Hay versus haylage: Forage type influences the equine urinary metabonome and faecal microbiota

Gut microbial communities are increasingly being linked to diseases in animals and humans. Obesity and its associated diseases are a concern for horse owners and veterinarians, and there is a growing interest in the link among diet, the intestinal microbiota and metabolic disease.

Assess the influence of long-term hay or haylage feeding on the microbiota and metabolomes of 20 Welsh mountain ponies.

Longitudinal study.

Urine, faeces and blood were collected from 20 ponies on a monthly basis over a 13-month period. Urine and faeces were analysed using proton magnetic resonance (¹ H NMR) spectroscopy and faecal bacterial DNA underwent 16S rRNA gene sequencing.

Faecal bacterial community profiles were observed to be different for the two groups, with discriminant analysis identifying 102 bacterial groups (or operational taxonomic units, OTUs) that differed in relative abundance in accordance with forage type. Urinary metabolic profiles of the hay- and haylage-fed ponies were significantly different during 12 of the 13 mo of the study. Notably, the urinary excretion of hippurate was greater in the hay-fed ponies for the duration of the study, while ethyl-glucoside excretion was higher in the haylage-fed ponies.

The study was undertaken over a 13-month period and both groups of ponies had access to pasture during the summer months.

The data generated from this study suggest that the choice of forage may have implications for the intestinal microbiota and metabolism of ponies and, therefore, potentially their health status. Understanding the potential implication of feeding a particular type of forage will enable horse owners to make more informed choices with regard to feed, especially if their horse or pony is prone to weight gain.