Mixed ensiling plus nitrate destroy fiber structure of rape straw, increase degradation, and reduce methanogenesis through in vitro ruminal fermentation.

BACKGROUND: Better utilization of rape straw can provide alternative strategies for sustainable ruminant and food production. The research reported here investigated changes in the carbohydrate composition of rape straw as a result of mixed ensiling with whole-crop corn or inoculated with nitrate, and the consequent effects on ruminal fermentation through in vitro batch culture. The three treatments included: rape straw and corn silage (RSTC), and ensiling treatment of rape straw with whole-crop corn (RSIC) or with calcium nitrate inoculation (RSICN). RESULTS: Ensiling treatment of rape straw and whole-crop corn or plus nitrate enriched lactic acid bacteria and lactate. The treatments broke the fiber surface connections of rape straw, leading to higher neutral detergent soluble (NDS) content and lower fiber content. Ensiling treatments led to greater (P < 0.05) dry matter degradation (DMD), molar proportions of propionate and butyrate, relative abundance of the phylum Bacteroidetes and genus Prevotella, and lower (P < 0.05) methane production in terms of g kg-1 DMD, molar proportions of acetate, and lower acetate to propionate ratio than the RSTC treatment. The RSICN treatment led to the lowest (P < 0.05) hydrogen concentration and methane production among the three treatments. CONCLUSION: Ensiling treatments of rape straw and whole-crop corn destroy the micro-structure of rape straw, promote substrate degradation by enriching the phylum Bacteroidetes and the genus Prevotella, and decrease methane production by favoring propionate and butyrate production. Nitrate inoculation in the ensiling treatment of rape straw and whole-crop corn further decreases methane production without influencing substrate degradation by providing an additional hydrogen sink. © 2023 Society of Chemical Industry.

Effects of Dietary Nonfibrous Carbohydrate/Neutral Detergent Fiber Ratio on Methanogenic Archaea and Cellulose-Degrading Bacteria in the Rumen of Karakul Sheep: a 16S rRNA Gene Sequencing Study.

The study was conducted to investigate the effects of dietary nonfibrous carbohydrate (NFC)/neutral detergent fiber (NDF) ratio on methanogenic archaea and cellulose-degrading bacteria in Karakul sheep by 16S rRNA gene sequencing. Twelve Karakul sheep were randomly divided into four groups, each group with three replicates, and they were fed with four dietary NFC/NDF ratios at 0.54, 0.96, 1.37, and 1.90 as groups 1, 2, 3, and 4, respectively. The experiment lasted for four periods: I (1 to 18 days), II (19 to 36 days), III (37 to 54 days), and IV (55 to 72 days); during each period, rumen contents were collected before morning feeding to investigate on methanogenic archaea and cellulose-degrading bacteria. The results showed that with an increase in dietary NFC/NDF ratio, the number of rumen archaea operational taxonomic units and the diversity of archaea decrease. The most dominant methanogens did not change with dietary NFC/NDF ratio and prolongation of experimental periods. Methanobrevibacter was the most dominant genus. At the species level, the relative abundance of Methanobrevibacter ruminantium first increased and then decreased when the NFC/NDF ratio increased. When the dietary NFC/NDF ratio was 0.96, the structure of archaea was largely changed, and the relative abundance of Fibrobacter sp. strain UWCM, Ruminococcus flavefaciens, and Ruminococcus albus were the highest. When the dietary NFC/NDF ratio was 1.37, the relative abundance of Butyrivibrio fibrisolvens was higher than for other groups. Based on all the data, we concluded that a dietary NFC/NDF ratio of ca. 0.96 to 1.37 was a suitable ratio to support optimal sheep production. IMPORTANCE CH4 produced by ruminants aggravates the greenhouse effect and cause wastage of feed energy, and CH4 emissions are related to methanogens. According to the current literature, there is a symbiotic relationship between methanogens and cellulolytic bacteria, so reducing methane will inevitably affect the degradation of fiber materials. This experiment used 16S rRNA gene high-throughput sequencing technology to explore the balance relationship between methanogens and cellulolytic bacteria for the first time through a long-term feeding period. The findings provide fundamental data, supporting for the diet structures with potential to reduce CH4 emission.

Effects of Dietary Non-Fibrous Carbohydrate (NFC) to Neutral Detergent Fiber (NDF) Ratio Change on Rumen Bacteria in Sheep Based on Three Generations of Full-Length Amplifiers Sequencing.

The study was conducted to investigate the effects of dietary NFC/NDF ratio change on rumen bacteria in sheep. Twelve Karakul sheep were assigned randomly into four groups fed with four dietary NFC/NDF ratios of 0.54, 0.96, 1.37, and 1.90 and they were assigned into groups 1, 2, 3, and 4, respectively. The experiment was divided into four periods: I (1-18 d), II (19-36 d), III (37-54 d), and IV (55-72 d). In each period, the first 15 d were used for adaption, and then rumen fluid was collected for 3 d from each sheep before morning feeding. The fluid was analyzed with three generations of full-length amplifiers sequencing. Results showed that the bacterial diversity of group 4 was decreased in period III and IV. At the phylum level, Bacteroidetes (37-60%) and Firmicutes (26-51%) were the most dominant bacteria over the four periods. The relative abundance of Bacteroidetes, Firmicutes, Tenericutes, and Spirochaete changed with dietary NFC/NDF ratio change over the four periods, but there was no difference among groups over the four periods (p > 0.05). At the genus level, unidentified-Lachnospiraceae was the dominant genus, and its relative abundance in group 3 was high during the period I and III (p < 0.05). The relative abundance of Mycoplasma in group 4 was high in the period I and II (p < 0.05). The relative abundance of Succiniclasticum was high in group 2 of period II (p < 0.05). At the species level, the relative abundance of Butyrivibrio-fibrisolvens was found to be high in group 3 during periods I and III (p < 0.05). The main semi-cellulose-degrading bacteria and starch-degrading bacteria were low, and there was no significant difference among groups over four periods (p > 0.05). Taken together, the dietary NFC/NDF ratio of 1.90 decreased the diversity of bacteria as a period changed from I to IV. While the main phylum bacteria didn't change, their relative abundance changed with the dietary NFC/NDF ratio change over the four periods. The most prevalent genus was unidentified-Lachnospiraceae, and its relative abundance was higher in dietary NFC/NDF ratio of 1.37 than other groups. Similarly, the main cellulose-degrading species was higher in the treatment of dietary NFC/NDF ratio of 1.37 than other groups.