Determining nitrogen requirements of Aceros and Buceros hornbills

Over 2 months, seven feeding trials were conducted at St. Catherines Island, GA, to quantify protein intake and utilization in captive mature nonreproducing Aceros (n=3 spp.) and Buceros (n=2 spp.) Hornbills were fed homogeneous isocaloric diets. A mixture of Bird of Paradise pellets, grapes, and raisins was offered to the birds as grape‐sized balls, supplemented with diced cantaloupe melon to maintain hydration. To vary the protein level (range 10.8–22.6%) within the diets, different amounts of a powdered soy protein supplement were added to the mixture. Test diets were fed for 3 consecutive days. Birds were weighed to test for differences among diets. All excreta and diet samples were collected for nitrogen (N) analysis. Feeding trials were separated by a 4‐day period, in which the bird's regular diet was fed. Data were analyzed for N balance, N equilibrium (regression of N intake vs. N excretion) and body mass. Regression analysis of N balances of the nine birds showed that the N equilibriums ranged from 0.081 to 0.595 g N/kg^0.75/d with an average of 0.387±0.298. No differences in N balances were found between Aceros and Buceros hornbills. The methodology of this study suggested a dietary crude protein (CP) requirement of 7.3±3.0% dry matter (DM) in a diet containing 4.0 kcal. However, this value was determined by extrapolation and has not been experimentally determined to be adequate. In this study, the hornbills maintained body mass on a diet containing 10.8% CP (with energy at 4.0 kcal/g DM). Zoo Biol 27:282–293, 2008. © 2008 Wiley‐Liss, Inc.     

Enhanced production and partial characterization of an extracellular polysaccharide from newly isolated Azotobacter sp. SSB81

A strain was selected by its highest extracellular polysaccharide (EPS) production ability compare to other isolates from the same rhizospheric soil. The selected strain was identified by 16S rDNA sequencing and designated as SSB81. Phylogenetic analysis of the gene sequence showed its close relatedness with Azotobacter vinelandii and Azotobacter salinestris. Maximum EPS (2.52 g l⁻¹) was recovered when the basal medium was supplemented with glucose (2.0%), riboflavin (1 mg l⁻¹) and casamino acid (0.2%). The EPS showed a stable viscosity level at acidic pH (3.0–6.5) and the pyrolysis temperature was found to be at 116.73 °C with an enthalpy (ΔH) of 1330.72 Jg⁻¹. MALDI TOF mass spectrometric result suggests that polymer contained Hex₅Pent₃ as oligomeric building subunit. SEM studies revealed that the polymer had a porous structure with small pore size distribution indicating the compactness of the polymer. This novel EPS may find possible application as a polymer for environmental bioremediation and biotechnological processes.     

Toward a new practical energy evaluation system for dairy cows

Energy evaluation systems translate an animal's net energy (NE) requirements into feed metabolisable energy requirements (MER). The Feed into Milk (FiM) project (Agnew RE, Yan T, France J, Kebreab E and Thomas C 2004. Energy requirement and supply. In Feed into Milk. A new applied feeding system for dairy cows (ed. C Thomas), pp. 11-20. Nottingham University Press, Nottingham, UK) proposed a new system to predict MER of dairy cows that is, in contrast to previous energy evaluation systems for cattle, independent of feed quality. The FiM system shares this characteristic with an energy evaluation system for ad libitum-fed cattle proposed in 1994 by Tolkamp and Ketelaars (T&K). The FiM system requires nine parameters to translate requirements for NE into MER for dairy cows, while the T&K system for cattle requires only two for the same purpose. This paper analyses the contribution of each of the parameters to the final MER predictions, the differences in MER prediction between the two systems and the underlying causes of these differences. The systems differ considerably in their estimates of the NE that is required for maintenance and in their (implicit) assumptions about the partial efficiency of ME utilisation for lactation. The T&K system is based on a constant partial efficiency of ME utilisation, but in the FiM system this efficiency changes with milk yield (MY) and shows a sharp discontinuity that is at odds with the underlying biology. These are the two main causes of the differences in MER predictions. Nevertheless, over a range of MYs between 10 and 40 kg, and for cows maintaining, gaining or losing weight, the MER predictions of the two systems are very similar with maximum differences of up to ±2% only. FiM predictions of MER are systematically higher than T&K predictions for cows with very low and very high MY. It is concluded that the FiM system could reduce parameter requirements with negligible effects on MER predictions. The combination of a very high maintenance NE parameter and a curvilinear model with two subsequent corrections leads to internal inconsistencies in the FiM system. The T&K system is much simpler but it might benefit from including more recent information for the estimation of its parameters.     

农作物需水量随气候变化的响应研究

利用甘肃省近80个气象站1961~2000年的常规气象观测资料以及夏秋主要粮食作物平均生育期资料,采用FAO推荐的Penm an-M on te ith公式结合作物系数,计算了各站夏秋主要粮食作物的需水量,分析作物需水量随时间和空间的变化特点以及对气候变化的响应.结果表明:农作物需水量与种植区的气候类型关系十分密切,从干旱-半干旱-半湿润-湿润地区其需水量呈现减小的趋势,越是干旱的地区作物需水量越大,越是湿润的地区作物需水量越小.作物需水量随气候变化的响应比较明显,在干旱、半干旱地区表现尤为突出.不同作物品种需水量相差较大,对气候的响应机制也有差异,一般来说夏粮的需水量小于秋粮,夏粮需水量对气候变化的响应比秋粮敏感.     

Modeling with a view to target identification in metabolic engineering: A critical evaluation of the available tools

The state of the art tools for modeling metabolism, typically used in the domain of metabolic engineering, were reviewed. The tools considered are stoichiometric network analysis (elementary modes and extreme pathways), stoichiometric modeling (metabolic flux analysis, flux balance analysis, and carbon modeling), mechanistic and approximative modeling, cybernetic modeling, and multivariate statistics. In the context of metabolic engineering, one should be aware that the usefulness of these tools to optimize microbial metabolism for overproducing a target compound depends predominantly on the characteristic properties of that compound. Because of their shortcomings not all tools are suitable for every kind of optimization; issues like the dependence of the target compound's synthesis on severe (redox) constraints, the characteristics of its formation pathway, and the achievable/desired flux towards the target compound should play a role when choosing the optimization strategy. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Germination of <i>Eryngium regnellii</i>: a major species for ecological restoration of plant-pollinator interactions in the Southern Pampas (Buenos Aires,Argentina)

Eryngium regnellii Malme belongs to the largest genera in the Apiaceae family, with 250 species worldwide and 65 represented in South America. It is a herbaceous species typical of hill plant communities, which, along with remnant grassland patches, are the most relevant natural habitats for the maintenance of diversity in the Southern Pampas. Eryngium regnellii is key to the maintenance of pollination mutualisms, being a generalist (displaying a diverse assemblage of pollinators) and ubiquitous species (present in all studied sierras). However, fragmentation of the Pampean landscape due to agricultural intensification has led to the loss of natural environments. Therefore, the reintroduction of E. regnellii in strategic places would facilitate the occurrence of wild pollinators, while favoring pollination services in the agroecosystem. The germination requirements of E. regnellii were studied because a better knowledge of the reproductive biology of this species would provide information relevant to its reproduction and reintroduction into degraded areas. Germination percentages and mean time to germination were evaluated, using one control and two pre-germination treatments: chemical scarification with sulfuric acid, and mechanical scarification with sand paper. Chemical scarified seeds did not germinate. Mechanically scarified and control seed groups showed no significant differences either in germination percentages (49% and 59% respectively) or in mean germination time (13 and 14 days, respectively). Results indicate that E. regnellii shows no physical dormancy, and does not require specific pre-germination treatments for germination under the studied laboratory conditions. The high germination capacity of E. regnellii, along with its ecological attributes, make it a potential species for restoring plant-pollinator interactions in the fragmented landscapes of the Southern Pampas.     

Biosimilars: Key regulatory considerations and similarity assessment tools

A biosimilar drug is defined in the US Food and Drug Administration (FDA) guidance document as a biopharmaceutical that is highly similar to an already licensed biologic product (referred to as the reference product) notwithstanding minor differences in clinically inactive components and for which there are no clinically meaningful differences in purity, potency, and safety between the two products. The development of biosimilars is a challenging, multistep process. Typically, the assessment of similarity involves comprehensive structural and functional characterization throughout the development of the biosimilar in an iterative manner and, if required by the local regulatory authority, an in vivo nonclinical evaluation, all conducted with direct comparison to the reference product. In addition, comparative clinical pharmacology studies are conducted with the reference product. The approval of biosimilars is highly regulated although varied across the globe in terms of nomenclature and the precise criteria for demonstrating similarity. Despite varied regulatory requirements, differences between the proposed biosimilar and the reference product must be supported by strong scientific evidence that these differences are not clinically meaningful. This review discusses the challenges faced by pharmaceutical companies in the development of biosimilars.     

Consequences of inferring diet from feeding guilds when estimating and interpreting consumer–resource stoichiometry

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