Ruminants are born with an undeveloped physical, metabolic, and microbial rumen. Rumen development is limited under artificial rearing systems when newborn animals are separated from the dam, fed on milk replacer, and weaned at an early age. This study aims to evaluate the effects of early-life inoculation of young ruminants with rumen fluid from adult animals. Eighty newborn goat kids were randomly allocated to 1 of 4 experimental treatments and inoculated daily from d 1 to wk 11 with autoclaved rumen fluid (AUT), fresh rumen fluid obtained from adult goats fed either a forage diet (RFF) or concentrate-rich diet (RFC), or absence of inoculation (CTL). Goat kids were artificially reared with ad libitum access to milk replacer, starter concentrate, and forage hay. Blood was sampled weekly and rumen microbial fermentation was monitored at 5 (preweaning), 7 (weaning), and 9 wk of age (postweaning). Results indicated that inoculation with fresh rumen fluid accelerated the rumen microbial and fermentative development before weaning. As a result, RFC and RFF animals had higher solid feed intake (+73%), rumen concentrations of ammonia-N (+26%), total volatile fatty acids (+46%), butyrate (+50%), and plasma β-hydroxybutyrate (+48%), and lower milk intake (-6%) than CTL and AUT animals at wk 5. Inoculation with fresh inoculum also promoted early rumen colonization by a complex and abundant protozoal community, whereas CTL animals remained protozoa free. Although all kids experienced moderate growth retardation during 1 wk after weaning, inoculation with fresh rumen fluid favored the weaning process, leading to 2.2 times higher weight gain than CTL and AUT animals during wk 8. Some of these advantages were retained during the postweaning period and RFF and RFC animals showed higher forage intake (up to +44%) than CTL and AUT animals with no detrimental effects on feed digestibility or stress levels. The superior microbial load of RFC compared with RFF inoculum tended to provide further improvements in terms of forage intake, plasma β-hydroxybutyrate, and rumen protozoa, whereas AUT inoculation provided minor (if any) advantages with respect to CTL animals. Although no differences were noted on animal growth, this study suggests that early life inoculation of goat kids with rumen microbiota can represent an effective strategy to accelerate the rumen development, facilitating a smooth transition from milk to solid feed and to the potential implementation of early weaning strategies.

Ruminants play an important part in global food security, but also emit methane, which contributes to global warming. Rumen microbes strongly influence the energy retention efficiency from the host’s plant-based diet and produce methane as a by-product. While thousands of novel microbial genomes have been assembled from metagenomic sequence data, their culturability is ill-defined. Here, different media (Med10, Med2, and MedTC) were used to isolate co-cultures of microbes from rumen fluid. Thirty-four OTUs were identified belonging to the phyla Bacillota (75.28 ± 6.34%), Bacteroidota (19.99 ± 4.85%), Pseudomonadota (2.46 ± 2.01%), and Actinomycetota (2.09 ± 1.07%). The most abundant genera were Selenomonas (28.08 ± 11.71%), Streptococcus (22.67 ± 6.06%), Prevotella (18.71 ± 4.02%), and unclassified Lachnospiraceae (11.50 ± 2.54%), and 31 significantly enriched on at least one medium, with each medium successfully culturing a distinct range of microbes. The composition of the source rumen fluid was vastly different from those cultured. Bacteroidota (52.53 ± 5.10%) predominated, with Bacillota (41.00 ± 3.96%), Methanobacteriota (5.12 ± 1.94%), Pseudomonadota (1.22 ± 0.78%), and Actinomycetota (0.12 ± 0.08%) comprising the rest. The most abundant genera were Prevotella (29.13 ± 4.16%), Butyrivibrio (18.21 ± 2.08%), Succiniclasticum (15.57 ± 5.03%), unclassified Bacteroidetes (13.91 ± 1.67%), and unclassified Prevotellaceae (9.50 ± 2.01%). These data further emphasize the importance of using defined media to select for different microbial taxa. This is essential to understand the complex workings of the rumen microbes to enhance digestion efficiency and reduce the loss of energy that could potentially be utilized by the host. IMPORTANCE: This research demonstrates that using a range of culture media, containing a wide variety of substrates, can lead to the culture of key rumen microbes. The knowledge of which of these microbes is selectively enriched on each medium is essential to understand how to grow these microbes in co-culture and isolate them in pure culture for further investigation. In addition, this research shows the stark disparity between the population of rumen microbes grown in co-culture and those found in the rumen itself. This further demonstrates the need for a targeted approach to growing and isolating these microbes. Learning how these microbes respond to culture media with different nutritional compositions will lead to a better understanding of the rumen microbiota, and this research provides a valuable insight into how selective media can target the enrichment of different microbes. This knowledge will contribute to increasing ruminant digestion efficiency and reducing methane production.

Climate change is exerting significant negative impacts on various sectors, with livestock farming being particularly affected. One of the most pressing challenges in this context is the growing shortage in the availability of conventional fodder. This scarcity has intensified the search for alternative feed sources, with particular interest in underutilized resources often considered waste due to limited knowledge of their nutritional value. This study aimed to assess whether watermelon plant silage (WPS) could be used as a forage source in ruminants. The chemical composition of WPS and alfalfa hay (AH) was analyzed. Results showed similar protein content (21.1 vs. 18.9 g CP/100 g DM, respectively), with WPS exhibiting higher crude fat content (3.16 vs. 1.29 g/100 g DM) but lower hemicellulose (9.95 vs. 14.6 g/100 g DM) and cellulose (20.0 vs. 26.8 g/100 g DM) content compared to AH. In the first in vitro trial, WPS and AH were incubated independently to compare their fermentation behavior. WPS produced a higher concentration of short chain fatty acids (SCFA) (65.9 vs. 61.0 mM; P = 0.304), lower proportions of propionate (P = 0.001), and higher proportions of isobutyrate (P = 0.001). In a second in vitro trial, a formulated goat diet (commercial concentrate and AH in a 1:1 ratio) was used as a control to assess the impact of replacing 25% and 50% of AH with WPS. Trends towards higher value were observed in pH and CH4 concentration as AH was replaced by WPS. The study concluded that WPS could serve as a viable fodder to replace AH in conventional goat diets, simultaneously reducing agricultural waste and serving as a regenerative model for implementing circular economy strategies in affected agronomic sectors.

Ruminants play an important part in global food security, but also emit methane which contributes to global warming. Microbes in the rumen strongly influence the energy retention efficiency from the host’s plant-based diet and produce methane as a by-product. While thousands of novel microbial genomes have been assembled from metagenome sequence data, their culturability is ill-defined. Here different media were used to isolate microbes from rumen fluid. 34 genera were grown, and the majority belonged to the phylum Bacillota (75.28% ± 6.34), Bacteroidota (19.99% ± 4.85), Pseudomonadota (2.46% ± 2.01), and Actinomycetota (2.09% ± 1.07). The most abundant genera were Selenomonas (28.08% ± 11.71), Streptococcus (22.67% ± 6.06), Prevotella (18.71% ± 4.02), and unclassified Lachnospiraceae (11.50% ± 2.54). When comparing the mean relative abundance of these genera between media, 31 were significantly enriched on at least one medium. The composition of the source rumen fluid was vastly different to those cultured. Bacteroidota (52.53% ± 5.10) predominated, with by Bacillota (41.00% ± 3.96), the archaeal Euryarchaeota (5.12% ± 1.94), Pseudomonadota (1.22% ± 0.78), and Actinomycetota (0.12% ± 0.08) comprising the rest. The most abundant genera were Prevotella (29.13% ± 4.16), Butyrivibrio (18.21% ± 2.08), Succiniclasticum (15.57% ± 5.03), unclassified Bacteroidetes (13.91% ± 1.67), and unclassified Prevotellaceae (9.50% ± 2.01). These data further emphasise the importance of using defined media to selectively enrich for different microbial taxa. This is essential to understand the complex workings of the rumen microbes to enhance digestion efficiency and reduce the loss of energy as methane.

An in vitro and an in vivo study were conducted to investigate the effects of a blend of cinnamaldehyde, eugenol, and capsicum oleoresin (CEC) on rumen fermentation parameters, animal performance, and methane (CH₄) emissions in dairy cows. Continuous culture fermenters (CCF) were utilized to test one of two treatments: (1) CON; no supplementation and (2) CEC supplemented at 0.0125 g/d. The basal diet consisted of grass hay and concentrate (50:50). Supplementation with CEC increased (p < 0.01) total volatile fatty acids (VFA; mM) and decreased (p = 0.02) CH₄ concentration compared with CON in vitro. Additionally, protozoa abundance tended (p = 0.07) to decrease in CEC compared with CON. The in vivo experiment utilized forty Holstein-Friesian dairy cows (32% primiparous and 68% multiparous) averaging 163 ± 48 days in milk (DIM) and 38 ± 6.2 kg/d of milk yield (MY). Cows were blocked by parity and randomly assigned to one of two treatments: (1) CON; no supplementation and (2) CEC supplemented at 1.2 g/cow/d. The basal diet consisted of grass hay and concentrate (40:60). Individual CH₄ emissions were recorded using the sniffer technique. Dry matter intake (DMI) and eating rate were increased (p < 0.01; 3.6% and 5.2%, respectively), while feed efficiency decreased (p < 0.05) in CEC compared with CON. Additionally, CEC decreased (p = 0.02) CH₄ yield by 16.4% and tended to reduce daily CH₄ production (p = 0.09) and CH₄ intensity (p = 0.08) by 13.4% and 14.0%, respectively. Supplementing CEC decreased CH₄ concentration in vitro and CH₄ yield in vivo without negatively impacting performance parameters.

The study aimed to evaluate the nutritional value of watermelon plant silage (WPS) and to assess the effect of replacing alfalfa hay (AH) with WPS in a diet formulated for dairy goats on the basis of two in vitro trials. The study used four goats as donors of rumen microbiota to analyze in vitro fermentation parameters. The chemical composition analysis revealed that WPS and AH had similar protein content (21.1 vs. 18.9 g CP/100 g DM), but WPS had lower contents of organic matter (77.4 vs. 89.6 g/100 g DM), neutral detergent fiber (36.3 vs. 49.4 g/100 g DM), acid detergent fiber (26.4 vs. 34.6 g/100 g DM), acid detergent lignin (6.40 vs. 8.01 g/100 g DM), and amino acids (716 vs. 874 g AA/kg N) compared to AH. Conversely, WPS had higher crude fat content (3.09 vs. 1.29 g/100 g DM) and different macro- and micromineral content values than AH. In a first in vitro trial, WPS and AH were incubated independently to compare their fermentation behaviour, indicating that the metabolizable energy tended to be higher for WPS compared to the AH diet (6.67 vs. 5.72 MJ/kg DM; P = 0.058). WPS fermentation produced higher concentrations of total volatile fatty acids than AH (66.6 vs. 53.3 mM; P = 0.037), lower proportions of propionate and valerate (P ≤ 0.022), higher proportions of isobutyrate (P = 0.001), and showed similar gas production (GP) kinetics, as degradation rate and its potential release, and estimated organic matter digestibility. In a second in vitro trial, a formulated goat diet (consisting of commercial concentrate and AH in a 1:1 ratio) was used as a control to assay the impact of replacing 25 and 50 % of AH by WPS. Trends were observed in several parameters, such as a linear increase in GP rate (P = 0.088), organic matter digestibility (P = 0.067), and CH4 concentration in the gas produced (P = 0.094) as AH was replaced by WPS. The study concluded that WPS could serve as a viable fodder to replace AH in conventional dairy goat diets while simultaneously reducing agricultural waste and serving as a regenerative model for implementing the circular economy strategy in the affected agronomic sectors.