The following is from a presentation by Ken Nordlund, clinical professor in the School of Veterinary Medicine at the University of Wisconsin-Madison, at the Cow Longevity Conference in late August. The conference was sponsored by DeLaval.
Q: Housing factors are as important as the ration itself ― maybe even more so ― in explaining why some cows sail through the transition period and others struggle. Is there one factor that seems to stand out?
A: A great ration can be fed, but if there are housing issues like overstocked pre-fresh pens, insufficient bunk space and inadequate bedding, that great ration will not deliver great results.
Feed bunk access affects how much the cows eat, which impacts fresh-cow diseases.
Sufficient space at the feeding fence for all transition cows to eat simultaneously appears to be the most important determinant of transition cow performance in our current industry.
In very practical terms, we are recommending a minimum of 76 cm (30 inches) of bunk space per Holstein cow in pre-fresh and post-fresh pens for a 90-minute period after fresh feed is delivered and after every milking.
To determine feeding space/cow, it is important to focus on length of bunk as opposed to counting self-locking stanchions or headlocks. In the U.S., headlocks come in a number of widths, including 61, 69, and 76 cm (24, 27, and 30 inches) intervals between each unit. Our video studies show that lactating Holstein cows fill a row of 61 cm (24 inches) headlocks to a maximum of 80 percent at peak feeding periods. This 80 percent maximal fill rate occurred in two and three row pens, each with various stall-stocking densities, suggesting that the finding was independent of the number of cows per headlock. Converting these numbers, it suggests that lactating Holstein cows will voluntarily fill a bunk at a spacing of one cow per 76 cm (30 inches). It is likely that pregnant prepartum cows would take even more space than lactating cows.
These recommendations for 76 cm (30 inches) of space assume that the pens are equipped with lockups or other vertical dividers between feeding spaces. If the cows are fed at a post-and-rail feeder, additional space should be provided in this situation as dominant cows appear to clear subordinates more quickly.
While we focus the most attention on bunk space in the close-up and fresh pens, the actual number of cows in these pens usually changes every day. If cows are transferred into the close up pen on a weekly basis, and if cows move to calving pens on a daily basis, there will be wide weekly swings in the number of cows in the pen. In addition, there will usually be seasonal changes in stocking pressure that track seasonal infertility and recovery by 10 months. Because of these pen dynamics, it is more useful to focus on the longer term capacity of the pens.
The traditional approach to sizing close up and fresh pens is to calculate the average number of calvings per week by dividing the total number of calvings in the past year by 52 weeks per year. Then the average number of calvings/week is multiplied by the target number of weeks in the pen. For example, if a dairy has an average of 20 calvings per week and the planned duration of stay in the close up pen is 3 weeks, most planning manuals suggest that the close up pen should be designed to house 60 cows. By definition, pens designed in this manner are overstocked half of the time.
We prefer to build special needs pens to accommodate the surges in numbers of special needs cows. Based upon a review of a number of Midwestern herd records, we have recommended sizing close-up and fresh pens for 140 percent of the average number of calvings. In the example from the paragraph above, we would recommend provision of not 60, but 84 stalls in the pre-fresh pen with an available bunk that is 73 meters (240 feet) in length. Sizing these pens on this basis will mean that these pens are overstocked less than 10 percent of the time. There are also times when pens sized on this basis appear to be substantially under-stocked, or as some would say, “grossly overbuilt.” Our estimations of the impact of this practice suggest that this makes economic sense. Each stall and headlock in a pre-fresh pen has a multiplier effect in that it impacts the start of 10 to 15 lactations each year.