Feeding the Weanling
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Author: Dr Nerida McGilchrist | PhD Equine Nutritionist and Founder of My Happy Horse
Weanlings are funny little creatures, endlessly curious, prone to mischief and constantly walking the tricky balance between growing fast enough to achieve their genetic potential but not growing so fast that they end up with bone or joint disease.
And because of this balance that must be achieved between growth and skeletal health, their nutrition can be challenging. Enough but not too much energy, high quality protein and all the minerals they need in the correct ratios to ensure the minerals can be absorbed are the most important aspects of weanling nutrition.
This article discusses each of these dietary components in some detail and 3 methods for feeding weanlings in different circumstances are given.
ENERGY
The amount of energy (or calories) you provide in your weanling’s diet is what is going to determine how quickly your weanlings grow and how much body condition they are carrying. Growth rate and body condition in weanlings are, in my opinion, the two most important parameters to manage.
If you allow your weanlings to grow too quickly or carry too much body condition you will put them at increased risk of bone and joint diseases like contracted tendons and OCD. If your weanlings grow too slowly you may end up with stunted horses that don’t reach their genetic potential.
Ideal growth rate
Managing the amount of dietary energy a weanling eats allows you to manage how quickly your weanling is growing and how much body condition it carries.
The table below gives you a guide to how much weight a thoroughbred weanling should gain per day (please note these growth rates indicative for a horse expected to mature at 500 to 550 kg).
| Age | Average Bodyweight (kg) | Optimum ADG (kg/day) |
|---|---|---|
| 4 months (120 d) | 200 | 0.9 |
| 6 months (180 d) | 250 | 0.75 |
| 9 months (270 d) | 320 | 0.6 |
| 12 months (365 d) | 375 | 0.55 |
| 18 months (545 d) | 460 | 0.4 |
Maintaining steady weanling growth rates will reduce the risk of developmental orthopaedic diseases and ensures your weanlings grow to their full size.
To calculate average daily weight gains, weigh your weanlings at 21 to 28 day intervals. Weighing at shorter intervals increases the risk of a falsely elevated or depressed weight gain. Shorter weighing intervals mean that when the weanling last ate, drank, urinated or defecated will have a big impact on apparent calculated daily weight gains.
You can calculate average daily weight gain as follows:
Average Daily (weight) Gain (ADG) = (Current weight – previous weight) / days since previous weight was taken
Ideal body condition score
A weanling’s body condition should be maintained between 4.5 and 6 (on the Henneke System of condition scoring that uses a scale of 1 to 9) and shouldn’t be allowed to exceed a condition score of 6. IN a condition score of 4.5 the ribs will be JUST visible. At a condition score of 6 the ribs won’t be visible, but you only need to use a relatively light pressure to feel them.
Adjusting growth rate or condition score
If your weanling is growing slower than you would like, the amount and/or the digestibility of feed (and therefore dietary energy) you are feeding needs to be increased.
If your weanling is growing too quickly or is too heavy in condition, the amount of feed (and therefore dietary energy) must be reduced.
You must be sure to feed sources of dietary energy that are easy for young horses to digest. If you are feeding cereal grains and particularly corn and barley, they MUST be cooked before they are fed (e.g. extruded, micronized, steam flaked, boiled).
Oats doesn’t need to be cooked but it is best fed rolled or steam flaked as many young horses don’t chew oats well enough to be digested and you will find large numbers of undigested oats in these weanling’s manure.
High energy fibres like beet pulp, soy or lupin hulls and copra meal can also be used for weanlings and will have the added benefit of adding fibre variety to their diet. This fibre variety should then help to support microbiome diversity which has been shown to be important for future performance potential (Leng et al 2024).
PROTEIN
For me, the quality of protein in a weanling’s diet makes the biggest visual difference to how they look. Weanlings on high quality protein diets will be muscular and well developed. Those on poor quality protein diets often appear underdeveloped and ‘weak’.
Because a weanling is growing and developing, protein and protein quality are critical in ensuring you are providing all the right building blocks for growth and muscle and bone development.
Not providing enough protein, or providing poor quality protein will result in a stunted weanling with poor muscle development. Low protein diets can also contribute to weanlings becoming fat, as they don’t have the building blocks to grow, so instead they lay down all their excess dietary energy as body fat.
High quality forages and particularly alfalfa/lucerne can provide much of a weanling’s daily protein requirement. Where additional supplementary feeds are needed, soybean or soybean-based feeds are the best source of protein for growing horses as they contain high concentrations of the essential amino acids needed for muscle and bone development.
Canola meal, lupins and faba beans are also good sources of protein.
Cottonseed meal should be avoided as its content and availability of the most limiting amino acid, lysine, is poor. Weanlings on cottonseed meal-based diets (common in Australia where it will often be listed on feed labelling as ‘vegetable protein meal’) are frequently poorly muscled and underdeveloped.
Traditionally, breeders have sometimes feared feeding protein to their growing horses for fear of causing developmental disease in the bones and joints. But it is important to remember, protein itself does not cause developmental orthopaedic diseases and restricting protein intake below requirements will stunt growth as well as affect bone and muscle development.
Overfeeding protein however will have the effect of increasing energy intake beyond requirements and cause rapid growth rates and an increased risk of developmental orthopaedic disease. Your weanlings need enough, but not too much high-quality protein.
MINERALS
Minerals play a MAJOR role in determining the future structural soundness of your weanlings. Failure to meet your weanling’s mineral requirements, and particularly calcium, phosphorous, magnesium, copper, zinc, manganese and sodium means your weanling won’t have the necessary nutrients to build sound bone and cartilage. Deficiencies of other minerals like iodine and selenium can also limit growth rates and contribute to muscle disease.
I am yet to analyse a pasture or hay sample that contains a concentration of all these minerals high enough to meet a weanling’s requirements. In addition, most improved pastures I have analysed have an unbalanced calcium to phosphorus ratio, with phosphorus commonly higher than calcium when the grasses are in their vegetative phase and growing rapidly. This mineral imbalance is sometimes severe, with calcium to phosphorus ratios as low as 0.3: 1 observed!
When phosphorus is higher than calcium, it puts weanlings at high risk of a phosphorus induced calcium deficiency. And this puts them at very high risk of developmental orthopaedic disease.
Meaning a weanling will ALWAYS need to be supplemented with minerals at the very least to meet requirements and balance mineral ratios.
There are a few ways to add minerals to your weanlings’ diet.
Depending on your weanlings’ need for additional calories, minerals can be supplemented in the form of a complete feed, where the minerals are mixed in with a sweetfeed/textured feed, cube or pellet.
Alternatively, minerals or can be fed as a low dose rate mineral supplement or balancer pellet. Weanlings should also always have access to a salt lick.
And in the situation where you need to balance the diet’s calcium to phosphorus ratio, my best success in doing this and reducing the incidence of bone and joint diseases like OCD is to use a feed/balancer pellet in conjunction with lucerne/alfalfa hay. The alfalfa hay helps to increase calcium intake while also reducing phosphorus intake as weanlings will typically eat less of the high phosphorus pasture when the hay is fed.
VITAMINS
Vitamins are essential for all horses and weanlings are no exception. Failure to meet vitamin requirements can slow growth rates, affect feed intake and predispose the weanling to infectious diseases.
Weanlings grazing green pasture and supplemented with a good quality complete feed, supplement or balancer pellet will generally have their vitamin requirements met. If you are feeding weanlings under drought conditions, particular attention must be paid to their vitamin intake as it is green pasture that usually provides a majority of their vitamin intake.
Three ways to feed
There are three main ways I use to feed weanlings. These are:
Balancer pellet plus forage – in situations where there is an abundance of pasture and growth rate is fast enough (or too fast) on pasture alone, using a high quality balancer pellet together with some lucerne/alfalfa hay allows you to meet mineral requirements, balance mineral ratios and meet essential amino acid requirements without overfeeding energy.
When feeding using this method, it also allows you to add higher energy and protein ingredients to the diet to maintain growth as pasture quality drops. For example, oats, extruded barley, stabilised rice bran, lupins, beet pulp, soybean meal or well-cooked full fat soybean, copra meal, oils or other suitable and available ingredients may be added to the diet to increase energy and protein intake as pasture quality drops.
Complete/fortified feed plus forage – When pasture quality is not as good and/or during winter when weanling growth tends to slow, a feed can be used at up to 1% of a weanling’s bodyweight per day. This is equivalent to 2.5 kg/day for a 6-month-old, 250 kg weanling.
It is important to ensure that if the feed is grain based, the feed has been well cooked to ensure proper digestion of the starch.
Concentrate feed or feed + balancer pellet – in situations where you need more than a balancer pellet, but less than the full amount of a fortified complete feed, you can use a concentrated feed that has a lower feeding rate OR you can use a combination of a feed + balancer pellet, adjusting the amount of each to keep mineral intake balanced as your weanlings’ requirements for energy and protein increases or decreases.
For example if your weanling needed just a little bit more energy than a balancer pellet could provide, you may give 1/3 the feeding rate of a complete feed, PLUS 2/3 the feeding rate of the balancer pellet. If your weanling needs more energy, you may change this to ½ the feeding rate of both the feed and the balancer.
Or, easier still, use MyHappy.Horse to design and balance diets for you!!
Let them grow!
All too often I see young horses underfed because their owner is so petrified of bone disease. The key to growing out sound young horses is to feed a balanced diet, NOT a restricted diet.
If you feed correctly to maintain a steady growth rate whilst meeting all the youngster’s protein, mineral and vitamin requirements, the risk of bone and joint disease is radically reduced.
Feeding correctly in the first 12 months of a horse’s life gives you the best chance at having a well grown yet sound horse in the future.
Good luck, have fun and be sure to use MyHappy.Horse to really get weanling nutrition right! 😊
About the Author
Dr Nerida McGilchrist
Dr Nerida McGilchrist is an Australian equine nutritionist with a PhD and over two decades of experience. As the founder of Equilize Horse Nutrition, and advisor to some of the world's largest nutrition companies, she’s built an international reputation for blending science with practical solutions. Now, she’s bringing her expertise to My Happy Horse to make advanced nutrition accessible to all.