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Using less energy on dairy farms

Author: Janey

Sep. 23, 2024

Using less energy on dairy farms

Introduction

OMAFRA recommends alternative designs to tie-stalls for new construction. Producers should exercise caution when considering the construction of a new tie-stall barn. We continue to recommend using available information and best practices to improve cow comfort and efficiencies within existing tie-stall barns. However, given the depreciation period and lifespan of a new barn, consider investigating alternative housing systems for long-term viability.

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Dairy farms use a lot of energy, but there are many opportunities on a dairy farm to reduce energy use and save money.

Energy benchmarking

Research on dairy farms in Ontario found that, on average, dairy farms used 800 &#; 1,400 kWh/cow/year.

These values are used to compare overall energy use between farms and establish a benchmark for evaluation. All energy benchmark values in Table 1 are significantly higher for the tie stall farms.

The wide span of energy-use-per-cow values in each category of farm indicates that there is the potential to conserve energy and push the top values down. For comparison, the average Ontario household uses around 12,000 kWh per year &#; the equivalent to what 10 dairy cows use per year on an average farm.

There are many ways to further reduce energy use on a dairy operation. The Ontario study found five areas of dairy operations that accounted for almost 90% of the electrical energy used:

  • milk cooling
  • vacuum pumps
  • water heating
  • lighting
  • ventilation
Table 1. Energy benchmarking data for dairy farms. Free stall dairy kWh/cow/year kWh/hectolitre Maximum 1,009 14 Average 837 8 Minimum 571 5 Tie stall dairy kWh/cow/year kWh/hectolitre Maximum 1,946 20 Average 1,417 14 Minimum 668 7

Consider reducing energy use in these areas. Energy is used mostly for milk production (milk cooling, vacuum pumps and water heating) and lighting, the second-largest reason for energy consumption on dairy farms. Figure 1 shows an overall average energy use profile for audited dairy farms in Ontario.

Figure 1. Average energy use profile for audited dairy farms in Ontario.
  • Milk system - 23%
  • Milk cooling - 21%
  • Water heating - 15%
  • Lighting - 14%
  • Ventilation - 12%
  • Feed handling - 7%
  • Misc - 6%
  • Waste handling - 2%

Milk cooling

Cooling milk is where most of the energy is used. Fresh milk must be cooled from 37˚C to 4˚C within 1 hour of the end of milking, so it can be stored until it is picked up by the milk truck. This means that the bulk tank condenser unit must extract a lot of heat, quickly, to make the process efficient. This process uses a lot of energy and produces a lot of heat. There are real potential energy savings if the heat can be recovered and used again.

Milk pre-cooler systems

Milk pre-cooler or well water pre-cooler systems remove heat from the milk before it enters the bulk milk tank (Figure 2). Pre-coolers are installed on the milk line and operate as heat exchangers through which water flows to partially cool the milk.

Figure 2. Well water pre-coolers (plate cooler).

The most common type of pre-cooler consists of a series of stainless steel plates separated by gaskets that form flow channels on opposite sides of each plate. Cool well water flows down the channel on one side, while warm milk flows up the other side. The milk's temperature drops as it transfers its heat to the cool water on the opposite side of the plate. The plate heat exchanger is extremely efficient for fast pre-cooling.

When properly installed, a pre-cooling system that uses a 2:1 flow rate (two parts water to each part of milk) can get the milk temperature to within 2˚C of the water temperature. Lower well water temperatures result in additional cooling. Higher water temperatures do not give as good results.

The well water, which warms up 7˚C&#;9˚C, can be used for watering the cows &#; in warm weather, cows will drink 3&#;4 L of water for every litre of milk produced. Otherwise, it can be discarded or used for washing equipment or washing down the parlour and holding area floor.

The pumping rate for water depends upon the milking rate. If the 2:1 ratio is selected, the water pump and well must supply water at twice the milking rate, measured in litres or gallons per minute. It is important to make sure that the well can supply water at this rate.

By using milk pre-coolers, bulk tank condensers run for a shorter time to cool the milk at higher pumping rates, resulting in electricity savings. However, it may be difficult to justify the costs of the pre-cooling system based on these savings alone.

The money saved by installing an in-line cooler depends on several factors such as herd size, number and size of compressors, type of refrigerant used and the age of the bulk tank. It is estimated that the investment will pay for itself in as little as 2 years.

Milk heat reclaimers

Once the milk enters the bulk milk tank, it must be cooled to preserve its quality. The air-cooled condensers typically used for this process are not as energy efficient as water-cooled condensers, which can recover 20%&#;50% of the heat removed from the milk.

There are two types of water-cooled condensing systems:

Total water-cooled condensing system. Water is used to cool the condenser and the condenser motor, then fed into the hot water system. In general, 1 L of milk will produce 1 L of hot water at approximately 46˚C. Large amounts of warm water are produced by this system. Excess warmed water may be fed to the livestock or discarded. The compressor can be designed to switch to air cooling when the cooling water reaches a certain temperature, making the system more energy efficient.

Refrigeration heat recovery unit (RHR). RHR is an add-on recovery unit that is connected to the refrigerant line of an existing or new air-cooled system (Figure 3). These systems remove much of the superheat from the compressed gaseous refrigerant; however, the air-cooled condenser must remove the residual heat. The pre-warmed water is stored in a tank. The storage tanks range in size from 190&#;450 L. Common brand names are Therma-Stor, Heat-Bank, Fre-Heater, Century-Therm, SuperHeater.

Figure 3. Milkhouse heat reclaimer & compressors.

Pros and cons of a milk pre-cooler system

If you use electricity to heat water, heat recovery may help reduce water heater expenses. However, a number of factors dictate whether a milk pre-cooler can be incorporated into a system.

The water well's capacity to provide water (flow and amount) is important. For a constant-speed milk pump, use a water-to-milk volume ratio of 2:1. Milk flow rates are shown in Table 2.

For a 1-hp milk pump, the milk flow rate is 160 L/min (35 gpm) and the water flow rate is 320 L/min (70 gpm), using the 2:1 ratio.

Table 2. Typical milk pump flow rates. Horsepower Typical flow rate L/min (gpm) 2:1 Water flow rate L/min (gpm) ½ 110 (25) 230 (50) ¾ 135 (30) 270 (60) 1 160 (35) 320 (70) 2 205 (45) 410 (90) 3 270 (60) 540 (120)

Existing water pipe size may also limit the water flow rate. Table 3 shows the maximum flow rate, at 275 kPa (40 psi) water pressure, for water pipes of various diameters.

Table 3 shows the minimum water pipe diameter as 32 mm (1¼ in.) for a 30-m (100-ft) pipe and a flow rate of 320 L/min (70 gpm). If these physical conditions cannot be met or would incur large expenses to achieve, a pre-cooler may not be cost-effective.

Table 3. Pipe size and length vs. water flow rate (at 275 kPa (40 psi)) Pipe diameter
mm (in.) Flow rate L/min (gpm)
15-m (50-ft)
Length of pipe Flow rate L/min (gpm)
30-m (100-ft)
Length of pipe 13 (½) 40 (9) 30 (6) 19 (¾) 120 (27) 80 (18) 25 (1) 250 (55) 180 (39) 32 (1¼) 450 (100) 320 (70)

Heat reclamation from the compressor is almost always a worthwhile investment because of the lower water heating costs, which are normally reduced by up to 50%. Disadvantages of heat reclaimers include the need for regular maintenance for optimal performance and the loss of heat to keep the milk house warm in the winter, although there is usually more heat available than is needed to heat water.

Pre-coolers and RHR units are competing technologies. Heat removed with a pre-cooler cannot be used for water heating. Typically, either an RHR unit or a pre-cooler will be economical for farms with less than 100 cows, but not both. For farms with more than 150 cows, usually both will be economical, although this depends on energy costs.

Variable speed drives

Milking equipment is one of the biggest energy users on dairy farms. Variable speed drives (VSDs, also known as variable frequency and adjustable speed drives) may be used on the vacuum pump and milk pump.

Vacuum pumps

The VSD attaches to the existing vacuum pump to constantly monitor the vacuum level and change the motor speed accordingly. On the vacuum pump, savings for existing systems of at least 50% (65%&#;70% is typical) can be achieved. For designs based on the new specification, savings can be as low as 30%. This system maintains the vacuum level by adjusting the motor speed (Figure 4).

Figure 4. The variable speed drive (noted as an ASD) maintains a constant vacuum while varying milk flow. Source: Wisconsin Public Service Corporation.

In a vacuum pump upgrade, a farmer changed from two vacuum pumps with a 7.5-hp motor each (Figure 5) to a vacuum pump with a 10-hp motor and vari-speed control (Figure 6). This switch resulted in a 5-hp upfront savings and an additional saving on the vari-speed control. The second vacuum pump with a 7.5-hp motor was kept for back-up.

Figure 5. Before: two vacuum pumps with 7.5-hp motors. Figure 6. After: one vacuum pump with 10-hp motor with vari-speed control.

When to use a variable speed drive

Table 4 provides a general guideline on daily hours of use of the vacuum pump to give the variable speed drive a reasonable payback period of 5 years. Actual payback varies depending on conditions on the farm, the price of electricity and the capital cost of the VSD.

Milk pumps

A variable-speed milk pump is used as an accessory to a pre-cooler or well water&#;cooled heat exchanger. A variable&#;speed milk pump slows the milk flow through the plate cooler, which results in a higher water-to-milk flow ratio and more cooling of the milk in the pre-cooler. Refrigeration compressor run time is reduced. The variable speed feature replaces the standard on/off liquid level controller. It allows the milk level in the receiving jar to be maintained by turning the milk pump speed up or down. The energy savings associated with this type of system vary with pump size and hours of use per day.

Table 4. Variable-speed vacuum pumps. Vacuum pump size
(hp) Minimum operating
(hours per day) 5 12 7.5 8 10 6.5 15 5 20 3.5

Note:It is very important to have variable speed controllers wired and installed correctly to avoid problems with transient voltage.

Scroll compressors

The scroll compressor is a simple design of two scrolls &#; one that oscillates and another that is fixed &#; that compress and move refrigerant more efficiently and reliably than traditional compressors. Gas refrigerant is compressed when one spiral travels around a second standing spiral, creating smaller and smaller gas pockets and higher gas pressures. By the time the refrigerant is released, it is fully pressurized. Suction is continuous and pulse-free because all gas pockets are in various stages of compression at all times.

A scroll compressor can result in reduced energy costs. Scroll compressors require less current than regular compressors and can run on single-phase electricity. A scroll compressor runs at a lower decibel level and vibrates less than a reciprocating compressor. Scroll compressors last longer than conventional compressors. With only one moving part and no metal-to-metal contact, there are no seals to tear and no lubrication needed.

Scroll compressors use 15%&#;20% less electricity than standard compressors. Additional benefits of scroll compressors in today's dairies include:

  • quieter
  • fewer breakdowns
  • longer life

Tip: Keeping air-cooled condensing units clean can result in a 3%&#;5% reduction in energy use.

Electric water heater

Connect the water heater to a timer to ensure water is not heated unnecessarily. Purge 9&#;14 L (2&#;3 gal) twice yearly from the drain tank of the water heater. Convert to a high-efficiency gas, oil or propane heater/boiler system. Insulate the water heater and at least the first 6 m (20 ft) of pipe from the water heater. Consider installing a solar hot water system.

Lighting systems

Lights that operate daily for long durations year-round have faster paybacks than lights that are only turned on for a few minutes a day. The quicker the payback, the more appealing an energy-efficient lighting system is for most farm owners and managers.

The best type of system depends on a number of factors including room temperature, mounting height, size of area to be lit and payback period. Energy costs from light systems can be reduced by 15%&#;75%.

An easy way to switch to a more energy-efficient lighting system is the replacement of incandescent bulbs with compact fluorescent lamps (CFLs) with equivalent light output. The compact fluorescent system is screwed into the existing socket; no rewiring is needed.

Some CFLs have a rated life of 10,000 hours. Other energy-efficient lighting systems require more effort. Installation of the tube fluorescent or high-intensity discharge (HID) lamp systems requires rewiring and a lighting design to ensure that the area is evenly lit at the right light intensity.

CFLs come in a range of power ratings, from 5&#;42 W screw-in versions and up to 55 W in hard-wired models. As a guide, a 4:1 ratio, incandescent-to-CFL wattage, yields equivalent light output. Generally, compacts are a good, low-cost retrofit. CFLs for barns need to be approved for damp locations (Figure 7).

Figure 7. Compact fluorescent lighting comes in many different shapes to suit the application. Note the water&#;resistant fixture on this 18-W CFL.

Incandescent lamps are cost-effective where lights are only turned on occasionally, such as in storage rooms. Fluorescent tube systems are well suited to areas such as tie stall, free stall or loose housing barns and some parlours with high ceiling heights

Fluorescent tubes come in a variety of lengths and diameters and are typically rated for 20,000 hours. Typically, farms use 1.2-m (4-ft) lengths. Tube diameter is measured in multiples of an eighth of an inch. T12s (3.8 mm (1.5 in.) diameter) &#; the old standard &#; are being replaced by T8 and T5 tubes.

The new recommendation for barns where the ceiling height is less than 3.6 m (12 ft) is the T8 fluorescent fixture with electronic ballast, mounted in weatherproof fibreglass or plastic housing with a continuous gasket between the lens and the fixture (Figure 8). These units are more than four times as efficient as regular incandescent lights and up to 30% more efficient than T12 fluorescent tubes.

Figure 8.T-8 fluorescent lights in dairy barn.

The lamps last at least 20 times longer than regular-life incandescent lamps and are an ideal energy-efficient alternative to incandescent, compact fluorescent and T12 fluorescent systems. T5 is more efficient than T8 and is commonly installed in barns where the ceiling height is greater than 3.6 m (12 ft).

In areas requiring high-pressure washing, waterproof fixtures are required to prevent moisture from getting into the T8 and T5 fixtures.

Ventilation

In a dairy facility, the best way to reduce energy used for ventilation is to maximize natural ventilation whenever possible. In barns ventilated by fans, choose high efficiency fans. Always look for AMCA (Air Movement and Conditioning Association), University of Illinois BESS&#;tested fans or independent fan performance data. Buy rated fans and properly size the fans and corresponding air inlets based on good design principles. A recent innovation for hot weather cooling in dairy barns is the high-volume, low-speed (HVLS) ceiling fan (Figure 9).

Figure 9.High-volume, low-speed fan.

These fan units may be up to 7.2 m (24 ft) in diameter and are operated by a 1&#;2-hp motor. While the units are expensive to purchase, the payback period falls into the 4&#;5-year range, depending on the electricity prices and installation costs at the time.

Regular maintenance and cleaning of the whole ventilation system will pay off with reduced energy costs in the range of 15%&#;50%. Regular maintenance and cleaning will also reduce repair and replacement costs &#; for instance, dirty fan blades and louvers can reduce fan capacity by more than 40% (Figure 10). Regular ventilation inspection will ensure that fans will operate at full capacity. Figure 11 shows a fan with blades broken off; the fan is exhausting little or no air.

Figure 10. Dirty fan needing cleaning. Figure 11. Fan with broken blades.

Energy-efficient waterers

Keeping livestock drinking water from freezing is an important task on a dairy farm. In the winter, protect water bowls from freezing unless they are in a heated area. Water bowls can be electrically heated (Figure 12) or frost- (energy-) free (Figure 13) in dry cow/heifer barns.

Figure 12. Heated water bowl in a slatted-floor cold dairy barn.

 

Figure 13.Frost-free water bowl.

Heated systems rely on a power source (electric, natural gas, propane, solar, etc.) to heat the pipe and water in the tank. The use of insulation contains the heat and improves the energy efficiency.

Energy-free systems make use of geo-thermal energy to keep the water from freezing. A dry well or riser pipe surrounds the water supply pipe. The dugout, which holds the water, is well insulated. The circulation of fresh water through the pipe and tank keeps the system from freezing. Size this system properly to ensure adequate circulation of the water. If there are not enough cattle, circulation may be inadequate and freezing can occur.

Cows prefer to drink from open surfaces. Therefore it is preferable to use an insulated, heated waterbowl, than one where the water surface is protected with an insulated lid or ball. For cold, dry cow or heifer housing where the animals are not drinking as much water, the energy-free water bowls are a good alternative to adding heat.

Conclusion

This Factsheet outlines areas on dairy farms where energy can be saved. In particular, upgrading milking equipment such as milk pre-coolers and using vacuum pump technology and scroll compressors can result in a 30%&#;50% savings. Maintaining, cleaning or using energy-efficient ventilation systems can result in a 15%&#;50% savings, and using energy-efficient lighting systems can resulting in a 15%&#;75% savings.

Check with local electrical utilities to see if there are any financial incentives for any of these energy-saving technologies

Goto Windmax Power to know more.

This factsheet was written by S. Clarke, P. Eng., (retired), Energy and Crop Systems Engineer, OMAFRA, Kemptville and H. House, P. Eng., (retired), Dairy and Beef Housing and Equipment Engineer, OMAFRA, Clinton.

Cross-Ventilated Barns for Dairy Cows: New Building ...

The most important factors that determine the selection of the type of housing for dairy cattle are cost, animal comfort, worker&#;s efficiency, durability, and a favorable return on investment. Since the first low-profile cross-ventilated (LPCV) barn started to operate in South Dakota in the fall of , at least six more facilities have been built in that state using this technology, and dozens of them have been built in the rest of the country. Although LPCV barns (enclosed, year-round controlled environment) are a new concept in the dairy industry, housing systems similar to LPCV barns have been used for a long time in the swine and poultry industries. In the United States, the number of dairy farms with more than 500 cows has increased in the last decade by more than 21%, from 2,795 dairies in to 3,400 in . This new facility design would be suitable for these larger dairy operations.

Please check this link first if you are interested in organic or specialty dairy production.

One peculiarity of this design is that it merges conventional barns (4 or 6 rows of freestalls) under the same roof, eliminating the space required to separate each barn. For example, when two traditional barns of 4 rows are merged, a new LPCV housing with 8 rows is developed (Figure 1). The interior of the building is similar to the conventional barns. The main difference is the presence of baffles that hang approximately half-way from the ceiling and are attached to the barn columns (Picture 1). The function of these baffles is to increase the air velocity and redirect air toward the freestalls. To reduce the height in the center of the barn, the slope of the roof changes from a 4:12 pitch in conventional barns to a 0.5:12 pitch in LPCV barns. The height of the side walls is identical in both types of facilities (minimum 12 feet), but because there is less roof slope, the height at the center of the barn is lower in the LPCV barn; thus, the name low-profile. On one of the side walls, there are exhaust fans (Pictures 2 and 3) and on the opposite side, there is the air intake (made of evaporative panels in some cases; Picture 4); thus, the name cross-ventilated. The access doors to the alleys are situated on the front end, similar to conventional barns (Picture 5).


Figure 1. Example of a 667-foot long LPCV barn, with front doors to access each alley and a central alley that connects the pens with the parlor.

 


Picture 1. Metal baffles placed in between two rows of freestalls.

 


Picture 2. Interior view of the side wall made up of fans.

 

 


Picture 3. Exterior view of the side wall made up of fans.

 


Picture 4. Interior view of the side wall with the air intake made of evaporative panels.

 


Picture 5. Front view of an 18-row LPCV barn.

 

 

 

Dimensions

The width required for a conventional barn of 4 rows (103 feet) can be observed on the top of Figure 2, with head-to-head freestalls and a central feeding alley. By merging two, three, or four barns of this type, an LPCV barn is formed of 8, 12, or 16 rows with widths of 213, 317, and 420 feet, respectively (bottom of Figure 2). Figure 3 shows a conventional barn with 6 rows (120 feet). A frontal section of LPCV barns can be observed on the bottom of Figure 3 of 12 (250 feet), 18 (370 feet), and 24 (490 feet) rows, obtained by merging two, three, or four conventional barns of 6 rows. The LPCV housing requires approximately 3-foot wide alleys along the lateral walls to allow for access to the fans and evaporative panels and to perform maintenance. The examples in Figures 2 and 3 have been designed with identical alleys and freestall dimensions. The freestalls have a length of 9 feet, the feed lanes are 19 feet wide, and the pen feed and back alleys are 14 and 10 feet, respectively. The design and dimensions described in this article are just an example of an LPCV barn, but there can be variations. For example, two rows of freestalls can be separated and placed head-to-head to form two independent rows tail-to-tail. Another variation would be to have a feed lane along the lateral walls and in this case, it would not be necessary to have an access alley to the fans and evaporative panels (Pictures 2 and 6).


Figure 2. Top: Front view of a conventional barn with 4 rows of freestalls. Bottom: Front view of an LPCV barn with 8, 12, or 24 rows.

 


Figure 3. Top: Front view of a conventional barn with 6 rows of freestalls. Bottom: Front view of an LPCV barn with 12, 18, or 24 rows.

 


Picture 6. Interior view of the side wall with 2 rows of nozzles (red arrows).

 

 

The main disadvantage of 6-row barns compared to 4-row barns is an approximately 40% reduction in feeding space (3 rows of freestalls per feedbunk). This can result in a reduction of optimum feed intakes and can negatively impact milk production. In addition, the alley area available to each cow decreases in similar proportion, which results in overcrowding. Due to the lower investment per cow housed, barns with 6 rows are highly used, particularly in larger dairies. If the width of the 4-row barn is increased by 17%, the number of freestalls increases almost by 40%, when there are 6 instead of 4 rows. In addition, increasing to 6-row barns results in a 37% reduction in natural ventilation (Chastain, ), which might become a problem on hot summer days.

Variations in dimensions and housing capacity can be seen in Table 1. In barns with a length of 667 feet, the number of rows of freestalls increases from 4 in conventional to 24 in LPCV barns. The width of the alleys and length of the freestalls are identical to those in Figures 1, 2, and 3. Due to their extreme length, the building is divided in the middle by a 33-foot wide central alley that connects the pens with the milking parlor and allows access for cleaning and bedding equipment. There are then 317-foot long pens on each side of the central alley. Each pen has four cross alleys connecting the feed alley with the back alley. In these cross alleys, there are 15 feet long for locating the waterers. The side alleys that are situated along the lines of fans and evaporative panels are 3 feet wide. The width of the freestalls is 4.1 feet, ideal for cows&#; 1,400 to 1,500 pounds of body weight. The bunk space per cow is 2.6 feet with pens that have 2 rows of freestalls and 1.6 feet for pens with 3 rows. The alley area per cow goes from 63.4 square feet in pens with 2 rows to 38.8 square feet in pens with 3 rows. The number of freestalls in each pen is 120 for pens with 2 rows and 196 for pens with 3 rows. The housing capacity increases by 480 freestalls in 4-row conventional barns and up to 3,136 in LPCV barns with 24 rows (3 rows per pen).

 

Table 1. Dimensions (feet) and housing capacity of different barn types with a total length of 660 feet.

 

One of the advantages of the LPCV system compared to the conventional system is less space requirement (smaller footprint). To facilitate natural ventilation, conventional barns need to be separated from other buildings at least 100 feet or 1.5 times the width of the barn (Brouk et al., ). The surface area needed to build a 16-row LPCV barn such as in Table 1 is 280,140 square feet. However, the area required to build four conventional barns of 4 rows each is 474,904 square feet. Although both examples have 1,920 freestalls, the area required increases by 72% in the conventional system. The area needed per cow goes from 146 square feet in a 16-row LPCV barn to 247 in a 4-row conventional barn. This is one point to consider due to the increase in agricultural land prices during the last few years. In addition, this smaller building footprint reduces the distance that cows need to travel from the pens to the milking parlor. Cows that walk less have more time for other activities such as eating or resting. These benefits increase as milking frequency is increased.

There are several options in the number of doors needed to allow equipment access to the cow alleys. One of them is to place a door in each alley (Picture 5). The other option is to place doors exclusively in the feeding lanes (Picture 7) and access pen alleys from the central alley that connects the pens with the milking parlor. The width of this alley depends on the maneuvering space required for each type of machine. With this design, the number of doors in a 24-row LPCV barn may be reduced from 20 to 4. 


Picture 7. Front view of a 24-row LPCV barn.

Ventilation

The ventilation system consists of exhaust fans, baffles, and air inlets. In contrast with conventional systems in which mechanical ventilation is used exclusively during hot weather, in LPCV systems, ventilation needs to work 24/7 year round. Therefore, backup generators and alarm systems are required additions. 

The fans refresh the air inside the barns with outside air to reduce the indoor concentration of gases and heat. One of the advantages of LPCV barns is the possibility to maintain constant air velocity year round. The performance of the fans depends on their diameter, number of blades, operational speed, and potency of the motor. The suggested fan dimensions are between 4 and 6 feet in diameter. They are placed on the opposite wall of the barn to the evaporative panels that form the air inlets along the side wall. One advantage of the LPCV is that the flow of air is across the barn, parallel to the freestalls, and can thus flow in between cows that are lying down. It is not necessary or desirable for all fans to be working during the colder months, but it is still important to run some fans to reduce the concentration of gases inside. Some farms control their ventilation system according to the concentration of ammonia in the barn. At lower ambient temperatures, the opening of the air inlet can be reduced to avoid freezing of the manure.

The baffles are placed longitudinally on the interior columns (Pictures 1 and 7). Their function is to increase the air speed in the freestall area from 3 to 4.4 feet/second up to 8.8 to 11.7 feet/second (Harner and Smith, ). In addition, they redirect the air toward the area of the freestalls. The bottom of the baffles is located at least 6 feet from the floor, and it continues uninterrupted toward the ceiling. Therefore, the baffles do not interfere with the movement of the animals. Baffles can be constructed with rigid (generally metal) or flexible (similar to tarp) materials.

The air inlets can consist of evaporative panels. These panels are made of cellulosic fiber with channels that allow the air to be humidified as it passes through the openings. Water circulates over the pad as air is drawn through it, and all excess water is re-circulated in the system. The air temperature decreases as moisture increases, which results in the lowest air temperature when air is 100% saturated with water. This is not the usual situation, as maximum saturation efficiency is 85% in most evaporation panels. On the other hand, high relative humidity is not recommended for adequate animal comfort. The saturation efficiency of the panels depends on the air speed that goes through them. At lower speeds, the air has more time to incorporate moisture, and thus the efficiency increases. To obtain saturation efficiencies of 70% and 80%, air speeds of 6.7 and 3.3 feet/second are needed, respectively. Due to the quality/price relationship, 6-inch thick panels are utilized more frequently in cattle housing. Water is added to the evaporative panels only during the warmer months when animal cooling is desired.

Some dairies have opted to substitute the evaporative panels with high-pressure water spray systems. These are placed on the side wall where the air intake is located and send water droplets through aspersion. Several rows of nozzles are needed to ensure homogeneous air saturation (Picture 6). The advantage of this system is that it allows more natural light to enter the barn. For optimum performance, both cooling systems need periodic maintenance and soft water with low mineral content.

Other Considerations

An important consideration with LPCV barns is to have an adequate artificial lighting system due to the fact that the building is completely enclosed. The recommendation for lactating dairy cows is 16 to 18 hours of continuous light each day, followed by 6 to 8 hours of darkness (Dahl, ). To observe a production response in lactating cows, an intensity of 15 foot-candles at 3 feet from the floor of the stall is recommended (Dahl, ). However, dry cows exposed to 8 hours of light and 16 hours of dark produced 7 lb/day more milk in the next lactation (Miller et al., ). It is necessary for the walls and ceiling to be well insulated to minimize the problems with condensation in the winter and heat transmission by radiation in the summer. Insulation materials such as polyurethane spray, flexible fiberglass sheets, rigid panels, etc. are commonly used. To avoid moisture accumulation between the insulation and the roof, it is very important to seal the junctions. An additional consideration is that these insulation materials are highly combustible.

Lobeck et al. () measured aerial ammonia and hydrogen sulfide concentrations in LPCV barns, naturally ventilated (NV) barns, and compost-bedded pack barns (CB). Ammonia concentrations (ppm, LS Mean ± SE) were 3.9 ± 0.35 for CB, 5.2 ± 0.35 for CV, and 3.3 ± 0.35 for NV barns. The CV barns had greater concentrations than CB and NV barns (P = 0.049 and P = 0.005, respectively), whereas CB and NV barns were similar. Summer had the highest concentration of ammonia in all three housing systems (P < 0.001). A separate analysis was performed to determine if there were differences in ammonia concentrations from the inlet to the exhaust side in LPCV barns. Ammonia concentrations were lower in the inlet side than the exhaust side of the barn (4.0 ± 0.27 vs. 6.2 ± 0.27, respectively; P < 0.001). Even though an increase in ammonia concentration was observed, this should be of no biological consequence as, according to the National Institute for Occupation Safety and Health (NIOSH), ammonia exposure should not exceed 25 ppm. Hydrogen sulfide concentrations (ppb, LS Mean, 95% CI) were 13, 9-19 for CB; 32, 22-45 for CV; and 17, 12-24 for NV barns. LPCV barns had higher concentrations than CB and NV barns (P < 0.006 and P = 0.044, respectively), whereas CB and NV barns were similar. Hydrogen sulfide concentrations (ppb, LS Mean, 95% CI) on the inlet side within LPCV barns were lower than the exhaust side of the barn (19, 11-34 vs. 41, 24-71; P < 0.001). As the air moved through the barn, it was picking up the hydrogen sulfide that was being released from the degradation of the manure. The recommended exposure limit for hydrogen sulfide by the NIOSH is 10 ppm.

In addition, there might be considerations about animal well-being that favor LPCV barns. Different housing types were evaluated (six LPCV barns, six compost-bedded pack barns, and six conventional naturally ventilated freestalls) in a study conducted on 18 commercial dairy farms in Minnesota and eastern South Dakota (Lobeck et al., ). There was a tendency for greater cow comfort (comfort index = cows lying down in a stall divided by all animals touching a stall; 85.9% vs. 81.4%) and stall usage (stall usage index = cows lying down divided by all animals in the pen not eating; 76.8% vs. 71.5%) in LPCV barns compared to conventional barns, respectively. Dairy cattle housed in compost-bedded pack barns had reduced lameness and hock lesions compared with those housed in freestalls. However, there were no differences in body condition, respiration rates, mastitis prevalence, culling, or mortality between housing types.

 

Main Advantages and Disadvantages of LPCV Systems

Advantages:

  • maintain a controlled environment year round;
  • produce a constant air velocity and air flow between cows that are lying down in the freestalls;
  • reduce the distance between pens and the milking parlor, enabling cows to spend more time eating and resting plus reduced hoof wear;
  • allow for greater control of flies and birds;
  • might improve animal welfare

Disadvantages:

  • greater energy use and fan maintenance costs due to forced ventilation year round;
  • only useful for large facilities; minimum suggested is 400 cows;
  • it can cause ventilation problems in the winter with temperatures below freezing because it needs a minimum number of fans working, and these reduce the temperature causing manure to freeze;
  • In climates with high relative humidity, the cooling system by evaporation is less efficient to prevent heat stress than in dry climates.

Author Information

Fernando Díaz-Royón1, Marcia I. Endres2, and Álvaro D. García1

1Dairy Science Department, South Dakota State University

2 Department of Animal Science, University of Minnesota

Cited Literature

Brouk, M.J., J.F. Smith and J.P. Harner. . Heat stress abatement in four-row freestall barns. In: Proc. of the Western Dairy Management Conference. Pp. 161-166.

Chastain, J.P. . Designing and managing natural ventilation systems. In: Proc. of the Dairy Housing and Equipment Systems: Managing and planning for profitability. NRAES publication 129. Pp. 147-163.

Dahl, G.E. . Photoperiod control improves production and profit of dairy cows. In: Proc. of  the Western Dairy Management Conference. Pp. 27-30.

Harner, J.P. and J.F. Smith. . Low-profile cross-ventilated freestall facilities &#; A 2-year summary. In: Proceedings of the High Plains Dairy Conference. Pp. 65-77.

Lobeck, K.M., M.I. Endres, K.A. Janni, S.M. Godden, and J. Fetrow. . Environmental characteristics and bacterial counts in bedding and milk bulk tank of low-profile cross-ventilated, naturally ventilated, and compost-bedded pack dairy barns. Appl. Eng. Agric. 28(1):117&#;128.

Lobeck, K.M., M. I. Endres, E.M. Shane, S. M. Godden, and J. Fetrow. . Animal welfare in cross-ventilated, compost-bedded pack, and naturally ventilated dairy barns in the upper Midwest. J. Dairy Sci. 94:-.

Miller, A.R., R.A. Erdman, L.W. Douglass, and G.E. Dahl. . Effects on photoperiodic manipulation during the dry period of dairy cows. J. Dairy Sci. 83:962-967.

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