Making silage for dry cows

18 June 2018

Producing good quality silage with a high nutritional value is always key to support the lactating cow’s milk yields.

However, as dry cow nutrient requirements are different from lactating cows, it is equally important to consider making silage more suited for the dry cow’s needs.

Traditionally, dry cows have been considered as non-producers in the herd and have not been as intensively managed as the lactating cow. However, we now know that many problems, such as retained placenta, mastitis, metritis, milk fever and ketosis, can be traced back to dry period management and nutrition.

As most dry cow diets are predominately silage based, the nutrients within silage will largely dictate the success of the diet. Therefore, producing a silage tailored for dry cows can help get cows off to a good start in lactation with fewer health problems and better milk production. This article aims to give some simple planning tips to make silage that is more suitable for dry cows therefore, helping to reduce problems around calving and increase herd profitability.

1. Potassium (K) content

The potassium (K) content of grass silage is recognized as an important issue because a high K concentration in dry cow diets is one of the major risk factors for milk fever. As K has a positive charge (cation), it counteracts the negative charge (anions) in the diet that help the cow control blood calcium levels. This is particularly important during the 3 to 4 weeks before calving.

Trouw Nutrition analysis of grass silages during 2017-2018 show an average K content of 2.45%. Grass silages with these K levels have the potential to cause health problems associated with subclinical milk fever, especially when fed during the last 3 to 4 weeks before calving. Trials from Australia and America show that when forages with these higher K levels are fed to dry cows, although anionic salts help, they cannot completely correct the dietary cation and anion balance to ideal levels. Therefore, producing grass silage with a low K level (target below 1.8%) is a major help in lowering the risk of milk fever and increasing cow health around calving.

Soil analysis can identify fields with low soil K. Trouw Nutrition can help with grass mineral analysis to identify grass with a low K content suitable for making dry cow silage. Generally, grass harvested from fields with no applications of slurry or K fertilizer, have a lower K content. It may take a few years before the grass K content declines to ideal levels. Letting grass mature more in the field before harvesting is also preferable because K content declines with grass maturity. Silage that is harvested later in the season tends to have lower K, but it must not have received any application of slurry.

2. Energy density

Studies show that if dry cows are in good body condition score and over-consume energy, they have reduced intakes after calving, higher body tissue loss and more health problems. Therefore, offering moderate energy diets helps to prevent this and silage harvested later in the season or from mature grass are more suited for dry cows (ME < 10.8 MJ/kgDM). However, if dry cows are in low body condition score, studies have shown that dry cow concentrates can improve immune function around the time of calving.

A good quality dry cow concentrate with the correctly designed mineral and vitamin pack is essential for dry cows. Always ask your local nutritionist for advice...