Today, however, we see more and more farms targeting higher stocking densities, both at the freestalls and the feedbunk. Although stocking above this 120% benchmark may seem advantageous, producers can begin to see reduced economic return due to negative effects on cattle behavior.
While competing for resources, cows can experience underlying stress. Furthermore, adding additional stress on overcrowded cows from management, cow comfort or nutrition can exacerbate negative effects. However, it is important to realize that not all animals experience the same levels of stress in an overcrowded environment. Negative effects target subdominant cows, typically smaller or younger animals who tend to lose out on access to important resources (lying time, feeding time) to meet behavioral and, ultimately, production needs throughout the day.
Sometimes it can be difficult to observe the negative impacts of significant overcrowding, as only some of the pen is affected. As an example, let’s look at the performance of three cows in an overcrowded pen. Two of them perform at 100% of potential (dominant cows in the pen), but one of them performs at only 70% (subdominant cow). Averaged together, you have an overall score of 90%, much closer to the expected potential of the pen and differences that are often hard to see.
However, pushing higher levels of stocking density will continue to separate the potential of animals, sometimes even limiting the top performers. This can impact not only short-term efficiency but increase in severity with long-term use, affecting culling percent and cow longevity.
In order to maximize your herd’s potential when overcrowding, we must focus on nutritional and management strategies to address changes in subdominant cow behavior and minimize extra stressors.
Nutritional strategies
1. Add physically effective fiber or uNDF240 – Overstocking can have devastating impacts on rumen pH, up to double the effect of dietary changes. Due to a lack of freestalls, subdominant animals must shift rumination behavior from a comfortable lying position to standing in open alleys. Recent research from the Miner Institute found a relationship between ruminating while standing with increased sub-acute ruminal acidosis (SARA), likely due to a lack of buffer production with the alternative rumination location. Supplementing 2 pounds dry matter of straw increased both physically effective fiber and undigestible fiber (uNDF240) in the ration and mitigated SARA during overstocked conditions.
2. Re-evaluate physical characteristics of TMR – In order for subdominant cows to receive the same mixed ration hours after dominant cows have had their pick, we need to minimize sortability of the TMR. Adding water, liquid sugar or whey to feeds can help stick grains to forages, leading to more uniform intake of grain throughout the pen. Have your nutritionist shake out the feed using a Penn State Particle Separator. Avoid too much fiber in the top screen, as this can be easily sorted and can also lead to longer feeding times. Forage in the top pan must be chewed to shorter lengths for bolus creation and swallowing. Therefore, excess fiber on the 19-millimeter pan can extend time it takes cows to feed, limiting the feedbunk resource for subdominant animals.
3. Avoid slick bunks/alter feeding management – Cattle will prioritize resting during evening and nighttime hours, resulting in limited freestall resources. Due to this, subdominant animals will adjust their feeding patterns, maintaining dry matter intake (DMI) through feed consumption during nighttime hours. Avoid slick bunk feeding strategies in overcrowded herds, as running out of feed will limit the subdominant cow’s ability to maintain intake. Feeding responses can also be manipulated through changes in management. Ensuring constant feed access through extra feed pushups will help subdominant cows achieve access to feed after dominant cows are done. More importantly, new feed delivery will stimulate feeding behavior, more so than feed pushup. Increasing feeding frequency can redistribute cows in the pen, allowing access to freestalls for subdominant cows. It can also help regulate more even feeding behavior throughout the day, minimizing the risk of slug feeding behavior.
4. Additive/biohydrogenation support – With significant impact on rumen pH, overcrowding can also lead to lowered milkfat responses. Yeast fermentation products can help minimize changes in ruminal pH while 2-hydroxy-4-methylthio butanoic acid (HMTBa) sources can help support de novo butterfat production and reduce alternative biohydrogenation. I also recommend bicarbonate/sesquicarbonate both supplemented in the TMR as well as additional access in the pen. Monitoring consumption from the pen access can be a useful tool in evaluating changes in feed and feeding management that has caused more buffer intake and SARA. Finally, consider biotin and chelated minerals to support hoof strength and health challenged by excessive standing times in overcrowded pens.
Management strategies
1. Maximize usability of resources – When a subdominant cow finally has access to limited resources in the pen, we want to make sure she takes advantage of them and quickly, before they’re gone. This includes maximizing stall comfort with extra bedding, comfortable/groomed/level stall surfaces and proper stall loop/neck rail/breast board placement. We want to avoid any factors that would limit her want to utilize the resource when she finally gains access, so cow comfort is key. I also like to walk pens to evaluate broken or uncomfortable stalls/headlocks. Measuring these gives a better understanding of the realistic stocking density.
2. Prioritize cleanliness and proper milking protocols – Under normal conditions, most cows after milking will eat, drink, then lie down. In overcrowded pens, subdominant animals often find this time to regain access to a stall, lying down immediately upon return from the parlor. In this case, the cow’s teat ends may still be open from their previous milking, and this can lead to an increased risk of mastitis and higher somatic cell counts (SCCs). Ensuring consistent and proper teat coverage with post-dip, regularly cleaning stalls and using lime and extra bedding can all help minimize exposure and risk.
3. Ensure a proper hoof health program – With limited freestall access, overstocking results in increased standing times in pens. This can put undue stress on feet and legs, placing cows at more risk of hoof health issues. Develop a consistent footbath program to limit infectious disease, consider scrabbling concrete to limit slips and falls or rubber flooring to ease stress on legs and implement a consistent trimming schedule throughout the year, with a target of two trims per lactation. Furthermore, work with your farm consultants to monitor locomotion scoring over time, particularly if cows are exposed to long-term overcrowding.
4. Minimize time budget interruption – With limited time to achieve their lying and feeding needs, additional time constraints can exacerbate these resource restrictions for subdominant cows. Evaluate parlor efficiency to limit time outside the pen. Bed and scrape pens while cows are in the parlor, if possible, to limit further disturbance. Minimize time spent locked for vet, herd check or breeding.
While some overcrowding can boost economic efficiency, excessive overcrowding can negatively affect cattle behavior, leading to diminishing economic returns. However, through understanding these behavioral changes, we can implement both nutritional and management strategies to reduce secondary stress and increase production and well-being in these systems. 
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Mac Campbell
- Dairy Specialist
- Cargill
- Email Mac Campbell
