Reducing environmental stressors to improve dairy cow comfort

A pressing, and often-overlooked matter that poses a significant challenge on most of today's dairy farms is maintaining cow comfort. There are a wide variety of environmental stressors that must be taken into consideration in a dairy operation, and they have a direct impact on the production level of the cows. Some of these stressors include; heat stress, poor ventilation, improper stall/feed-bunk design, and not having adequate access to water. Conditions such as these are not only stressful to the cows, but also greatly affect their physiology and productivity. Fortunately, there are practical and economical solutions available to deal with these issues.

Ventilation/Reducing heat stress:

When addressing dairy cow heat stress problems, one must first realize that the thermal neutral zones for cows are very different than for that of people. You must also realize that heat stress is a function of temperature as well as relative humidity. In areas such as Kentucky that are known for their hot, humid summers, heat stress is much more of a pressing concern than cold stress. As the temperature heat index (THI) approaches 68, dairy cows begin to experience decreases in milk production caused by heat stress. At a THI of 55 to 60 the negative effects on reproduction can be seen. It has been found that, on average, cows experience these effects at least one day in all months of the year other than December and January. Based on these facts, it is apparent that a dairy producer needs to focus on developing facilities to decrease the effects of heat stress rather than cold stress. Listed below are some practices that could be employed in order to reduce some of the effects of heat stress.

Barn Orientation:

There are many factors that must be taken into consideration when deciding how to orient a barn, which houses cows. The direction is typically characterized by the direction of the ridge running along the roof of the barn. In order to maximize the use of natural ventilation, it is favorable that it be oriented so that the majority of the winds in the warmer months are perpendicular to the barns ridge. You must also take into account the effect of sunlight penetration into the barn. This can cause unused areas of the barn due to the increased heat cause by the sunlight. Having eaves that extend out past the barn sidewall, and orienting the barn in a way that prevents sunlight penetration during the summer months can help to reduce this problem. Barns with a north-south orientation have greater sunlight exposure than one that is oriented east-west. Stall usage in barns located on the east and west outside walls of north-south oriented barns are especially impacted by this solar radiation. Decreasing the effects of sunlight is crucial for heat stress abatement. An east-west oriented barn provides this necessary protection more effectively than one oriented north-south. It is important to note that it is not always practical to orient a barn in this manner, due to the topographical profile of the land. On a farm with rolling hills, the orientation of the barn should be directed in a way to minimize the effects of solar radiation as much as possible.

Ridge Vent:

Ridge vents are an opening in the roof of the dairy barn used in order to facilitate natural ventilation. In order to maintain adequate cow comfort, dairy cows should be exposed to a continuous supply of fresh, clean air. Having a vent in the roof of the barn allows for there to be a constant exchange of air, which helps reduce the amount of heat, dust, gasses, odors, airborne pathogens, as well as moisture from inside. The idea behind this practice is that hot, moist air will rise and exit through the roof of the barn. It has been found that the steeper the slope of the roof, the better the results. A general rule of thumb that has been developed in order to help a dairy farmer make a decision on barn design, is that the slope of the roof needs to be at least 3 inches of rise (height) for every 12 inches of run (length). Ridge vent size should be based on the width of the building, and have at least 3 inches of opening for every 10 feet of barn width.

Sidewalls:

Open sidewalls in a dairy cattle barn facilitate airflow. No obstructions should be placed in front of the sidewalls that would prevent winds that facilitate natural ventilation. A dairy farmer should strive for sidewalls that are 14-16 ft high, and are at least 75% open in order to take full advantage of the benefits. In order to compensate for potential rain entering the barn, an overhang of 3 to 4 feet should be provided. It is important to note that natural ventilation can also be supplemented with mechanical ventilation in order to further reduce the effects of heat stress.

Fans/sprinklers:

Fans and sprinklers should be thought of as a form of supplemental cooling only, and when used in conjunction with appropriate ventilation can significantly increase cow comfort during hotter parts of the year. Fan placement should be strategic, and when incrementally installing them throughout a facility close attention should be paid to which part of the operation receives them first. The holding pen should always be on top of the priority list. In addition to that you would want to focus on; close-up dry cows, calving area, fresh cow area, and of course the milking herd (high group then low if present).

- Proper placement of the fans should also be taken into consideration when looking at these different areas. Fan placement in the milking herd barn is especially crucial due to the fact that it can encourage cows to rest in the free-stalls, and stay at the feed bunk longer. Improper placement could result in unfavorable behaviors such as resting in the alleyway. Ideally, fans should be placed over the feed alley, as well as each individual row of free-stalls. The spacing of the fans should be longitudinally down the barn, and a general rule of thumb used is to not space them any more than 10 times the diameter of their blades. For example, a fan with a blade diameter of 3 feet should be placed no more than 30 feet away from another 3-foot fan. Wider spacing will result in the cows not being sufficiently cooled. Fans should be hung vertically, and located high enough off the ground to not interfere with the cattle. They should also be tilted slightly downward at a 20 degree angle, aimed at the bottom of the next fan in its line. This ensures you are getting the maximum cooling effect from available fans.

- By coupling the cooling effects of fans with sprinklers, you can take full a dvantage of evaporative cooling effects during the hotter months. The idea behind this practice is that the sprinklers create water droplets that wet the cows hair and skin, and the fans force air over it causing the water to evaporate, thus cooling the cow. The droplets must be large enough to adequately wet the skins surface, and has to be applied in a manner to allow time for them to evaporate. These systems should ideally be located in a shaded area where cows are most likely to experience heat stress, such as the holding pen or feed-bunk. Fans should run continuously when cows are present, while sprinklers are on timers with variable intervals based on the temperature. This “on” “off” cycle allows there to be sufficient time for the water to evaporate, and subsequently decreases water usage.

Stall/feed-bunk design:

Free-stall design:

Proper free-stall design has a significant impact on dairy cow health and performance. Due to the fact that this is where these cows will be spending the majority of their time, we want it to be as stress-free and comfortable for them as possible. Cow comfort is defined as minimizing the stressors the cow experiences while maximizing milk production and animal well-being. The purpose of a free-stall is to provide the cow with a clean, comfortable, dry resting place, that is large enough to accommodate a natural resting, rising, and reclining motion. By having an appropriately designed free-stall, you eliminate the risk of the cows resting in unfavorable, dirty places such as the alleyway, which can cause issues with hygiene as well as lameness. Typical dimensions are based on cow size, and can be seen in the table below:

Source: Graves et al. 2005.

As you can see, the dimensions of the stalls are based on the weight of the animal. It is ideal to design all stalls to accommodate the largest animal within your herd. By doing it this way, you never have to worry about there being a cow that is not comfortable in the stalls, and having to deal with all of the associated problems (lameness, hygiene, hock abrasions, etc).

Feed-bunk design:

The main purpose of dairy cattle facilities is to provide a comfortable environment that will allow for cows to meet their natural behavioral and physiological needs. There are many factors to take into consideration when talking about the feeding environment that can potentially influence the cows access to feed, including the amount of feed-bunk space available for each animal, as well as the actual design of the feeding area. Inadequate space per animal can cause there to be aggression issues, and some cows not getting an adequate amount of feed. It has been shown that an increase in feed-bunk space can cause an increase in feeding activity across the herd, as well as less aggressive behaviors being observed. For the milking herd, it is ideal to provide at least 24" of feed bunk space per cow. The barriers that separate the cows from the feed (ex: headlock), can also influence feeding behavior. These barriers were designed with the intention of allowing cows equal access to feed, but some of these designs can actually limit the cow’s ability to freely access feed. It has been found that the use of headlocks compared to a post and rail type barrier can effectively reduce aggression at the feed- bunk, as well as improve access to feed for socially submissive cows during peak feeding times. The height of the neck rail also plays an important role in cow comfort. Bunks should be designed to allow for at last 19-21” of throat height, and neck rails should be located at least 48” off the actual cow platform. The table below shows the appropriate dimensions for a post and rail feed system throughout the animal’s life based on their weight and age.

Ultimately, the farmer will have to decide if any of the above recommendations will fit their individual situation. Reducing the environmental stressors discussed takes planning, as well as intensive management. Not all farms can utilize these solutions in a manner that would be well suited for their operation. With proper management and ample planning, these solutions can be achieved practically and economically on a farm with the goal of maximizing profitability.

By: Bailey Smith, Barbara Wadsworth, and Donna Amaral-Phillips
From the Kentucky Dairy Notes

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