The dry period lasts for six to eight weeks, and can be divided into two periods, the so-called Far-off period and the Close-up period. The Far-off period begins at the start of the dry period up to three weeks before calving and functions as a time for healing of the udder tissue and any udder infections. The Close-up period begins three weeks before calving up to calving itself and focuses on preparation for the next lactation. The main overarching goal during the dry period is to ensure that the next lactation runs as smoothly as possible.
Figure 2. Overview of lactation cycle of dairy cattle
There are various approaches to the best method and moment of starting a dry period, and whether it is even particularly useful. But it is in any case important that the cow doesn’t produce too much milk at the point at which she goes dry, preferably less than 12–14 litres a day. If a cow exceeds this limit, they run the risk of udder infection. To achieve such low production, it is important to reduce concentrate rations and to milk the cow less often. Also, if possible, it is sensible to lower the protein supply in the feed of these animals to suppress milk production.
The use of dry-period injectors is the most common form of inducing a dry period. It is important here to first milk the cow dry and to work hygienically. Use enough alcohol for this and wear gloves. This reduces the risk of udder infections. The use of udder care products is recommended as this type of product promotes the circulation of the udder, ensuring the more effective removal of bacteria and dead udder tissue.
Good feed during the dry period is essential to ensure that the next lactation is effective. Cows with a high condition score will burn excess fat in early lactation to meet their energy requirements. This increases the risk of ketosis. However, the animals must not become too lean during the dry period as this often comes at the cost of the milk production that follows calving. So it begins with the correct condition score when the cow enters the dry period, with a condition score of around 3.5 being taken as the best target. Figure 3 below shows the ideal BCS (Body Condition Score) progression during lactation (Friggens et al. 2004).
Figure 3. BCS progression during lactation (Friggens et al. 2004)
During the dry period, adequate structure-retaining feed must be supplied with a crude protein concentration of between 12 and 14 percent (Schothorst 2011). For heifers, the preference is to provide around 14 or 15 percent crude protein to support muscle growth. With such rations, the rumen is kept full and active so the cow is better able to digest large volumes of feed after calving. However, the total energy level of the rations must be kept limited (around 850 VEM), especially at the beginning of the dry period (if possible). This helps to prevent the cow fattening as in this period the cow can eat large volumes of feed, without needing the energy directly. In the second part of the dry period, it’s good to increase energy levels in the rations to prepare the cow for the lactation, and because it has a large energy demand in this period, partly due to the start of milk production.
One important factor in the dry period is that the cation-anion balance (CAB) is closely monitored, or the difference between the number of positive ions and negative ions, expressed in milli-equivalents per kg. We recommend providing feed rations with negative CAB during the dry period. This increases the discharge of acidic anions (chlorine and sulphur), ensuring the body mobilises calcium (Bethard et al. 1998). This stimulates the calcium metabolism, which is important in early lactation to prevent milk fever and other problems. Feeding anionic salts to reduce CAB is a good way to keep the calcium metabolism active (Schothorst 2011). The uptake of rations must be monitored as these salts are not a tasty supplement.
Another factor that must be monitored is the availability of adequate and clean drinking water (bioSecure). The through-flow of the water troughs for cows in the dry period is less as fewer cows drink from them. This can come at the cost of water quality and water uptake. Lower water uptake also means lower feed uptake, which can negatively affect energy balance.