Are your cows overstocked?
Does it really matter if cows are overstocked in a pen? Research shows that there are several ways in which overcrowding negatively impacts cows.
How different is the feed at various locations along the feed bunk? That was one of the measures reported at a Michigan State University Extension meeting of a TMR audit performed by feed company representatives on a local farm. At the time, I thought it was interesting, but did not appreciate how significant it can be.
Combine variation in feed quantity or quality along a feed bunk with overcrowding in a pen, and you will get competition with winners and losers. Julie Huzzey from the University of British Columbia, presented a paper on the significance of competition during overcrowding situations at the 2013 Tri-State Dairy Nutrition Conference. Video footage of a pen with headlocks along the feed bunk indicated that even two head of cattle competed for a slug of higher quality feed at one of the headlocks, even though normal quality feed was available at all of the other headlocks.
Research has better defined the negative impacts of overcrowding of cow pens, not only in performance, but also physiologically and behaviorally. The losers of competition will hold back profitability of your whole herd.
Producers who routinely overcrowd pens often use various justifications. Some will say that at any one time they expect a certain proportion of their cows to be lying down, a proportion to be eating and the remainder to be in between those two states. It sounds legitimate, but how true is it, especially considering the social nature of these animals that prefer to engage in certain activities, such as feeding, at the same time?
Others may say that they don’t see any decrease in production per cow when feedbunk space per cow decreases. Cows do attempt to compensate. However, even in compensation there may be additional problems. We’ve long known that cortical levels increase in cows during stress and that overcrowding is a stress that increases cortisol production. Huzzey reported that increased cortisol may change energy metabolism and result in higher NEFA (non-esterified fatty acids) levels.
One method that cows compensate for overcrowding at the feed bunk is to consume feed at a faster rate while spending less time at the feed bunk. While dry matter intake may not decrease in these cows, the effectiveness of the cow in nutrient absorption and digestibility may be reduced significantly due to the slug feeding.
Studies by Huzzey also showed when the stalls are limited, cows will lay down at the expense of spending time at the feed bunk. For instance, when cows in overstocked groups – in this case by 50 percent – return from milking, they are more likely to go lay down than to go to the feed bunk. In fact, they lay down 13 minutes sooner than cows did where the density of cows per stall was 1:1.
When space is limited, cows will attempt to displace cows standing at the feed bunk by head butting. Animals in a group may be classified as those who are “less successful” at displacing others (they are more often displaced), “moderately successful” (they are as likely to displace others as to be displaced) or “highly successful” (displace others more often than they are displaced). In a mixed group, the low success group is generally heifers. The low success group has higher cortisol levels and is the group that will benefit the most from regrouping or lower density.
Short-term overcrowding may be necessary in expanding herds or when heifer calf births are high. Cattle can compensate to some degree for these times unless they are vulnerable for other reasons. Transition groups should be considered high risk and overcrowding either the feed bunk or stall space should be avoided. Close up dry cows may not be able to compensate or recover from competition for feeding or lying space.
It can be tempting to overcrowd groups regularly, but we are learning more about the negative impacts on cow health, welfare and ultimately cow productivity and profitability. Give your cows the space they need, and they will give you the performance you need. Management should change in order to reduce the impacts of overcrowding. More frequent feeding and pushing up of feed, more frequent scraping of manure and good bed maintenance should be priorities.