Browsing by Subject "Age"

Now showing 1 - 2 of 2

Analysis of aging-related changes and influencing factors on the metabolome of beef
(2023) Bischof, Greta; Gibis, Monika
Aging of beef is necessary to improve its flavor and tenderness. There are two most common aging types, dry-aging and wet-aging. Dry-aged beef is often associated with a higher eating quality than wet-aged beef. The term “dry-aged beef” is not legally defined, so authentication methods are needed to protect the consumers from food fraud. During beef aging, the metabolome of beef changes due to the postmortem metabolism. This dissertation focuses on the aging method as a postmortem process and the resulting changes in the metabolome. As a hypothesis of this study, it was postulated that the detection of these metabolic changes due to aging of beef is feasible by 1H NMR spectroscopy and based on these measurements the evaluation of an authentication model for the aging method of beef is possible. In order to test this hypothesis, a sample preparation and measurement method was developed and based on this, potential influencing factors such as sampling position in muscle, breed and sex were investigated on the metabolome of fresh and aged beef. In the first part of this thesis, the sample preparation and the 1H NMR measurement method were developed. In the sample preparation, the polar fraction of the metabolome was extracted from 200 mg of beef, allowing 24 samples to be prepared in parallel. The sample preparation and the measurement method were validated, and the first aged beef samples were analyzed to check if the aging-related changes in the metabolome could be detected by this method. In the second part of this thesis, the sampling position in the muscle were analyzed for changes or differences in the metabolome due to its location in the muscle. The results showed that the metabolome changes along the length of the M. longissimus thoracis et lumborum, but the influence of the aging type and aging time was more pronounced in the metabolome of beef. The comparison of the surface and the inner part of wet-aged and dry-aged beef showed that the metabolome of dry-aged beef differed greatly between the surface and the inner part, despite the exclusion of the moisture content by freeze-drying and the low microbial load. There were only slight differences between the surface and the inner part for wet-aged beef, which could be due to the influence of microbiota and their metabolites. Therefore, the sampling location in the M. longissimus thoracis et lumborum was determined as precisely as possible for the further studies. The muscles were cut into ten pieces from cranial to caudal and dry-aged or wet-aged for 0, 7, 14, 21, and 28 days, in duplicates. The third part of this thesis focuses on the potential influencing factors such as breed and sex of the animals. Fresh and aged beef samples from three cattle types (heifer, cow, and young bull) and two different breeds (‘Fleckvieh’ and ‘Schwarzbunt’) were analyzed by targeted and non-targeted 1H NMR spectroscopy. Both factors were shown to influence the metabolome of fresh and aged beef. Therefore, these factors had to be included in the authentication model based on both targeted and non-targeted model. The calculation of the authentication model was the main part of this thesis and showed a good prediction of cattle type, breed, aging time and aging type of beef. The authentication model was based on the combination of multiple models of PLS-R and PLS-DA. The model for predicting the cattle type showed an accuracy of 99 %, and the models for predicting the breed depending on the cattle type showed an accuracy of 100 %. Aging time could be predicted with an error of 2.28 days. The statistical models for aging type were separated by aging time based on the determination of aging time. The model for predicting the aging type of 28-day aged samples had an accuracy of 99 %. The other statistical models for predicting aging type were additionally separated by cattle type and breed, and their accuracy ranged from 90 % to 100 %. In conclusion, an authentication model to determine the cattle type, breed, aging time and aging type of beef was developed in this dissertation. Therefore, it is possible to authenticate beef samples using a single 1H NMR spectrum. In future studies, it would be useful to extend this authentication model to other samples of other breeds and influencing factors.
Impact of age and weaning time on the gut microbiome and the potential host-microbe interactions in calves
(2021) Amin, Nida; Seifert, Jana
The period from birth until the end of weaning is critical for calves as they undergo extreme stress caused by maternal separation, transportation, and weaning related dietary shifts, that can cause long-lasting effects on animal behaviour, health as well as future production parameters. Monitoring the development of microbial ecosystem throughout the gastrointestinal tract of calves and host-microbe interactions during the challenging life periods such as perinatal and weaning is essential for sustainable ruminant production. The present thesis provided new insight on the suitability of buccal swabs as an alternative to complex stomach tubing method for predictive analysis of rumen microbial communities. The changes in oral, rumen and faecal microbial community structure of female German Holstein calves from 8-days to 5-months of age as well as during early- and late-weaning event were identified. The oral microbiota plays a crucial role in animal health. A high dominance of oral pathogens was observed during the first 11-weeks of calves’ life. Similar to the oral microbiota, faeces of 8-day-old calves also showed high abundances of certain opportunistic pathogenic bacteria. Both oral and faecal pathogens showed a decrease in abundance with age and after weaning event in the earlyC group, indicating the age and weaning-dependent maturation of the host immune system. The establishment of dense microbial communities in the faeces of 8-day-old (experimental day 1) pooled herd milk and milk replacer fed Holstein calves was shown and it was dominated by phyla Firmicutes and Actinobacteria and potential lactose- and starch-degrading bacterial species, but as the calves aged and became more mature (5-months of age), their rumen and faecal bacterial communities were dominated by potential fibre-utilizing bacterial genera. The weaning related dietary transitions are critical for calves as their gastrointestinal tract undergoes several modifications, enabling them to digest plant-based diet during the postweaning period. Thus, it was proposed that the age at which animals should be weaned must be carefully considered as it clearly impacted the gastrointestinal tract microbial communities and plasma metabolic profiles of calves in the present study. Early introduction of roughages in the diet of 7-week-old calves increased the abundances of plant fiber degrading bacteria and decreased the abundances of potential lactose- and starch-degrading bacteria in the buccal cavity, rumen and faeces, indicating the weaning-related increase in fiber ingestion and the decrease in milk consumption of the early-weaned group. However, when roughages were introduced in the diet of late-weaned calves at 17-weeks of age, no significant modifications in the structure of gastrointestinal tract microbial communities were observed. Similar to the microbiome, plasma metabolic profiles of early-weaned calves during days 42–112, showed lower concentrations of most of the amino acids, few biogenic amines, and sphingomyelins as compared to the late-weaned calves, suggesting that the liquid diet could provide certain metabolites that can be transported into the bloodstream through gastrointestinal tract. Similarly, the weaning-dependent changes in the quantity of dietary protein, fat and carbohydrates resulted in substantial changes in amino acid metabolism of the early-weaned group. The early-weaning event not only impacted the host microbiome and metabolome but also the host-microbe metabolic interactions as the abundances of potential lactose- and starch degrading bacteria and plasma concentrations of amino acid, biogenic amines and sphingomyelins were strongly positively correlated, both were negatively impacted by the early-weaning event. Thus, it can be concluded that late-weaning was beneficial as it allowed better adaptability of microbes to weaning-related dietary shifts, perhaps due to the greater maturation of their gastrointestinal tract with age as compared to the early-weaning group.