So what do we mean by forage?; how much should be feed? and nutritionally can we just feed forage to equines?

Definitions

Forage: high fibre whole plant (except roots): includes cool (C3) and warm season (C4) grasses (incl. C3 & C4 cereal plants) and legumes1 . May be fed fresh (i.e. grass pasture) or preserved.

Roughage: high fiber feedstuff generally obtained as a crop residue or a by-product e.g. straw, cereal hulls, beet pulp. Typically used interchangeably with the term forage.

‘Foraging’ used to encompass all feed intake activities of horses both on pasture and in housing situations.

Preserved forages typically fed to equines:

• Straw: stalks of harvested cereal plants, preserved through drying: DM2 content ideally above 85%.
• Hay: grasses/legumes preserved at a DM content ideally above 85%: Preserved through drying.
• Haylage: grasses/legumes stored airtight whilst only semi-wilted and with DM content ≥ 50% (and typically < 85%): Preserved through being airtight with some (but variable) fermentation. WSC content may be very similar to that of the grass when it was harvested.
• Silage: for forages (incl. grain grasses such as corn) stored moist and airtight with DM contents below 50%: Preserved through fermentation and therefore WSC should be lower than that of the grass when harvested.

Key Take Home Messages

FORAGE should be the foundation of all equine diets (for health and welfare reasons)

• Equines at a healthy weight (i.e. not overweight) should ideally be fed forage ad libitum and at least 1.5% of their bodyweight in DM per day.
• Even equines in very high intensity work should be fed at least 1.25% of bodyweight (e.g. 6.25kg DM for a 500kg horse) in DM as forage.
• Even in weight resistant animals during a weight loss programme do not recommend <1% BW DM. NB Equines (especially some ponies) can eat ~1%BW in DM within 3hrs and up to ~5%BW DM/day.

Important where-ever possible to Match forage (type/intake provision/timings etc.) to individual needs

• Nutritionally variable within and between grass types and stage of maturity when cut.
• Need to make changes slowly especially if very different nutrient profiles/types of forage.
• Avoid prolonged periods without forage provision.

Forage ANALYSIS is key BUT recognise

• Analytically variable depending on sampling, laboratory methodology etc. especially for Water-soluble carbohydrate content.
• Need to understand the variability of any analytical method used by a chosen lab (which should have good in-house quality control systems).

Unlikely forage alone will meet optimal nutrient needs: especially at certain life stages/work intensities

• Studies in Standardbreds have shown that it is possible to train (both growing and mature horses), and race, horses provided with forage as the only source of dietary protein and energy: BUT digestibility, protein and energy content must be appropriately high.
• Most, if not all, forage-based rations will require an equine specific vitamin- and mineral balancer or an amino-acid, vitamin-mineral balancer which complements that forage
  • Especially if feeding soaked forage
  • Especially if on a restricted diet
• Need to be aware of any possible specific nutrient considerations linked with the forage type being fed as well as any non- nutrient aspects such as hygienic quality.

Recommendations

• Forages, especially when sold commercially, should come with a guide as to the likely range of key analytical values that an individual ‘bale’ of that forage would provide.
• ‘We’ should work together to agree optimal methods for analysis of key analytes to enable common interpretation.

References in presentation

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• 2018, Effects of grain species, genotype and starch quantity on the postprandial plasma amino acid response in horses, Research in Veterinary Science, 118, 295- 303, https://doi.org/10.1016/j.rvsc.2018.02008

• Chavez, S. J., Siciliano, P. D., and Huntington, G. B., 2014,  Intake estimation of horses grazing tall  fescue (Lolium arundiaceum)  or fed tall fescue hay. Journal of animal science, 92  (5), 2304-2308. https://doi.org/10.2527/jas.2013-7719

• Essen-gustavson, B., Connysson M., and Jansson, A., Effects of crude protein intake from forage-only diets on muscle amino acids and glycogen levels in horses in training.  Equine Veterinary Journal, 42, 341-346. https://doi.org/10.1111/j.2042-3306.2010.00283.x

• DeBoer, M. L., Martinson, K. L. Kuhle, K. J., Sheaffer C. C., and Hathaway, M. R., 2019. Plasma Aminoacid Concentrations of Horses Grazing Alfalfa, Cool-Season Perennial Grasses, and Teff. Journal of equine veterinary sciences, 72, 72-78. https://doi.org/10.1016/j.jevs.2018.10.013

• Douglas, K., de la Fuente, G., Harris, P. A., Girdwood, S. E., Pinloche, E., Geor, R. J., Nielsen, B. D., Schott II, H. C., Elzinga, S., and Newbold, C. J., 2014. Characterisation of faecal bacteria community in adult and elderly horses fed a high fibre, high oil, or high starch diet usin 454 pyrosequencing. PloS one, 9(2), p.e87424, https://doi.org/10.1371/journal.pone.0087424 

• Dugdall, K., Curtis, G. C., Cripps, P., Harris, P. A., and Argo, C. McG., 2011. Effects of season and body condition on appetite body mass and body composition in ad libitum fed pony mares. The Veterinary Journal, 190 (3), 329-337. hhttps://doi.org/10.1016/j.tvjl.2010.11.009

• Gomez, A., Sharma, A. K., Grev, A., Sheaffer, C., and Martinson, K., 2021. The horse gut microbiome responds in a highly individualized manner to forage lignification. Journal of Equine Veterinary Science, 96, p.103306. https://doi.org/10.1016/j.jevs.2020.103306

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• Longland, A. C., Barfoot, C., and Harris, P. A., 2016. Effects of grazing muzzles on intakes of dry matter and water-soluble carbohydrates by ponies grazing spring, summer and autumn swards, as well as autumn swards of different heights. Journal of Equine Veterinary Science, 40, 26-33. https://doi.org/10.1016/j.jevs.2015.09.009

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• Morrison, P. K., Newbold, C. J., Jones, E., Worgan, H. J., Grove-White, D. H., Dugdale, A. H., Barfoot, C., Harris, P. A., and Argo, C. McG., 2020. Effect of age and the individual on the gastrointestinal bacteriome of ponies fed a high-starch diet. PLoS ONE 15(5): e0232689. https://doi.org/10.1371/journal.pone.0232689

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• Wood, I., Lancaster, B. E., and Rogers, C. W., 2019. The feeding and management of Thoroughbred and Standardbred Racehorses displaying clinical signs of recurrent exertional rhabdomyolysis. New Zealand Journal of Animal Science and Production, 79, 26-31. 

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