Extreme weather can increase the trend for people to add large amounts of salt to their horse’s daily feeds, despite actual requirements or what may be coming from the rest of their diet. While horses need sodium or chloride to continue to sweat, it’s important to remember that commonplace blanket recommendations like “add 10g of salt per 100kg of bodyweight” don’t take into account a horse’s specific condition.
Take this horse’s diet for example, shown in the graph below. If we add 10g/100kg of bodyweight to his diet, his sodium intake is well over 200% of what he needs. In extreme heat conditions, this may well be accurate, but once it cools off, this is way more sodium than he needs.
What does excessive salt do to the bacteria in their gut? Salt is, after all, one of the best-known and most widely used anti-bacterial agents in the world.
A paper published in ‘Nature’ (one of the most reputable journals in the world) showed that in both humans and mice, adding more salt than normal to a diet affected the gut bacterial populations – in some cases even entirely wiping out certain strains of bacteria. The researchers were then able to link those shifts in gut bacteria to high blood pressure, which may help to explain the link between high salt diets and hypertension.
For horses, feeding excessive salt is unlikely to have any benefit and may be negatively affecting the good bacteria in your horse’s gut. When using FeedXL, be sure to meet but not exceed your horse’s requirement for sodium with salt that is added to the diet. Then leave free choice salt out so that they can top up any extra requirements they may have.
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Comparison of equine dietary iron requirements to iron concentrations of 5,837 hay samples
N. Richards and B.D. Nielsen, 2018
Introduction
Iron is essential for the production of red blood cells. According to the 2007 Horse NRC, Fe requirements are 50 ppm for growing foals, lactating and pregnant mares, and 40 ppm for all other classes of horses. The 2005 NRC suggested a maximum tolerable Fe concentration of 500 ppm using data from other species. It is claimed that excess dietary Fe is causative of horses becoming insulin resistant.
Athletic horses, and particularly those in Thoroughbred racing, are often supplemented with Fe in an attempt to improve performance. Supplementation is commonly carried out without any formal analysis of the diet to determine if additional iron is required. Forages are typically high in iron and supply a majority of iron in all equine diets.
This study looks at the iron concentration in forages typically fed to equines and whether iron from forage is enough to meet the iron requirement of an athletic horse.
Methods
Nutrient concentrations from hay samples submitted for analysis in 2017 and for which Fe was measured were obtained from Equi-Analytical representing 3,060 grass, 1,193 legume, and 1,584 mixed hay samples.
Iron concentration was measured using inductively-coupled plasma mass spectrometry (ICP). Analysis methodology is available from Dairy One. Statistical analysis was performed using Proc MEANS of SAS.
Results
Iron was highest in Legume and Mixed Mainly Legume Hays and lowest in Grass Hay (Table 1). All hay types had a mean iron concentration more than five times that required by athletic horses and a median iron concentration more than three times.
From all hay samples (n = 5,837), 707 contained Fe at or above the suggested tolerable threshold of 500 ppm, while only 81 contained Fe at less than 50 ppm. Further, only 15 contained Fe at less than 40 ppm.
Discussion
A 500 kg horse in heavy work has an iron requirement of 500 mg/day (NRC 2007; based on a daily feed intake of 2.5% bodyweight and a requirement of 40 ppm). Forage intake is often restricted by Thoroughbred trainers. But even when fed at 1% of bodyweight to a 500 kg horse, these hays will supply an average 1,060 mg to 2,230 mg of iron per day, supplying more than 200% of daily iron requirements in the forage component of the diet alone.
Fortified grain concentrates are fed at an average 2.5 kg/horse per day in Australian Thoroughbred racing stables (Richards 2003). These concentrates have an average iron concentration of 190 ppm (FeedXL.com), adding an additional 475 mg/day of iron to the diet of these horses. Almost 60% of Australian Thoroughbred trainers then add an iron supplement to their horses’ diets (Richards 2003). It is expected similar trends would be found in the USA.
Based on this broad diet analysis, forage is able to meet the daily iron requirement of athletic horses. When iron from fortified feeds and supplements is added, there would be few racehorses receiving less than 300% of their daily iron requirement. It’s not unexpected that many horses would be receiving in excess of 500% of their daily iron requirement
What About Insulin Resistance
Given the dearth of Thoroughbred racehorses that are insulin resistant, despite Fe supplementation in combination with diets that can easily supply amounts beyond requirements, it seems unlikely excess Fe causes insulin resistance. However, it is recognized insulin resistant horses may have elevated serum ferritin.
References
Council NR. Nutrient Requirements of Horses: Sixth Revised Edition. Washington, DC: The National Academies Press, 2007.
Richards N, Hinch G, Rowe J. The effect of current grain feeding practices on hindgut starch fermentation and acidosis in the Australian racing Thoroughbred. Aust Vet J 2006;84:402-407.
HUGE THANKS to Equi-Analytical for providing the data to write this paper, which was presented as a poster at the recent International Conference on Equine Exercise Physiology (ICEEP).
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Sunbleaching in horses appears to be influenced by a combination of sun exposure and sweat.
An unintentional experiment
One of our Nutritionist’s horses lives in a region where flies are prevalent, so the horses wear fly masks during the daytime. They also experience extreme heat, reaching temperatures upwards of 40 degrees Celsius (100°F), which has caused significant sweating behind the ears where the mask straps sit.
A striking observation from this experiment is evident in a liver chestnut horse prone to summer bleaching. Areas where the horse sweated around the mask strap have bleached severely due to the combined effect of sweat and sunlight exposure. Interestingly, under the strap where no sunlight reached, the coat color remains unaffected. This phenomenon highlights the role of sweat in enhancing sunbleaching patterns.
Additional bleaching could be found around the flanks and shoulders, areas where sweating is more pronounced. This reinforces the correlation between sweat, sun exposure, and the resulting bleaching effect, despite adequate dietary intake of copper and zinc, as confirmed by FeedXL and pasture analysis.
It’s notable that another horse, with a distinct coat type characterized by different color, length, thickness, and texture, does not experience any bleaching whatsoever. This suggests that certain coat types are more susceptible to bleaching than others, influenced by both genetics and environmental factors such as climate.
In conclusion, sunbleaching in horses appears to be a complex interaction involving sunlight, sweat, specific coat characteristics, and regional climate conditions. Understanding these factors can help horse owners better manage and protect their horses’ coats during periods of intense sunlight and heat exposure
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Setaria should really be classified as toxic for horses. It is a subtropical pasture with such high levels of oxalate that it makes it almost impossible to prevent Secondary Nutritional Hyperparathyroidism (Bighead disease) in horses grazing this grass.
Grasses like kikuyu and buffel grass readily cause bighead disease with an oxalate content of around 15 g/kg. Setaria contains anywhere between 30 and 80 grams of oxalate per kg of (90% dry matter) pasture… which translates to HUGE amounts of calcium being needed to balance the calcium to oxalate ratio to prevent bighead.
We have seen horses go from normal to severely affected in a matter of months on setaria. So if you have setaria in your pasture you need to be very aware of what you are feeding and how well this is meeting calcium (as well as phosphorus and magnesium) requirements.
FeedXL will help you in calculating the calcium to oxalate, calcium to phosphorus and calcium to magnesium ratios to keep your horse healthy. BUT, the first step is identifying that you have this grass in the first place so you know you need to be on your game with managing nutrition!
Here are some photos (below) of setaria on the NSW mid-north coast… setaria everywhere! Please take a look at the photos and then in your paddocks to see if you have setaria. And if you do, please do something sooner than later to prevent severe and often life-threatening calcium deficiency.
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Teff Hay seems to be gaining popularity as a hay option for many horse owners and because it is sold as a low starch low sugar hay it is starting to be recommended in place of Rhodes Grass Hay.
BUT, if you are lucky enough to have access to Rhodes Grass Hay, here are some things to think about before considering a swap:
1. Rhodes Grass Hay is low in oxalate, containing approximately 2.5 to 3 g/kg of oxalate.
Teff Hay is moderate to high in oxalate at 10 to 12 g/kg. This means Teff needs careful supplementation of calcium, phosphorus and magnesium to prevent it from causing Bighead Disease. With Rhodes being so low in oxalate Bighead is not an issue (though you do still need to make sure you correctly balance the diet for minerals and vitamins as forages rarely contain enough to meet a horse’s requirement).
2. Rhodes Grass Hay is more reliable and consistent when it comes to the low starch, low sugar characteristic.
From the analyses we have seen coming through here at FeedXL, Teff can be high in starch, with one analysis sent through showing an as-fed starch content of 7.1% and total NSC of 13.7% which, for a laminitic horse, is going to be too high. While soaking would more than likely bring this non-structural carbohydrate (NSC) level back down to safe levels it makes for much more time-consuming feeding… so if you have access to Rhodes Grass it would be much easier to use this.
3. Teff Hay causes some odd behavioural issues in some horses and this is normally associated with an alkaline fecal pH.
We have no way of explaining this, and it doesn’t happen with all horses on Teff so I don’t know if all Teff Hay is the same or if there is a certain variety that causes this issue.
So, while Teff gives people in cooler climates a low NSC option which is welcome, it is not yet well understood and not without its issues. If I had a choice between Teff and Rhodes I would go with Rhodes Hay every time.
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