The effects of torula yeast as a protein source on apparent total tract digestibility, inflammatory markers, and fecal microbiota dysbiosis index in Labrador Retrievers with chronically poor stool quality

This study examined the effects of varying protein sources on apparent total tract digestibility, inflammatory markers, and fecal microbiota in Labrador Retrievers with historically poor stool quality. Thirty dogs (15 male, 15 female; aged 0.93 to 11.7 yr) with stool quality scores ≤2.5 on a 5-point scale (1 representing liquid stool and 5 representing firm stool) were randomly assigned to 1 of 3 nutritionally complete diets with differing protein sources and similar macronutrient profiles: 1) chicken meal (n = 10); 2) 10% brewer's yeast (n = 10); or 3) 10% torula yeast (n = 10). Another 10 dogs (five male, five female) with normal stool quality (scores ranging from 3 to 4) received diet 1 and served as negative control (NC). All dogs were fed diet 1 for 7 days, then provided their assigned treatment diets from days 7 to 37. Daily stool scores and weekly body weights were recorded. On days 7, 21, and 36, blood serum was analyzed for c-reactive protein (CRP), and feces for calgranulin C (S100A12), α1-proteinase inhibitor (α1-PI), calprotectin, and microbiota dysbiosis index. Apparent total tract digestibility was assessed using the indicator method with 2 g titanium dioxide administered via oral capsules. Stool scores were greater in NC (P < 0.01) as designed but not affected by treatment × time interaction (P = 0.64). Body weight was greater (P = 0.01) and CRP lower (P < 0.01) in NC dogs. Dry matter and nitrogen-free extract digestibility did not differ among groups (P ≥ 0.14). Negative controls had greater fat digestibility compared to BY (94.64 ± 1.33% vs. 91.65 ± 1.25%; P = 0.02). The overall effect of treatment was significant for protein digestibility (P = 0.03), but there were no differences in individual post hoc comparisons (P ≥ 0.07). Treatment did not affect S100A12 or α1-PI (P ≥ 0.44). Calprotectin decreased at a greater rate over time in TY (P < 0.01). The dysbiosis index score for BY and TY fluctuated less over time (P = 0.01). Blautia (P = 0.03) and Clostridium hiranonis (P = 0.05) abundances were reduced in BY and TY. Dogs with chronically poor stool quality experienced reduced body weights and increased serum CRP, but TY numerically increased protein digestibility, altered the microbiome, and reduced fecal calprotectin. Torula yeast is a suitable alternative protein source in extruded canine diets, but further research is needed to understand the long-term potential for improving the plane of nutrition and modulating gut health.

Amino Acid Digestibility of Different Formulations of Torula Yeast in an In Vitro Porcine Gastrointestinal Digestion Model and Their Protective Effects on Barrier Function and Inflammation in a Caco-2/THP1Co-Culture Model

Single-cell protein from torula yeast (Cyberlindnera jadinii) grown on lignocellulosic biomass has been proven to be an excellent alternative protein source for animal feed. This study aimed to evaluate the amino acid (AA) digestibility by estimating intestinal absorption from three yeast-based ingredients, produced by cultivating C. jadinii on hydrolysate, using either mixed woody species (drum- (WDI) or spray-dried (WSI)) or corn dextrose (drum-dried (DDI)) as the carbon source. Further, the protective effect of intestinal digests on activated THP1-Blue™-induced epithelial damage and cytokine profile was evaluated. Total protein content from these three ingredients ranged from 34 to 45%, while the AA dialysis showed an estimated bioaccessibility between 41 and 58%, indicating good digestibility of all test products. A protective effect against epithelial-induced damage was observed for two of the three tested products. Torula yeast cultivated on wood and drum-dried (WDI) and torula yeast cultivated on wood and spray-dried (WSI) significantly increased transepithelial electrical resistance (TEER) values (111-147%, p < 0.05), recovering the epithelial barrier from the inflammation-induced damage in a dose-dependent manner. Further, WSI digests significantly reduced IL8 (250.8 ± 28.1 ng/mL), IL6 (237.9 ± 1.8 pg/mL) and TNF (2797.9 ± 216.3 pg/mL) compared to the blank control (IL8 = 485.7 ± 74.4 ng/mL, IL6 = 478.7 ± 58.9 pg/mL; TNF = 4273.5 ± 20.9 pg/mL) (p < 0.05). These results align with previous in vivo studies, supporting torula yeast-based ingredients as a high-quality protein source for pigs, protecting the intestinal barrier from inflammatory damage, and reducing the pro-inflammatory response. We provided novel insights into the mechanisms behind the health improvement of pigs fed on torula yeast-based ingredients, with potential applications for designing nutritional interventions to recover intestinal homeostasis during critical production periods, such as weaning.

Torula yeast may improve intestinal health and immune function of weanling pigs

An experiment was conducted to test the hypothesis that inclusion of a conventional torula yeast or a torula yeast produced from forestry byproducts (i.e., woody torula yeast) in diets for weanling pigs instead of fish meal and plasma protein improves growth performance and intestinal health of pigs. A total of 120 weanling pigs (6.53 ± 0.78 kg) were allotted to three treatments with ten replicate pens per diet. Pigs were fed one of three diets from days 1 to 14 post-weaning (phase 1), whereas all pigs were fed a common diet in phase 2 (days 15 to 28). The three treatments in phase 1 included a control diet with 5% fish meal, 3.5% plasma protein, and no torula yeast. The second diet contained 1.5% fish meal, 14% woody torula yeast, and no plasma protein, whereas the third diet contained 1.5% fish meal, 14% conventional torula yeast, and no plasma protein. Fecal scores were assessed every other day. On day 7, one pig per pen was euthanized to collect ileal tissue and mucosa for determination of morphology and for ribonucleic acid (RNA) sequencing analysis. At the end of phases 1 and 2, blood samples were collected and concentrations of cytokines, plasma urea nitrogen (PUN), peptide YY, immunoglobulin G, total protein, and albumin were analyzed. Results indicated that both torula yeast sources could replace fish meal and plasma protein without affecting growth performance, intestinal morphology, or blood characteristics of pigs. Pigs fed a diet containing torula yeast had improved (P < 0.05) fecal scores during phase 1. Pigs fed the conventional torula yeast diet had greater (P < 0.05) concentration of interleukin-2 compared with pigs fed the control diet. On day 14, greater (P < 0.05) concentrations of interleukin-4 and interleukin-10 were observed in pigs fed the diet containing the woody torula yeast or conventional torula yeast compared with pigs fed the control diet. Results from the RNA sequencing indicated that 19 of 24 analyzed genes involved in digestion and absorption of protein and vitamins were downregulated in pigs fed the diet containing woody torula yeast compared with pigs fed the control diet. However, only two genes (i.e., ANKS4B and FAM54A) were downregulated in pigs fed the woody torula yeast diet compared with the conventional torula yeast diet. In conclusion, using woody or conventional torula yeast instead of fish meal and plasma protein in the phase 1 diet for weanling pigs may improve intestinal health without influencing growth performance of pigs.

Does Ammonia Released from Protein-Based Attractants Modulate the Capture of Anastrepha obliqua (Diptera: Tephritidae)?

Simple Summary

The West Indian fruit fly, Anastrepha obliqua (family Tephritidae), is an important pest of mango and guava in the Neotropical region. Previous studies have indicated that ammonia is involved in fruit fly attraction to sources of food, particularly if protein is present. In laboratory experiments, flies were attracted to ammonia solutions of increasing concentration. In contrast, fly captures by different protein-based attractants were not related to the quantity of ammonia released by the attractant. Flies also responded differently to yeast suspensions of different alkalinity that released different amounts of ammonia. In field experiments, flies were strongly attracted to yeast in ammonia solutions after 24 h, but this effect did not persist when measured over a 7-day period. We conclude that A. obliqua flies are attracted to ammonia solutions in the absence of other stimuli, but attraction to protein-based attractants or alkaline yeast suspensions is not correlated with the quantity of ammonia released by these substances. Ammonia is an important component in fruit fly attraction, which also seems to depend on the presence of other compounds derived from protein food sources in different stages of decomposition.

Abstract

Tephritid fly responses to food-based attractants involve a complex range of food-derived semiochemicals, including ammonia. We performed laboratory and field experiments to compare the attraction of Anastrepha obliqua (Macquart) to ammonia with the attraction to commercial food attractants and torula yeast at a range of pHs. A positive correlation was established between the concentration of ammonia in solution (1.5–150 mM ammonium solution) and gaseous ammonia released by bottle-type traps. This resulted in an asymptotic response in captures of A. obliqua flies in traps that released 99–295 µg ammonia/h. Pairwise comparisons in laboratory cages revealed that traps baited with 150 mM ammonia solution captured similar numbers of A. obliqua as traps baited with Biolure 2C, CeraTrap, and hydrolyzed protein products (Captor, Winner, and Flyral) plus borax, despite the low quantities of ammonia (11–56 µg/h) released from these attractants. Subsequent choice experiment captures in traps containing ammonia solution were similar or higher than those of commercial attractants, with the exception of Winner + borax, but were not correlated with the ammonia released from attractants. Captures of flies in traps containing ammonia solution were increased by the addition of 1% torula yeast or torula yeast alkalized with sodium hydroxide or borax despite differences in the quantities of ammonia released. Fly captures generally increased with increasing alkalization of torula yeast (pH 7.5–9.5). In the field, torula yeast in ammonia solution captured similar numbers of A. obliqua flies as Captor + borax when traps were evaluated after 24 h but not after a 7-day trapping period. Traps baited with ammonia solution or Winner + borax were significantly less attractive than Captor + borax in both field experiments. We conclude that A. obliqua flies are attracted to ammonia solutions of increasing concentration, up to 150 mM, in the absence of other stimuli, whereas attraction to commercial attractants or alkalized torula yeast is not correlated with the release of ammonia.

Effect of torula yeast on growth performance, diarrhea incidence, and blood characteristics in weanling pigs

Two experiments were conducted to test the hypothesis that torula yeast may replace animal and plant proteins in diets for weanling pigs without negatively impacting growth performance or blood characteristics. In exp. 1, 128 weanling pigs (6.71 ± 0.76 kg) were allotted to four treatments with four pigs per pen and eight replicate pens per diet. Pigs were fed one of four diets from day 1 to 14 post-weaning (phase 1), whereas all pigs were fed a common diet in phase 2 (day 15 to 28). The four dietary treatments included a control diet with 5% fish meal, 2.5% plasma protein, and no torula yeast. The second diet contained 5% fish meal, 4.75% torula yeast, and no plasma protein. The third diet contained 2.5% plasma protein, 6% torula yeast, and no fish meal, and the last diet contained 10.75% torula yeast, no fish meal, and no plasma protein. The inclusion of torula yeast was calculated to replace the amount of digestible Lys provided by fish meal, plasma protein, or both fish meal and plasma protein in the control diet. During the initial 14 d, fecal scores were visually assessed. At the end of phase 1, blood samples were collected and tumor necrosis factor-α (TNF-α), blood urea nitrogen (BUN), peptide YY, immunoglobulin G, total protein, and albumin were analyzed. Results indicated that torula yeast could replace fish meal and plasma protein without affecting growth performance, fecal scores, or blood characteristics of pigs. In exp. 2, 160 weanling pigs (6.11 ± 0.62 kg) were allotted to one of four diets with five pigs per pen and eight replicate pens per diet. Phase 1 diets contained 0%, 10%, 18%, or 26% torula yeast, whereas phase 2 diets contained 0%, 8%, 14%, or 20% torula yeast. Torula yeast was included in diets at the expense of animal proteins and soybean meal. On days 14 and 28, blood samples were collected and concentrations of cytokines, BUN, total protein, and albumin were analyzed. Phase 2 gain-to-feed ratio (G:F) linearly increased (P < 0.01) as the concentration of torula yeast increased in the diets. The concentration of albumin on day 14 linearly increased (P < 0.05) and the concentration of TNF-α was linearly reduced (P < 0.01) as the concentration of torula yeast increased in the diets. In conclusion, under the conditions of this research, torula yeast could replace fish meal and plasma protein without affecting the growth performance of pigs, but inclusion of increasing levels of torula yeast improved G:F of pigs, which may be because of greater nutrient utilization.

Torula yeast has greater digestibility of amino acids and phosphorus, but not energy, compared with a commercial source of fish meal fed to weanling pigs

Three experiments were conducted to test the hypothesis that the standardized ileal digestibility (SID) of AA, concentrations of DE and ME, and the standardized total tract digestibility (STTD) of P in a source of torula yeast are not different from values obtained in Menhaden fish meal. In experiment 1, six weanling barrows (initial BW: 11.7 ± 0.4 kg) were prepared with a T-cannula in the distal ileum and allotted to a replicated 3 × 3 Latin square design with 3 diets and 3 periods. In each period, there were 5 d of adaptation and 2 d of collection. Two cornstarch-based diets using the torula yeast or fish meal as the sole source of AA and a N-free diet were formulated. The SID of CP and all AA was greater (P < 0.05) in torula yeast than in fish meal. In experiment 2, 24 weanling barrows (initial BW: 14.4 ± 1.1 kg) were individually housed in metabolism crates and allotted to a corn-based diet or 2 diets based on a mixture of corn and torula yeast or corn and fish meal. Feces and urine samples were collected for 4 d following a 5-d adaptation period. There were 8 replicate pigs per diet and fecal and urine materials were collected. Results of this experiment indicated that there were no differences in the concentration of DE and ME (DM basis) between torula yeast and fish meal. In experiment 3, a total of 32 weanling barrows (initial BW: 11.9 ± 1.1 kg) were allotted to 4 diets and 8 replicate pigs per diet. Pigs were placed in individual metabolism crates. The torula yeast or fish meal were used in 2 diets containing either 0 or 500 units of microbial phytase. Feces samples were collected as described for experiment 2. The STTD of P in torula yeast was greater (P < 0.05) than in fish meal, but regardless of ingredient, there was no effect of the inclusion of phytase in the diets. In conclusion, the SID of AA and the STTD of P in torula yeast is greater than in fish meal, but values for the concentration of DE and ME in torula yeast are not different from those in fish meal. Therefore, the torula yeast that was used in the present experiments may be included at the expense of fish meal in diets fed to weanling pigs if the concentration of standardized ileal digestible AA is considered in the formulation.