Dry Cow Feeding Strategy
Straw, corn silage, grass hay, corn stover, soybean straw – the list can be lengthy when it comes to suitable forages for dry cows. Ultimately, your choice in picking the perfect forage or combination of forages for your dry cows will depend on your available equipment, method of feeding and cost of production.
Why has there been so much interest in dry cow feeding over the past 10 years? There are vast bodies of evidence and research proving the link between what a cow eats and her health at the time of calving. Evidence shows a successful dry cow diet will help prevent several problems at freshening, such as retained placenta, milk fever and reduced feed intake. This helps prevent other problems after calving, such as displace abomasum, ketosis and delayed breeding.
Overweight cows seem to have the most problems at freshening, so a feeding program that prevents high body condition score in the previous lactation and dry period ensures the cow will be healthy at the time of freshening. Excellent cow comfort, access to a perfect diet 24-hours daily and adequate space for the cow to eat and sleep are not only important for lactating cows but equally as important for dry cows. The other culprits that can severely deteriorate cow health at the time of freshening include lameness, high somatic cell count at dry-off and too long or short of a dry period (ideally 45 to 60 days).
Whether you feed a single diet during all stages of the dry period, or a two-stage (far away-close up) diet, the forage or combination of forages used in your dry cow diet should have certain traits, including adequate energy, palatability, low cation and adaptability.
Ensuring an intake of 15 to 16 mega calories (Mcal) of net energy lactation (NEl) per day for normal sized Holstein heifers or dry cows before calving has been shown to prevent big drops in feed intake around calving. This controlled energy (CE) intake will help prevent rapid fat loss in early lactation, which is a risk factor for ketosis. In most cases, a diet based on corn silage or other forages commonly fed to lactating dairy cattle will exceed this caloric goal. Limit feeding a high-energy diet comes with challenges due to the constant flux of cows in and out of a dry pen, as well as dominance and preference of individual cows has led to the practice of CE high-fibre diets. It is difficult to find a forage that meets all four traits. It is important to adapt the dry cow to the forages consumed in the lactation diet, but often there is no other option but to feed corn silage as the dominant part of the diet, and grass or alfalfa silage in small amounts. Therefore, feeding dry cows straw or other calorie-diluent forages in combination with lactating silage(s) is an important strategy. Many high-fibre and low-energy forages, such as straw, late-cut grass and stover, are typically low in potassium, helping reduce the incidence of milk fever.
Corn silage is the queen of dry cow forages but provides higher-than-required energy. It is palatable, low in potassium and adapts the cow to the most common forage in Canadian lactating diets. Whether it is a high-energy brown midrib (BMR) variety or a moderate-energy conventional hybrid, the amount of corn silage fed should not lead to excessive energy intake when coupled with supplemental concentrates (15 to 17 Mcal). Typical corn silage with 45% neutral detergent fibre (NDF) often needs to be limited to 10 to 15 kgs (as fed basis) daily, and fed along with a high-fibre diluent, such as fine chopped wheat straw (2 to 4 kgs). Because corn silage is a fermented feed, it should be fed daily to dry cows to ensure consistent intake. In most cases, corn silage is not a risk factor for milk fever.
Recently, we have seen novel approaches to reducing corn silage’s energy content in order to match energy requirements of a CE dry cow diet. In some cases, growers have selected late maturing (high-heat unit) varieties, or intentionally planted later in the growing season (July or after second cut). In both cases, the plant’s lack of maturity at the time of typical harvest results in a higher NDF and lower starch, which has lower energy density. The challenge of adequate dry down can be alleviated by waiting for a killing frost. This method comes with risks of crop loss due to weather, and the need to have a storage space for this specialized crop.
Grass provides low to moderate energy and good palatability, but depending on fertility and maturity, it can pose some risk for milk fever due to potassium contents above 2.0. In some cases, grass can be the sole forage fed to dry cows, assuming it is not too high in energy and potassium. Mature grass, with an NDF of 70%, can be used as a diluent or bulky high-fibre feed along with corn silage. It is important to fine chop the hay or silage in order to reduce the risk of sorting the total mixed ration (TMR). If the grass is fed as baled hay or silage, it should be replenished once or twice daily to ensure consistent intake. The greatest advantage of using fine chopped hay is its palatability compared with straw. Grass varieties, such as orchard, timothy and reed canary grass, have a hollow stem, possibly allowing better rumen retention at the time around calving when intake goes down. An interesting method for grass silage is to harvest in July after heading, when the crop reaches peak NDF content. Naturally, the standing crop will be drier at heading than at a younger stage of growth, so a minimal amount of time is required for wilting before forage harvesting (sometimes no time). This method uses all the equipment most farms already have, and this type of crop can replace the straw in the diet.
The preferred high-fibre diluent forage when fed along with corn silage is straw because it’s readily available and consistent in quality. Straw has high NDF, low energy and low potassium. However, it is imperative the straw is fine chopped to prevent sorting in a TMR diet. The benefits of feeding straw to lower the energy content of dry cow diets can be easily lost if it is too long and leads to sorting in the feed bunk. Therefore, prevention of sorting is highly critical to its success. Straw should be chopped with a forage harvester (12mm or less) at time of harvest and stored in a dry shelter. Bales should be finely chopped at time of feeding with a harvester, bale chopper or TMR mixer equipped with well-maintained knives. To get the proper size of straw in the TMR mixer, premix the straw bales alone for an extended period of time (30 mins), empty the mixer and reload with the precise amount needed. Mixing straw along with other components of the diet will lead to over processing the silage. Adequately chopped straw should be 10 to 30mm in length with few particles greater than 5cm. Water should be added in order to maintain 55% TMR moisture.
Various types of straw are available in Canada. Cows tend to prefer varieties of straw without awns. Some straw, such as spring wheat, are more brittle and easier to fine chop, leading to many producers selecting wheat straw and other awnless cereal straws, such as barley. Oats are more difficult to fine chop because of the thick stem. Cereal silage is a common dry cow forage in many parts of Canada. However, some varieties have a high-starch content (high energy) and still need to be further diluted with a low-energy forage, such as straw.
Ultimately, the choice of forage will depend on cost and availability. In some regions, straw can be purchased for less than $100/MT, making it a logical choice for dry cow feeding. In other areas, the cost of growing grass may be less dependent on climate and land value, therefore, making grass the most suitable forage. In most areas, corn silage will be the predominant choice because of its attributes. Supplemental concentrates fed to dry cows should complement the forage chosen, providing adequate protein, minimizing milk fever and boosting the immunity by feeding proper levels of minerals and vitamins. Focusing on controlled energy intake, managing sorting at the feed bunk and allowing adequate space for dry cows to eat and sleep can go a long way to fresh cow success.
Guidelines for dry cow diets and nutrient values of common dry cow forages.
|Nutrient||Dry Cow Diet||Corn Silage||Wheat Straw||Mature Grass Hay|
|DMI, kg||13 or greater|
|CP %||12-15% (1,200g MP)||8||4||10|
|NEL, Mcal/kg||1.3 (15-16 Mcal total)||1.5||1.0||1.2|
|Ca||.6 (1.5 for anion diet)||0.2||0.3||0.2|
|K||1.4 or less||1.0||0.8||1.5|