Why do cattle eat soil and stones?

19 June 2020

Over recent weeks, some farmers have reported cattle eating soil and stones from hedges and laneways.

This is a condition called pica and can be serious as some cattle can die after ingesting so much foreign material.

It is difficult to find any strong research on pica as it does not regularly occur on farms however, there are a few on-farm scenarios that are associated with this condition.

 1. Ketosis 

Pica can occur in early lactation dairy cows, generally in the first 2 weeks after calving. If the high-yielding cow’s energy requirement is higher than the energy supplied by the diet, this results in negative energy balance. To try to meet the energy demands, the cow breaks down body fat to use as a source of energy and one of these breakdown products is ketones. High ketone levels in the blood is termed ketosis. Although relatively rare, these blood ketones can result in pica. However, there are usually other obvious signs as well, such as a strange gait or walk, staggering and even aggressive behavior.

 2. Acidosis

Fibre is an important part of the diet to maintain rumen health. Although the rumen can function on low fibre levels, it takes time for the rumen bacteria to adapt. Rapid changes in grass fibre content, even between fields, can result in rumen acidosis and pica. Other signs of rumen acidosis to watch out for are milk butterfat depression and loose manure. If rumen acidosis is the reason for these signs, your nutritionist may recommend some buffer feeding around milking time to increase the fibre intake.

 3. Low Sodium

Salt, and in particular sodium deficiency is associated with pica. Grass sodium concentrations are typically at their lowest during the summer months (see the green line in Figure 1). Heavy slurry applications are associated with high levels of potassium and low sodium contents. If cattle diets are heavily reliant on grass with a low concentrate intake, this can result in low blood sodium levels for the cattle. You can ask your nutritionist to send grass samples to the Trouw Nutrition lab for mineral analysis or ask your vet to take some blood samples to check for blood sodium concentration.

 4. Low Phosphorus

Grass phosphorus concentrations are also typically at their lowest during the summer months (see the blue line in Figure 1). Periods of lush grass growth can be associated with low phosphorus concentration in grass and this can contribute to low blood potassium levels if concentrate intakes are low. Trouw Nutrition’s mineral analysis will measure grass phosphorus concentrations otherwise, your vet can take some blood samples to check for blood phosphorus concentrations. It is important to check phosphorus levels first and only supplement to the appropriate levels.

 

In summary, pica can be seen in individual cows with ketosis, and in multiple cattle in herds with acidosis and low sodium or phosphorus levels. Your nutritionist or vet can help you find out which is most likely and put the corrective measures in place.

 

By Dr Mark Little, Technical Manager