Mineral supplementation on the approach to calving

The final six weeks of pregnancy is the most critical phase in both the dairy and suckler cow production cycle. Nutritional management during this period has a major influence on the health and performance of both the cow and unborn calf, including post-calving fertility, which is fundamental to overall herd profitability.

In 2023, the average calving interval across the UK dairy industry was 394 days, representing nearly £43,000 of losses for a typical 250-cow herd.

Dry cow management

The foundation of dry cow management is to first ensure that cows are in the correct body condition score (BCS) of 2.5-3.0 at calving. This will help to prevent many of the common calving-related issues. Cows which are over-conditioned at calving will be at increased risk of dystocia and metabolic diseases such as ketosis, whereas cows which are under conditioned typically produce lower quality colostrum and have more problems getting back in calf. To ensure that cows are in the correct BCS for calving, we need to satisfy the cows appetite and fill-up the rumen, whilst controlling energy intake to prevent cows becoming overfat. Practically, this is achieved by diluting grass silage with low-energy forage such as chopped straw.

Providing the correct balance of calcium, phosphorus and magnesium is also essential. To help activate calcium mobilisation mechanisms in preparation for lactation, dry cow diets should contain a high level of magnesium (0.4%) and relatively low level of calcium (<0.3%) and phosphorus (<0.3%). Magnesium is also essential for the prevention of staggers in grazing cattle and will support an easy calving process as it is required for muscle contraction.

Milk fever

High yielding dairy herds with a greater risk of milk fever may consider altering the dietary cation anion balance (DCAB) of the diet through the addition of anionic salts and use of low DCAB forages. This approach to milk fever prevention is highly successful, however requires careful management, including regular forage mineral analysis and urine pH testing. The ration should be thoroughly mixed and feed intakes monitored closely, as anionic salts can be unpalatable.

The importance of trace elements

The correct supply of trace elements and vitamins is also essential for both the cow and calf. All these nutrients are essential for optimal health and productivity, however during the dry period, iodine, selenium and vitamin E are of particular importance for calf health and vigour. Copper is required for energy metabolism and uterus recovery post-calving, therefore has a major influence on subsequent fertility. Copper in the ration can be ‘locked up’ by a number of antagonists including molybdenum, sulphur and iron. This has implications for copper requirements, particularly in grazing cattle. Adequate levels of trace elements and vitamins are also important for colostrum quality, with colostrum production beginning around six weeks before calving. Other nutritional supplements such as mannan-oligosaccharides (MOS) and beta glucans derived from yeast can help support cow immune function to maximise nutrient partitioning into colostrum production, leading to improved colostrum quality for the calf.