Protein Evaluation of Feedstuffs for Horses

The German Society of Nutrition Physiology has proposed a new protein evaluation system for horse feeds to estimate pre-cecally digestible crude protein (pcdCP) and amino acids (pcdAA) from chemical properties. A total of 71 feeds for horses were chemically tested and evaluated according to the new protein evaluation system. A feeding trial with eight horses tested whether differences in estimated pcdAA and neutral detergent soluble CP (NDSCP) in the diet were reflected by post-prandial (ppr) kinetics of plasma lysine (Lys) by feeding a complementary feed (control = CTRL) with 1.02 g Lys/100 kg body weight (BW) as well as three diets with 3.02 g Lys/100 kg BW, as follows: (i) CTRL with synthetic AA (CTRL + synAA); (ii) CTRL with soybean meal (CTRL + SBM); and (iii) lucerne pellets (LUC). In comparison to CTRL, the areas of curves (AUCs) of ppr plasma Lys differed: CTRL < CTRL + SBM (p < 0.01) < CTRL + synAA (p < 0.05). For 71 feeds, the estimated pcdCP was correlated with the CP content (p < 0.001), NDSCP (p < 0.001), and ash-free neutral detergent fiber (p < 0.001). A mean neutral detergent insoluble CP content of at least 3-5% can be assumed in horse feed. It is speculated that the predicted availability of Lys from LUC seems to be underestimated by the new protein evaluating system. The influence of chewing and microbiota in vivo needs to be considered in horses.

Multiomics Integrated Analysis Identifies SLC24A2 as a Potential Link between Type 2 Diabetes and Cancer

Background

So far, type 2 diabetes (T2D) is considered as an independent risk factor for various cancers, but the underlying mechanism remains unclear. Methods. SLC24A2 was first identified as a key gene strongly associated with fasting plasma glucose (FPG). Then, overlapped differentially expressed genes (DEGs) between T2D verse control and SLC24A2-high verse SLC24A2-low were extracted and imported into weighted correlation network analysis. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and gene set enrichment analysis were used for functional enrichment analysis of DEGs. Least absolute shrinkage and selection operator was utilized to build a T2D prediction model. Timer and K-M plotters were employed to find the expression and prognosis of SLC24A2 in pan cancer.

Results

Interestingly, both DEGs between T2D verse control and SLC24A2-high verse SLC24A2-low enriched in cancer-related pathways. Moreover, a total of 3719 overlapped DEGs were divided into 8 functional modules. Grey module negatively correlated with T2D and FPG and was markedly involved in ribosome biogenesis. Ten SLC24A2-related genes (RRP36, RPF1, GRWD1, FBL, EXOSC5, BCCIP, UTP14A, TWISTNB, TBL3, and SKIV2L) were identified as hub genes, based on which the LASSO model accurately predicts the occurrence of T2D (AUC = 0.841). In addition, SLC24A2 was only expressed in islet β cells and showed abnormal expression in 17 kinds of cancers and significantly correlated with the prognosis of 10 kinds of cancers.

Conclusion

Taken together, SLC24A2 may link T2D and cancer by influencing the ribosome function of islet β cells and play different prognostic roles in different cancers.

Analysis of Host Jejunum Transcriptome and Associated Microbial Community Structure Variation in Young Calves with Feed-Induced Acidosis

Diet-induced acidosis imposes a health risk to young calves. In this study, we aimed to investigate the host jejunum transcriptome changes, along with its microbial community variations, using our established model of feed-induced ruminal acidosis in young calves. Eight bull calves were randomly assigned to two diet treatments beginning at birth (a starch-rich diet, Aci; a control diet, Con). Whole-transcriptome RNA sequencing was performed on the jejunum tissues collected at 17 weeks of age. Ribosomal RNA reads were used for studying microbial community structure variations in the jejunum. A total of 853 differentially expressed genes were identified (402 upregulated and 451 downregulated) between the two groups. The cell cycle and the digestion and absorption of protein in jejunal tissue were affected by acidosis. Compared to the control, genera of Campylobacter, Burkholderia, Acidaminococcus, Corynebacterium, and Olsenella significantly increased in abundance in the Aci group, while Lachnoclostridium and Ruminococcus were significantly lower in the Aci group. Expression changes in the AXL gene were associated with the abundance variations of a high number of genera in jejunum. Our study provided a snapshot of the transcriptome changes in the jejunum and its associated meta-transcriptome changes in microbial communities in young calves with feed-induced acidosis.

What Would Be Good for All Veterinarians to Know About Equine Nutrition

Nutrition and management have enabling and supporting roles to play in the health, welfare, and performance of equines. Poor or inappropriate nutrition may therefore impose limits on an animal's ability to perform and adversely affect health and welfare. Understanding the gastrointestinal tract from a nutrition perspective can help to reduce the risk of certain clinical problems. This article outlines key factors with respect to the equine digestive tract and discusses relevant aspects of ration formation. Forage is highlighted, because inappropriate forage provision is one of the key limitations in many horse diets.

Nutritional Influences on Skeletal Muscle and Muscular Disease

Skeletal muscle comprises 40% to 55% of mature body weight in horses, and its mass is determined largely by rates of muscle protein synthesis. In order to support exercise, appropriate energy sources are essential: glucose can support both anaerobic and aerobic exercise, whereas fat can only be metabolized aerobically. Following exercise, ingestion of nonfiber carbohydrates and protein can aid muscle growth and recovery. Muscle glycogen replenishment is slow in horses, regardless of dietary interventions. Several heritable muscle disorders, including type 1 and 2 polysaccharide storage myopathy and recurrent exertional rhabdomyolysis, can be managed in part by restricting dietary nonstructural carbohydrate intake.

The effect of time of feeding on plasma amino acids during exercise and recovery in horses

Feeding management in horses suggests feeding horses in advance of exercise, particularly the grain portion of the diet. Plasma amino acids (AA) peak at 3 to 6 h postfeeding depending on the AA. The timeframe between feeding and exercise may affect the availability of AA during and after exercise. The purpose of this study was to observe the differences in plasma AA in horses fed prior to exercise or after exercise. Eight light type horses were fed a diet with adequate protein and AA for horses in light to moderate exercise. After an adjustment period, horses completed a standardized exercise test (SET). Relative to the SET, horses were fed either 2 h prior (PRE horses) to the SET, 1 h after completing the SET (POST horses), or horses remained fasted throughout the sampling period (FASTED horses). Plasma was drawn prior to exercise, at the peak of exercise as well as at 1, 2, 4, and 7 h postexercise. Plasma was analyzed for AA, glucose, lactate, creatinine, creatine kinase, ammonia, urea-N, and 3-methylhistdine. After completion of the SET and sampling period, horses entered a 1-wk recovery period, which was followed by another SET. The protocol repeated until horses rotated through all feeding protocols in the study (three SETs). The majority of the plasma AA were elevated in PRE horses compared with POST horses prior to the SET until 2 h postexercise where POST horses' plasma AA concentrations became elevated and remained elevated until the end of the sampling period. In that same time frame, plasma AA for the PRE group decreased out to the end of the sampling period. The elevation of plasma AA in POST horses would be expected as they were fed at 1 h postexercise, whereas PRE horses were reaching a 4 h postfeeding time frame at this point. This elevation was not observed for plasma concentrations of isoleucine, leucine, methionine, and histidine. Concentrations of these AA initially were greater for POST horses in the postexercise period; however, they declined more rapidly than the other AA. The rapid decrease of some of the plasma AA concentrations may suggest uptake by muscle for recovery. This in conjunction with a decrease in plasma creatine kinase concentrations for POST horses suggests that feeding postexercise may facilitate better muscle protein balance (synthesis vs. breakdown) in the recovery period following exercise.

Amino acid requirements in horses

Evaluating amino acid requirements, specifically threonine requirements, in horses will enable better feed formulation and result in economic production, improved animal health, and reduced environmental pollution. However, the current knowledge of protein and amino acid requirements in horses is still limited. Because horses have a unique digestive system and consume a variety of feed ingredients, their protein digestibility may be affected than other species by different feed composition, and thus amino acid requirements are susceptible to vary between situations. Therefore, a careful evaluation of amino acid requirements with a proper method is needed for various conditions. This review will also provide comprehensive information that needs to be considered when designing an amino acid requirement study in horses.

Plasma disposition of gabapentin after the intragastric administration of escalating doses to adult horses

Background

In humans, gabapentin an analgesic, undergoes non‐proportional pharmacokinetics which can alter efficacy. No information exists on the pharmacokinetics of dosages >20 mg/kg, escalating dosages or dose proportionality of gabapentin in horses.

Hypothesis and Objectives

Gabapentin exposure in plasma would not increase proportionally relative to the dose in horses receiving dosages ≥20 mg/kg. To assess the plasma pharmacokinetics of gabapentin after nasogastric administration of gabapentin at dosages of 10 to 160 mg/kg in adult horses.

Animals

Nine clinically healthy adult Arabian and Quarter Horses.

Methods

In a randomized blinded trial, gabapentin was administered by nasogastric intubation to horses at 10, 20 mg/kg (n = 3) and 60, 80, 120, 160 mg/kg (n = 6). Plasma was collected before and at regular times over 64 hours after administration of gabapentin. Gabapentin was quantified using a validated chromatographic method. Dose proportionality was estimated using a power model. Pharmacokinetic parameters were estimated using compartmental pharmacokinetic analysis.

Results

Plasma pharmacokinetics parameters of gabapentin were estimated after nasogastric administration at dosages of 10 to 160 mg/kg. Gabapentin plasma concentration increased with dose increments. However, the area under the concentration curve from zero to infinity and maximal plasma concentration did not increase proportionally relative to the dose in horses.

Conclusions and Clinical Importance

Gabapentin exposure in plasma is not proportional relative to the dose in horses receiving nasogastric dosages of 10 to 160 mg/kg.

Dietary nitrogen utilisation and prediction of amino acid requirements in equids

The equine population represents an important sector of animal agriculture and, thus, contributes to environmental contamination. The horse industry lags behind other livestock industries in developing prediction models to estimate N and amino acid (AA) requirements aimed at precision feeding and management to optimise animal health and performance while mitigating nutrient excretion. Effective predictions of N utilisation and excretion are based on knowledge of ingredient protein quality and the determinants of N and AA requirements. Protein quality is evaluated on the basis of N and AA digestibility and AA composition. Amino acid composition of grains, pulses and oil seeds is extensive, but there is large deficit on that of forages. Several studies have reported on pre- and post-caecal N digestibility in horses, demonstrating that a large proportion of N from forages is metabolised post-caecally. Few have reported on AA digestibility. It is proposed that whole-tract (i.e. faecal) N and AA digestibility be used in evaluating feed-ingredient protein quality in equids to begin designing predictive models of N and AA requirements. Nitrogen gain and AA composition in deposited tissues and their corresponding efficiency of utilisation are the key determinants for a prediction model. We estimated that N utilisation for maintenance is 0.74. Maintenance requirements for N and AA were derived from faecal N and AA losses in horses and expressed as a function of dry-matter intake and from integument losses in swine. Relative to our factorial model, the NRC (2007) requirement for lysine and N is overestimated when based on a segmented curve and a breakpoint. When based on N equilibrium, lysine NRC (2007) requirement estimate agrees with our factorial model estimate, while N requirement is underestimated. The pool of AA profile used to express requirements of other essential AA has a large impact on requirement, as shown, in particular, for threonine. Threonine requirement based on faecal endogenous AA profile is higher than is lysine requirement for maintenance and lactation.

Small-intestinal or colonic microbiota as a potential amino acid source in animals

Factors affecting physiological impacts of the microbiome on protein nutrition are discussed for hind-gut fermenters (humans, pigs, rodents). The microbiome flourishes in all gastrointestinal organs, and is a major source of amino acids to fore-gut fermenting animals. In humans, rats and pigs the net effect of microbiome biomass synthesis on amino acid requirements is much less certain. Dietary proteins, amino acids, peptides, endogenous-secreted protein and recycled urea may all be utilized as nitrogen source by growing bacteria in the small intestine and colon. The inclusions of radiolabelled amino acid precursors will result in labeled bacteria which can be digested and absorbed in the ileum and to some degree in the colon. This does not necessarily indicate a significant nutritional role of the microbiome in humans, pigs and rodents. The physiological attributes required for small-intestinal and colon microbiome utilization are a vigorous proteolytic digestion with pancreatic or intestinal enzymes and the presence of amino acid transporters. Findings to date seem to suggest that these two physiological attributes for effective bacterial protein utilization are present in the small intestine; however, these attributes have a much lower capacity/impact in the colon. The gastrointestinal microbiome is likely a protein source of medium to high nutritional quality, but overall the microbiome is not an important amino acid source in humans and animals fed amino acids at requirement levels.

Ileal and faecal protein digestibility measurement in humans and other non-ruminants – a comparative species view

A comparative non-ruminant species view of the contribution of the large intestinal metabolism to inaccuracies in nitrogen and amino acid absorption measurements is provided to assess potential implications for the determination of crude protein/amino acid digestibility in adult humans consuming lower digestible protein sources. Most of the amino acids in the hindgut are constituents of the microorganisms and significant microbial metabolism of dietary and endogenous amino acids occurs. Bacterial metabolism of nitrogen-containing compounds leads to a significant disappearance of nitrogen in the large intestine. Literature data show that some 79 % of the nitrogen entering the large intestine of the horse is absorbed. For dogs, sows, and growing pigs these estimates are 49, 34 and 16 %, respectively. The coefficient of gut differentiation of humans compares closely to that of dogs while the coefficient of fermentation in humans is the lowest of all non-ruminant species and closest to that of cats and dogs. Large intestinal digesta transit times of humans compare closest to adult dogs. Significant amino acid metabolism has been shown to occur in the large intestine of the adult dog. Use of the growing pig as an animal model is likely to underestimate the fermentation of amino acids in the human large intestine. Based on the significant degree of fermentation of nitrogen-containing components in the large intestine of several non-ruminant species, it can be expected that determination of amino acid digestibility at a faecal level in humans consuming low quality proteins would not provide accurate estimates of the amino acids absorbed by the intestine.