Effect of replacing oat fodder with fresh and chopped oak leaves on in vitro rumen fermentation, digestibility and metabolizable energy

Antioxidants in Animal Nutrition: UHPLC-ESI-QqTOF Analysis and Effects on In Vitro Rumen Fermentation of Oak Leaf Extracts

The genus Quercus supplies a large amount of residual material (e.g., bark, acorns, leaves, wood), the valorization of which can favor a supply of antioxidant polyphenols to be used in the pharmaceutical, nutraceutical, or cosmeceutical sector. The recovery of specialized metabolites could also benefit livestock feeding, so much so that polyphenols have gained attention as rumen fermentation modifiers and for mitigating the oxidative imbalance to which farm animals are subject. In this context, leaves of Quercus robur L. from Northern Germany were of interest and the alcoholic extract obtained underwent an untargeted profiling by means of ultra-high-performance liquid chromatography/high-resolution tandem mass spectrometry (UHPLC-HRMS/MS) techniques. As triterpenes and fatty acids occurred, the alcoholic extract fractionation pointed out the obtainment of a polyphenol fraction, broadly constituted by coumaroyl flavonol glycosides and condensed tannins. Total phenol, flavonoid and condensed tannins content assays, as well as antiradical (DPPH^● and ABTS^+●) and reducing activity (PFRAP) were carried out on the alcoholic extract and its fractions. When the effects on rumen liquor was evaluated in vitro in terms of changes in fermentation characteristics, it was observed that oak leaf extract and its fractions promoted an increase in total volatile fatty acids and differently modulated the relative content of each fatty acid.

Nutritional potentialities of some tree leaves based on polyphenols and rumen in vitro gas production

Aim:

The study was conducted to evaluate eight tree leaves based on polyphenolic content and rumen in vitro incubation and gas production technique (RIVIGPT) for their nutritive potentiality.

Materials and Methods:

Eight selected tree leaves, namely Sesbania grandiflora, Melia dubia, Dillenia spp., Artocarpus heterophyllus, Commiphora caudata, Moringa oleifera, Leucaena leucocephala, and Acacia auriculiformis, were selected for proximate composition, forage fiber fractions, total phenolics (TPs), non-tannin phenols (NTPs), total tannins (TTs), condensed tannins (CTs), and hydrolysable tannins (HTs); RIVIGP with and without polyethylene glycol (PEG); and in vitro dry matter digestibility (IVDMD) (modified in vitro two stage) analysis was conducted. On the basis of RIVIGPT, the in vitro digestible organic matter (IVDOM) and dry matter intake (DMI) was calculated.

Results:

Crude protein (CP) content of tree leaves ranged from 9.59 to 25.81%, neutral detergent fiber (NDF) 28.16 to 53.33%, acid detergent fiber (ADF) 21.26 to 41.7%, acid detergent lignin (ADL) 3.62 to 21.98%, TP 1.83 to 17.35%, TT 0.40 to 15.47%, and CTs 0.02 to 15.26%. IVDMD (%) was ranged from 64.95 to 88.12. The mean metabolizable energy (ME) (MJ/Kg) of tree leaves estimated with and without PEG was 7.75±0.56 and 8.75±0.39, in vitro gas production at 24 h (IVGP²⁴) (ml) 31.06±4.14 and 37.09±2.64, initial gas production (a) (ml) 0.49±0.63 and 1.33±0.72, potential gas production (D) (ml) 38.74±4.27 and 43.79±2.44, rate of gas production (k) (h⁻¹) 0.11±0.02 and 0.11±0.013, t_1/2(ml) 9.81±2.41 and 7.42±0.80, in vitro gas production at 96 h IVGP⁹⁶ (ml) 39.50±4.430 and 45.14±2.65, the predicted IVDOM (%) 55.44±4.15 and 61.98±3.03, and DMI (g/Kg W^0.75) 103.1±14.76 and 104.3±10.16, respectively. The addition of PEG showed an improvement in IVGP²⁴, IVGP⁹⁶, ME, predicted IVDOM, and predicted DMI. CP was positively correlated with ME, IVGP²⁴, IVGP⁹⁶, a+b, k (r=0.749, p<0.05), IVDMD, IVDOM, and DMI (r=0.838, p<0.05) and negatively correlated with a and t_1/2. NDF, ADF, and ADL contents were negatively correlated with ME (r=0.899, p<0.05), IVGP²⁴ (r=−0.867, p<0.05), IVGP⁹⁶ (r=−0.858, p<0.05), a+b (p<0.05), k (r=−0.828, p<0.05), IVDMD, IVDOM (r=−0.853, p<0.05), and DMI and positively correlated with a and t_1/2. TP, TT, and CT were negatively correlated with ME, IVGP, IVGP⁹⁶, a+b, k, IVDMD, IVDOM, and DMI and positively correlated with a (r=0.808, p<0.05) and t_1/2. ME (MJ/Kg) was positively correlated with IVGP²⁴ (r=0.938, p<0.05), IVGP⁹⁶ (r=0.875, p<0.05), a+b (r=0.813, p<0.05), k (r=0.731, p<0.05), IVDMD, IVDOM (r=0.985, p<0.05), and DMI (r=0.727, p<0.05) and negatively correlated with a and t_1/2.

Conclusion:

In the present study, the potentiality of tree leaves was assessed based on CP, ADF, ADL, TP, CT, IVGP, ME, IVDMD, predicted IVDOM, and predicted DMI. Based on this, it can be concluded that S. grandiflora, M. dubia, M. Oleifera, and L. leucocephala were graded as best; A. heterophyllus and C. caudata as moderate; and Dillenia spp. and A. auriculiformis as lowest potential ruminant feed.