Nutritive value of sun-dried common reed (Phragmites australis) leaves and its effect on performance and carcass characteristics of the growing rabbit

The nutritive value and potential use of sun-dried common reed (<em>Phragmites australis</em>) leaves (CRL), for growing rabbits was studied by comparing 3 diets (regression method) containing an increasing incorporation rate of CRL: 0% (control, CRL0), 15% (CRL15) and 30% (CRL30) in substitution for the control diet (356 g neutral detergent fibre (NDF) and 197 g crude protein (CP)/kg). Three groups of 37 rabbits (individually caged) were fed the 3 diets <em>ad libitum</em> from weaning (35 d, mean weight: 722±142 g) to 77 d of age. The faecal digestibility of the diets was measured between 42 and 46 d of age in 10 rabbits per group. CRL can be considered high-fibre roughage, as it contained 64% of NDF (38% of ADF and 10% ADL) and 10.2% of CP. The digestible energy (DE) content of CRL calculated by regression was null (–1.8±0.29 MJ/kg as fed). CP digestibility reached 29%, corresponding to a digestible crude protein concentration of 29.0±5.6 g/kg as fed basis. The fibre digestibility was reduced with CRL incorporation. Dietary incorporation of CRL impaired the rabbit growth (34.2 vs. 31.5 g/d during the period 35-77 d without CRL or with CRL (CRL15 and CRL30), respectively; P=0.002). Consequently, feed conversion was impaired with the high incorporation rate in feed (30%). Health status or main slaughter traits were not affected by CRL incorporation rate. Thus, the sun-dried common reed leaves had a poor nutritive value for growing rabbits and it can be considered a high-fibre feedstuff, interesting to supply low digested fibres (cellulose) and lignin.

Bilberry pomace in rabbit nutrition: effects on growth performance, apparent digestibility, caecal traits, bacterial community and antioxidant status

Agricultural by-products could be used as alternative raw materials in rabbit nutrition as they have been found to be highly nutritious and low cost feeding sources. The aim of this study was to estimate the nutritive value and potential use of bilberry pomace (BP) for growing rabbits. A total of 144 Grimaud rabbits (35 days old) were allotted to four groups and fed with a diet containing increasing level of BP: BP0 (basal diet), BP5, BP10 and BP15 containing 0, 50, 100 and 150 g/kg respectively. Growth trial lasted 48 days; apparent digestibility was evaluated, starting at 46 days of age, over 4 consecutive days. The nutritive value of BP was measured using the mean digestibility of the experimental diets. At 83 days of age, rabbits were slaughtered: blood, and liver and kidney samples were collected in order to determine the blood parameters and the antioxidant enzyme activities of the tissues. Moreover, caecal content was sampled and gut microbiota assessed by means of amplicon-based high-throughput 16S rRNA sequencing and PCR-denaturing gradient gel electrophoresis. The digestible protein was estimated to 104 g/kg of DM while digestible energy to 9.44 MJ/kg DM for incorporation rate up to 150 g/kg. During the finishing period, average daily feed intake and feed conversion ratio showed linear response to BP increase (P=0.008 and &lt;0.001, respectively). During all the period, both parameters decreased linearly and quadratically with increasing BP inclusion levels (P&lt;0.001) up to 100 g/kg of BP. A significant effect of the antioxidant status was found in the kidneys and liver (P&lt;0.05) where the glutathione peroxidase activity increased as the BP increased. As far as gut microbiota is concerned, BP increased the relative abundance of the Clostridium, Oscillospira, Ruminococcus and Ruminococcaceae species which were clearly associated with the BP inclusion level. In conclusion, BP showed a potential use as an alternative protein and fibre sources for growing rabbits.

Assessment of multi-mycotoxin adsorption efficacy of grape pomace

Grape pomace (pulp and skins) was investigated as a new biosorbent for removing mycotoxins from liquid media. In vitro adsorption experiments showed that the pomace obtained from Primitivo grapes is able to sequester rapidly and simultaneously different mycotoxins. Aflatoxin B1 (AFB1) was the most adsorbed mycotoxin followed by zearalenone (ZEA), ochratoxin A (OTA), and fumonisin B1 (FB1), whereas the adsorption of deoxynivalenol (DON) was negligible. AFB1 and ZEA adsorptions were not affected by changing pH values in the pH 3-8 range, whereas OTA and FB1 adsorptions were significantly affected by pH. Equilibrium adsorption isotherms obtained at different temperatures (5-70 °C) and pH values (3 and 7) were modeled and evaluated using the Freundlich, Langmuir, Sips, and Hill models. The goodness of the fits and the parameters involved in the adsorption mechanism were calculated by the nonlinear regression analysis method. The best-fitting models to describe AFB1, ZEA, and OTA adsorption by grape pomace were the Sips, Langmuir, and Freundlich models, respectively. The Langmuir and Sips models were the best models for FB1 adsorption at pH 7 and 3, respectively. The theoretical maximum adsorption capacities (mmol/kg dried pomace) calculated at pH 7 and 3 decreased in the following order: AFB1 (15.0 and 15.1) > ZEA (8.6 and 8.3) > OTA (6.3-6.9) > FB1 (2.2 and 0.4). Single- and multi-mycotoxin adsorption isotherms showed that toxin adsorption is not affected by the simultaneous presence of different mycotoxins in the liquid medium. The profiles of adsorption isotherms obtained at different temperatures and pH and the thermodynamic parameters (ΔG°, ΔH°, ΔS°) suggest that mycotoxin adsorption is an exothermic and spontaneous process, which involves physisorption weak associations. Hydrophobic interactions may be associated with AFB1 and ZEA adsorption, whereas polar noncovalent interactions may be associated with OTA and FB1 adsorption. In conclusion, this study suggests that biosorption of mycotoxins onto grape pomace may be a reasonably low-cost decontamination method.