Effects of different grains on bacterial diversity and enzyme activity associated with digestion of starch in the foal stomach

Growth performance, nutrient digestibility, fecal microbial diversity and volatile fatty acid, and blood biochemical indices of suckling donkeys fed diets supplemented with multienzymes

BACKGROUND

As the foal grows, the amount of breast milk produced by the donkey decreases. In such cases, early supplemental feeding is particularly important to meet the growth needs of the foal. Foals have an incompletely developed gastrointestinal tract with a homogenous microbiota and produce insufficient amounts of digestive enzymes, which limit their ability to digest and utilize forage. Improving the utilization of early supplemental feeds, promoting gastrointestinal tract development, and enriching microbial diversity are the hotspots of rapid growth research in dairy foals. Plant-based feeds usually contain non-starch polysaccharides (NSPs), including cellulose, xylan, mannan, and glucan, which hinder nutrient digestion and absorption. In addition, proteins and starch (both biomolecules) form a composite system mainly through non-covalent interactions. The proteins wrap around the surface of starch granules and act as a physical obstacle, thereby inhibiting water absorption and expansion of starch and decreasing the enzyme's catalytic effect on starch. Glyanase, β-mannanase, β-glucanase, cellulase, protease, and amylase added to cereal diets can alleviate the adverse effects of NSPs. The current study determined the effects of adding multienzymes (glyanase, β-mannanase, β-glucanase, cellulase, protease, and amylase) to the diet of 2-month-old suckling donkeys on their growth performance, apparent nutrient digestibility, fecal volatile fatty acid (VFA) and pH, fecal bacterial composition, and blood biochemical indices.

RESULTS

On day 120 of the trial, fecal samples were collected from the rectum of donkeys for determining bacterial diversity, VFA content, and pH. Moreover, fresh fecal samples were collected from each donkey on days 110 and 115 to determine apparent digestibility. The multienzymes supplementations did not affect growth performance and apparent nutrient digestibility in the donkeys; however, they tended to increase total height gain (P = 0.0544). At the end of the study, the multienzymes supplementations increased (P < 0.05) the Observed species, ACE, Chao1, and Shannon indices by 10.56%, 10.47%, 10.49%, and 5.01%, respectively. The multienzymes supplementations also increased (P < 0.05) the abundance of Firmicutes, Oscillospiraceae, Lachnospiraceae, Christensenellaceae, Christensenellaceae_R-7_group, and Streptococcus in feces, whereas decreased (P = 0.0086) the abundance of Proteobacteria.

CONCLUSIONS

Multienzymes supplementations added to a basal diet for suckling donkeys can increase fecal microbial diversity and abundance.

Effect of micronization and meal size of corn grain on glycemic response and in vitro hindgut acidosis potential in horses

This study aimed to 1) evaluate the interaction of corn grain micronization and starch levels per meal on equine plasma glucose, and 2) determine if micronization affects the risk of hindgut acidosis. Six mature (aged 6 to 10 years), healthy, non-pregnant mares (initial body weight [BW]: 301 to 463 kg) were used in a 2×3 factorial cross-over design. The treatments included two forms of corn grain (ground and micronized flaked) at three levels of starch (1, 1.5, and 2 g/kg BW per meal). The blood was sampled before and 30, 60, 90, 120, 180, 240, and 300 min after morning feeding and the glucose concentration in the plasma was determined. Small intestine and hindgut dry matter (DM) disappearances of ground and micronized corn were also compared using in vitro techniques. Micronized flaked corn grain showed three times more in vitro enzymatic DM disappearance (p < 0.001) compared with ground corn. Residues of in vitro enzymatic digestion of micronized flaked corn fermented 38.59 % faster than ground corn during in vitro hindgut incubation. The horses that consumed micronized flaked corn had higher post-prandial plasma glucose concentrations (p < 0.001). Increasing starch levels per meal from 1-2 g/kg BW resulted in higher plasma glucose concentrations (P = 0.005). However, no interaction of processing and starch meal size was found. Overall, processing the corn grain by micronization or increasing starch level per meal increased the plasma glucose concentrations, but the magnitude of the increases did not match that expected from in vitro studies.