The Carbon Budget Impact of Sagebrush Degradation

More than 20,000 km2 of sagebrush (Artemesia spp.) ecosystems within the Great Basin have been replaced, often following wildfire, by the nonnative winter annual cheatgrass (Bromus tectorum). At a field site in the central Snake River Plain of southern Idaho, the impact of this invasion on the soil carbon (C) reservoir has been evaluated and the potential soil C benefits of bunchgrass (Agropyron cristatum) seeding was assessed. Using a large soil C dataset (n = 850), differences in total organic carbon and root biomass were quantified in immediately-adjacent sagebrush, cheatgrass, and bunchgrass communities. Statistical significance was determined by employment of nonparametric analysis using bootstrap resampling and the two-population Kolmogrov-Smirnov test for statistical significance. Replacement of sagebrush by cheatgrass following fire has resulted in a 50% loss in below-ground carbon (56 to 29 Mg C ha-1, over a 27 yr period), with decreased root-C accounting for 20% of the total below-ground carbon loss. Bunchgrass seeding immediately following the fire reduced the amount of C lost to sagebrush degradation by 30% (31 vs. 40 Mg C ha-1). There is a positive relationship between above-ground biomass and below-ground soil carbon, however C loss is an order of magnitude greater in below-ground compared to above-ground C pools (27 vs. 3 Mg ha-1). Observed changes in soil structure, in particular the loss of large soil aggregates, and altered soil moisture conditions may contribute to the observed soil carbon loss. Extension of these results to the entire Great Basin, suggest the total below ground carbon loss with cheatgrass invasion is on the order of 60 Mt C and projected losses may exceed 2 Gt C. Conversely, treatment with bunchgrass or recovery of the original sagebrush may achieve similarly large carbon storage benefits

Digestibility in selected rainbow trout families and modelling of growth from the specific intake of digestible protein

The experiments aimed to clarify variations in digestibility of dietary nutrients in rainbow trout. Furthermore, the objective was to study how differences in digestibility might be related to growth and feed utilisation at various growth rates. When comparing the results from the experiments it appeared that particularly protein digestibility was closely related to specific growth rate and feed conversion ratio at high growth rates. As a tool to visualise the relationship between protein digestibility and growth of rainbow trout a growth model was developed based on the specific intake of digestible protein, and general assumptions on protein content and protein retention efficiency in rainbow trout. The model indicated that increased protein digestibility only partly explained growth increase and that additional factors were important for growth increment

A synthesis of the effects of cheatgrass invasion on the US Great Basin carbon storage

Non‐native, invasive Bromus tectorum (cheatgrass) is pervasive in sagebrush ecosystems in the Great Basin ecoregion of the western United States, competing with native plants and promoting more frequent fires. As a result, cheatgrass invasion likely alters carbon (C) storage in the region. Many studies have measured C pools in one or more common vegetation types: native sagebrush, invaded sagebrush and cheatgrass‐dominated (often burned) sites, but these results have yet to be synthesized. We performed a literature review to identify studies assessing the consequences of invasion on C storage in above‐ground biomass (AGB), below‐ground biomass (BGB), litter, organic soil and total soil. We identified 41 articles containing 386 unique studies and estimated C storage across pools and vegetation types. We used linear mixed models to identify the main predictors of C storage. We found consistent declines in biomass C with invasion: AGB C was 55% lower in cheatgrass (40 ± 4 g C/m2) than native sagebrush (89 ± 27 g C/m2) and BGB C was 62% lower in cheatgrass (90 ± 17 g C/m2) than native sagebrush (238 ± 60 g C/m2). In contrast, litter C was \u3e4× higher in cheatgrass (154 ± 12 g C/m2) than native sagebrush (32 ± 12 g C/m2). Soil organic C (SOC) in the top 10 cm was significantly higher in cheatgrass than in native or invaded sagebrush. SOC below 20 cm was significantly related to the time since most recent fire and losses were observed in deep SOC in cheatgrass \u3e5 years after a fire. There were no significant changes in total soil C across vegetation types. Synthesis and applications. Cheatgrass invasion decreases biodiversity and rangeland productivity and alters fire regimes. Our findings indicate cheatgrass invasion also results in persistent biomass carbon (C) losses that occur with sagebrush replacement. We estimate that conversion from native sagebrush to cheatgrass leads to a net reduction of C storage in biomass and litter of 76 g C/m2, or 16 Tg C across the Great Basin without management practices like native sagebrush restoration or cheatgrass removal

Interactive effects of dietary protein/lipid level and oil source on growth, feed utilisation and nutrient and fatty acid digestibility of Atlantic salmon

Although the use of fish meal (FM) and fish oil (FO) has been extensive in Atlantic salmon culture, there is a growing need for less reliance on these commodities. Moreover, it is crucial for the aquafeed industry to optimise the use of dietary protein and to improve the protein utilisation in salmon diets. The interactive effects of the dietary protein/lipid level and rapeseed oil (RO) inclusion on growth, feed utilisation, nutrient and fatty acid (FA) digestibility and whole body chemical composition of large Atlantic salmon (Salmo salar L.), reared at summer water temperatures (11.6 °C), were investigated in a ten week feeding trial. The fish (initial weight 2053 g) were fed six isoenergetic diets in a factorial design containing 350 g kg−1/350 g, kg−1, 330 g kg−1/360 g kg−1, 290 g kg−1/380 g kg−1 of protein/lipid for high protein (HP), medium protein (MP) and low protein (LP) diets, respectively. At all protein/lipid levels the oil source was either FO or RO (60% of the added oil). At the end of the trial the final weights ranged from 3340–3664 g and the FCR from 0.99– 1.10. The protein level did not affect significantly any of the growth parameters but the oil source had a significant effect on final weight, specific growth rate (SGR) and thermal growth coefficient (TGC), showing improved growth with RO inclusion. This could be explained by the significantly higher lipid digestibility of the fish fed the diets containing RO (86.1 vs. 92.2%) which was probably affected by the diet FA composition; the apparent digestibility coefficient (ADC) of saturated FA, and to a lesser extent of unsaturated FA and especially monoenes, was improved by RO inclusion. The protein ADC was significantly affected by the protein level indicating a higher ADC for the HP diets compared to the LP (80.1 vs. 77.7%, respectively). Regarding the whole body composition, moisture was significantly affected by both factors, the fat content was significantly affected only by the oil source, while significant interactions were shown for the protein content. In conclusion, the results of this study suggest that low protein/high lipid diets can be used with no negative effects on the growth, FCR and chemical composition of Atlantic salmon reared at high water temperatures. Moreover, the replacement of FO with RO can enhance the growth of the fish as well as the nutrient and FA digestibility of the diets

Growth, biochemical response and liver health of juvenile barramundi (Lates calcarifer) fed fermented and nonfermented tuna hydrolysate as fishmeal protein replacement ingredients

© 2018 Siddik et al. Conventional aquaculture feed materials available in Australia are expensive, which has prompted the search for alternatives that would be cost-effective and locally available. The present study was undertaken in order to maximize the use of a tuna hydrolysate (TH), which was produced locally from the tuna-processing discards. The growth performance, biochemical status, antioxidant capacity and liver health of juvenile barramundi (Lates calcarifer) were assessed. Two series of isonitrogenous and isocaloric diets labelled as TH50, TH75(non-fermented tuna hydrolysate) and FTH50, FTH75(fermented tuna hydrolysate) were formulated to replace FM at 50% and 75%, respectively. A basal diet without the TH supplementation was used as a control. The experimental diets were fed to the triplicate groups of fish three times a day for 56 days. The results of the experiment revealed that fish fed on both fermented and non-fermented TH-containing diets significantly reduced (p < 0:05) the final body weight, weight gain and specific growth rate compared to the control. The highest apparent digestibility coefficients for dry matter, protein and lipid were obtained in the control group, and decreased with the increasing level of TH in the diets. However, the whole-body proximate compositions and the blood biochemical indices of fish were not affected by the TH inclusion in the diets. The fish fed on TH diets of TH50, FTH50and TH75exhibited reduced (p < 0:05) glutathione peroxidase (GPx) activity compared to the control; whereas the FTH75exhibited no difference with the control. The excessive inclusion of TH in the diets of TH75and FTH75resulted in cytoplasmic vacuolization, with an increased amount of lipid accumulation, and necrosis in the liver tissue. These results indicated that the replacement of the FM protein with TH at 50% and 75% inclusion levels negatively affected the growth performance, feed utilization, and digestibility in juvenile barramundi; and it also increased the potential risk of hepatic failure in the fish. Further investigation is, therefore, required in order to optimize the TH levels in the fish diets which would be suitable for the growth of fish, as well as for maintaining the enhanced biochemical response in juvenile barramundi

Plant Products Affect Growth and Digestive Efficiency of Cultured Florida Pompano (Trachinotus carolinus) Fed Compounded Diets

Costs of compounded diets containing fish meal as a primary protein source can be expected to rise as fish meal prices increase in response to static supply and growing demand. Alternatives to fish meal are needed to reduce production costs in many aquaculture enterprises. Some plant proteins are potential replacements for fish meal because of their amino acid composition, lower cost and wide availability. In this study, we measured utilization of soybean meal (SBM) and soy protein concentrate (SPC) by Florida pompano fed compounded diets, to determine the efficacy of these products as fish meal replacements. We also calculated apparent digestibility coefficients (ADCs) for canola meal (CM), corn gluten meal (CGM), and distillers dried grains with solubles (DDGS), following typical methods for digestibility trials. Juvenile Florida pompano were fed fish-meal-free diets containing graded levels of SBM and SPC, and weight gain was compared to a control diet that contained SBM, SPC, and fish meal. Fish fed diets that contained 25–30 percent SBM in combination with 43–39 percent SPC had weight gain equivalent to fish fed the control diet with fish meal, while weight gain of fish fed other soy combinations was significantly less than that of the control group. Apparent crude protein digestibility of CGM was significantly higher than that of DDGS but not significantly different from CM. Apparent energy digestibility of DDGS was significantly lower than CGM but significantly higher than CM. Findings suggested that composition of the reference diet used in a digestibility trial affects the values of calculated ADCs, in addition to the chemical and physical attributes of the test ingredient

Different expressions of trypsin and chymotrypsin in relation to growth in Atlantic salmon (Salmo salar L.)

The expressions of trypsin and chymotrypsin in the pyloric caeca of Atlantic salmon (Salmo salar L.) were studied in three experiments. Two internal (trypsin phenotypes, life stages) and three common external factors (starvation, feeding, temperatures) influencing growth rates were varied. Growth was stimulated by increased temperature and higher feeding rate, and it was depressed during starvation. The interaction between trypsin phenotype and start-feeding temperature affected specific activity of trypsin, but not of chymotrypsin. Trypsin specific activity and the activity ratio of trypsin to chymotrypsin (T/C ratio) increased when growth was promoted. Chymotrypsin specific activity, on the other hand, increased when there was a reduction in growth rate whereas fish with higher growth had higher chymotrypsin specific activity resulting in lower T/C ratio value. During a rapid growth phase, trypsin specific activity did not correlate with chymotrypsin specific activity. On the other hand, a relationship between specific activities of trypsin and chymotrypsin could be observed when growth declined, such as during food deprivation. Trypsin is the sensitive key protease under conditions favouring growth and genetically and environmentally affected, while chymotrypsin plays a major role when growth is limited or depressed. Trypsin specific activity and the T/C ratio value are shown to be important factors in the digestion process affecting growth rate, and could be applicable as indicators for growth studies of fish in captive cultures and in the wild, especially when food consumption rate cannot be measured

Avanços recentes em nutrição de larvas de peixes

Os requisitos nutricionais de larvas de peixes são ainda mal compreendidos, o que leva a altas mortalidades e problemas de qualidade no seu cultivo. Este trabalho pretende fazer uma revisão de novas metodologias de investigação, tais como estudos com marcadores, genómica populacional, programação nutricional, génomica e proteómica funcionais, e fornecer ainda alguns exemplos das utilizações presentes e perspectivas futuras em estudos de nutrição de larvas de peixes