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

Microbiota characterization throughout the digestive tract of horses fed a high-fiber vs. a high-starch diet

Introduction

Diet is one of the main factors influencing the intestinal microbiota in horses, yet a systematic characterization of the microbiota along the length of the digestive tract in clinically healthy horses, homogenous for age and breed and receiving a specific diet is lacking.

Methods

The study used 16S rRNA amplicon sequencing to characterize the microbiota of the intestinal tracts of 19 healthy Bardigiano horses of 14.3  ±  0.7  months of age fed one of two diets. Nine horses received a high-starch diet (HS), and ten horses received a high-fiber diet (HF). After 129  days, the horses were slaughtered, and samples were collected from the different intestinal tract compartments.

Results and discussion

The microbiota alpha diversity indices were lower in the caecum, pelvic flexure and right dorsal colon of the horses fed the HS diet (False Discovery Rate, FDR  <  0.05). The values of beta diversity indicated significant compositional differences between the studied intestinal tract compartments according to the diet received (FDR  <  0.05). At the lower taxonomic level (genus or family), the HS diet was associated with a higher relative frequency of Enterobacteriaceae within the small intestine (jejunum and duodenum) (FDR  <  0.05). Within the hindgut (caecum and sternal flexure), the HS diet was associated with lower relative frequencies (i.e., a smaller core community) of bacteria belonging to Fibrobacteraceae and Prevotellaceae (FDR  <  0.05). Moreover, horses fed the HS diet displayed a higher relative abundance of Streptococcus in the caecum (FDR  <  0.05) and Fusobacterium in the sternal flexure (FDR  <  0.05), both of which are pathogenic bacteria responsible for inflammation diseases. Samples collected from the pelvic flexure and rectum of horses fed the HS diet showed significantly higher relative frequencies of Succinivibrionaceae (FDR  <  0.05) - amylolytic bacteria associated with acidosis. The relative frequencies of the Lachnospiraceae and Ruminococcaceae were lower in the feces collected from the rectum of horses receiving the HS diet vs. HF diet, indicating smaller core communities of these bacteria (FDR  <  0.05). Fibrous diets should be promoted to prevent dysbiosis of the microbiota associated with high-starch diet.

Does Feeding Management Make a Difference to Behavioural Activities and Welfare of Horses Reared for Meat Production?

Horses reared for meat production are generally fed a diet rich in starch with the aim of maximizing production performances. This study evaluated the effects of two feeding management systems on horse welfare by analysing the relative time spent engaged in different behavioural activities. Nineteen Bardigiano horses aged 14.3 ± 0.7 months were randomly assigned to one of two group pens: one group was fed high amounts of starch-rich concentrates (HCG; n = 10), the other was fed a fibre-based diet (HFG; n = 9). Behavioural activities performed by each horse were video-recorded over a 96-h period. A scan sampling process (n = 144 scans/horse/day; total n of scans sampled = 10,368) was used, and the scans were analysed according to a specific ethogram. The mean frequency (%/24 h) spent exhibiting each behavioural activity was calculated to obtain the time budget. After checking for normality (Shapiro–Wilk test), Student’s t tests (normally distributed data) and Mann–Whitney tests (not normally distributed data) were used to compare the time budgets of the two groups of horses (HCG vs. HFG). Principal Component Analysis (PCA) was applied to identify the components explaining the variability in behavioural activities between the two groups. K-means cluster analysis subsequently confirmed the PCA results. The behavioural activities associated with feeding horses a fibre-based diet correlated with better horse welfare compared with feeding horses a starch-based diet. Feeding horses a fibre-based diet resulted advantageous from both the welfare and economic perspective; it allowed horses to spend more time expressing feeding behaviours and reduced energy expenditure in the form of excitable, or “fizzy”, behaviours.