902 resultados para BEEF STEERS
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Few data exist on direct greenhouse gas emissions from pen manure at beef feedlots. However, emission inventories attempt to account for these emissions. This study used a large chamber to isolate N2O and CH4 emissions from pen manure at two Australian commercial beef feedlots (stocking densities, 13-27 m(2) head) and related these emissions to a range of potential emission control factors, including masses and concentrations of volatile solids, NO3-, total N, NH4+, and organic C (OC), and additional factors such as total manure mass, cattle numbers, manure pack depth and density, temperature, and moisture content. Mean measured pen N2O emissions were 0.428 kg ha(-1) d(-1) (95% confidence interval [CI], 0.252-0.691) and 0.00405 kg ha(-1) d(-1) (95% CI, 0.00114-0.0110) for the northern and southern feedlots, respectively. Mean measured CH4 emission was 0.236 kg ha(-1) d(-1) (95% CI, 0.163-0.332) for the northern feedlot and 3.93 kg ha(-1) d(-1) (95% CI, 2.58-5.81) for the southern feedlot. Nitrous oxide emission increased with density, pH, temperature, and manure mass, whereas negative relationships were evident with moisture and OC. Strong relationships were not evident between N2O emission and masses or concentrations of NO3- or total N in the manure. This is significant because many standard inventory calculation protocols predict N2O emissions using the mass of N excreted by the animal.
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On beef cattle feed pen surfaces, fresh and decayed manure is mixed with base rock or soil (base). Quantifying this mixing has beneficial applications for aspects including nutrient and greenhouse gas budgeting. However, no practical methods exist to quantify mixing. We investigated if measuring element concentrations in: (A) fresh manure, (B) base material, and (C) pen manure offers a promising method to quantify manure/base mixing on pen surfaces. Using three operational beef feedlots as study sites, we targeted carbon (C), and silicon (Si), which are the two most abundant and easily measurable organic and inorganic elements. Our results revealed that C concentrations were strongly (>15 times) and significantly (P < 0.05) higher whereas Si concentrations strongly (>10 times) and significantly (P < 0.01) lower in fresh manure than base material at all three sites. These relative concentrations were not significantly impacted by manure decay, as determined by an 18-week incubation experiment. This suggested that both of these elements are suitable markers for quantifying base/manure mixing on pens. However, due to the chemical change of manure during decay, C was shown to be an imprecise marker of base/manure mixing. By contrast, using Si to estimate base/manure mixing was largely unaffected by manure decay. These findings were confirmed by measuring C and Si concentrations in stockpiled pen surface manure from one of the sites. Using Si concentrations is a promising approach to quantify base/manure mixing on feed pens given that this element is abundantly concentrated in soils and rocks.
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There is uncertainty over the potential changes to rainfall across northern Australia under climate change. Since rainfall is a key driver of pasture growth, cattle numbers and the resulting animal productivity and beef business profitability, the ability to anticipate possible management strategies within such uncertainty is crucial. The Climate Savvy Grazing project used existing research, expert knowledge and computer modelling to explore the best-bet management strategies within best, median and worse-case future climate scenarios. All three scenarios indicated changes to the environment and resources upon which the grazing industry of northern Australia depends. Well-adapted management strategies under a changing climate are very similar to best practice within current climatic conditions. Maintaining good land condition builds resource resilience, maximises opportunities under higher rainfall years and reduces the risk of degradation during drought and failed wet seasons. Matching stocking rate to the safe long-term carrying capacity of the land is essential; reducing stock numbers in response to poor seasons and conservatively increasing stock numbers in response to better seasons generally improves profitability and maintains land in good condition. Spelling over the summer growing season will improve land condition under a changing climate as it does under current conditions. Six regions were included within the project. Of these, the Victoria River District in the Northern Territory, Gulf country of Queensland and the Kimberley region of Western Australia had projections of similar or higher than current rainfall and the potential for carrying capacity to increase. The Alice Springs, Maranoa-Balonne and Fitzroy regions had projections of generally drying conditions and the greatest risk of reduced pasture growth and carrying capacity. Encouraging producers to consider and act on the risks, opportunities and management options inherent in climate change was a key goal of the project. More than 60,000 beef producers, advisors and stakeholders are now more aware of the management strategies which build resource resilience, and that resilience helps buffer against the effects of variable and changing climatic conditions. Over 700 producers have stated they have improved confidence, skills and knowledge to attempt new practices to build resilience. During the course of the project, more than 165 beef producers reported they have implemented changes to build resource and business resilience.
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[EN]Conjugated linoleic acid (CLA) has many potential healthful properties, and beef is naturally enriched with CLA. Simple and rapid methods to measure total CLA were investigated to enable sorting of beef carcasses with potential enhanced economic value. Direct alcohol extraction combined with measuring absorbance was simple, accurate and perhaps the most viable method for rapid carcass sorting compared to methods using saponification or methylation followed by extraction.
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[EN]A comprehensive evaluation of the fatty acid composition of subcutaneous adipose tissue from beef cattle produced in western Canada was undertaken to determine if the current Canadian grading system is able to distinguish classes of animals with value added potential due to their fatty acid composition. Grades included youthful Canadian Yield Grade 1 A/AA beef, under (YUTM) and over (YOTM) 30 mo of age and the four mature grades (D1, D2, D2 and D4). Subcutaneous fat between the 12th and 13th ribs over the longissimus muscle was obtained from 18_21 animals per grade. Fatty acids were analyzed using a combination of silver-ion HPLC and GC with a highly polar 100 m column. There were no differences in total trans-18:1 content amongst grades, but adipose tissue from grade D1, D2 and D4 had more 11t-18:1 than YUTM (PB0.05), whereas adipose tissue from YUTM carcasses had more 10t-18:1 than all other grades (PB0.05). Adipose tissue from YUTM carcasses also had less total CLA (PB0.05) than the D grades, mainly due to a lower level of 9c,11t-CLA, but they had slightly more 7t,9c-CLA and 10t,12c-CLA (PB0.05). Adipose tissue from YOTM and D grades contained more n-3 fatty acids relative to YUTM (0.56% vs. 0.29%; PB0.05) and lower n-6:n-3 ratios (PB0.05). Overall, older animals (YOTM and D grades) had adipose tissue compositions with higher levels of fatty acids with reported health benefits. Taken together, these higher levels may provide opportunities for value added marketing if regulatory authorities allow claims for their enrichment based on demonstrated health benefits. Higher concentrations of beneficial fatty acids, however, need to be considered within the context of the complete fatty acid profile and it would be important to demonstrate their advantages in the presence of relatively high levels of saturated fatty acids.
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[EN]A survey of Canadian retail beef was undertaken with emphasis on the trans fatty acid (TFA) and conjugated linoleic acid (CLA) isomers, and compared with current health recommendations. Thirty striploin steaks were collected in the winter and summer from major grocery stores in Calgary (Alberta, Canada). Steak fatty acid compositions (backfat and longissimus lumborum muscle analysed separately) showed minor seasonal differences with lower total saturates (PB0.05) and higher total monounsaturates (PB 0.01) in winter, but no differences in total polyunsaturated fatty acids. The ratio of n-6 and n-3 polyunsaturated fatty acid in longissimus lumborum averaged 5.8. The average TFA content in longissimus lumborum was 0.128 g 100 g_1 serving size, and 10t-18:1 was found to be the predominant isomer (32% of total trans), while vaccenic acid was second most abundant (15% of total trans). The CLA content in longissimus lumborum was similar to that of backfat, ranging from 0.43 to 0.60% of total fatty acids and rumenic acid represented 60% of total isomers. Overall, there is still room for improvement in the saturated, mono- and polyunsaturated fatty acid composition of Canadian beef to meet general dietary guidelines for human consumption and additional targets should include reducing 10t-18:1 while increasing both rumenic and vaccenic acids.
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[EN]In an attempt to predict intramuscular fatty acid composition using easily accessible fat depots, between-tissue correlations were studied in 75 Asturiana de los Valles bulls with different levels of muscular hypertrophy, and 25 Asturiana de la Montan˜ a bulls. Trans-18:1 in intramuscular fat was highly and positively correlated with levels in subcutaneous and intermuscular fats, while levels of total n-3 were not correlated. Predicting intramuscular fatty acid composition using easily accessible depots is thus possible for some fatty acids exhibiting high between-tissue correlations (e.g., trans-18:1) but breed and tissue specific deposition may limit this for others (e.g., n-3 fatty acids).
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[EN]Most of the information indicating ageing improves tenderness has been collected on the loin and rib-eye muscles over relatively short ageing times, assuming that all muscles will react similarly. In the present study, the effect of extended ageing times on instrumental texture (56 d) and sensory characteristics (42 d) of six different beef sub-primals [striploin (SL), inside round (IR), outside round (OR), eye of round (ER), blade eye (BE) and chuck tender (CT)] was studied. The effects of two ageing temperatures (1and 58C) were also compared. In general, ageing increased tenderness (P<0.05) of SL, BE, ER and CT sub-primals, although BE shear force increased after 42 d of ageing. On the other hand, ageing had no effect on IR tenderness (P<0.05) and resulted in a decrease in tenderness of OR (P<0.05) until day 35, with a later increase after 42 d of ageing. Increasing ageing temperature (58C) had limited effect on tenderness, but ageing time and temperature increases led to lower flavour and higher off-flavour intensity (P<0.05) of the studied sub-primals. These results suggest that cutspecific maximum ageing times and rigid adherence to temperature maximums would be of benefit to optimize postslaughter processes and meat quality
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[EN]Trans fatty acids are found naturally in foods, particularly in those derived from ruminant animals, such as beef and dairy cattle. Over the past few decades, human consumption of trans fatty acids has increased, but this has been mainly from products containing partially hydrogenated vegetable oils. The correlation of trans fatty acid consumption with diseases such as coronary heart disease has been cause for concern, and led to recommendations to reduce their consumption. Trans fatty acids, however, have differing effects on human health. Therefore, in foods produced from ruminant animals, it is important to know their trans fatty acid composition, and how to enrich or deplete fatty acids that have positive or negative health effects. This review will cover the analysis of trans fatty acids in beef, their origin, how to manipulate their concentrations, and give a brief overview of their health effects.
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2.4. The author may post the VoR version of the article (in PDF or HTML form) in the Institutional Repository of the institution in which the author worked at the time the article was first submitted, or (for appropriate journals) in PubMed Central or UK PubMed Central or arXiv, no sooner than one year after first publication of the article in the Journal, subject to file availability and provided the posting includes a prominent statement of the full bibliographical details, a copyright notice in the name of the copyright holder (Cambridge University Press or the sponsoring Society, as appropriate), and a link to the online edition of the Journal at Cambridge Journals Online.
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In this study, random amplified polymorphic DNA (RAPD) analysis was used to estimate genetic diversity and relationship in 134 samples belonging to two native cattle breeds from the Yunnan province of China (DeHong cattle and DiQing cattle) and four intro
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Beef liver catalase molecules can stick tenaciously to the highly oriented pyrolytic graphite (HOPG) surface which has been activated by electrochemical anodization. The immobilized sample is stable enough for high resolution scanning tunneling microscope (STM) imaging. When the anodized conditions are controlled properly, the HOPG surface will be covered with a very thin oxide layer which can bind the protein molecules. Individual molecules of native beef liver catalase are directly observed in detail by STM, which shows an oval-shape structure with a waist. The dimensions of one catalase molecule in this study are estimated as 9.0 x 6.0x 2.0 nm(3), which are in good agreement with the known data obtained from X-ray analysis, except the height can not be exactly determined from STM. Electrochemical results confirm that the freshly adsorbed catalase molecules maintain their native structures with biological activities. However, the partly unfolding structure of catalase molecules is observed after the sample is stored for 15 days, this may be caused by the long-term interaction between catalase molecules and the anodized HOPG surface.
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In recent years, the potential to positively modulate human health through dietary approaches has received considerable attention. Bioactive peptides which are released during the hydrolysis or fermentation of food proteins or following digestion may exert beneficial physiological effects in vivo. The aim of this work was to isolate, characterise and evaluate Angiotensin-І-converting enzyme (ACE-І) inhibitory, antimicrobial and antioxidant peptides from the bovine myofibrillar proteins actin and myosin. In order to generate these peptides, the myofibrillar proteins actin and myosin were hydrolysed with digestive enzymes pepsin, trypsin and α-chymotrypsin, or with the industrial thermolysin-like enzyme “Thermoase”, Amano Inc. It was found that each hydrolysate generated contained peptides which possessed ACE inhibitory, antioxidant and antimicrobial activity. The peptides responsible in part for the observed ACE inhibitory, antioxidant and antimicrobial activity of a number of hydrolysates were isolated using the method of RP-HPLC and the bioactive peptides contained within each active fraction was determined using either MALDI-TOF MS/MS or N-terminal peptide sequencing. During the course of this thesis six ACE inhibitory and five antimicrobial peptides were identified. It was determined that the reported antioxidant activity was a direct result of a number of peptides working in synergy with each other. The IC50 values of the six ACE inhibitory peptides ranged in values of 6.85 to 75.7 µM which compare favourably to values previously reported for other food derived ACE inhibitory peptides, particularly the well known milk peptides IPP and VPP, IC50 values of 5 and 9 µM respectively. All five antimicrobial peptides identified in this thesis displayed activity against Escherichia coli, Salmonella typhimurium, Staphylococcus aureus and Listeria innocua with MIC values ranging from 0.625 to10 mM. The activity of each antimicrobial peptide was strain specific. Furthermore the role and importance of charged amino acids to the activity of antimicrobial peptides was also determined. Generally the removal of charged amino acids from the sequence of antimicrobial peptides resulted in a loss of antimicrobial activity. In conclusion, this thesis revealed that a range of bioactive peptides exhibiting ACE inhibitory, antioxidant and antimicrobial activities were encrypted in bovine myofibrillar proteins that could be released using digestive and industrial enzymes. Finally enzymatic hydrolysates of muscle proteins could potentially be incorporated into functional foods; however, the potential health benefits would need to be proven in human clinical studies.