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Nutrition: growth

ISSN 2398-2977

Podcast: Nutrition: growth


  • By the 7th month of gestation the fetus has only gained 17% birthweight.
  • Birthweight constitutes approximately 10% of the adult weight.
  • If a Thoroughbred   Thoroughbred  is <35 kg at birth, it is unlikely to grow to 15 hh.
  • Small foals born to small parents reach maximum size earlier than large foals born to large parents.
  • A higher proportion of horses >40 kg at birth go on to race than those of <40 kg at birth.
  • Late-born foals tend to be heavier and taller than early born foals.
  • Weaning age seems to have no influence on final size.
  • Differences in growth rate after neonatal period do not affect the final height and weight.
  • Maximum height and weight may be achieved earlier without dietary restriction, but diets with excess energy are linked to developmental orthopedic diseases, eg osteochondrosis   Bone: osteochondrosis  .
  • Restriction of feed during the growth period   →   delay in closure of growth plates   →   skeletal abnormalities, eg developmental orthopedic diseases (may be partly corrected during later growth).
  • Low feed intake over long periods will result in irreversibly small horses.
  • See also Nutrition: neonate   Nutrition: neonate  .
Print off the Owner factsheets on Feeding the young horse and Nutrition - keeping your horse on top form to give to your clients.

Feed requirements


Frequency and volume

  • Newborn foals first suck between 30 min and 2 h after birth.
  • First colostrum feed is essential for acquisition of passive immunity   Foal: failure of passive transfer (IgG)   via the immunoglobulins present.
  • A compromised foal may need to be fed parenterally and provided with supportive fluids   Foal: nasogastric intubation - intensive care  .
  • Deprivation of immunoglobulins occurs if sucking is delayed.
  • Immunoglobulin fraction of the colostrum falls to 10-20% of the initial value within 12-15 h of parturition.
  • Immunoglobulins do not cross the placenta in horses.
  • Immunity to environmental micro-organisms will depend on mare's exposure to local environment for a minimum of 2 weeks prior to foaling.
  • Colostrum is produced by selective secretion of humoral antibodies into the mammary gland during the last month of gestation:
    • IgG constitutes >80% of the immunoglobulins; the remaining 20% comprises IgA and IgM.
    • Colostrum is energy dense.
    • Has laxative properties.
    • Contains complement and lactoferrin that aid in defence against pathogens.
    • Contains epidermal growth factor that enhances gastrointestinal mucosa growth and help prevent gastric ulcers   Stomach: gastric ulceration - foal   which neonatal foals are subject to.
    • Colostrum is also rich in vitamin A   Vitamin A  .
  • If colostrum from dam is not available, substitute with colostrum from another mare in the same locality or from a cow   Nutrition: neonate  .
  • There are also lyophilized IgG   IgG   products commercially available that can be used to provide IgG.
  • Foals require 500 ml every 3-4 h up to at least 12 h after birth.
  • Milk yields depend on diet during pregnancy   Nutrition: brood mare  , water availability and the mare's mothering ability.
  • Small frequent feeds less likely to cause intestinal problems in foals.
  • Foals suck approximately 100 times/24 h in the first week of life for with each suckiling period lasting 1.3-1.7 min.
  • Frequency falls to 35 times/24 h by the tenth week. Nutrition is maintained by the foal increasing consumption of forage and concentrates.
  • Sucking frequency may be less when creep feed is offered.
  • See also Nutrition: neonate   Nutrition: neonate  .

Creep feeding

  • Foals can start eating hay or concentrates from 10-21 days old, some start at 3 days.
  • Creep can be introduced in the first week or when the foal shows an interest.
  • If milk supply is not adequate, provide creep feed.
  • Creep feeding also ensures maturation of the gastrointestinal tract so that abnormal fermentation does not occur at weaning.
  • At first, composition of the creep feed is based on dried skimmed milk with a gradual change to a young stock diet when foal reaches 8-12 weeks.
  • The type of diet the foal requires will be determined by growth rate and body condition.
  • If foals are on good pasture with a good milk supply from the mare, no additional feed will be required until 2-3 months old, ie 2 months prior to weaning.
  • Restricting creep feeds will reduce energy   Nutrition: energy  intake but also minerals   Nutrition: minerals  which may   →   developmental orthopedic disease.
  • Ensure mineral   Nutrition: minerals  intake is maintained if energy   Nutrition: energy  is restricted. Neonatal foals have higher trace mineral requirements than adult horses. Copper and zinc deficiencies have been implicated as a cause of developmental orthopedic diseases.
  • Commercially prepared products   Nutrition: commercial feeds  are available that provide concentrated sources of minerals without the energy of typical creep feed.

Orphan foals

  • Artificial rearing   Foal: artificial feeding  not usually attempted for Thoroughbred   Thoroughbred   orphan foals <40 kg.
  • Is essential for foal to receives colostrum within first 24 h of life and before any other source of nutrients.
  • Milk dead mare if possible. Many studs keep frozen colostrum, do not defrost aggressively as antibodies will be denatured.
  • Milk substitutes:
    • Proprietary milk replacers.
    • Follow manufacturers guidelines for mixing qualtities to ensure provision of sufficient nutrients.
    • Initially 280 ml given at 90 min intervals.
    • Milk production in mare linked to bodyweight (BW) - ponies average 5 l/100 kg BW and horses 3 l/100 kg BW.
    • After a few days, the daily intake of a foal will increase to 9-18 l and may increase to 36 l if drinking freely, depending on body size. Excessive intake    →    diarrhea   Diarrhea: neonate  . 
    • Restrict large foals and those with diarrhea to 18 l/day.
    • Make all diet changes slowly (over a period of 7-10 days).
  • Introduce a milk based creep, feed from 7 days and reduce liquid milk from 30 days as creep feed consumption increases.
  • Up to 3 kg dry feed may be consumed daily at 30 days, including only a small amount of hay.
  • Fostering- nurse mares, nanny goats.
  • Weaning- as early as 3 days may occasionally be necessary but very labor intensive. Usually occurs between 4 and 7 months as foal is no longer reliant on a milk based diet.

Young stock

  • Give 1.25-2 kg concentrate containing 16% protein/100 kg BW together with vitamins   Nutrition: vitamins  and minerals   Nutrition: minerals  over the first winter to supplement variable winter pasture.
  • Good doers, such as Warmbloods   Dutch warmblood  and natives, may require more concentrated nutrient sources designed to keep energy intake low to prevent weight gain.
  • If stabled, free access to good quality hay (about 0.5-2 kg/100 kg BW) is required in addition to concentrates.
  • Pasture and hay/haylage are unlikely to ever provide sufficient nutrients to meet the requirements of growing youngstock.
  • Forage analysis is beneficial in identifying mineral deficiencies. There is compensation for deficiencies in the concentrate ration.

Normal growth rate

  • After birth the most rapid period of growth is from 0-3 months which is when the youngsters nutritional requirements are greatest.
  • By 12 months foals achieve 60% mature weight, 90% mature height and 95% bone growth.
  • Of the three major tissues, bone matures first, followed by muscle and finally fat.
  • A young horse with an eventual mature weight of 450 kg gains 100 kg between 3 and 6 months at the average rate of 1 kg/day. Nutrition, health and weather conditions affect how much growth occurs on a day-to-day basis.
  • The growth rate declines thereafter and the subsequent 100 kg are gained when aged between 6 and 12 months and the subsequent 75 kg between 12 and 18 months.
  • Bigger breeds tend to mature later and may have increased nutritional requirements until they reach maturity.
  • Young horses and ponies which have achieved maturity and are in work can be fed hay and concentrate suitable for an adult horse.
  • Daily ration of concentrate: 0.75-1% of the BW/day.

Excess energy intake is associated with developmental orthopedic diseases   Bone: osteochondrosis  .

Daily requirements for thoroughbred youngstock to mature at 500 kg

Weanling (6 months old)

  • Digestible energy - 68 MJ.

Yearling (12 months old)

  • Digestible energy - 84 MJ.

Long yearling (18 months old) not in training

  • Digestible energy - 88 MJ.

Print-off the Owner factsheet onNutrition - keeping your horse on top form  Nutrition - keeping your horse on top form  andFeeding the older horse  Feeding the older horse  to give to your client.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Hintz H F (1992) Ed. Clinical nutrition.  Vet Clin North Am 6, (2).
  • Cymbaluk N F, Christison G I & Leach K H (1990) Longitudinal growth and analysis of horses following limited and ad libitum feeding. Equine Vet J 22, 198-204 PubMed.

Other sources of information

  • Frape D (2004) Equine Nutrition and Feeding. 3rd edn. Blackwell Publishing Ltd, UK. ISBN: 1405105984.