = 0·52-0·84). Crude protein prediction models from the Yara N-Tester and Fieldscout CM 1000 NDVI accounted for 70-89% and 44-73% CP variability, respectively, in Mulato II and Guinea grass. The Yara N-tester produced more accurate and reliable CP estimates based on very high concordance correlation coefficient [ CCC (0·73-0·91)] and low rMSPE, mean and regression bias. It is concluded that the Yara N-Tester produces more accurate and reliable CP estimates of tropical pastures. [ABSTRACT FROM AUTHOR]

In vitro ruminal fermentation techniques rely on the availability of fistulated ruminants for rumen fluid (RF), a major constraint for resource-poor institutions. An alternative would be to use faecal microbes. This study was therefore designed to compare the potency of fresh bovine faeces against RF as sources of microbial inocula for fermenting six contrasting tropical forages using the Tilley and Terry ( Journal of British Grassland Society, 18, 104-111) technique. Faecal inocula were prepared at concentrations of 250 g (Faec250), 300 g (Faec300), 350 g (Faec350), 400 g (Faec400) and 450 g (Faec450) fresh cow faeces per litre bicarbonate buffer. In vitro organic matter digestibility (IVOMD) increased with increasing concentration of faeces at 12-, 24- and 48-h incubation intervals. All faecal inocula except Faec450 had lower potency when compared with RF at all incubation intervals. Digestibility of forage substrates with Faec450 (533 ± 23 g kg−1 DM IVOMD) was comparable to RF (566 ± 5 g kg−1 DM IVOMD) after 48-h incubation. Faec450 showed greater potency on more fibrous and low-protein substrates than RF. The coefficient of determination of the regression models for predicting 12-, 24- and 48-h RF IVOMD from Faec450 were 0·914, 0·75 and 0·756 respectively. It was concluded that inocula prepared from 450 g cow faeces demonstrated great potential as a substitute and predictor for RF in 48-h IVOMD assays of tropical forages. [ABSTRACT FROM AUTHOR]