By Marianne Buza Murawski
It’s all too easy to crowd cows in barns; a slug of heifers freshened, fewer cows had problems and provided a reason for culling, and hey - another cow just means more milk in the tank. But crowding cows has consequences.
Overstocking dairy barns can impact the time budget and behavior of a dairy cow. Disruption of this time budget can occur if a dairy cow must wait for a stall to rest or when the cows are away from the pen for longer than 2.5-3.5 hours (e.g., during milking).
When a free stall barn is overstocked, the biggest impact will result in a decrease in rest time and rumination. According to research done by Rick Grant at the Miner Institute, every hour of rest a dairy cow gets after the first seven hours results in 3.7 pounds of milk. Cows will prioritize rest especially if they feel they have not had enough. This can lead to a shorter amount of time after the cow was milked before the cow goes to lay down. As a result, the teat ends may not have enough time to close which helps keep bacteria out. This is one of the reasons overstocking the free stalls can lead to a higher somatic cell count (SCC). SCC can also be elevated because cows may lie in the alley if no stalls are free. Also, an overstocked barn is a higher stress environment and has a higher pathogen load in that environment leading to increased SCC. In addition, when cows prioritize rest over feed, it will impact eating behavior. This leads to fewer, larger meals and lower fat test.
Pen sizes in free stall barns will also impact the time budget of a dairy cow. If the pens are large and overstocked the amount of time needed to get a group of cows through the milking parlor increases. This will lead to cows spending more than 2.5-3.5 hours in the holding pen or being milked. According to Nigel Cook at the University of Wisconsin-Madison, in North America, it is not uncommon for a dairy cow to be away from the pen for five hours a day. This will lead to a disruption of the time budget and less time for a cow to rest or eat. Ideally parlors and pen sizes should match to have cows in the holding pen for an hour or less. Overstocking free stall pens will create longer times in the holding pen. In addition, 3X milking will add to wait time in the holding pen compared to 2X milking. This will lead to a disruption of the time budget and less time for a cow to rest or eat.
Barn design plays into the impact that overcrowding will have. A six-row barn, stocked at 100% (one cow per stall) is overcrowded relative to feed bunk space (approx. 20 inches/hd) compared to a four-row barn (approx. 30 inches/hd). Width of scrape alleys and height of eaves also influence the impact of more manure in alleys and more cows breathing out hot, moist air when barns are overcrowded.
An overstocked free stall barn also can contribute to an increase in lameness because cows will spend more time standing. When a cow is standing, blood flow to the hoof area is restricted. Longer standing times can lead to inflammation and bruising of hoof lamina and cause hoof lesions. A cow that does not have a correctly shaped hoof stands on an unyielding surface, causing excess pressure on specific areas of the hoof. The result is inflammation, bruising and lameness.
Overcrowding affects different animals differently. When feed bunk space or bed space are limiting, boss cows will get their space at the expense of younger, weaker or less aggressive cows. The result will be a wider variation in cow performance within the group and the premature loss of some animals (death or cull) that may be genetically superior.
One pen where inadequate stalls will negatively impact a dairy herd is the transition cow pen. Michigan State University Extension recommends that the transition cow pen be only 80% stocked. Close-up dry and fresh cows are already predisposed to have decreased dry matter in-take and decreased rest. Plan ahead to ensure your transition animals have the space they need.
If a free stall barn is overstocked, some of the negative impacts can be reduced. Look at your herd and plan long-term strategic culling. One way to do this is to add a cow early to your do-not-breed list. Also look at your incoming heifers. If you have more than you need, sell them at a young age or sell them as fresh 2-year-olds. Adding extra bedding to your stalls will encourage a cow to lie down rather than stand or perch in her stall. If your cows have lameness issues because of standing time, putting rubber mats in your holding pen and parlor can help improve hoof health.
Farmers and managers should measure the time that cows are away from the pen to find out who much time away from rest their cows are. This is easy to do -the stopwatch feature on a smart phone will do the trick. Just track and see how long it takes a group of cows to get through the holding pen. It is important to track to the very last cow. Michigan State University Extension recommends start by watching the high producing group at all milkings to see how long it takes the cows to get through the parlor. The recommendation is that the cows are only in the holding pen for one hour for each milking for a total of two or three hours a day depending on the number of milkings. If it is found that cows are away from the pen for more than three hours a day, you can consider lowering your stocking density or changing how many cows are in the holding pen at a time.
Source : msu.edu