Estimating degradation of individual essential amino acids in fish meal and blood meal by rumen microbes in a dual-flow continuous-culture system.

Current feeding systems are based on the assumption that the AA profile of rumen undegraded protein is similar to that of the original feed. The objective of this experiment was to determine rumen bacterial degradation of individual essential AA in fish meal (FM) and blood meal (BM). Eight dual-flow continuous-culture fermentors were used in a completely randomized block design with a factorial arrangement of treatments and 3 replicated periods. Fermentors were supplied with 95 g of dry matter/d of isonitrogenous diets. Treatments contained a nonprotein N source (urea and tryptone) that was substituted with increasing proportions of FM or BM (0, 33, 67, or 100%). Diets consisted of 22.0% crude protein, 35.2% neutral detergent fiber, 34.6% nonfiber carbohydrates, 2.0% ether extract, and 9.2% ash. We hypothesized that the increase in the flow of individual AA would be attributed to the increase in the supply of the AA from each protein supplement. True organic matter degradation was decreased by increasing levels of FM or BM, but did not affect degradation of neutral detergent fiber and acid detergent fiber, total volatile fatty acids (VFA) concentration, or the molar proportion of propionate. There was a substrate by level of inclusion interaction in acetate molar proportion and branched-chain VFA. Butyrate concentration decreased linearly with increasing levels of FM and BM in treatment. Changes in branched-chain VFA reflected differences in content of branched-chain AA between supplements and the level of inclusion, although the quadratic effect suggests that other factors were involved. Ammonia-N concentration showed a substrate by level of inclusion interaction. Total dietary N and AA flows increased with increasing levels of FM or BM in treatment. The efficiency of bacterial crude protein synthesis was not affected by treatment, but the flow of bacterial N decreased in FM diets as the level of FM increased. Flows of AA increased linearly with increasing levels of the respective AA from supplements. Arginine, Ile, Met and Phe were more degradable, while His was more resistant to bacterial degradation. Results suggest that the resistance to rumen bacterial degradation of individual AA varies within FM and BM protein and may affect the estimates of dietary supply of individual AA to the small intestine.

Performance of surface and subsurface flow constructed wetlands treating eutrophic waters.

Three medium size constructed wetlands (CWs) with a total surface of 90ha are working since 2009 in the Albufera de Valencia Natural Park (Spain). Two of them are fed with eutrophic waters from l'Albufera Lake. Their objectives are both reduce the phytoplankton biomass and increase the biodiversity; consequently, improved water quality is returned to the lake. A "science based governance" of these CWs is ongoing inside the LIFE+12 Albufera Project to demonstrate the environmental benefits of these features. In this paper, results and relationships among hydraulic operation, physicochemical variables and plankton in two different CWs typologies, five free water surface CW (FWSCW) and one horizontal subsurface flow CW (HSSFCW), were analysed showing that CWs were capable of improving the water quality and biodiversity but showing clear differences depending on the CW type. The CWs worked under different hydraulic load rates (HLR) from <0.12 to 54.75myr-1. Inflow water quality was typical from eutrophic waters with mean values of chlorophyll a (Chl a) about 22-90µgChlal-1 and mean total phosphorus (TP) between 0.122 and 0.337mgl-1. The main conclusion is that HSSFCW was much more efficient than FWSCW in the removal of organic matter, suspended solids and nutrients. The biological role of several shallow lagoons located at the end of the CWs has also been evaluated, showing that they contribute to increase the zooplankton biomass, a key factor to control the phytoplankton blooms.

Biokinetic model for nitrogen removal in free water surface constructed wetlands.

In this article, a mechanistic biokinetic model for nitrogen removal in free water surface constructed wetlands treating eutrophic water was developed, including organic matter performance due to its importance in nitrogen removal by denitrification. Ten components and fourteen processes were introduced in order to simulate the forms of nitrogen and organic matter, the mechanisms of autotrophic and heterotrophic microorganisms in both aerobic and anoxic conditions, as well as macrophytes nitrogen uptake and release. Dissolved oxygen was introduced as an input variable with a time step of 0.5days for mimicking eutrophic environments: aerobic conditions were assigned during daylight hours and anoxic conditions during the night. The sensitivity analysis showed that the most influential parameters were those related to the growth of heterotrophic and autotrophic microorganisms. The model was properly calibrated and validated in two full scale systems working in real conditions for treating eutrophic water from Lake L'Albufera (València). In the studied systems, ammonium was mainly removed by the growth of autotrophic microorganisms (nitrification) whereas nitrate was removed by the anoxic growth of heterotrophic microorganisms (denitrification). Macrophyte uptake removed between 9 and 19% of the ammonium entering to the systems, although degradation of dead standing macrophytes returned a significant part to water column.

Technical note: a modified three-step in vitro procedure to determine intestinal digestion of proteins.

An in vitro, batch incubator (Daisy(II)) was used to simplify the 3-step, in vitro procedure (TSP) to reduce the cost and labor involved in the determination of intestinal digestion of proteins. Four tests were conducted to study the effects of the type of pepsin (P-7012 and P-7000; Sigma, St. Louis, MO), the type of bags used for the incubation of samples (R510 and F57; Ankom Technology, Fairport, NY), the amount of sample per bag (0.5, 1, 2, or 5 g), and the number of bags per incubation bottle (5, 15, 20, or 30 bags) on the estimated intestinal digestion of proteins. A soybean meal sample heated at 170 degrees C for 0, 0.5, 1, 2, 4, 6, or 8 h was used in all preliminary tests to determine the optimum conditions of the technique. The intestinal digestion of 12 protein supplements was determined using the Daisy(II) as well as the proposed TSP techniques. Results using the 2 types of pepsin were highly correlated: P-7012 = (0.99 +/- 0.04 x P-7000) -0.29 +/- 2.33 (r2 = 0.99, P < 0.001, n = 14). Intestinal digestion of soybean meal samples obtained from the TSP assay were highly correlated with those obtained using the Daisy(II) incubator with Ankom R510 bags: Daisy(R510) = (1.37 +/- 0.06 x TSP) -15.45 +/- 3.85 (r2 = 0.98, P < 0.001, n = 14); and Ankom F57 bags: Daisy(F57) = (1.33 +/- 0.06 x TSP) -15.76 +/- 3.87 (r2 = 0.98, P < 0.001, n = 14). Although there was a bias in these equations, when the whole protocol was applied to the determination of intestinal digestion of the 12 protein supplements using the TSP or the Daisy(II) technique with the Ankom R510 bags, the data were highly correlated: (0.93 +/- 0.12 x TSP) + 6.78 +/- 9.09 (r2 = 0.84, P < 0.001, n = 12). The amount of sample per bag and the number of bags per incubation bottle did not affect the estimates of intestinal digestion of proteins. These results indicate that the use of up to 30 nylon bags (Ankom R510) with 5 g of sample in each Daisy(II) incubation bottle could be used to estimate intestinal digestion of proteins in ruminants.