In a document published by John Brouillette, and Nancy Spanski for the Dairy Management Program of the Cornell University Animal Science Department (Publication Date 4/29/98):

"Stall design and surfaces are the number one factor that influences cow comfort." 

"The objective of the resting area is to encourage cows to lie down as much as possible. Research by Metcalf and Rulquin point to the increased blood flow across the mammary gland when dairy cows lie down compared to when standing. The increased blood flow (reported at 25% greater than when standing) results in increased nutritional efficiency and milk production. It's this point that most directly relates cow comfort to productivity. Cows are designed to eat, lie down, eat, lie down, over and over again. If, cows stand simply because it hurts when they lie down, or it is physically difficult to lie down, the pattern will be broken and she will not consume those last mouthfuls of dry matter that translate into additional milk production. In the many past nutrition seminars, emphasis has been placed on dry matter intake and how every pound of dry matter can yield two to 3 pounds of milk production. If a cow limits her dry matter intake because of uncomfortable stalls, poor ventilation, or result of injuries, the following consequences may occur:

• Excessive body condition loss will occur postpartum, particularly in first calf heifers.
• Excessive weight loss will lead to clinical and subclinical ketosis, other metabolic disorders, reduced reproductive efficiency, and reduced milk production.
• Excessive grain feeding, poorly balanced rations can cause laminitis in cows, or it can be induced if cows are standing for excessive periods of time on concrete surfaces.
• Herds where cows are under long term stress will likely have a higher cow turnover."

Did the link atop the page not work?  You can download the document here: cowcomfort.pdf  You will need the free Adobe Acrobat Reader available via the link below to view the document.