Changes in in vitro ruminal and post-ruminal degradation of tropical tannin-rich legumes due to varying levels of polyethylene glycol

The in vitro rumen exsheathment test for studying the effect of plant extracts on the exsheathment of Haemonchus contortus infective larvae

This study applied the in vitro rumen exsheathment test (IVRET) to evaluate the exsheathment kinetics of Haemonchus contortus infective larvae (L3) incubated in ruminal liquor (RL) containing acetone:water extracts of Acacia pennatula (AP), Gymnopodium floribundum (GF), Havardia albicans (HA) or Lysiloma latisiliquum (LL). The role of polyphenols in the biological activity of the evaluated extracts was also determined. Larvae were incubated in RL either alone or added with a different plant extract (AP, GF, HA, or LL) at 1200 μg/mL. Polyethylene glycol (PEG) was added to block polyphenols in each treatment (RL+PEG, AP+PEG, GF+PEG, HA+PEG, and LL+PEG). After incubation times of 0, 1, 3, 6, 9, and 24 h, the exsheathment process was stopped to count the number of ensheathed and exsheathed L3. A Log-Logistic model was used to determine the L3 exsheathment kinetics in the different RL treatments. The inflection point of the respective kinetic curves, which indicates the time to reach 50 % exsheathed L3 (T50), was the only parameter that differed when comparing the exsheathment models (99 % probability of difference). The T50 values obtained for GF, HA, and LL treatments (T50 = 7.11 - 7.58 h) were higher in comparison to the T50 of RL (5.72 h) (≥ 70 % probability of difference). The L3 incubated in RL added with GF, HA, and LL extracts delayed their exsheathment at 3 and 6 h of incubation (28.71 - 48.06 % exsheathment reduction) compared to the RL treatment. The T50 value for AP, AP+PEG, GF+PEG, HA+PEG, and LL+PEG were similar to RL and RL+PEG (T50 = 5.34 - 6.97 h). In conclusion, the IVRET can be used to identify plants with the potential to delay the exsheathment of H. contortus L3 in the ruminal liquor. The acetone:water extracts of G. floribundum, H. albicans, and L. latisiliquum delayed the T50 of H. contortus exsheathment, which was evident at 3 and 6 h of incubation in ruminal liquor. The observed exsheathment delay was attributed to the polyphenol content of the extracts.

Effects of Dietary-SCFA on Microbial Protein Synthesis and Urinal Urea-N Excretion Are Related to Microbiota Diversity in Rumen

Two experiments were performed in this study. In Experiment 1, twenty goats were fed with an isonitrogenous diet, containing 28% Non-Fiber Carbohydrate (MNFC group, n = 10) or 14% NFC (LNFC group, n = 10). In the MNFC group, the ruminal concentration of Short Chain Fatty Acids (SCFA) increased, and pH declined. Compared with those in the LNFC group, the microbial protein synthesis in rumen and mRNA abundance of urea transporter B (UT-B) in rumen epithelium increased in the MNFC group, although serum urea-N (SUN) did not differ significantly between groups. Simultaneously, urinal urea-N excretion was reduced in the MNFC group. Significant correlations were found between rumen SCFA and UT-B and between UT-B and urinal urea-N excretion. Furthermore, the abundances of SCFA receptor of GPR41 and GPR43 increased in the rumen epithelium of the MNFC group. These results suggest that increases of SUN transported into the rumen and incorporated into microbial protein and decreases of urinal urea-N excretion are related to ruminal SCFA. This is supported by data from our previous study in which added SCFA on the mucosal side caused increases of urea transport rate (flux J_sm urea) from the blood to the ruminal lumen side. In Experiment 2, we used 16S rRNA Amplicon Sequencing to analyze the structure of the ruminal microbiota community in relation to SCFA. An additional eight goats were assigned into the MNFC (n = 4) and LNFC (n = 4) groups. The dietary ingredients, chemical composition, and feeding regimes were the same as those in Experiment 1. Constrained correspondence analysis (CCA analysis) revealed NFC promoted the expansion of microbiota diversity, particularly of SCFA-producing microbes. The function prediction of 19 upregulated Kyoto Encyclopedia of Genes and Genomes (KEGG) ortholog groups showed an NFC-induced increase of the types and abundances of genes coding for enzymes catalyzing N and fatty acid metabolism. Based on our present and previous investigations, our results indicate that, in goats consuming a MNFC diet, the facilitated urea transport in the rumen and improved urea N salvage are triggered by an expansion of ruminal microbiota diversity and are signaled by ruminal SCFA. This study thus provides new insights into the microbiota involved in the dietary modulation of urea-N salvage in ruminant animals.

Supplementation of Pelleted Hazel (Corylus avellana) Leaves Decreases Methane and Urinary Nitrogen Emissions by Sheep at Unchanged Forage Intake

This study is the first to quantify the effects of hazel (Corylus avellana) leaves on methane and urinary nitrogen emissions, digestibility, nitrogen and the energy balance of ruminants. Four experimental pellets were produced with 0, 30% and 60% hazel leaves, the latter also with 4% polyethylene glycol. Hazel leaves gradually replaced lucerne. The diet was composed of the pellets and grass hay (80%: 20%). Six adult sheep were allocated to all four treatments in a 6 × 4 crossover design. Including hazel leaves did not affect the feed intake, but it decreased the apparent digestibility of organic matter and fibre, especially at the high level. Methane emission was reduced by up to 25 to 33% per day, per unit of intake and per unit of organic matter digested. Urinary nitrogen excretion decreased by 33 to 72% with increasing levels of hazel leaves. The treatment with polyethylene glycol demonstrated that tannins in hazel leaves caused significant shares of the effects. In conclusion, the current results indicated a significant potential of hazel leaves as forage for ruminants to mitigate methane and urinary nitrogen emissions. Even high dietary hazel leaf proportions were palatable. The lower digestibility needs to be compensated with easily digestible diet ingredients.