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As an independent equine nutritionist, I frequently use the phrase ‘ad lib’ myself and I’ve heard owners using the phrase in a variety of scenarios. What exactly does ad-lib mean, and is it right for your horse? Maybe you're currently trickle feeding and ad-lib forage might be better for your horse. What is trickle feeding? In this article, I'll be dissecting these two feeding methods to help you understand how each will impact your horse and which one might be right for them. However, before we do this, we need to understand how your horse's digestive system is regulated.

How does a horse's digestive system work?

The digestive system starts in the mouth with chewing grinding fibres down into a more digestible structure. Chewing also stimulates saliva production, which helps buffer and control the acid concentration in the stomach.  
A horse's foregut consists of the stomach and small intestines. The stomach has 2 distinct regions, the squamous, or top part, which has no mucosal lining for protection against stomach acid, and the Glandular region, which does have a protective layer of mucous. The small intestine can be divided into 3 regions, the duodenum, jejunum and the ileum. Fats, proteins and simple carbohydrates are broken down by acids and enzymes in the foregut. The remaining portion of the food, mainly fibre and structural carbohydrates, passes through to the hindgut.
The hindgut comprises the cecum, the large colon and the small colon. Fibre digestion in the hindgut is driven by microbes, which are populations of bacteria and protozoa, collectively known as the gut-biome. Fibre digestion occurs by the gut-biome fermenting fibre or structural carbohydrates, into Volatile Fatty Acids (VFA’s) and short-chain fatty acids (SCFA’s), which the horse can then use for energy.  
The horse's digestive system has evolved over 45 million years to allow them to eat high volumes of nutritionally poor forage throughout the day. Unlike our digestive systems, which can function on a feast-and-famine diet, the horse’s digestive system is poorly equipped to cope with periods of 4 or more hours with nothing to eat. If restricted for too long without forage the concentration of the acid in the stomach increases, and the horse is at a higher risk of developing Equine Gastric Ulcer Syndrome (EGUS). In addition, prolonged periods without anything to chew have been shown to increase a horse’s stress level, and it can even encourage gorging when they are then allowed access to grass or preserved forages.    
Figure 1 image author -

What is ad-lib feeding?

The phrase comes from the Latin ‘ad libitum’, meaning to allow the horse to feed at its own will, rather than on a schedule. With horses, the practice of ad-lib feeding usually refers to the fibre or forage portion of their diet, rather than their bucket or compound feed. Fibre or forage options commonly include:
Grasses from grazing
  • Preserved forages such as Hay, Haylage and sometimes even straw
  • Commercially available, bagged, short-cut forages, often referred to as "chaff"
  • Commercially available high-fibre mashes, such as sugar beet
The design of a suitable diet for any horse should start with the choice of the types of forage and the amounts and manner in which their fibre provision is fed. This is because of how the horse's digestive system is designed (figure 1). The problems associated with forage restriction and prolonged periods without any forage provision certainly argue the case for ad-lib feeding. Ensuring that the horse can eat at its own will, with unlimited access to forages, and that the supply is never allowed to run out. This can be achieved with access to plentiful grazing or provision of hay or haylage in a volume sufficient to ensure it doesn’t run out. While this may be a suitable approach for horses who need to gain weight, broodmares or youngstock struggling to maintain body condition, or those in hard work that require sufficient calories to maintain performance and body condition, it is not a suitable approach for many horses and ponies.  
For overweight horses or good-doers prone to excessive weight gain, a never-ending supply of forage would likely result in obesity. Equine obesity is believed to affect over half the horses and ponies in the UK, and it causes an increased risk of Equine Metabolic Syndrome (EMS) or laminitis. Horses at risk of these conditions require steps to ensure that they are in an ideal body condition, to control their total calorie and sugar (fructans and water-soluble carbohydrates) intake, and to prevent extended periods without access to forage from occurring. In these situations, the ‘trickle feeding’ of forage is preferable to ‘ad lib’.  

What is trickle feeding?

Trickle feeding is not the same as ad-lib feeding, but I often hear the two phrases used interchangeably. Trickle feeding is a method of providing a controlled amount of forage, in a way to ensure that it lasts for a long enough time. If the daily allowance of hay/haylage was fed at once or split across 2 feeds per day, this would likely be eaten and gone very quickly. The horse would then be left for too long with nothing to chew on or eat and the risk of EGUS (Equine Gastric Ulcer Syndrome) would increase.  
Multiple methods can be used to reduce the time without forage down to an acceptable level. These can include: providing the hay or haylage in small holed, or double netted hay/haylage nets, feeding systems with grids and hay balls. Splitting the amount fed at each part of the day into multiple nets hung in different areas of the stable, grid feeders and hay balls can also reduce the rate at which the horse consumes its forage allowance, increasing how many intervals throughout the day that the forage is provided. For example, instead of 1/2 at 7am and the other 1/2 at 6pm, feed 1/4 at 7am, 1/4 at 12pm, 1/4 at 6pm and 1/4 at 9pm. This will reduce how long a horse is stood with nothing at any single time.
Controlling the amount of grass consumed per hour of turnout is more challenging.  To support trickle feeding of grass, measures can include restricting the duration of grazing, reducing the available area with strips or track systems, and a section of poorer grazing. Another method can be to control the amount of grass eaten with each mouthful, this might involve turning out into a heavily grazed area with only sparse, poor quality, short grass available, or with the use of a suitable grazing muzzle.            
As always if your horse is being fed ad-lib or by trickle feeding it is important to monitor for changes in body condition, behaviour or signs of ill health, and to contact your vet with any concerns. If you are in doubt as to which system would be best for your horse, or how you should best achieve this, you can again speak with your vet or you can seek help from a qualified equine nutritionist. If you contact Equinutrition, I would be more than happy to help.

Jennifer Little BSc Hons MSc RNutr PgCert - Equinutrition
Independent Equine Nutritionist
Published on 03-05-2024
Jennifer Little is a fully registered equine nutritionist, who has been working independently from feed companies since founding Equinutrition in 2021. Jennifer has worked in animal and equine nutrition in the UK and the USA for over 10 years. She is a member of the Association for Nutrition and the Society of Nutrition, also Equinutrition is an associate business with the British Equestrian Trade Association (BETA). Alongside her work, Jennifer is currently completing a PhD investigating equine obesity and methods to support owners. She strives to use her training, qualifications and experience to provide evidence-based advice without agenda for horse owners at all levels and disciplines.