Relationship between rumen ciliate protozoa and biohydrogenation fatty acid profile in rumen and meat of lambs

This study investigated the associations between abundance of rumen ciliate protozoa and the proportion of the main bioactive fatty acids related to rumen biohydrogenation, as 18:0, t10-18:1, t11-18:1, c9,t11-18:2, 18:3n-3 and 18:2 n-6, in rumen and meat of growing lambs, using data derived from 3 production experiments. A global correlation analysis and a linear regression analysis considering the effect of the experiment were performed. Ten of the 86 lambs involved in the experiments did not present ciliate cells in rumen liquor and the remaining lambs presented an average of 1.35 × 10⁶ciliates / ml rumen liquor. From the nine genera of ciliates identified, Entodinium was the most abundant, averaging 1.17 × 10⁶ cells / ml of rumen liquor. A large variation among lambs was observed for both rumen concentration and community structure of ciliates. Rumen t11-18:1 (P < 0.001) and meat deposition of t11-18:1 (P < 0.001) and of c9,t11-18:2 (P < 0.001) increased linearly with total ciliates, whereas the t10/t11 ratio in rumen (P = 0.002) and in meat (P = 0.036) decreased linearly. Entodiniomorphids seems to be strongly related with meat deposition oft11-18:1 and c9,t11-18:2 and with the reduction of the trans-10 shifted pathway. Completeness of RBH decreased linearly with Holotrichs (P = 0.029), Entodiniomorphids (P = 0.029), Isotricha (P = 0.011) and Epidinium (P = 0.027) abundances. Rumen 18:0 also decreased linearly with increasing counts of total ciliates (P = 0.015), Holotrichs (P = 0.020), Entodiniomorphids (P = 0.010) and Isotricha (P = 0.014). Rumen protozoa were positively linked with the deposition of healthy bioactive FA and simultaneously negatively associated with the occurrence of trans-10 shift.

Does virginiamycin supplementation affect the metabolism and performance of Nellore bulls grazing under low and high gain rates?

This study aimed to evaluate the effect of virginiamycin on the metabolism and performance of growing Nellore bulls under low and high gain rates on pasture. In experiment 1, 80 Nellore bulls (age = 12 ± 2 months, body weight = 258 ± 15 kg) were assigned to 16 paddocks in a 2 × 2 randomized block factorial arrangement. In experiment 2, 12 cannulated Nellore bulls were assigned to three 4 × 4 balanced Latin squares. The factors were: (1) mineral salt without or with virginiamycin, and (2) low or high gain rate. No interaction was noted between factors (p > .10). Animals fed virginiamycin had greater average daily gain (14%, p < .01), body weight (11 kg, p = .05), plasma nonesterified fatty acid (20%, p < .01), serum calcium concentration (2.62%, p = .04), and total protozoa (p = .03) and had the same bacterial proportion (p > .27). Animals with a low gain rate had greater serum urea concentration (19.6%, p < .01) and ruminal ammonia nitrogen (62%, p < .01). Thus, virginiamycin increases the performance and changes the metabolism of growing Nellore bulls under low and high gain rates on pasture.

An Investigation into Rumen Fungal and Protozoal Diversity in Three Rumen Fractions, during High-Fiber or Grain-Induced Sub-Acute Ruminal Acidosis Conditions, with or without Active Dry Yeast Supplementation

Sub-acute ruminal acidosis (SARA) is a gastrointestinal functional disorder in livestock characterized by low rumen pH, which reduces rumen function, microbial diversity, host performance, and host immune function. Dietary management is used to prevent SARA, often with yeast supplementation as a pH buffer. Almost nothing is known about the effect of SARA or yeast supplementation on ruminal protozoal and fungal diversity, despite their roles in fiber degradation. Dairy cows were switched from a high-fiber to high-grain diet abruptly to induce SARA, with and without active dry yeast (ADY, Saccharomyces cerevisiae) supplementation, and sampled from the rumen fluid, solids, and epimural fractions to determine microbial diversity using the protozoal 18S rRNA and the fungal ITS1 genes via Illumina MiSeq sequencing. Diet-induced SARA dramatically increased the number and abundance of rare fungal taxa, even in fluid fractions where total reads were very low, and reduced protozoal diversity. SARA selected for more lactic-acid utilizing taxa, and fewer fiber-degrading taxa. ADY treatment increased fungal richness (OTUs) but not diversity (Inverse Simpson, Shannon), but increased protozoal richness and diversity in some fractions. ADY treatment itself significantly (P < 0.05) affected the abundance of numerous fungal genera as seen in the high-fiber diet: Lewia, Neocallimastix, and Phoma were increased, while Alternaria, Candida Orpinomyces, and Piromyces spp. were decreased. Likewise, for protozoa, ADY itself increased Isotricha intestinalis but decreased Entodinium furca spp. Multivariate analyses showed diet type was most significant in driving diversity, followed by yeast treatment, for AMOVA, ANOSIM, and weighted UniFrac. Diet, ADY, and location were all significant factors for fungi (PERMANOVA, P = 0.0001, P = 0.0452, P = 0.0068, Monte Carlo correction, respectively, and location was a significant factor (P = 0.001, Monte Carlo correction) for protozoa. Diet-induced SARA shifts diversity of rumen fungi and protozoa and selects against fiber-degrading species. Supplementation with ADY mitigated this reduction in protozoa, presumptively by triggering microbial diversity shifts (as seen even in the high-fiber diet) that resulted in pH stabilization. ADY did not recover the initial community structure that was seen in pre-SARA conditions.

The Role of Ciliate Protozoa in the Rumen

First described in 1843, Rumen protozoa with their striking appearance were assumed to be important for the welfare of their host. However, despite contributing up to 50% of the bio-mass in the rumen, the role of protozoa in rumen microbial ecosystem remains unclear. Phylogenetic analysis of 18S rDNA libraries generated from the rumen of cattle, sheep, and goats has revealed an unexpected diversity of ciliated protozoa although variation in gene copy number between species makes it difficult to obtain absolute quantification. Despite repeated attempts it has proven impossible to maintain rumen protozoa in axenic culture. Thus it has been difficult to establish conclusively a role of ciliate protozoa in rumen fiber degradation. The development of techniques to clone and express ciliate genes in λ phage, together with bioinformatic indices to confirm the ciliate origin of the genes has allowed the isolation and characterization of fibrolytic genes from rumen protozoa. Elimination of the ciliate protozoa increases microbial protein supply by up to 30% and reduces methane production by up to 11%. Our recent findings suggest that holotrich protozoa play a disproportionate role in supporting methanogenesis whilst the small Entodinium are responsible for much of the bacterial protein turnover. As yet no method to control protozoa in the rumen that is safe and practically applicable has been developed, however a range of plant extract capable of controlling if not completely eliminating rumen protozoa have been described.

Chemotaxis toward carbohydrates and peptides by mixed ruminal protozoa when fed, fasted, or incubated with polyunsaturated fatty acids

In contrast to the well-characterized chemotaxis and migratory behavior between the dorsal and ventral locations of the rumen by isotrichids, we hypothesized that chemotaxis toward soluble nutrients maintains entodiniomorphid protozoa in the particulate fraction. The objectives of these experiments were to compare the dose-responsive chemotaxis (1) toward different glucose concentrations when ruminal samples were harvested from fed versus fasted cows; (2) toward increasing concentrations of glucose compared with xylose when protozoa were harvested from a fed cow; (3) toward peptides of bacterial, protozoal, and soy origin; and (4) toward glucose when mixed ruminal protozoa were previously incubated for 0, 3, or 6h in the presence of emulsified polyunsaturated fatty acids (PUFA; Liposyn II, Hospira, Lake Forest, IL). In experiment 1, isotrichid protozoa decreased chemotaxis toward increasing glucose concentration when cows were fasted. Entodiniomorphids exhibited chemotaxis to similar concentrations of glucose as did isotrichids, but to a lesser magnitude of response. In experiment 2, xylose was chemotactic to both groups. Xylose might draw fibrolytic entodiniomorphid protozoa toward newly ingested feed. In contrast, even though isotrichids should not use xylose as an energy source, they were highly chemoattracted to xylose. In experiment 3, entodiniomorphids were not selectively chemoattracted toward bacterial or protozoal peptides compared with soy peptides. In experiment 4, despite isotrichid populations decreasing in abundance with increasing time of incubation in PUFA, chemotaxis to glucose remained unchanged. In contrast, entodiniomorphids recovered chemotaxis to glucose with increased time of PUFA incubation. Current results support isotrichid chemotaxis to sugars but also our hypothesis that a more moderate chemotaxis toward glucose and peptides explains how they swim in the fluid but pass from the rumen with the potentially digestible fraction of particulates.

Effects of wortmannin, sodium nitroprusside, insulin, genistein, and guanosine triphosphate on chemotaxis and cell growth of Entodinium caudatum, Epidinium caudatum, and mixed ruminal protozoa

The mechanisms by which ruminal protozoa sense and migrate toward nutrients are not fully understood. Chemotaxis by many diverse eukaryotic cells is mediated by phosphatidylinositol-3-kinase, which is highly conserved in receptor tyrosine kinase (RTK) signaling pathways and consistently inhibited by wortmannin. In experiment 1a, increasing the concentration of wortmannin inhibited cell growth nonlinearly at 24h of a culture of the rumen protozoan Entodinium caudatum, but high variability prevented growth inhibition of Epidinium caudatum from reaching significance. In experiment 1b, increasing the insulin concentration recovered 24-h cell counts for both cultures, depending on wortmannin concentration. In experiment 2, addition of sodium nitroprusside (Snp; activator of protein kinase G for cilial beat reversal in nonrumen ciliate models) at 500µM or wortmannin at 200µM in beakers containing rumen fluid decreased random swimming by mixed entodiniomorphids into capillary tubes (inserted into beakers) containing saline. Both Snp and wortmannin increased chemotaxis into tubes containing glucose compared with the beaker control. For isotrichids, beaker treatments had no response. Glucose increased chemotaxis, but peptides decreased chemotaxis even when combined with glucose. In experiment 3, we assessed preincubation of genistein (a purported RTK blocker in nonrumen ciliate models) at 40 or 400µM in beakers and guanosine triphosphate (GTP; a universal chemorepellent in nonrumen ciliate models, perhaps mediated through an RTK) at 10 or 100µM combined with glucose in capillary tubes. Neither genistein nor GTP affected chemotaxis toward glucose for entodiniomorphids. However, GTP at 100µM reduced chemotaxis toward glucose for isotrichids. After the animal is fed, isotrichids that are depleted in glycogen migrate to the dorsal area of the rumen, and the rapid uptake of sugars is enhanced through strong chemotaxis but can be reversed by peptides or GTP. In contrast, entodiniomorphids are less intensely chemoattracted to glucose than isotrichids but are chemoattracted to peptides. Entodiniomorphids' chemoattraction appears to be integrated with slower but prolonged availability of energy from digesting starch and fiber.