Exploring fibrous ingredients for fish: The case of feeding sugar beet pulp to tambaquí (Colossoma macropomum)

For a long time, co-products of food processing have been used in animal feed, but far less in fish because of their assumed inability to cope with high-fiber diets. Research on feeding co-products to fish species that naturally consume fibrous diets are yet lacking. We here evaluated the impact of sugar beet pulp in the diet of tambaquí on nutrient metabolism, oxidative stress, inflammation, and intestinal histomorphometry. A total of 18 tambaquí fish (1616 ± 107 g; 2 years old) were randomly divided over 6 similar tanks with 3 fish per tank and randomly attributed to one of the six dietary treatments 0, 5, 10, 15, 20 and 25 % beet pulp addition and reared for 8 weeks. Water quality parameters (pH, NH3–N, EC, TDS, DO, and temperature) were assessed and recorded twice a week for each tank. A quadratic increase in intestinal villus length, paravilli and absorptive surface were observed with beet pulp addition. Ammonia and pH as quality indicators were significantly changing with beet pulp addition. A higher supply of glucogenic substrate to the citric acid cycle was noticed with beet pulp addition due to the positive correlation with blood propionylcarnitine: acetylcarnitine ratio while there was no effect on ketone body synthesis as measured through the 3-hydroxybutyrylcarnitine: acetylcarnitine ratio. No pronounced change of serum and whole fish histamine and lowered concentrations of serum malondialdehyde were observed with beet pulp addition. In conclusion, beet pulp induced a marked increase in intestinal villus architecture without signs of inflammation or oxidative stress. Large-scale studies need to clarify if these features lead to improved growth performance but this work opens options for further study. The non-linear pattern of some blood components with increasing beet pulp may call for future optimal dosing and feed form of beet pulp together

Retention of solutes and particles in the gastrointestinal tract of a grazing cervid: Père David’s deer (Elaphurus davidianus)

Ruminants are classified into three groups, according to their feeding behaviour: browsers, intermediate feeders and grazers. Corresponding to their dietary preferences, multiple morphological and physiological adaptations have been described, resulting in another classification: ‘moose-type’ and ‘cattle-type’ ruminants. Digesta retention patterns in the gastrointestinal tract (GIT) and reticulorumen (RR) are considered major criteria to distinguish these types, as cattle-type ruminants show shorter retention of fluids (measured by a solute marker) than of particles, while in moose-type ruminants, both are retained for more similar periods. To what extent these digestive types are specific to phylogenetic lineages is still unclear. We measured mean retention times (MRTs) of solutes and particles (2 and 20mm) in the strictest grazing cervid: the Père David’s deer (Elaphurus davidianus; n = 5; body mass = 155.0 ± 14.5 kg). The MRTs of solutes, small and large particles in the GIT were 34 ± 4, 60 ± 7 and 69 ± 9 h, respectively. The ratio of the MRTof small particles versus solutes in the RR was 2.0 ± 0.1, similar to other cattle-type ruminants. The results confirm the hypothesis that Père David’s deer can be classified as cattle-type ruminants, corresponding to both dietary preferences and previously described morphological traits. The results complement previous findings, showing that both cattletype and moose-type physiologies are found among bovids as well as cervids, indicating that these digestion types can be considered convergent adaptations

Exposure to the proton scavenger glycine under alkaline conditions induces Escherichia coli viability loss.

Our previous work described a clear loss of Escherichia coli (E. coli) membrane integrity after incubation with glycine or its N-methylated derivatives N-methylglycine (sarcosine) and N,N-dimethylglycine (DMG), but not N,N,N-trimethylglycine (betaine), under alkaline stress conditions. The current study offers a thorough viability analysis, based on a combination of real-time physiological techniques, of E. coli exposed to glycine and its N-methylated derivatives at alkaline pH. Flow cytometry was applied to assess various physiological parameters such as membrane permeability, esterase activity, respiratory activity and membrane potential. ATP and inorganic phosphate concentrations were also determined. Membrane damage was confirmed through the measurement of nucleic acid leakage. Results further showed no loss of esterase or respiratory activity, while an instant and significant decrease in the ATP concentration occurred upon exposure to either glycine, sarcosine or DMG, but not betaine. There was a clear membrane hyperpolarization as well as a significant increase in cellular inorganic phosphate concentration. Based on these results, we suggest that the inability to sustain an adequate level of ATP combined with a decrease in membrane functionality leads to the loss of bacterial viability when exposed to the proton scavengers glycine, sarcosine and DMG at alkaline pH

Effects of genotype and environment on forage yield, nutritive value and morphology of lablab (Lablab purpureus (L.) sweet)

The goal of the study is to determine the effect of genotype and environment on forage yield, forage nutritive value and to determine the relation between morphology and forage yield and nutritive value of lablab. Thirteen genotypes (one local and 12 improved) were replicated 3 times in a randomized complete block trial across three locations in Ethiopian lowlands namely, Bechi, Kite and Tepi. All forage samples were analyzed for dry matter (DM), crude protein (CP), and in vitro dry matter digestibility (IVDMD) using a combination of conventional nutritional analyses and near infrared reflectance spectroscopy. There was a significant (P < 0.001) effect of genotype, location and genotype*location on forage yield of DM, forage yield of CP, forage yield of IVDMD, CP, and IVDMD. The difference between means of minimum and maximum genotypes was 12.9 t/ha of DM, 3.12 t/ha CP, 8.22 t/ha IVDMD, 57 g/kg of CP and 56 g/kg of IVDMD. The correlation between plant morphology and forage yield and nutritive value was weak (r ≤ 0.41) in all locations and the combined data. Both genotype and location should be considered by the farmers when they decide to grow lablab for forage production. Morphological traits of lablab are not suitable to evaluate forage yield and nutritive value. Enhancing the awareness of farmers about the effect genetic-environment interaction effect of forage yield and nutritive value and the relation between morphology and yield and nutritive value would improve the uptake of lablab in mixed the farming system leading to more sustainable agricultural production

Overlay diagram of the flow cytometric histograms representing respiratory active and inactive <i>E.</i>

<p><i> coli subpopulations (a).</i> Inactive (1) and active (2) ETEC subpopulation are determined by CTC staining. Inactive cells do not stain because they lack respiratory dehydrogenase activity. Actively respiring cells are red fluorescent. Both populations are separated by the black line. Mean fluorescence intensity (MFI) presenting <i>E. coli</i> respiratory activity (b). Compared to the active control, ETEC exposed to glycine and sarcosine (50 mM, pH 9.5) showed a significant decrease in MFI after 15 min of incubation (p = 0.017 and p = 0.008, respectively). Data are expressed as means ± SD of triplicate experiments.</p

Overview of the MIC determination data for glycine, sarcosine, DMG and betaine.

<p>The inhibition of visible bacterial growth by concentrations ranging from 25 mM up to 200 mM of each test compound was investigated at a pH ranging from 6.5 to 10.0. The symbol (+) represents visible bacterial growth, while the symbol (−) represents no visible growth.</p

Maintaining <i>E. coli</i> pH homeostasis at physiological pH (a).

<p>During respiration, protons (H⁺) are pumped extracellularly, while ATP synthesis via the F_oF₁-ATP synthase complex moves protons intracellularly. F_oF₁-ATP synthase converts the free energy of the proton motive force (PMF) into the chemical energy source ATP. Under physiological conditions, the extracellular pH is more acid than the intracellular pH. The cytoplasmic membrane is negatively charged on the inside, and positively charged on the outside. (1) represents the cytoplasmic membrane, (2) represents the outer membrane. <b>Maintaining </b><b><i>E. coli</i></b><b> pH homeostasis under alkaline stress conditions (b).</b> To prevent cytosolic alkalinisation under extracellular alkaline conditions, the cytoplasmic pH is-next to other mechanism - also regulated by the import of protons by the upregulated ATP synthase and by a multitude of cation antiport systems, pumping in protons. The membrane potential (▵Ψ) is relatively increased (i.e. more negative) to compensate for the inverted proton concentration gradient (▵pH). <b>Exposure of alkaline stressed </b><b><i>E. coli</i></b><b> to proton scavenging amines such as glycine (c)</b>. When unprotonated glycine enters the neutral cytosol under extracellular alkaline conditions it becomes protonated. This causes membrane hyperpolarisation (1) by proton consumption and a higher ATP consumption in an effort to sustain pH homeostasis (2). These effects induced by proton scavenging lead to a loss of membrane integrity (3).</p

Ratiometric red/green fluorescence presenting <i>E. coli</i> membrane potential.

<p>Ratiometric membrane potential measurements showed a significant hyperpolarization of the ETEC membrane following exposure to glycine, sarcosine and DMG (50 mM, pH 9.5) after 90 min of incubation, compared to the control (p<0.0005, p = 0.002 and p<0.0005, respectively). In the betaine-exposed and control samples there is a time-dependent depolarization of ETEC. Data are expressed as means ± SD of triplicate experiments.</p

Overlay diagram of the flow cytometric histograms representing metabolically active and inactive <i>E.</i>

<p><i> coli subpopulations.</i> Inactive (cF⁻) (1) and active (cF⁺) (2) ETEC population are determined by cFDA staining. Inactive cells do not stain because they either lack the enzyme activity to metabolize cFDA to cF and/or cF diffuses freely through the membrane, while metabolically active cells are green fluorescent (cF⁺). Both populations are separated by the black line. The overall mean of triplicates and range are provided.</p

Total ATP concentration of <i>E. coli</i>.

<p>ETEC were exposed to glycine, sarcosine, DMG, betaine (50 mM, pH 9.5) and sterile PBS (control, pH 9.5) for up to 30 min. Already after 5 min of incubation, a significant (p<0.0005) loss of ATP occurs in the bacterial populations exposed to glycine, sarcosine and DMG, compared to the control and betaine sample. Data are expressed as means ± SD of triplicate experiments.</p