What is overcrowding? Overcrowding may be too simple of a term to use when we talk about dairy housing. You really need to ask, “What is it I am limiting to the cows?” There can be many limiting elements to any given housing system, but just like a chain the housing system is only as good as its weakest link. Start with the basics; air, water, feed, and stalls.
Stalls are the often-used metric to measure overcrowding. It easy to see, measure and calculate cows per usable stall. However, it may not be the limiting factor! Many times, it is one of the other basics of animal housing.
Feed space is also easy to measure. The total usable feed space divided by the number of cows in the pen gives inches per cow. Now the evaluation of that is much harder. The old golden rule of thumb is 24 inches per cow to allow all cows to eat at the same time. However, many of todays cows are a little wider than 24 inches or maybe don’t like to push together that tightly at the bunk. What animals are in the pen? Are first lactation animals mixed with older cows? Do submissive animals have to compete with boss cows to get bunk space? Feed access is also important. Ideally feed should be available 21 plus hours per day and consistently pushed up, so it is within reach when a cow gets her chance at the bunk. So, the question is how many cows can eat at one time, and is feed there? Some freestall layouts, like the 3 row or 6 row, will have limited feed space even when the stall stocking density is held to 100%.
When we look at air, we really are evaluating ventilation. The goal of any ventilation system is to maintain excellent air quality within the shelter by controlling moisture, temperature, gas and pollutant levels. Air quality inside the shelter should be equal to or better than air quality outside the shelter. While year-round ventilation is needed, summertime is when cows are most often stressed by poor ventilation with inadequate heat abatement. Natural ventilation, the most often used ventilation in freestall housing, is driven during the summer primarily by outside wind speeds and the opening(s) into the shelter. While as designers and managers of the housing system we don’t have any control over the outside wind speed, the size of the openings is within your control. As freestall housing has evolved over the years shelters have become much higher and much more open on the sidewalls in an effort to provide better natural ventilation during summer months. A key factor to summer ventilation is square feet of opening per cow. If the windward sidewall and/or endwall opening is 11 square feet plus per animal within the shelter, summertime ventilation is much better. If that opening is less than 8 to 9 square feet, ventilation is probably going to be compromised.
What about water. A couple of things to remember about water are; first it is the second most important thing you need for life, right after oxygen, second milk is 87% water, and third pound for pound cows drink twice as much water as they eat in TMR. So, water availability is an important factor when evaluating dairy housing. The easiest factor to evaluate is inches of water space per cow. Simply add up the accessible linear water space in the pen and divide by the number of animals in that pen. The goal is to be at 3inches plus per animal in lactating groups. If the waterer space is too low, can extra waterers be added to the pen, or larger waterers be installed in place of smaller ones? The harder factor to evaluated is flow rate of water to the watering stations. To get a handle on that you need to make some observations of the waterers during peak demand times such as right after cows return from milking or during parlor cleanup time. Are any of the waterers going dry, because the demand for water is out pacing the piping’s ability to deliver it to the waterer?
Other factors also come into play when pens are overstocked. As animal numbers within a given pen are increased animals have less open space to move from feed, to water, to rest, and socialize. Wider feed alleys and freestall alleys in newer housing is promoted for just this reason. Also, as numbers within the pen increase the time away from the pen during milking may increase if no changes are made to how groups are moved to and from the parlor. Ideally time away for the pen should be no more than 3 hours per day. Changes may be needed to increase parlor throughput or decrease the number of animals moved to the parlor at one time to optimized time cows have access to the resources within the shelter.
Limiting resources affects animal behavior such as feeding and resting time and aggression, and also the animal environment such as air quality, cleanliness and heat stress. In short there is no easy answer to the question “Can You Make Overcrowding Work for You?”. It really is dependent for how well you can manage and modify your given facilities to provide for the cows needs without limiting needed resources.