41 research outputs found
Systematic Review on Fractal Dimension of the Retinal Vasculature in Neurodegeneration and Stroke: Assessment of a Potential Biomarker
No full textIntroduction: Ocular manifestations in several neurological pathologies accentuate the strong relationship between the eye and the brain. Retinal alterations in particular can serve as surrogates for cerebral changes. Offering a "window to the brain," the transparent eye enables non-invasive imaging of these changes in retinal structure and vasculature. Fractal dimension (FD) reflects the overall complexity of the retinal vasculature. Changes in FD could reflect subtle changes in the cerebral vasculature that correspond to preclinical stages of neurodegenerative diseases. In this review, the potential of this retinal vessel metric to serve as a biomarker in neurodegeneration and stroke will be explored. Methods: A literature search was conducted, following the PRISMA Statement 2009 criteria, in four large bibliographic databases (Pubmed, Embase, Web Of Science and Cochrane Library) up to 12 October 2019. Articles have been included based upon their relevance. Wherever possible, level of evidence (LOE) has been assessed by means of the Oxford Centre for Evidence-based Medicine Level of Evidence classification. Results: Twenty-one studies were included for qualitative synthesis. We performed a narrative synthesis and produced summary tables of findings of included papers because methodological heterogeneity precluded a meta-analysis. A significant association was found between decreased FD and neurodegenerative disease, mainly addressing cognitive impairment (CI) and dementia. In acute, subacute as well as chronic settings, decreased FD seems to be associated with stroke. Differences in FD between subtypes of ischemic stroke remain unclear. Conclusions: This review provides a summary of the scientific literature regarding the association between retinal FD and neurodegenerative disease and stroke. Central pathology is associated with a decreased FD, as a measure of microvascular network complexity. As retinal FD reflects the global integrity of the cerebral microvasculature, it is an attractive parameter to explore. Despite obvious concerns, mainly due to a lack of methodological standardization, retinal FD remains a promising non-invasive and low-cost diagnostic biomarker for neurodegenerative and cerebrovascular disease. Before FD can be implemented in clinic as a diagnostic biomarker, the research community should strive for uniformization and standardization.sponsorship: SL has received a Ph.D. grant from VITO to performa joint Ph.D. between VITO and UZ Leuven. (VITO)status: Publishe
Nutrient digestibility and predicting the energy content of pig feeds
No full textWith 11 million slaughters per year, pigs are the most important production animal in Belgium. Feed is
the biggest cost factor in pig farming, especially the energy component. The aim of feed formulation
and production is to meet the nutrient requirements of pigs under the constraint of the available feed
ingredients (Chapter 1). Correct energy and nutrient evaluation is critical, especially given the increasing
amounts of fiber-rich co-products from human food production that are being included in pig feed.
Another difficulty is that feed digestibility and utilization depend on many factors related to either the
animal or to its growing conditions (Chapter 1). The net energy (NE) reflects best the true available
energy for pigs, but NE determination requires time-consuming and expensive in vivo digestibility
experiments. Potential methods to estimate NE in feeds include the use of tabular values of ingredients,
empirical models based on chemical parameters and/or the in vitro digestibility of organic matter and
near infrared spectroscopy (NIRS).
The following research objectives (Chapter 2) were defined:
• Study the interactions between fat and fiber level on nutrient digestibility and energy utilization
of pig feeds (Chapter 4)
• Evaluate the usefulness and accuracy of NIRS calibrations based on spectra from pig feed and
feces to predict their chemical composition as well as nutrient digestibility and NE (Chapter 5)
• Compare a) the use of feed tables, b) empirical models based on chemical and in vitro analyses
and c) NIRS calibrations based on feed and feces spectra for their accuracy in predicting feed
quality and more particularly NE, their applicability in practice and their limits (Chapter 6)
Data related to these objectives were gathered via three in vivo digestibility trials. In Chapter 3, the
protocol and details of the various methods used are described and justified. Main conclusions are: the
acid insoluble ash (AIA), that is naturally present in pig feeds, is reliable as marker to determine nutrient
digestibility via spot sampling of feces; AIA and TiO2 are equally reliable as external markers; the NE
of a feed increases with 0.0021 MJ per kg higher bodyweight; once-daily sampling and pooling feces
from two or three animals per pen is sufficient to determine in vivo digestibility.
The interactions between fiber-rich co-products and fat were investigated, as well as their possible
impact on nutrient digestibility and NE (Chapter 4). For this experiment, a low fiber (LF) and a high
fiber (HF) diet were formulated. From these two basal diets, 8 additional diets were derived by adding
20 or 40 g/kg of either pig fat or soy oil. Compared to LF diets, HF diets had a lower (P<0.05)
standardized digestibility for all nutrients except for NDF. However, higher fiber levels in the diet did
not affect the digestibility of the added fat. The standardized digestibility of fat in the HF diets with
added fat was higher (P<0.05) than that of the non-fat supplemented basal diet, whereas no significant
(P>0.05) differences in fat digestibility among the LF diets were observed. Increasing fat level appeared
to negatively affect the fat-free organic matter digestibility, in particular NDF. On the other hand, the
negative effect of fat addition on digestibility and NE was relatively small in comparison to the extra
energy added by the fat. Therefore, no special consideration should be given when adding extra fat to a
fiber-rich diet to meet pigs’ energy requirements.
For prediction of the chemical composition of pig feed and feces, as well as nutrient digestibility and
NE, the usefulness and accuracy of NIRS calibrations based on combined spectra were investigated
(Chapter 5). Near infrared spectroscopy appeared to accurately predict (residual prediction deviation,
RPD>3; R²>0.8) most organic components and moisture content of pig feed and freeze-dried feces. The
NE was better estimated using feed spectra than feces spectra, with a standard error of cross validation
(SECV) of 0.33 and 0.46 MJ/kg, respectively. Combining feed and feces spectra resulted in an overall
better estimation of the digestibility and NE, especially with merging (SECV=0.26 MJ/kg) and
subtracting (SECV=0.27 MJ/kg). Finally, this study highlighted the importance of the cross-validation
method when the dataset contains several feces spectra (alone or combined) from the same feed. Indeed,
cross-validation may lead to over-optimistic results when the group to be validated contains spectra that
are not independent.
The use of tabular values, empirical models and NIRS to estimate nutrient composition and NE were
compared (Chapter 6). This evaluation was based on 62 compound feeds, and 28 among them had known
ingredient composition. In addition to the accuracy of each approach, their applicability in practice and
practical limitations were compared. Feed tables predicted most chemical components accurately
(R²>0.90), with exception of crude ash, sugar, acid detergent lignin and moisture, the latter being
strongly underestimated (-16 g/kg). The standard error of estimate (SEE) for NE with tabular values
amounted to 0.29 MJ/kg. Using empirical models based solely on chemical parameters resulted in a SEE
of 0.21 MJ/kg. Incorporating in vitro digestibility resulted in a decrease of SEE to 0.18 MJ/kg. The SEE
of a NIRS calibration based on feed spectra alone resulted in a SEE of 0.33 MJ/kg, whereas the
combination of feed and feces spectra decreased this error to 0.26 MJ/kg. The use of feed tables allows
a cheap and fast estimation of the chemical composition and NE, but it is only suitable for feeds of
known and common ingredient composition and is not so accurate. The use of empirical models allows
to accurately estimate the NE of feeds even with unknown composition, but relies on quite expensive
and time-consuming analyses. Finally, NIRS calibration based on feed and feces spectra allows for a
fast estimation of NE, but is less precise than empirical models and requires a specific sample
preparation.
Finally, the general discussion, conclusions and recommendations are presented (Chapter 7), where the
results are discussed in depth and put into perspective. Important attention points are the limitation of
NIRS accuracy for evaluating compound feeds due to the complexity and heterogeneity of the matrix;
the error (0.033 MJ/kg) in the determination of the in vivo NE reference value due to sampling, animal
variation and laboratory analysis, which represents the maximum achievable accuracy for the predicting
models; and the practical limitation and applicability of each method. Future research could consider a
combination of estimation methods and it would be interesting to integrate the energy and protein (amino
acid) balance
Genotypic and phenotypic diversity of triticale in relation to cell wall digestibility
No full textClimate models predict higher average temperatures, and more frequent and severe drought spells in Europe. Triticale (× Triticosecale Wittmack) is one of the most promising alternative forage crops due to its high yield potential under dry growing conditions. However, its nutritive value for ruminants should be improved. Therefore, breeding triticale forage varieties with a high cell wall digestibility is an interesting strategy.
The main objective of this PhD research was to get a better understanding of cell wall digestibility in triticale forage at both the phenotypic and genotypic level. To this purpose, a collection of 120 winter triticale genotypes of European and North American breeding origin was assembled. In this research, NIRS calibrations were successfully developed as tool to screen cell wall digestibility in triticale forage. When tested in field experiments, a large phenotypic and genotypic variability in cell wall digestibility among triticale genotypes harvested at the soft dough developmental stage was observed. Further, our phenotypic dataset was combined with genotypic data to perform a genome-wide association study. This study allowed to decipher the genetic architecture of cell wall digestibility in triticale and to identify phenotypic traits related to this trait. Moreover, the genomic regions identified in this doctoral research are of great value for breeders aiming to improve cell wall digestibility in triticale forage. Lastly, since triticale forage will be mostly fed as silage, the silage characteristics of soft dough triticale were studied. Our results showed that harvesting triticale at the soft dough stage guaranteed a good silage quality in terms of pH, fermentation losses, and aerobic stability
Padrões da distribuição nictemeral do comportamento ingestivo de vacas leiteiras, ao início e ao final da lactação, alimentadas com dieta à base de silagem de milho Ingestive behavior nycterohemeral patterns of dairy cows, at the beginning and at the end of lactation, fed a corn silage based diet
Get PDFOs efeitos dos estádios de lactação inicial e final sobre o comportamento e a distribuição nictemeral do comportamento ingestivo foram avaliados com oito vacas leiteiras, consumindo uma dieta à base de silagem de milho. A análise espectral das séries de tempos horários de mastigação (ingestão ou ruminação) foi realizada usando os dados modificados pela transformação finita de Fourier. Foi realizada análise de variância destes dados e a análise dos periodogramas e diagramas de fase. A duração média das refeições e o consumo de matéria seca foram superiores, enquanto o tempo unitário de ruminação foi inferior no período inicial em relação ao final da lactação. A distribuição dos tempos de ingestão e de ruminação nos estádios inicial e final de lactação seguiu, respectivamente, periodicidades de 24, 12, 8 e 4 horas e de 24, 12 e 8 horas. Foi constatado efeito significativo do estádio de lactação para o tempo gasto ingerindo e ruminando no componente de ritmo 4. O estádio da lactação influenciou alguns parâmetros do comportamento ingestivo e sua ritmicidade.The effects of the stage of lactation upon the ingestive behavior nycterohemeral patterns were evaluated with eight dairy cows eating a corn silage based diet. Spectral analysis was performed through application of the finite Fourier transformation upon hourly duration of eating or ruminating time series. Variance analysis and inspection of phase diagrams and periodograms were done upon modified data. The mean meal duration and dry matter intake were larger while the unitary ruminating time was inferior at the beginning than at the end of the lactation. Nycterohemeral patterns of time spent eating or ruminating at the beginning and at the end of lactation followed mainly periodicities of, respectively, 24, 12, 8 and 4 hours and 24, 12 and 8 hours. A significant effect of stage of lactation was observed at the rhythm component 4 for both time spent eating and ruminating. Lactation stage affected some parameters of ingestive behavior and its rhythmicity patterns
Degradation of dietary oligofructose and inulin in the gastro-intestinal tract of the rabbit and the effects on caecal pH and volatile fatty acids
Get PDF[EN] Three experimental fattening diets were each fed ad libitum to 12 animals of 8-9 weeks of age (initial weight 2,257 ± 87 g). The diets contained 0% (Control), 2% oligofructose (OF) (Raftifeed(R) OPS) or 2% inulin (Raftifeed(R) IPS). After an adaptation period of 10 days, the individually caged rabbits received the same diets with Cr2O3 as a marker. For the 24 h before they were euthanised (between 08:30 and 09:00), rabbits wore a plastic collar to prevent caecotrophy. Dietary treatment affected gut acidity only in the caecum where a tendency to a reduced pH in the inulin-fed rabbits was observed. The total caecal concentration of volatile fatty acids was similar among dietary treatments but a significant (P<0.05) change occurred in inulin-fed rabbits with an increase of butyrate proportion (17.6, 20.2 and 22.6% for control, OF and inulin rabbits, respectively) at the expense of acetate (75.0, 72.3 and 70.1%, respectively). Fructans were not detected in the ileum, caecum or faeces of control rabbits, indicating that both types of oligosaccharides originating from the raw materials were degraded quickly. Significant amounts of the b(2-1)-fructans were still present in the ileum content of both OF and inulin fed rabbits (1.78 and 1.63% DM). Apparent ileal digestibility of fructans was 100% in control rabbits but significantly lower (P<0.01) in OF (35.3%) and inulin (49.2%) fed rabbits. The absence of fructans from caecal and faecal samples confirms their complete fermentation by the caecal microbial flora. However, with the methodology used (which increased variability) and the limited number of replicates (4 pooled samples/diet), no significant difference in the degradation due to the chain length of the inuline-type fructans was detected.The authors are grateful to the Orafti company (Tienen, Belgium) for their financial and analytical support. They acknowledge the skilled technical support of A. Vermeulen and J. M. Vanacker.Maertens, L.; Aerts, J.; De Boever, J. (2004). Degradation of dietary oligofructose and inulin in the gastro-intestinal tract of the rabbit and the effects on caecal pH and volatile fatty acids. World Rabbit Science. 12(4):235-246. https://doi.org/10.4995/wrs.2004.569SWORD23524612
Assessing plant type and the nutritive value of silage maize in the perspective of the Belgian official variety trials
Get PDFRoughage evaluation of maize and grass silage based on chewing activity measurements with cows
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