The rumen microbiota is vital for the health and growth performance of the host animal, mainly due to its role in the fermentation of ingested feed within the rumen. Attaining a better understanding of the development of the bacterial community and fermentation in the rumen can provide the theoretical basis for regulating feed utilization. This study analyzed the development of rumen bacteria in lambs from birth to 4 months of age using 16S-rRNA amplicon sequencing data and studied its relationship with ruminal fermentation. Serum levels of metabolites were monitored at 30, 60, 90, and 120 days of age, and the RandomForest approach was used to determine age-related changes in rumen bacteria. Levels of blood metabolites, ruminal fermentation, the rumen bacterial community and its functions were all affected by the age of the lambs (P < 0.05). Based on the Bray-Curtis distance within the age groups of the rumen microbiota, the similarity increased sharply after the lambs were weaned at 60 days of age (P < 0.05). The similarity between the samples collected from birth to 90 days of age and those collected at 120 days of age, increased after 20 days of age, reaching a maximum at 90 days vs. 120 days (P < 0.05). Some age-associated changes in the microbial genera were correlated with changes in the concentrations of volatile fatty acids and the levels of microbial crude protein in the rumen, including positive correlations between main volatile fatty acids and the genera of Prevotella 1, Lachnospiraceae NK3A20 group, Ruminococcus gauvreauii group, Ruminococcaceae UCG-014, and Ruminococcus 2 (P < 0.05). These results indicated that the microbial community and the function of rumen was not well-established before 20 days of age, so there is a degree of plasticity in the rumen bacterial community during the first 20 days of post-natal development in lambs, and this might provide an opportunity for interventions to improve rumen fermentation and, thus, increase their growth performance.

Although rumen fluid transplantation (RT) has been developed to confer benefits for adult ruminants by altering gastrointestinal tract microbiota, the question remains whether RT can also benefit weaned lambs. Hence, in this study, thirty-eight pre-weaning lambs were randomly assigned to one of three treatment groups: control lambs (CON) received 25 ml of normal saline solution, and lambs in two RT groups received 25 ml of rumen fluid either from 3-month-old lambs (LT) or from one-year-old adult ewes (AT). The effects on their growth performance, nutrient digestibility, some blood parameters and gastrointestinal tract microbiota were monitored. There were differences (P < 0.05) in rumen bacterial composition between the groups at weaning, at 3 months and at 1 year. Rumen fluid transplantation decreased (P < 0.05) average daily feed intake, average daily gain in live weight and apparent digestibility of ether extract in the LT group, and it decreased (P < 0.05) apparent digestibility of NDF and ADF in the AT group. Rumen fluid transplantation also increased (P < 0.05) concentrations of serum immunoglobulin A in the AT group and increased (P < 0.05) serum concentrations of interleukin-6, interferon alpha and D-lactate in both LT and AT groups. Bacterial α-diversity in the rumen and rectum was not affected by RT (P > 0.05), but a bacterial community change was observed after RT, and the abundance of some dominant bacteria in both rumen and rectum changed after RT (P < 0.05). Analysis of correlations between the parameters indicated that the altered gastrointestinal microbiota and accelerated maturity of rumen microorganisms induced by RT caused some impairment of gastrointestinal integrity and immunity, which led to decreased feed intake, reduced feed digestibility and lower growth performance of the weaned lambs. In conclusion, rumen fluid transplantation altered the gastrointestinal microbiota causing adverse effects on feed intake, feed digestibility and growth performance of the weaned lambs.

In this study, we aimed to establish the correlation between ruminal fermentation parameters and the bacterial community by comparing those of the goat, sheep, and cow, thus illustrating the main bacteria causing the difference in rumen fermentation among goats, sheep, and cows and providing a new idea for improving the feed digestibility of ruminants. Rumen fluid from goats (Taihang White cashmere goat, n = 6), sheep (Hu sheep, n = 6), and cows (Holstein cow, n = 6) was collected using oral intubation and immediately brought back to the laboratory for a fermentation test with the same total mixed ration (TMR) feed in vitro. The rumen bacterial composition was measured by high-throughput sequencing of 16S rRNA genes in the MiSeq platform, the gas production (GP) was recorded after 2, 4, 6, 8, 10, 12, 24, 36, and 48 h of fermentation, and the feed nutrient digestibility and the rumen fluid parameters were determined after 48 h of fermentation. The results showed that the 48 h GP of the sheep group was higher than that of the cow group (p < 0.05), and the theoretical maximum GP was higher than that of the goat and cow groups (p < 0.05). The organic matter digestibility (OMD), dry matter digestibility (DMD), crude protein digestibility (CPD), and gross energy digestibility (GED) of the sheep group were higher than those of the goat and cow groups (p < 0.05). The ammonia nitrogen (NH₃-N), microbial protein (MCP), and total volatile fatty acids (TVFA) concentrations of the sheep group were higher than those of the other groups (p < 0.05), and the pH of the sheep group was lower than those of the other groups (p < 0.05). The 16S rRNA gene sequencing revealed that bacterial composition also differed in the rumens of the sheep, goat, and cow groups (ANOSIM, p < 0.05). We then used a random forest machine learning algorithm to establish models to predict the fermentation parameters by rumen bacterial composition, and the results showed that rumen bacterial composition could explain most of the ruminal fermentation parameter variation (66.56%, 56.13%, 65.75%, 80.85%, 61.30%, 4.59%, 1.41%, −3.13%, 34.76%, −25.62%, 2.73%, 60.74%, 76.23%, 47.48%, −13.2%, 80.16%, 4.15%, 69.03%, 32.29%, and 89.96% for 48 h GP, a (GP of quickly degraded part), b (GP of slowly degraded part), c (GP rate), a + b (theoretical maximum GP), DMD, OMD, GED, CPD, NDFD, ANDF, pH, NH₃-N, MCP, acetic acid, propionic acid, butyric acid, valeric acid, TVFA, and A:P (acetic acid–propionic acid ratio), respectively). A correlation analysis revealed that Lactobacillus, Prevotellaceae_UCG-003, Selenomonas, Peptostreptococcus, and Olsenella significantly correlated with most in vitro fermentation parameters (p < 0.05). A comprehensive analysis showed that rumen fermentation parameters and bacterial composition differed in goats, sheep, and cows. The ruminal fermentation parameters of GP, a, b, c, a + b, pH, NH₃-N, propionic acid, valeric acid, and A:P could be accurately predicted by rumen bacteria (explanation > 55% of variation), and the Lactobacillus, Prevotellaceae_UCG-003, Olsenella, Selenomonas, and Peptostreptococcus were the main bacteria that affected the in vitro fermentation parameters of goats, sheep, and cows.

The aim of this study was to investigate the involvement of prolactin (PRL) on development of secondary skin follicles in cashmere goats. Goats were randomly assigned to either a bromocriptine treatment or control group. Samples of cashmere fiber, blood, and skin were collected from all goats after 1 mo. The results indicated that the length, growth rate, and diameter of fibers were not influenced (P > 0.05) by the inhibition of PRL resulting from the treatment with bromocriptine. There was a tendency for increases in total follicle number, primary and secondary follicle numbers, and in the ratio of secondary to primary follicles following treatment with bromocriptine, but these differences were not significant (P > 0.05). The percentage of active secondary follicles in anagen was increased (P < 0.05) in the bromocriptine-treated goats, but there was no effect of treatment on the percentage of active primary follicles. Bromocriptine decreased (P < 0.05) circulating concentrations of PRL and Insulin-like growth factor 1 (IGF1) and increased (P < 0.05) those of melatonin (MT), but there was no effect of this treatment on the serum concentrations of cortisol, growth hormone, tetraiodothyronine, and triiodothyronine. In bromocriptine-treated goats, mRNA expressions of PRL and MT membrane receptor 1a (MTNR1a) were decreased (P < 0.05) and mRNA expression of MT nuclear receptor (RORα) was increased (P < 0.05), but there was no effect of the treatment on expression of long PRL receptor, short PRL receptor, MT membrane receptor 1b and IGF1. It is concluded that inhibition of PRL promotes secondary hair follicle development in the anagen phase, possibly by downregulating MTNR1a and up-regulating RORα gene expression in the skin.

A subpopulation of Yanshan cashmere goats with crimped fibre has emerged in a closed population in recent years, but little is known about differences in cashmere production performance, skin characteristics, and fibre-style-related genes between goats with different cashmere fibre styles. Therefore, the aim of this study was to investigate fibre characteristics, cashmere yield, hair follicle traits, and fibre-style-related genes in cashmere goats with the two cashmere fleece styles-non-crimped and crimped. Based on the cashmere fibre type, 80 six-month-old female Yanshan cashmere goats were used in this study: 40 goats with non-crimped fleece (NCF) and 40 with crimped fleece (CF). The growth performance and cashmere production of the goats were recorded. Skin samples were collected to determine hair follicle traits and gene sequencing. The results indicated that there were no differences in initial live weight, final live weight, average daily feed intake, and average daily gain between the two groups of goats (P > 0.05). The total yield of cashmere and the stretched length of fibre of the CF goats were higher (P < 0.01 and P < 0.05, respectively) and fibre diameter was lower (P < 0.05) than that of the NCF goats. There were no between-group differences in the density and activity of primary and secondary hair follicles, secondary-to-primary fibre ratio, depth of primary follicles, or epidermal thickness. However, the depth of secondary follicles and dermal thickness were higher (P < 0.05) in NCF goats than in CF goats. There were mutations in the KRT5, KAP8, KRT8, KRT74, KRT34, KRT1, KRT71, KRT6A, KAP6, KRT81, and KRT83 genes, four of which caused amino acid changes. The allele and genotype frequencies of base mutations in the KRT5, KAP8, KRT34, KRT1, KRT6A, KRT81, and KRT83 genes were different in the NCF and CF goats (P < 0.05). The distribution and content of the secondary structure elements and tertiary structures of proteins differed between the wide-type and mutated KRT1 and KRT6A proteins. KRT1, KRT6A, KRT71, and TGFα mRNA expression levels were significantly higher in CF goats than in NCF goats (P < 0.05). It is concluded that cashmere goats that have fleece with crimped fibres produce a greater yield of fleece with finer diameter fibres than those with conventional straight cashmere fibres. These differences in fibre properties may be associated with mutations in the genes coding for KRT1 and KRT6A.

Solid-state fermentation is known to improve plant-based feed nutritional quality; however, the association between microbes and metabolite production in fermented feed remains unclear. We inoculated corn–soybean–wheat bran (CSW) meal feed with Bacillus licheniformis Y5-39, Bacillus subtilis B-1, and lactic acid bacteria RSG-1. Then, 16S rDNA sequencing and untargeted metabolomic profiling were applied to investigate changes in the microflora and metabolites, respectively, and their integrated correlations during fermentation were assessed. The results indicated that trichloroacetic acid soluble protein levels showed a sharp increase, while glycinin and β-conglycinin levels showed a sharp decrease in the fermented feed, as confirmed by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Pediococcus, Enterococcus, and Lactobacillus were predominant in the fermented feed. Overall, 699 significantly different metabolites were identified before and after fermentation. Arginine and proline, cysteine and methionine, and phenylalanine and tryptophan metabolism were the key pathways, with arginine and proline metabolism being the most important pathway in the fermentation process. By analyzing the correlation between the microbiota and metabolite production, lysyl–valine and lysyl–proline levels were found to be positively correlated with Enterococcus and Lactobacillus abundance. However, Pediococcus was positively correlated with some metabolites contributing to nutritional status and immune function. According to our data, Pediococcus, Enterococcus, and Lactobacillus mainly participate in protein degradation, amino acid metabolism, and lactic acid production in fermented feed. Our results provide new insights into the dynamic changes in metabolism that occurred during the solid-state fermentation of corn–soybean meal feed using compound strains and should facilitate the optimization of fermentation production efficiency and feed quality.