By Eliza MacKereth, Graduate TRAC Ruminant Productivity Consultant
Sulphur is a macro mineral necessary in the diets of many animals, in particular, ruminants. The macro mineral is commonly found in essential amino acids as well as in the B-vitamins thiamine and biotin. In the rumen, ruminal microbes reduce sulphur to sulphide, which is an important substrate used by rumen microorganisms for protein synthesis and other cellular functions1. Although excess levels of sulphide can limit cellulose digestion in animals when in high concentrations, sulphur supplementation is known to improve cellulose digestion and contribute to the synthesis of vital amino acids2. Although most ruminant diets, particularly pasture-based diets, have sufficient available sulphur, it remains a component that should be carefully considered when animals are receiving supplementary feeding or a TMR. It has been shown that in some cases providing additional dietary sulphur can lead to increased production3.
SULPHUR FEEDS AND SUPPLEMENTS + REQUIREMENTS
It is important for producers to understand which feeds and supplements contain high or low levels of sulphur, alongside the recommended daily intake of the target animal. Most ruminants need 0.18-0.24% DM of dietary sulphur content4, however this varies depending on the level of concentrate. The higher the proportion of concentrate in the animal’s diet, the lower the recommended amount of sulphur. The Beef National Research Council (NRC) recommends that sulphur intake shouldn’t exceed more than 0.3% DM for beef feedlot cattle and 0.5% DM in cattle with diets that have more than 40% forage.
Sulphur rich feeds:
Forages (i.e., legumes and brassicas)
Grains, oilseeds, and protein-rich feed ingredients i.e., soybean meal
Lucerne hay (variable depending on environmental factors & processing methods)
Water (varies depending on location)
Sulphur is commonly supplemented into diets through inorganic salts such as Epsom salt or less commonly, ammonium sulphate.
EFFECTS ON PRODUCTIVITY
Overall, wool producing sheep require higher levels of sulphur per kg of bodyweight compared to cattle. This is due to wool containing high levels of sulphur. The sulphur content of wool can range between 2.7-4.2%, depending on the diet5.
Sulphur Supplementation Effects:
Wool-producing sheep | Improved quantity + quality of wool6 |
Enterprise | Effect |
Dairy cattle | Improved production of milk solids, fat and protein |
Beef cattle | Improved weight gain and carcass grading7 |
A study investigating the effect of sulphur supplementation in cattle grazing pasture with a sulphur content of 0.08-0.12%, the group in which 18% sulphur content salt blocks were introduced noted live weight gain improved by approximately 200g/head/day8.
One of the main effects that sulphur has on productivity is the relationship between the concentration of dietary sulphur and dry matter intake. This relationship is positively correlated, and as intake drives production, it can be observed that the inclusion of sulphur supplementation in the diet where required can have significant effect on productivity.
DEFICIENCY + TOXICITY
Deficiency of sulphur in livestock is often caused by low-sulphur diets or the grazing of sulphur deficient pastures without adequate supplementation. Sulphur deficient pastures occur most commonly in areas that receive heavy rainfall, have recently been burnt, and in sandy or weathered soil.
Most commonly sulphur toxicity occurs due to high sulphur levels in water sources, and rarely occurs in pastures. Breakouts of sulphur toxicity, or associated illnesses such as polioencephalomalacia (PEM) often occur during hot weather periods, when the water intake of the animal is increased. If animals are showing symptoms of toxicity, they should be monitored, and feed testing should be performed.
SYMPTOMS + SIGNS
TOXICITY:
Physical symptoms:
Smell of hydrogen sulphide on breath
Anorexia
Loose manure- watery & black in severe cases
PEM (clinical sign)
Nervous system collapse due to excess hydrogen sulphide gas production within the rumen
Secondary copper deficiency
High dietary sulphur leads to decreased absorption of: Copper, Iron, Zinc and Selenium.
DEFICIENCY:
Poor growth
Loss of BCS (reduced appetite + weight loss)
Rough coat
Hoof irregularities
Increased salivation
RISKS LEADING TO PEM
PEM (polioencephalomalacia) is a neurological disorder that can be acute, and with rapid diagnosis, the animal’s symptoms can be reduced and in some cases the animal can recover. However, if the disorder is left untreated for a prolonged period, the damage may be irreversible.
Sudden transitions to high sulphur diets can lead to microbes producing high amounts of toxic hydrogen sulphide, meaning that high risk periods occur during ruminal adaptation.
Prevention of PEM includes avoiding sudden dietary changes, keeping total dietary sulphur below the recommended daily intake and increasing dietary roughage in high-risk groups.
SULPHUR IN WATER
The sulphur content of water should not be overlooked when incorporating sulphur into ruminant diets. Some water sources can have high sulphur content due to the presence of sulphur or magnesium sulphate salts. Sulphur-induced PEM cases are often closely associated with poor water quality. During times of hot weather when water consumption increases, sulphur toxicity and PEM cases increase throughout herds.
In summary, the macro-mineral sulphur plays a vital role in ruminant nutrition and should be carefully considered in all ruminant production systems. The role sulphur plays in the rumen is vital for cellular functions, and supplementation of the mineral should be considered to increase productivity. However, it is important to ensure the animals needs are met and not exceeded to avoid instances of toxicity or deficiency. Producers must carefully consider sulphur in terms of water quality, forage composition and supplementation. When considering these factors, it is also important that producers have an adequate understanding of the potential risks associated with sulphur toxicity or deficiency to allow them to better identify whether sulphur supplementation is an appropriate addition to their system and to allow early identification of inadequate dietary sulphur.
For more information or to discuss this article further,
please get in touch with your local TRAC Expert In Ruminant Productivity
on 08 8733 1888 or email us at info@totalresult.com.au
Our Consultants
EXPERTS IN RUMINANT PRODUCTIVITY
Tom Thorn
0427 243 319
Owen Rees
0429 437 823
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REFERENCES
1 (Shah, A.M., et. al., 2020), 2 (Silva, C.J.D, et.al., 2014), 3 (Tisdale, 1977), 4 (Kelzer, J., 2021), 5 (Broad, A., et. al., 1969), 6 (Tisdale, 1977), 7 (Hill, et al. 1984), 8 (Archer, K.A., et. al., 1978)
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