UBC Dairy Research Report
Overstocking typically occurs in two areas of the barn: at the freestall and at the feed bunk. Producers overstock dairy cattle to save building costs, or because herds grow before barns can be expanded to accommodate more cows. Overstocking can also occur unintentionally; even when each cow has access to a freestall (i.e. one-to-one, or 100% stocking rate, for cows-to-stalls). Differences in barn layout can mean that cows have adequate feeding space in barns with two rows of freestalls but too little feeding space in barns with three rows of stalls in each pen. This is because two-row pens have to be longer in order to house the same number of cows as a three-row pen, providing approximately 50% more bunk space per cow.
Open complete pdf: Overstocking: At the Stall and the Feed Bunk
In summary, these studies illustrate the effects of overstocking at the freestalls and the feed bunk; overstocking reduced the time cows (especially subordinate animals) can access the resource (i.e. lying space or feed), and increases unwanted behaviours (i.e. standing and competition for feed). Transition cows are more vulnerable to these effects, especially in terms of reductions in feed intake (that increase the risk of transition diseases) and increased standing time (that increase the risk of lameness). The effects of overstocking at both the freestalls and the feed bunk on displacements are also more harmful for submissive cows. Submissive cows may be especially at risk for disease during the transition period because they show reduced intakes, stand more and lie down less. Whether these cows are submissive by nature, or temporarily submissive due to their ill health, is not known and is a focus of future research.