In Vitro Assessment of Fecal Inocula From Horses Fed on High-Fiber Diets With Fibrolytic Enzymes Addition on Gas, Methane, and Carbon Dioxide Productions as Indicators of Hindgut Activity

Comparison of forages’ digestion levels for different in vitro digestion techniques in horses

BACKGROUND

Forages are widely used in horse diets. Different in vitro techniques are being tried to determine the fermentation levels of forages in the horse digestive tract.

OBJECTIVES

This study aimed to evaluate the digestion levels of four dry forages commonly used in horse nutrition: alfalfa herbage, meadow hay, wheat straw, and Italian ryegrass. In vitro total digestion (TDT), in vitro Sunvold-large intestine digestion (SDT) and in vitro Menke-large intestine digestion (MDT) techniques were compared.

METHODS

The study determined in vitro true dry matter digestion (T-DMD), in vitro true organic matter digestion (T-OMD) and in vitro true neutral detergent fibre digestion (T-NDFD). Additionally, concentrations of straight short-chain fatty acids (SCFAs; acetic acid - AA, propionic acid , butyric acid, and valeric acid ) and branched short-chain fatty acids (BSCFA) were assessed.

RESULTS

The highest in vitro T-DMD, T-OMD and T-NDFD values were determined by the in vitro TDT for the four forages (p < 0.05). In vitro T-DMD and T-OMD values of alfalfa herbage were higher than those of Italian ryegrass, meadow hay and wheat straw in the in vitro TDT (p < 0.001). In addition, in vitro T-DMD and T-OMD values of alfalfa herbage in the in vitro SDT were higher than those of meadow hay and wheat straw (p < 0.001). In the in vitro TDT, the molarity of AA, total SCFA and BSCFA in the digestion fluid of alfalfa herbage was higher than those of other forages (p < 0.05).

CONCLUSION

The in vitro total enzymatic + fermentative digestion technique for horse forages revealed higher values than the in vitro fermentative digestion techniques. In general, the higher the non-structural carbohydrate and crude protein contents in the forage, the higher the results of the in vitro TDT compared to the other techniques.

The in vitro digestion and fermentation characteristics of feedstuffs inoculated with cecal or colic fluid of Dezhou donkey

The present study was conducted to evaluate the in vitro dry matter disappearance (IVDMD) and fermentation characteristics of 6 fibrous feedstuffs incubated with donkey cecal or colic microorganisms. The fibrous feeds were corn straw (CS), wheat straw (WS), peanut vine (PNV), peanut shell (PNH), wheat shell (WH) and wheat bran (WB), which are commonly applied in large-scale donkey farms in China. After 48 h fermentation, the highest IVDMD occurred in WB, and the lowest occurred in PNH (P<0.05) regardless what inoculum applied. The IVDMD was positively correlated with OM (R=0.42, P<0.01), CP (R=0.76, P<0.01) and EE (R=0.56, P<0.01), while it was negatively correlated with NDF (R=0.75, P<0.01) and ADF (R=0.79, P<0.01). In terms of volatile fatty acids (VFAs), the greatest net VFA production also occurred in WB (P<0.05). The acetate and branched-chain volatile fatty acid (BCVFA) proportions were greater in the colon culture fluids than in caecum (P<0.05), but the propionate proportions were lower in colon than in caecum (P<0.05). This resulted in an increase in the ratio of acetate to propionate in colon culture fluids. In summary, based on the highest IVDMD, net VFA production and CP content occurring with the lowest contents of both NDF and ADF, WB had the highest nutritive value compared to other fibrous substrates. The extent of feed degradation and fermentation depended mainly on the nature of the incubated feedstuffs. Nevertheless, further study is required to investigate these fibrous feeds on hindgut fermentation and in vivo nutrient digestibility.

Caecal fermentation characteristics of commonly used feed ingredients

BACKGROUND

Commercial horse feeds use cereal grains and by-products; however, their effects on the caecal environment remain poorly characterised.

OBJECTIVE

Characterise the effect of commonly used feed ingredients on caecal pH and volatile fatty acid (VFA) concentration.

STUDY DESIGN

6 × 6 Latin square.

METHODS

Two days prior to the start of the study, 6 caecally cannulated Quarter horses were moved into individual stalls where Smooth bromegrass hay (brome) was offered at 2.0% BW/d split between 2 feedings (0600 and 1800). On day 0, caecal digesta was collected every 2 h for 12 h relative to the 0600 feeding to establish control values for horses consuming only brome (HAY). On day 1, horses began consuming their respective treatments which consisted of beet pulp (BP), maize (M), dehydrated alfalfa (A), oats (OAT), soybean hulls (SBH), or wheat middlings (WM) at 0.25% BW/d split into 2 feedings. On day 7 of each treatment period, caecal digesta was collected every 2 h for 12 h and analysed for pH and VFA. Data were analysed using mixed ANOVA with repeated measures, fixed effects of treatment and time and random effects of horse and period.

RESULTS

There was a main effect of hour (P ≤ .05) indicative of post-prandial shifts in caecal metabolites. There were no main effects of treatment on pH or VFA concentration (P ≥ .3). Effects of hour × treatment (P ≤ .04) were observed for all response variables. Regardless of treatment or hour, caecal pH remained well within normal limits. Three horses exhibited signs of lower oesophageal choke immediately after consumption of BP pellets.

LIMITATIONS

Interactions between ingredients when mixed for formulation of a concentrate warrant further research. Furthermore, a short adaptation period was chosen to mimic common management practices.

CONCLUSION

Minimal differences in caecal fermentation parameters were detected when ingredients were fed at a common inclusion level.

Equine Contribution in Methane Emission and Its Mitigation Strategies

Greenhouses gas emission mitigation is a very important aspect of earth sustainability with greenhouse gasses reduction, a focus of agricultural and petrochemical industries. Methane is produced in nonruminant herbivores such as horses because they undergo hindgut fermentation. Although equine produce less methane than ruminant, increasing population of horses might increase their contribution to the present 1.2 to 1.7 Tg, estimate. Diet, feeding frequency, season, genome, and protozoa population influence methane production equine. In population, Methanomicrobiales, Methanosarcinales, Methanobacteriales, and Methanoplasmatales are the clade identified in equine. Methanocorpusculum labreanum is common among hindgut fermenters like horses and termite. Naturally, acetogenesis and interrelationship between the host and the immune-anatomical interaction are responsible for the reduced methane output in horses. However, to reduce methane output in equine, and increase energy derived from feed intake, the use of biochar, increase in acetogens, inclusion of fibre enzymes and plant extract, and recycling of fecal energy through anaerobic gas fermentation. These might be feasible ways to reducing methane contribution from horse and could be applied to ruminants too.