Horses grow up to around 7 years old. Their growth plates don’t fuse until they are 7 in some cases. The fetlock joints fuse early but the vertebrates in the back can take longer to fuse. Training youngsters may help bones as they go through a modelling and remodelling process of the soft bone. This could also be a disadvantage to the muscle as it wont have formed yet as the bone forms before the muscle. Turning out young horses is a good idea as they have light exercise.
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Rapid growth is undesirable, and it wont effect the ultimate height the horse ends up at. The foal should be adapted to hard feed before weaning by introducing creep feeds. If the change onto hard feed is abrupt then the horses average daily gain is usually lower. This causes the foal to have to catch up on growth and it can risk muscular skeletal problems. A fibre based diet is better and a bit of creep feed can be added to this. A probiotic may also be beneficial as this helps the foals hind gut digestion from the microbes, especially as these need to be adapted to the feed to be able to digest it.
Through the first winter a steady consistent growth is wanted. The appetite is around 2.5-3.5% of daily body weight. Rough pasture and good quality hay may be harder to come by in the winter so adding a compound feed may be necessary. This should be split into at least two meals. A typical compound giving to a foal contains no maize, oats and barley as they are deficient in amino acids and these are important for growth. Wheat is a good feed to be given if it is micronised. There is often soya in these feeds as this has a lot of high quality protein. Molasses is also in them as this contains a pre-caecally digested CHO. Calcium and phosphorus are also included in the correct ratios. For the yearlings first summer it is best to turn it out on good quality pasture. The compound feed may then be stopped. This will help their gut also.
Protein is important in their diet, for the bones. If they are deficient in crude protein they will have a reduced bone circumference and a reduced bone density. This will put more stress on the bone especially if they are ridden a lot or on hard ground.
Calcium and phosphorus is required at a ratio of 1.7:1. This helps the skeleton and gives it rigidity and strength. Deficiency of these can cause rickets in youngsters, bone fractures, developmental orthopaedic disorders, delayed plate closure and osteochondrosis dessicans which are small lesions where hardening of the bone has failed. Calcium can also be deposited in places such as the head if there is too much causing lumps.
Vitamin D is also important in youngsters. It helps to control calcium levels. A deficiency can cause osteomalacia (rickets) and an increased risk of fractures
Feeding youngsters is different to feeding horses at maintenance as it is very important they are receiving the correct levels of nutrients to help them grow correctly and avoid problems.