To improve cow comfort, health and milk production in the following lactation, dry cow management needs to include truly short day length as well as effective heat stress prevention. Done right, this approach allows cows and heifers to more fully express their genetic capacity to produce milk.

The dry cow resort

Create an environment where cows can find comfort and relaxation during the critical six to eight weeks leading up to calving by turning a conventionally designed transition barn into a “dry cow resort” by adding just a few features and functions:

1. Enclosed barn, facilitating short-day lighting (SDL) with walls and roof blocking ambient light

• Do not use clear or translucent curtains, wall panels or roof panels.
• Do use black curtains or opaque, solid panels.
• Do not use a conventional open-peak ridge.

2. Mechanical ventilation system

• Supply sufficient amounts of air while blocking ambient light.
• Include air inlet openings adjustable for summer and winter needs while maintaining ambient light exclusion.

3. Effective cooling of animals

• Provide sufficient air speed over animals.
• When needed, provide additional cooling by wetting animals or using evaporative pads (in lower humidity conditions).

Why a dry cow resort barn is cost-effective

This analysis will use a marginal approach, comparing the added economic benefits of using a dry cow resort barn with the additional cost of upgrading from a conventional, naturally ventilated transition barn. The following examples are based on a herd of 588 cows (500 milking, 88 dry).

Effect of short-day lighting on milk income over feed cost

The main economic benefit of using short-day lighting (SDL) during late pregnancy is an expected increase in milk production in the following lactation. For all cows, whether on long-day lighting (LDL) or not when lactating, providing SDL during the dry period increases their production by about 7 pounds per cow per day in the subsequent lactation. For a conservative estimate, let’s only assume half of that increase. The average cow on LDL can achieve about 50 percent of the expected 5-pound response to LDL if exposed to natural day length during the dry period. In comparison, cows on LDL during the previous lactation but exposed to SDL during their dry period are perfectly reset and able to respond fully to LDL in the next lactation.

Consistently providing short day length for all cows when dry would allow them to achieve the full response to LDL when returning to the milking string. Thus, for most herds practicing LDL, we can expect an increase of 6 pounds per cow per day as a result of providing SDL during the dry period. For herds where cows receive LDL both when lactating and dry, changing to SDL during the dry period may increase production during the next lactation by as much as 8.5 pounds per cow per day.

Example for a 500-cow milking herd:

6 pounds milk (increase from SDL during dry period) x 365 days = 2,190 pounds per cow per year x 500 cows = 1,095,000 pounds (10,950 hundredweight [cwt])

10,950 cwt x $14 (milk price per cwt) = $153,300

Amount of feed needed to produce additional revenue:

1,095,000 pounds/3 pounds milk per pound dry matter (DM) = 365,000 pounds DM x 12 cents per pound DM = $43,800

Added milk income over feed cost:

$153,300 - $43,800 = $109,500

Effect of heat abatement on milk income over feed cost

Preventing heat stress during late pregnancy can increase milk production by 10 pounds per cow per day during the following lactation. Improved health and immunity for the mother animals and their offspring are important outcomes of preventing heat stress during late pregnancy, although difficult to quantify. In this article, we only attempt to estimate the economic value of preventing loss of milk production after freshening and avoiding reduced future milk production by daughters and granddaughters of heat-stressed dry cows and near-calving heifers.

This estimate is for a moderate heat stress area where cooling of dry cows is expected to increase the average production for all cows during the following lactation by 25 percent times 10 pounds, the equivalent of 2.5 pounds per cow per day:

2.5 pounds per cow per day x 365 = 913 pounds per cow per year

For 500-cow herd:

500 cows x 913 pounds per cow per year = 456,500 pounds (4,560 cwt per year)

4,560 x $14 (milk price per cwt) = $63,840 added revenue per year

Amount of additional feed needed:

456,500 pounds/3 pounds milk per pound DM = 152,167 pounds DM x 12 cents per pound DM = $18,260

Added milk income over feed cost:

$63,840 - $18,260 = $45,580 per year

This is based on increased milk by the cows and heifers themselves during their following lactation, as a result of effective cooling during late pregnancy.

Lower milk production is also observed among daughters and granddaughters of dams that were heat-stressed in late pregnancy. A decrease of 8 pounds per cow per day for the duration of their first and second lactations has been shown for both the second and third cow generations. The impact was calculated, assuming that future additional milk income would come from one daughter and one granddaughter for each case of preventing heat stress for one dry cow or heifer.

Production losses in the second and third generations happen only for those daughters and granddaughters that are raised as replacements and reach calving age. Our assumption that each heat-stressed dry cow and heifer contributes one daughter and one granddaughter to the future herd, who then complete two lactations, may overstate the future impact on the herd by one case of heat-stress. To offset this, we include only half the production increase suggested by research, basing the estimate on 8 pounds more milk per day during one 340-day lactation for one daughter and one granddaughter:

2 offspring x 340-day lactation x 8 pounds per day = 5,440 pounds added future milk increase due to cooling of one first-generation dam during late pregnancy

With a replacement rate of 33 percent, our example herd of 500 lactating and 588 total cows needs a minimum of about 195 heifer calves born every year and raised to calving age. In a moderate heat stress area, 25 percent of dry cows and near-calving heifers would be heat stressed. Thus, the effect of cooling would prevent heat stress for 25 percent of the 195 heifer-producing calvings (49 calvings per year). The total future increase in milk production by one daughter and one granddaughter due to cooling of the first-generation dam is estimated at:

49 x 5,440 = 266,560 pounds = 2,666 cwt

At a milk price of $14, this adds $37,324 of revenue. At a marginal feed efficiency of 3 pounds of milk per pound of DM, the amount of feed needed to produce the added revenue is:

266,560 pounds/3 pounds = 88,853 pounds DM

At 12 cents per pound DM, this corresponds to a feed cost of:

88,853 x 12 cents = $10,662

The added milk income over feed cost:

$37,324 - $10,662 = $26,662 per year

Because this additional income is expected years into the future, we calculated its net present value (NPV) based on an inflation rate of 4 percent. For the whole herd, the NPV of added milk income over feed cost for the avoided milk loss during future daughters’ first lactation was estimated at $11,851. For granddaughters, the corresponding NPV was $9,741. The total added NPV of added milk income over feed cost in the second and third cow generations is:

$11,851 + $9,741 NPV = $21,592

For our example herd (500 lactating, 588 total cows) in an area of moderate heat stress, the net revenue of cooling as a direct response by the cooled cows and heifers themselves during their subsequent lactation was previously estimated at $45,580 per year (milk income over feed cost). Add to this an estimated net present value of $21,592 of milk income over feed cost created by second- and third-generation cows when their first-generation dams are protected from heat stress during late pregnancy. The total annual net revenue from cooling dry cows and heifers was estimated at $67,172 ($45,580 + $21,592) per year for this herd.

Additional costs to build and operate a dry cow resort barn

Compared to a naturally ventilated conventional transition barn, the following modifications are needed for the barn to function as a dry cow resort and to obtain the previously described benefits:

Effective ventilation for an enclosed barn (e.g., tunnel ventilation):

• Estimated initial investment per cow space: $260
• Cost of ownership (10-year amortizing, 5 percent APR): $33 per cow space per year
• Cost of operation: $70 per cow space per year
• Total cost of ownership and operation: $103 per cow space per year

Soaker system for wetting cows:

• Initial investment per cow space: $20 ($10 per five-year period)
• Annual cost of ownership (10-year amortizing, 5 percent APR): $2.60 per cow space
• Annual cost of water used: $2.30 per cow space
• Total annual cost of ownership and operation: $4.90 per cow space

Exclusion of ambient light:

• Modification of sidewalls and supply air inlets: Cost to be determined, not included in analysis

Why the investment is worth it

An appropriately designed transition barn for a 588-cow herd (including a one-week stay in the post-fresh pen) may provide space for about 30 percent of total cows, housing about 176 cows and heifers at 1.4 times the average weekly freshening rate.

The increased milk income over feed cost, as a result of providing effective SDL during late pregnancy, was estimated at $109,500 per year for a herd with 588 total cows. A conservative estimate of increased milk income over feed cost due to prevention of heat stress during late pregnancy was $67,172 per year for this herd. Thus, the total estimated added milk income over feed cost was $176,672 per year.

The annual cost for adding a tunnel ventilation system was estimated at $103 per cow space, and for adding a soaker system, the annual cost was $5 per cow space. The total annual cost (ownership and operation) for adding these features to a basic, naturally ventilated transition barn equals $108 per cow space, or $19,008 per year for a modified transition barn sized for a herd of 588 total cows (176 cow spaces). Not considering added costs of modifying side walls and supply air inlets to exclude ambient light – upgrading to dry cow resort management leaves an annual profit of $157,664 ($176,672 - $19,008) for the example herd. This corresponds to $896 per cow space per year ($157,664/176) in the transition barn.

This amount of profit corresponds to payments for a loan of $7,000 at 5 percent interest when amortized over 10 years. The per stall cost of building a transition barn may be in the $3,500 to $4,000 range. Although the cost of features to exclude ambient light was not included, it appears that dry cow resort management may not only be a profitable upgrade to a conventional, naturally ventilated transition barn, but it could actually pay for the entire cost of a new barn, still leaving a considerable net profit.

The estimated cost-effectiveness of the dry cow resort approach is based on the added revenue from additional milk produced by using a transition barn designed and equipped for effective SDL year-round and for effective cooling of dry cows and near-calving heifers during late pregnancy when needed. The analysis was for a geographical location with moderate heat stress.

The profitability of SDL will remain much the same for the entire U.S. In areas with more severe and extended periods of hot weather, the cooling of dry cows will generate considerably more net profit than in this example. Depending on the location, the proportion of net profit as a result of practicing SDL and dry cow cooling may each vary between 40 and 60 percent.

When thinking about upgrading to a dry cow resort barn, the Dairyland Initiative program at University of Wisconsin – Madison is a valuable source of information. Excellent online information is provided about barn design to achieve top cow comfort, effective ventilation and cooling. Effective SDL in the transition barn and LDL in the lactating cow barn generates more than half of the estimated net profit as a result of using a dry cow resort barn. Consider involving a specialized professional in your planning, to ensure the lighting systems meet all the requirements for effective SDL and LDL. Getting it right the first time is always cost-effective.  

Gunnar Josefsson is a consultant with Dairy Lighting Solutions LLC. Email Gunnar Josefsson.

PHOTO: Along with mechanical ventilation, sidewalls and air inlets capable of excluding ambient light are key to creating a “dry cow resort,” an environment that combines short-day lighting and heat stress relief. Photo by Peggy Coffeen.