The Importance of Sodium in Ruminant Production Systems

Eliza MacKereth
Oct 1
5 min read

By Eliza Mackareth, TRAC Ruminant Productivity Consultant

Sodium is a crucial dietary component for ruminant animals. Important bodily functions, such as nerve and muscle function and water balance/osmotic pressure, require adequate levels of sodium. Sodium is absorbed by ruminants through the diet and only small quantities can be stored in the body. For this reason, consistent and regular dietary sodium intake is key.

Sodium is lost through sweat, milk, saliva, faeces and urine. These losses increase during hot weather and stress events; hence, it is important to consider dietary sodium levels during these periods. Sodium in saliva assists in maintaining ruminal pH through acting as a ‘rumen buffer’ in the form of sodium bicarbonate. Salivation, which is stimulated by long fibres and rumination, occurs regularly throughout the day; hence, a consistent intake is necessary.

Some inland soils are known to be sodium-deficient, which can often lead to the production of sodium-deficient pastures or forages. It is important to perform forage testing and tissue testing on dietary components to comprehend whether sodium deficiency is a risk factor for your herd.

Which Feeds

Sodium content of pastures can vary greatly depending on variety, stage, soil type, and season. Sodium is not essential for pasture growth in many varieties, yet it is still absorbed by many species. Maize, lucerne and kikuyu are known to be often low in sodium in both pasture or ensiled forms, regardless of soil content. It is best to assess Na content through forage testing.

Some feeds that are high in salt are:

Fodder beet – 0.4%
Chicory- 0.2%
DDG pellets- 0.3%*

*byproducts can vary greatly

Supplements

Sodium supplementation can come in many forms; however, the most common form is in sodium chloride (salt). Sodium chloride contains 40% sodium. Supplementation can come in many forms such as drenching, dusting feeds or loose lick forms. Loose lick is best as animals are able to consume adequate amounts as needed in a timely manner. Salt lick blocks contain many binders; therefore, they are time-consuming for animals who are otherwise grazing or ruminating. Loose lick salt can be presented as straight salt or can be presented in a mineral mix with other vital minerals. In grazing-based systems, it is often best to provide salt separately rather than using practices such as dusting forages, as when salt is not measured correctly or distributed evenly throughout the feed, issues surrounding palatability may arise. Although it is very effective to drench with salt, salt is lost rapidly through the body each day, so it is best to supplement little and often.

Deficiency & Toxicity

Ruminants have a high tolerance for sodium and can self-regulate intake, meaning it is highly unlikely for sodium toxicity to occur. However, sodium deficiency is a common occurrence in herds and can often go undiagnosed.

Some signs include:

Licking of coats
Reduced appetite
Reduced water intake -
(water intake = milk production & DMI)
Severe deficiency can lead to dehydration
Pica
Weight loss

Lack of sodium can also lead to reduced rumen functionality due to lower levels of saliva buffering meaning ruminal microbes are more likely to be affected by pH changes.

Effects on Productivity

Throughout multiple trials that have been undertaken, sodium supplementation seems to have a positive effect on productivity. In Figures 1 and 2, it can be seen that a significant increase in the litres of milk was seen, however, no significant difference was seen in the components of the milk. This trial was undertaken using salt drenching, and a response was seen after 2 weeks. Other trials have noted a higher Na:K ratio in the saliva; higher sodium in saliva has a positive effect on buffering due to the production of sodium bicarbonate. Other trials have noted no difference in LW in milking cows; however, there are links to increased DMI, thus sodium supplementation could be useful in body condition/weight gain of non-lactating animals.

Requirements

Lactating dairy cow = 0.2% of DM

Cows produce 150L of saliva/day- hence need lots of sodium for buffering

It is important to keep in mind that sodium has an antagonistic relationship with potassium, magnesium and calcium, therefore additional sodium should be provided in diets that are high in these minerals.

Cellular

Sodium is the principal cation in extracellular fluid; therefore, it has a big influence on osmotic pressure and maintains water balance in animals. It plays a role in the movement of solvent molecules (i.e., water) across the cell membrane and throughout the body/cells.

One of the most important cellular functions that sodium plays a role in is the sodium-potassium pump, which is important for maintaining membrane potentials. An example of a membrane potential is that the difference generated by the Na:K pump creates an electrical gradient that is crucial for both nerve transmission and muscle contractions. The Na:K pump transports 3 Na ions out of the cell and 2 K ions into the cell, or vice-versa. Cells can swell if the concentration of Na in the ECF (extracellular fluid) is lower than intracellular fluid.

Sodium also aids in regulating the acid-base balance in the ECF, therefore maintaining the cell pH. It does this through the sodium-proton exchanger which assists in the regulation of cell pH, volume and intracellular sodium concentration. Sodium is also essential for the absorption of glucose, galactose, peptides and AAs. It is known to increase the gastric absorption of calcium in the abomasum.

Sodium Mineral Interrelations

Sodium is known to have relations with many other minerals, in particular potassium. Potassium’s antagonist relationship with sodium means that high dietary levels can decrease sodium absorption. This is important to consider when applying fertilisers that are high in potassium. It is important to consider tissue testing or additional sodium supplementation when high potassium fertilisers are applied. Often cases of low iron are found to also be deficient in sodium.

Sodium Content In Water

Sodium can often be present in varying concentrations in water supplies. It is always recommended to assess the salinity of water sources in livestock production systems. If the sodium concentration of the water is too high, animals may refuse to drink the water, leading to a loss of production. Reduced water intake leads to reduced feed intake, therefore inhibiting productivity. It is important to regularly test water quality at all water points, especially in bores and dams. If sodium levels are high, in some cases it may not be necessary to supplement sodium.

Summary

Sodium supplementation can have a significant productivity increase in ruminants, as well as assisting with cellular processes that are vital in maintaining animal health. The amount of sodium that an animal intakes per day is dependent on a variety of factors such as feed types and amounts, water quality and sodium supplementation. To determine the intake, testing must be undertaken on both feed and water. It is also recommended to monitor animals for any signs of sodium deficiency to ensure early detection and allow intervention through supplementation. Given the role that sodium plays in the health and productivity of livestock, it is evident that all producers should consider evaluating both dietary sodium levels and water quality before providing sodium supplementation where necessary.

To discuss Sodium in your Ruminant Production System,

please get in touch with your local TRAC Expert In Ruminant Productivity today,

on 08 8733 1888 or email us at info@totalresult.com.au