Both the amount of starch in the feed and the type of feed processing have a significant impact on blood glucose and insulin. The misapplication of these factors can result in abnormally high insulin levels and laminitis. Although horses in hard work and needing high grain intakes benefit from these processing methods – they are inappropriate for horses with insulin dysregulation ie PPID, EMS and pregnancy. And, it’ s not just the mare that experiences faster, higher and longer rises in insulin – it impacts the growing foal too. www. jenquine. com
37 higher and remain elevated for longer in pregnant mares and this is particularly pronounced with high starch / sugar feeds. Both starch and sugar stimulate insulin release and because pregnant mares already have elevated insulin, they need to be protected from surges caused by inappropriate choice of feeds.
TABLE 1. FEED LABELS INGREDIENTS and PROCESSING METHODS that flag caution and are best avoided for pregnant mares. Recommendations for pregnant mares, weanlings^ and EMS horses and ponies * are that the feed has less than 10 % NSC( starch + sugar) and < 4 % starch.
Barley |
average starch 60 % sugar 3 % = 63 % NSC |
Bran / pollard |
average starch 23 % sugar 7 % = 30 % NSC |
Cereal by-products |
include bran, pollard, wheat middlings and mill-run = 30 % NSC |
Cereal co-products |
generally corn or wheat meal, hominy feed, bran and pollard = 30 % NSC |
Corn |
approximately 73 % starch and 2 % sugar = 75 % NSC |
Millmix |
contains wheat pollard and bran = > 30 % NSC |
Millrun |
contains bran and pollard = > 30 % NSC |
Molasses |
average 65 % sugar = 65 % NSC |
Wheat |
average starch 70 % sugar 3 % = 73 % NSC |
Rice bran( fibre < 4 %) |
average starch 42 % sugar 4 % = 46 % NSC |
Micronised |
The feed is ' cooked ' making it more digestible and dramatically increasing the availability |
of glucose- which can cause a profound increase in glucose and the glycaemic response. |
Extruded |
Extrusion increases starch digestibility making it easily converted to glucose and absorbed. |
^ in young growing horses, insulin fluctuations are linked to developmental orthopaedic diseases. * 90 % of laminitis in horses and ponies is due to insulin dysregulation
STOMACH ULCERS AND PERI-NATAL COLIC: Although horse owners often roll and boil cereal grains, the most common commercial processes are grinding, micronizing, extruding / expanding and flaking – the objective being to increase the nutritional value of the feeds by enhancing the availability of starch. Starch is transformed into glucose by bacteria, digestive juices and enzymes in the stomach and small intestine. Compared to grinding, micronising and extruding increase the rate of starch fermentation and breakdown in the stomach. But this is not necessarily a good outcome as the starch alters the microflora in the non-glandular portion of the stomach- eventually causing conditions such as ulcers. Starch-rich feeds also delay stomach emptying, prolonging exposure of the stomach to acid – another risk factor for stomach ulcers( ESGD and EGGD). Feeds high in starch also increase the risk of colic.
THE FOAL: INSULIN AND DEVELOPMENTAL ORTHOPAEDIC DISEASES: Blood glucose and insulin flow through the placenta from the mare to the developing foal. Here they influence the organs and systems that control glucose and insulin dynamics including the structure of the pancreas and the development of joint cartilage. After birth, foals of mares fed starch / sugar concentrates during pregnancy have higher insulin levels for up to 18 months of age. They are also more susceptible to osteoarticular lesions – including all forms of developmental orthopaedic diseases( DOD) such as bone cysts, physitis and OCD. Foals from mares on high sugar / starch feeds have abnormal insulin and inflammation from 160 days to 12 months of age.
This is the major risk period for developmental orthopaedic diseases and even moderate amounts of starch / sugar during pregnancy predispose the foal to osteochondral lesions between 7 and 12 months of age.
Both the amount of starch in the feed and the type of feed processing have a significant impact on blood glucose and insulin. The misapplication of these factors can result in abnormally high insulin levels and laminitis. Although horses in hard work and needing high grain intakes benefit from these processing methods – they are inappropriate for horses with insulin dysregulation ie PPID, EMS and pregnancy. And, it’ s not just the mare that experiences faster, higher and longer rises in insulin – it impacts the growing foal too. www. jenquine. com
The pregnant mare presents a difficult challenge since feed supplementation is indicated for at least the last 4 months to support rapid foetal foal growth. Being a broodmare has been identified as a risk factor for obesity and laminitis and it can be hard to manage increasing body weight in pregnant mares. Mares increase their body weight by around 15 % during pregnancy – with the majority gained between days 230 and 290 days gestation. The last third of pregnancy is the time of increased foetal foal growth – which often coincides
2025 AQHA YEARBOOK ~ MAY / JUNE ISSUE