Christine King BVSc, MANZCVS (equine), MVetClinStud
Beware of cereal hays and chaffs
be careful with oaten, wheaten, and barley hay/chaff
Cereal hays include oat ('oaten'), wheat ('wheaten'), and barley. These hays are sold by the bale and they are chopped and sold as chaff for horses, either as plain chaff (e.g., oaten chaff) or in various combinations with each other and with lucerne (e.g., a common "triple chaff" combo contains oaten, wheaten, and lucerne chaff).
Except for lucerne, these plants are all part of the large family of Grasses (Poaceae or Graminae). The cereal subgroup consists of the Grass species that have been carefully cultivated as food crops for humans — i.e., for the production of grain (oats, wheat, barley, corn, rice, sorghum, rye, etc.). Herein lie their upside and their downside...
Cereals grow in a wide range of geographic areas, and they store well after harvest (when properly dried), so cereal hays/chaffs are widely available throughout the year.
In fact, sometimes cereal hays are the only decent-quality hay/chaff available — unless you've made the effort to find a reliable supply of good quality grass hay, which I highly recommend.
It is mostly tradition and the perpetual cycle of consumer demand (customers will continue to buy whatever is available and request what they're used to) that keeps hay growers focused on legume and cereal hays instead of grass hays. But the more horse owners request good quality grass hays of hay growers and feed merchants, the more widely available grass hays will become.
Their origin as grain crops is also their biggest downside, because cereal hays and chaffs can be too high in sugars for many horses. While small amounts are generally well tolerated, these hays and chaffs can pose serious risk when they are the main or sole forage fed to horses.
Here is where things get a bit fuzzy, because there is no standard stage of harvest for cereal hays. As a result, the nutritional values for these hays, and chaffs made from them, cover a vast range.
For example, the following graph shows the average nutrient content of three different cereal hays over the past two growing seasons (2019-20 and 2020-21), as reported by the Feed Central feed testing lab in Toowoomba, QLD.
Source: Feed Central newsletter, May 2021
NDF, neutral detergent fibre; ADF, acid detergent fibre; CP, crude protein; ME, metabolisable energy (Mj/kg DM); WSC, water-soluble carbohydrates. Except for ME, all values are percentages, on a 100% dry matter basis (water removed).
I'm particularly interested in the averages for WSC, or water-soluble carbohydrates. These are the most problematic components of pasture grasses and of hays and chaffs in carb-sensitive horses. Water-soluble carbs include the simple sugars, oligosaccharides, and fructans that increase a horse's risk for laminitis, obesity, digestive disorders (colic, diarrhoea), behavioural problems, and exercise-related muscle damage ('tying up'), just to name the most common problems.
As a general rule, carb-sensitive horses need a diet that contains less than 10% WSC. Notice that in both years, the average WSC for all three of these cereal hays was well above 10%. These hays would not be a good choice as the primary forage for carb-sensitive horses.
But those are just the average values. I asked Feed Central to send me the range of WSC values (minimum to maximum) for the samples they tested:
Source: Feed Central, supplied on request.
All values are percentages, on a 100% dry matter basis (water removed).
For each of these cereal hays, the minimum WSC was below the threshold of 10% in both years, although it was close for barley and wheaten hay last year.
More disturbing is the maximum WSC, which ranged from about 29% to almost 40%. These values are 3 to 4 times higher than recommended for carb-sensitive horses.
Perhaps the biggest problem is that it's impossible to tell just by looking at a cereal hay or chaff what its WSC content is.
That goes for most other nutrient values as well, including crude protein. The average crude protein values in the graph above (9–11%) are adequate for the needs of most adult horses who are not pregnant or lactating. But those are just the average values; the minimum values will likely be too low for even the most inactive horse.
Test or leave
I'm a big fan of forage testing to determine the nutrient content of pastures and hays. That said, unless you're buying large quantities of cereal hay or chaff, it's generally not cost-effective to test it before you buy or feed it.
If you have a horse who would benefit from a low-WSC diet (which is most of them), it would probably be best to limit or leave the cereal hays and chaffs, and do your best to find some good-quality grass hay instead. The more cereal hay or chaff you feed, the more likely you are to run into problems if that hay/chaff is high in WSC.
The more we request good quality grass hays from hay growers and feed merchants, the more consistent the supply will become and the broader the range of options there will be. It may take us a few years to get there, but market forces are powerful things!