Why bioavailability of trace elements is important in ruminants

A new third-generation source of trace elements can offer livestock significant health and production benefits.

Trace elements are only needed in very small quantities by food-producing animals but have an important role to play in maintaining antioxidant status, immune response, growth, and reproduction.

While the required intakes for supporting ruminant productivity and overall health may be small, sourcing the correct type of trace elements is key.

The bioavailability of a nutrient – the portion that is absorbed after it is ingested and utilised for normal physiological functions – has a huge impact on its value to the animal.

The bioavailability of a mineral from any feed depends on its accessibility, absorbability, retainability and functionality (Suttle, 2010).

Traditionally, inorganic salts, predominantly sulphates and oxides, or organic trace elements such as chelates, or those complexed to organic ligands or nano minerals, were incorporated into an animal’s diet.

Hydroxy trace minerals are a third-generation source which have been shown by Lu et al., 2010 and Shaeffer et al., 2017, to be more bioavailable than traditional sources and, as a consequence, have significant benefits to the animal.

Hydroxy trace elements are more soluble at the lower pH levels in the stomach and the small intestine where they are broken down, providing these essential minerals throughout the gastrointestinal tract. They provide higher absorption and bioavailability in ruminants (Shaeffer et al., 2017).

Other benefits of feeding hydroxy minerals include:

· Non-oxidative

· Insoluble in the rumen

· Greater palatability (Caramalac et al., 2017)

· Non-hygroscopic

· Free of dust

· Greater stability within feed

· No impact on essential nutrients such as vitamins and fats

Overall, hydroxy trace elements are cost-effective and more bioavailable to the animal.

In livestock feed, hydroxy forms of trace minerals are provided in the forms of copper hydroxy chloride (Cu2OH)3Cl), zinc hydroxy chloride (Zn5(OH)8Cl2) and manganese hydroxy chloride (Mn2(OH)3Cl).

It is commonly understood that copper has complex interactions with other trace elements such as molybdenum, sulphur and iron. These antagonists can, to varying degrees, reduce copper availability which often makes copper supplementation tricky.

When comparing hydroxy copper with copper sulphates, the hydroxy form has a much lower solubility in water (Miles et al., 1998). It also tends to be more resistant to interactions with antagonists such as molybdenum and sulphur in the rumen. Therefore, an hydroxy copper source should be more available for absorption following solubilisation in the acid environment of the abomasum. Other researchers (Vanvalin et al., 2019) also observed greater liver copper levels when comparing hydroxy source with inorganic trace element source. Poultry studies (Luo et al., 2005 and Kim et al., 2019) have also shown better bioavailability when hydroxy sources are used in broiler chicks and layers.

Hydroxy zinc is another desirable source compared to zinc oxides, as shown in a study that examined weanling piglet diets in enhancing growth performance at a lower dosage (1500 ppm) of hydroxy zinc, compared to 3000 ppm of zinc oxide (Zhang and Guo, 2007).

Similarly, in growing steers, Shaeffer et al. (2017) estimated the bioavailability of zinc from two different sources – hydroxy and sulphate. Steers were supplemented with either 25mg Zn/kg DM from either a hydroxy or sulphate source. The study showed an increased zinc bioavailability in the cattle supplemented with the hydroxy source, reflected by higher plasma zinc concentrations. The increased bioavailability of zinc from the hydroxy form compared to sulphates can be related with its lower solubility in the rumen.

A study by Wagner et al., 2016 found hydroxy forms of both copper and zinc to be effectively absorbed and utilised by yearling steers. The study showed that, compared to current industry feeding practices, they can be fed at a lower dose without negative impact on growth performance, carcass traits and liver zinc and copper status.

References

Caramalac LS, Netto AS, Martins PGMA, Moriel P, Ranches J, Fernandes HJ, Arthington JD, 2017. Effects of hydroxychloride sources of copper, zinc, and manganese on measures of supplement intake, mineral status, and pre-and postweaning performance of beef calves. Journal of Animal Science 95(4): 1739-1750.

Kim JW, Kim JH, Shin JE, Kil DY, 2016. Relative bioavailability of copper in tribasic copper chloride to copper in copper sulphate for laying hens based on egg yolk and feather copper concentrations. Poultry Science 95(7): 1591-1597.

Luo XG, Ji F, Lin YX, Steward FA, Lu L, Liu B, Yu SX, 2005. Effect of dietary supplementation with copper sulfate or tribasic copper chloride on broiler performance, relative copper bioavailability and oxidative stability of vitamin E in feed. Poultry Science Association 84(6): 888- 893.

Shaeffer GL, Lloyd KE, Spears JW, 2017. Bioavailability of Zinc hydroxychloride relative to zinc sulfate in growing cattle fed a corn –cottonseed hull-based diet. Animal Feed Science and Technology 232: 1-5.

Suttle NF, 2010. Mineral Nutrition of Livestock. 4th ed. CABI Publ., Wallingford, Oxfordshire, UK.

Vanvalin KR, Genther ON, Laudert SB, Hansen SL, 2019. Relative bioavailability of organic and hydroxy copper sources in growing steers fed a high antagonist diet. Journal of Animal Science 97(3): 1375- 1383.

Wagner JJ, Engle TE, Caldera E, Neuhold KL, Woerner DR, Spears JW, Heldt JS, Laudert SB, 2016. The effect of zinc hydroxychloride and basic copper chloride on growth performance, carcass charecteristics, and liver zinc and copper status at slaughter in yearling feedlot steers. The Professional Animal Scientist 32(5): 570- 579.