鸡群整齐度的重要性

鸡群的整齐性有益于生产性能这个观点早已得到了大家的公认。为了追求更好的整齐度,营养学家们需要在满足畜禽需要的同时尽可能减少变异、降低安全系数,从而节省饲料成本和提高动物生产性能,尽管在养殖场中提高生产效率的方法不单单减少体重变异这一种。     

The Influence of Tallow on Rumen Metabolism,Microbial Biomass Synthesis and Fatty Acid Composition of Bacteria and Protozoa

Abstract

Rumen metabolism, microbial biomass synthesis and microbial long chain fatty acid composition were studied in lactating cows fed at two levels of dry matter intake (L, 8.6 kg DM and H, 12.6 kg DM) with 0, 4 and 6% added tallow at the low feed level (L0, L4 and L6) and 0, 2, 4 and 6% at the high feed level (H0, H2, H4 and H6).

Fibre digestibility was not significantly affected by tallow addition. Increasing tallow level in the diet decreased the total VFA concentration, the ratio of acetic acid to propionic acid and the ammonia concentration in the rumen. Crude fat and fatty acid content in bacterial and protozoal dry matter increased with increased tallow level, especially due to an increase in fatty acids originating from the feeds. Microbial synthesis in the rumen and flow of amino acids to the duodenum was highest for medium fat intake at the high feed level.     

Effect of Days Post-Partum, Breed and Ovum Pick-Up Scheme on Bovine Oocyte Recovery and Embryo Development

The objective of this study was to investigate (i) the effect of two different ovum pick-up (OPU) schemes (once vs twice weekly aspirations) on oocyte recovery rate, quality and subsequent in vitro embryo development, (ii) the influence of days post-partum on oocyte recovery and (iii) possible differences in OPU results from two different herds. In group A, OPU was performed twice weekly in two Holstein Friesian (HF) and three Danish Red and White (DRW) cows from a private herd. In the research herd, two groups of eight HF cows were investigated: group B (OPU once weekly) and group C (OPU twice weekly). The collected oocytes were subsequently submitted to in vitro embryo production. More oocytes were recovered from the private herd when compared with the research herd. In the research herd, the twice weekly scheme aspirated more oocytes than the once weekly scheme. The quality of the retrieved oocytes was significantly different between groups B and C but not between groups A and C, and HF cows yielded higher quality oocytes than DRW cows (p = 0.029). Oocytes from group C showed higher level of embryonic development than group B oocytes. No differences in blastocyst rates were observed between groups A and C. Session affected the number of retrieved oocytes and subsequent developmental rates, with these being lower in the first compared with the last sessions. Finally, there was no significant effect of days post-partum in the number and quality of the retrieved oocytes, likely because of the small group size and high variation between sessions.     

Genomic selection allowing for marker‐by‐environment interaction

Genomic selection has been routinely implemented in plant breeding in two stages. The first stage usually omits the marker information and estimates adjusted means of genotypes across environments. The second stage uses the adjusted means to predict genomic breeding values. However, if the effects of markers vary substantially between different environments, it may be important to account for this variation for varieties adapted to different environments. Using two maize data sets, we investigated whether modelling the marker‐by‐environment interaction can improve the predictive ability of genomic selection relative to modelling genotype‐by‐environment interaction alone. Modelling the marker‐by‐environment interaction did not substantially increase the predictive ability relative to modelling only the genotype‐by‐environment interaction for the two tested data sets. Thus, genomic selection, carried out in a stagewise fashion, such that the marker information is omitted until the last stage of the process, may suffice for most practical purposes. Moreover, predictive ability did not reduce substantially even when the number of markers with consistent effects across environments used for genomic prediction was reduced to about 50.     

Ancient experiments: forest biodiversity and soil nutrients enhanced by Native American middens

The legacy of ancient human practices can affect the diversity and structure of modern ecosystems. Here, we examined how prehistoric refuse dumps (“middens”) impacted soil chemistry and plant community composition in forests along the Chesapeake Bay by collecting vegetational and soil nutrient data. The centuries- to millennia-old shell middens had elevated soil nutrients compared to adjacent sites, greater vegetative cover, especially of herb and grass species, and higher species richness. Not only are middens important archaeological resources, they also offer a remarkable opportunity to test ecological hypotheses about nutrient addition over very long time scales. We found no evidence, for example, that elevated nutrients enhanced invasion by non-native species as predicted by the fluctuating resource hypothesis. However, we did find that elevated nutrients shifted community structure from woody species to herbaceous species, as predicted by the structural carbon-nutrient hypothesis. These results highlight the long-lasting effects that humans can have on abiotic and biotic properties of the natural environment, and suggest the potential for modern patterns of species’ distributions and abundances to reflect ancient human activities.     

Hemostatic biomarkers in dogs with chronic congestive heart failure

BACKGROUND: Chronic congestive heart failure (CHF) in humans is associated with abnormal hemostasis, and abnormalities in hemostatic biomarkers carry a poor prognosis. Alterations in hemostatic pathways can be involved in the pathogenesis of CHF in dogs, and microthrombosis in the myocardium could contribute to increased mortality. HYPOTHESIS: That plasma concentration or activity of hemostatic biomarkers is altered in dogs with CHF and that these factors predict mortality. ANIMALS: Thirty-four dogs with CHF caused by either dilated cardiomyopathy (DCM, n=14) or degenerative valvular disease (CDVD, n=20) compared with 23 healthy age-matched control dogs were included in this study. Dogs with CHF were recruited from 2 referral cardiology clinics, and control dogs were owned by friends or colleagues of the investigators. METHODS: Clinical examination and echocardiography were performed in all dogs. Plasma fibrinogen and D-dimer concentrations, antithrombin and protein C activity, and thrombin-antithrombin complex (TAT) were measured in all dogs. RESULTS: Dogs with CHF had significantly higher fibrinogen (P = .04), D-dimer (P = .002), and TAT concentration (P < .0001), lower antithrombin (P < .0001) and protein C activity (P < .001) compared with control dogs. None of the hemostatic biomarkers were associated with risk of death. CONCLUSIONS AND CLINICAL IMPORTANCE: There is evidence of a procoagulant state in dogs with CHF. The lack of predictive value for survival might be due to the small number of dogs examined. Further studies are necessary to investigate the presence and importance of microthrombosis in dogs with CHF.     

Assessing the influence of genotype and temperature on polyphenol composition in cloudberry (Rubus chamaemorus L.) using a novel mass spectrometric method

A high-throughput abbreviated liquid chromatography mass spectrometric (ACMS) method was used to assess the relative influence of genotype and temperature on polyphenol composition in cloudberries. Principal component analysis (PCA) plots of the collated ACMS data showed a separation between crosses based on their female parents (Nyby or Fjellgull). Crosses with Nyby as the female parent had higher relative levels of masses assignable to certain ellagitannin derivatives. Crosses with Fjellgull had higher levels of distinctive masses assignable to quercetin derivatives (including a hydroxy-3-methylglutaroyl hexose derivative not previously identified in cloudberry) and anthocyanin derivatives. There was also a separation between samples grown at lower and higher temperatures, which was driven by m/z signals associated with ellagitannins and notably a major component, sanguiin H-6. Therefore, abbreviated MS techniques can discern genetic and/or environmental influences in polyphenol composition and can quickly assess quality in breeding programmes or in response to environmental changes.     

Enzymatic interesterification of butterfat with rapeseed oil in a continuous packed bed reactor

Lipase-catalyzed interesterification of butterfat blended with rapeseed oil (70/30, w/w) was investigated both in batch and in continuous reactions. Six commercially available immobilized lipases were screened in batch experiments, and the lipases, Lipozyme TL IM and Lipozyme RM IM, were chosen for further studies in a continuous packed bed reactor. TL IM gave a fast reaction and had almost reached equilibrium with a residence time of 30 min, whereas RM IM required 60 min. The effect of reaction temperature was more pronounced for RM IM. TL IM showed little effect on the interesterification degree when the temperature was raised from 60 degrees C to 90 degrees C, whereas RM IM had a positive effect when the temperature was increased from 40 degrees C to 80 degrees C. Even though TL IM is an sn-1,3 specific lipase, small changes in the sn-2 position of the triacylglycerol could be seen. The tendency was toward a reduction of the saturated fatty acid C14:0 and C16:0 and an increase of the long-chain saturated and unsaturated fatty acids (C18:0 and C18:1), especially at longer residence times (90 min). In prolonged continuous operation the activity of TL IM was high for the first 5 days, whereafter it dramatically decreased over the next 10 days to an activity level of 40%. In general, the study shows no significant difference for butterfat interesterification in terms of enzyme behavior from normal vegetable oils and fats even though it contains short-chain fatty acids and cholesterol. However, the release of short-chain fatty acids from enzymatic reactions makes the sensory quality unacceptable for direct edible applications.     

Carbon partitioning in a wet and a semiwet subarctic mire ecosystem based on in situ C pulse-labelling

In this study we quantify the partitioning of recent assimilates to above- and below-ground carbon (C) pools in two subarctic mire ecosystems - wet minerotrophic and semiwet ombrotrophic mire - using in situ ¹⁴C pulse-labelling. Ecosystem C partitioning to rhizomes, coarse roots, fine roots, dissolved organic carbon (DOC) and microbes were quantified twice  during the growing season at three different soil depths. Finally the ¹⁴C-partitioning data from this and a previous study were combined to estimate the overall C partitioning of the three main vegetation types of a Scandinavian subarctic mire in early and late summer.The semiwet ombrotrophic ecosystem hosted a much larger root biomass on an area basis compared to the wet minerotrophic ecosystem which might be due to differences in the soil nutrient level. Microbial C was found to be the largest C-pool in both ecosystems. Ecosystem ¹⁴C partitioning was poorly related to plant biomass for the semiwet and the wet ecosystem. Overall a higher partitioning of recent assimilates to below-ground compartments was apparent in August-September compared to June-July, while the opposite was found for the above-ground C-pools. In the semiwet ecosystem twice as much ¹⁴C was found in DOC compared to the wet ecosystem, where root density, litter and above-ground biomass were important controls of the ¹⁴C-recovery in DOC. Plant-derived DOC was estimated to be 15.4 versus 12.9 mg C m⁻² d⁻¹ in the semiwet and wet ecosystem, respectively.Graminoid dominated and dwarf shrub dominated vegetation types of the subarctic mire Stordalen differ with respect to the relative amount of recently assimilated C partitioned to C-pools with “slow” versus “fast” decomposition rate. The capacity for sequestration of recently fixed C within “slow” C-pools might affect the ecosystem C balance (NEE) and C-storage. The potential for vegetation changes might therefore be an important factor to consider in studies of response of ecosystem C-dynamics to global change factors in subarctic mires.