Evaluation of different ensiling methods for Saccharina latissima preservation: influence on chemical composition and in vitro ruminal fermentation.

Saccharina latissima is a brown seaweed that could be used in ruminant feeding, but its fast deteriorating and seasonal growth nature limit their utilisation in the practice. Ensiling could be used as a preservation method, but information of its effects on the nutritional value of the seaweed is limited. This study evaluated the in vitro ruminal fermentation of different S. latissima silages using ruminal inoculum either from goats fed a mixed diet (60:40 oat hay:concentrate) or from sheep fed a high-forage diet (90:10 alfalfa hay:concentrate) to simulate different small ruminant production systems. S. latissima was ensiled in vacuum bags without additives (Control), with formic acid (4 g/kg seaweed; FA), with lactic acid bacteria (LAB) or with LAB after a pre-wilting treatment to reach a seaweed dry matter (DM) content of 30% (30LAB). Ensiling S. latissima decreased (p < 0.05) the content in DM, neutral detergent fibre and total extractable polyphenols, but nitrogen and fat content were unaffected. For both ruminal inoculums, ensiling decreased (p < 0.05) the asymptotic gas production after 120 h of fermentation (excepting for FA silage with goats' inoculum), but the total volatile fatty acid (VFA) production was unaffected. The VFA profile shifted towards greater (p < 0.05) acetate and lower (p < 0.05) propionate proportions in all silages compared with the pre-ensiling S. latissima. When goats inoculum was used, greater (p < 0.05) CH4 production compared with pre-ensiling S. latissima was observed in all silages, except Control one, which led to greater (p < 0.05) CH4/total VFA ratio. In contrast, no differences among samples (p > 0.05) in either CH4 production or CH4/total VFA ratio were observed when sheep' inoculum was used. Fermentation of all samples started earlier with goats' inoculum than with sheep' inoculum, which was attributed to the different diet fed to the animals. These results suggest that ensiling S. latissima with either formic acid or lactic acid bacteria could be a viable conservation method to preserve the nutritive value.

Mitigation of ruminal methane production with enhancing the fermentation by supplementation of different tropical forage legumes.

The aim of this research was to evaluate the influence of forage species adapted to the tropical region of Ecuador on gas production, enteric methane, digestion, and ruminal fermentation. The tree forage evaluated were C. arborea, E. fusca, B. forficata, E. poeppigiana, C. argentea, G. sepium, C. tora, and F. macrophylla. Ruminal fluid of four adult sheep fistulated with permanent cannulas in the rumen was used in the in vitro gas production technique. The in vitro gas production parameters were lower (P < 0.05) in the C. arborea (A = 41.68 mL gas/g DM, c = 0.044%/h and Lag = 1.654 h) and the average gas production rate for B. forficata was 1.017 mL/h (P < 0.05). C. arborea presented higher (P = 0.0001) effective degradation and real DM digestibility (40.461 g/kg and 82.51 mg/g, respectively). With respect to VFA, the highest (P < 0.05) proportion of acetic, propionic, and butyric was observed in C. arborea, G. sepium, and E. poeppigiana (72.52, 23.09, and 7.44 mol/100 mol, respectively) and the lowest (P = 0.0001) ratio: acetic/propionic was observed in G. sepium (2.92 mol/100 mol). The content of NH3-N (mg/L) showed no difference. The lowest (P = 0.0001) methane production was observed in C. arborea (1.23 mL CH4/g DM). The use of forage species of tropical climate rich in secondary metabolites in ruminant diets has the capacity to reduce the gas production and enteric methane; however, this is at the expense of the reduction of the fermentation of organic matter in the rumen.