Stocking Density and Your Herd.

 By Jaclyn Krymowski.

 Stocking density (or rate) is a bit of a fine line for dairymen to walk. It’s a tricky subject because while there’s plenty of research on the topic, it’s still not an exact science. Not to mention, what is “ideal” for your farm might change due to fluctuations in cost of production or herd management strategy.

One thing we do know for certain is something as simple as how many animals are in a pen has a significant impact. Beyond cow comfort, this touches areas of management, production, finances and even animal health.

No matter how your animal movement flows, density matters for pens that are stagnant and those that are fluid. At times you may be tight and others very flexible. Whatever the case, you will want to monitor on a regular basis and make adjustments as soon as possible if there’s harm to your animals or finances.

What’s the big deal?
When talking about stocking density, the industry typically refers to percentages. For clarity, being stocked at 100% means every cow has her own freestall in a pen. Hypothetically, this allows every cow to lie down at the same time for as long as they all want.

Density also refers to bunk space on a lot there is one stanchion, head lock or adequate room for every animal to eat at the exact same time with no one left waiting.

Realistically, most pens are routinely stocked over 100%. After all, what is the likelihood every single cow’s time budget will synchronize for them to all lie down at the same time?

While keeping your density at 100% or less is certainly not necessary for your herd to exhibit normal behavior and keep comfortable, there is a point where overstocking will negatively affect comfort and production.

Not to mention, the finances of adding more stalls, or not utilizing all the stalls you’ve invested in, is no small consideration.

It’s pretty obvious why overstocking feed bunks is detrimental as what might happen to feed intake is self-explanatory. But when it comes to stall space, it’s tempting to ask what’s the big deal?

Plenty of research hours have been dedicated specifically to a dairy cow’s time budget. These aren’t just animal preferences or social behaviors. How a cow uses her time is closely linked to her health and well-being.

Research has shown us, as a rule of thumb, cows should be able to spend at least 10 hours a day lying down. Many prefer to spend well over this when possible.

When this portion of her time budget is insufficient, other behaviors are also shown to be altered. These could be decreased feed intake or lessened social behavior due to increased cortisol levels. Metabolic issues and decreased rumen activity are also known to accompany these issues.

By the numbers
A question that’s been asked time again does overstocking reach the point where there’s a notable negative impact? Or, how much of a negative impact can a group tolerate before it takes a hit on well-being or production?

At rates over 120%, lying active seems to decrease as presented by Dr. Peter Krawczel at the 2012 Southern Dairy Conference in his review of eight different studies. He also cited a study showing that sick and young animals were the most affected by overstocked pens compared to their healthier or holder penmates.

Production is one parameter directly impacted by suboptimal behavior patterns. According to the University of Kentucky white paper, What is the Optimum Stocking Density for Your Housing System?, an additional hour of resting time and increased rumination was associated with an increase of two pounds of milk per cow per day. This broke down to, with a hypothetical herd of 100, a potential of 200 lbs. more milk per day at an estimated value of an additional $1,098 per month.

As expected, there is also research to suggest milk quality suffers when pens are stocked at higher densities. Besides being directly stress-related, this can also have to do with decreased sanitation and not enough room at the feed bunk.

The University of Kentucky also cites certain groups may benefit from more lying space. Cows that are excessively stressed at important periods such as transition or illness are likely to drop their milk output during a later point in their cycle.

Some research has found fresh cows’ incidence of metabolic diseases goes down when stocking density is below 100%. Of course, it’s important to note these issues hinge on many other factors. But, when you can afford it, why not give these at-risk animals as much space as you can?

Let’s not forget bunk stocking density, which is especially relevant to open lots. Overstocking at bunks may impact time budget and animal behavior similar to freestall overstocking, according to a Michigan State University white paper by Marianne Buza.

This is attributed to cows on the lower end of the pecking order needing to stand and wait for a chance to eat. The rumen can be affected as well, due to these cows eating faster and larger amounts at once when they finally get a chance.

The industry standard for bunk space is at least 24 inches per animal, but Michigan State recommends 30 inches as preferable.

Your farm
Of course, there are times where you cannot afford but to stock at higher densities. It could be a glut of fresh cows coming, an excess of heifers, or a number of other situations.

But you want to be able to identify at what point the impact is too much for your particular farm. In certain cases, it may be necessary to consider investing in additional space.

It’s fairly simple to go through and calculate your density. Even if you think you are within “reasonable” parameters (which can have different definitions), it can be advantageous to do a professional evaluation. This can be as simple as running your data through a calculator model with the specifics for your farm. These can be found from some university extension websites, such as Florida Dairy Extension, or dairy consulting agencies.

It’s a good practice to crunch the numbers on a somewhat regular basis to see your farm’s specific potential and status at different points in time. Remember, what is the most economic stocking density can also fluctuate based on milk prices, feed costs and other issues.

In a similar way, farms that have activity monitoring systems can evaluate behavioral patterns and changes to see if their current system is allowing all animals to have a favorable time budget.

No matter your preferred method of analysis, determining if a particular stocking density is “good” or “bad” involves individual due diligence. However, it is one worth the while to investigate. Beyond a shadow of a doubt is that cows require adequate time to do all the behaviors that keep them healthy in an environment that allows them to do so and doesn’t promote stress.