Qualities of Hay
Oaten and lucerne hay is well regarded by farmers for its fibre content, energy value, and palatability for livestock. These features are incredibly important for ruminants, like cattle, deer, sheep, and goats, as their digestive systems are unique.
The Nutrient Requirements for Dairy Cattle from the National Research Council indicates that extreme potassium deficiency in lactating cows (defined as 0.06% to 0.15% potassium in the diet on a dry matter basis) results in a decrease of potassium in plasma and milk, and a substantial reduction in feed intake decreased weight gains and diminished milk production.
It is therefore important that we provide an adequate level of potassium to dairy cows to meet nutritional and welfare goals. According to Dr. Dan Undersander, an extension and research forage agronomist with the University of Wisconsin, the degree of potassium required varies depending on whether or not the cow is dry or lactating and whether or not the cow is close to calving.
In a dry cow we’d like to see the potassium degree level in the hay in the 2-2.5% range,” he explains. “But we want potassium degrees levels above 2.5% up to 4% when they’re milking.
Source of quote.
When Potassium is Needed…and When It Isn’t
Providing a higher level of potassium in early lactation diets (<75 days of milking) is important. Research suggests that cows can frequently be poor in potassium in their early lactation period as this cohort excrete more potassium than in other lactating phases. Increasing the level of potassium in the diet at this early lactating phase, studies suggest that this can help improve milk production, milk fat production, and composition.
While higher potassium levels are important to optimise milk production and quality at many stages of a dairy cow’s life, there is one crucial stage where low potassium diets are favoured: in the weeks preceding calving.
In the 3-6 weeks just prior to calving, massive quantities of calcium are transferred from the cow’s blood to her mammary gland to be part of the colostrum the calf requires after birth. A high potassium diet (a cationic diet) increases a cow’s blood alkalinity, which interferes with this calcium mobilisation and absorption. This leaves the cow vulnerable to hypocalcemia, or milk fever, and is a major cause of downer cows. It is essential that potassium levels are not excessive at this time prior to calving.
How to Influence Potassium Level In Forages
Undersander and others emphasise that, whilst it takes planning and effort, it is possible to produce a supply of low-potassium forages that dry cows require.
Some suggestions include:
• Soil testing – High-producing fields must be sampled each year, due to the fact that nutrient composition rapidly changes in these type of fields, and potassium levels in forage will correspondingly fluctuate.
• Plant testing – Discover which fields produce high potassium forages suitable for cows in their early lactating phase, and which fields produce the lower potassium fodder required in the dry cow diet during the pre-calving stage.
• Early vs Mature cuttings – A young plant has a greater mineral content material than a more mature plant. By cutting hay at a more mature stage, you will have a correspondingly lower potassium level than an earlier cutting.
• Cutting height of lucerne – Potassium tends to accumulate at higher concentrations in the stems than the leaf of lucerne, especially in the higher stems.
• Rain Affected Hay – As potassium is a water-soluble mineral, hay that has been rained on will have had potassium leach out of the product.
• Fertiliser – Potash fertilisers provide a high-quality source of potassium to crops. Potassium is a key nutrient required for optimal stand health, quality, and yield in lucerne crops.
