Most producers that have farrow to finish operations of any size, have made some calculations, usually based on some rule of thumb to decide how many nursery and finisher spaces they need (or wean-to-finish spaces). Implicit or perhaps even explicit in this choice is a stocking density and anticipated productivity of the sow herd. Most rules of thumb assign so many "turns" to the facility and back calculate the number of spaces needed by weekly flow expectation from the sow herd.
We would expect this to be in flux over time since average sow herd productivity has been rising and changes like movement to wean-to-finish, disease eradication (where successful), season of the year and changes in lactation length all conspire to make flow predictions a little difficult. Here again, most producers take up the slack with stocking density and sometimes even early marketing out of finishers to free up space.
I was at a farm recently where a trial was taking place which required the weighing of all of the weaned pigs. It is really amazing to see the variation. The most surprising thing to me was the largest pig weighed so far was 23lbs achieved in 21 days. A high health herd and three week lactation length was producing monster sized pigs. This farm turns the nursery 8 to 8.5 times a year since 5-6 weeks generates a 50-60 lb pig. What it makes me think about is the decision to size the buildings which was made about 10 years ago. How far off were the rules of thumb used at that time...plenty is the answer.
So how do you decide how many finishing buildings you need in an effort to extract the maximum profitability out of the finishing phase. Nobody wants to be tinkering constantly with average weights and building inventory but many producers never consider it until either the buildings have been so crammed for so long that they are convinced the situation has changed and another building is necessary or an adjustment down in the breeding targets becomes necessary.
We know for sure that in any economic problem such as optimal finishing weights, which targets profit maximization, the proper analysis is to look at the next steps and decide, do I continue with the next step (what is the additional cost and additional revenue of that step) or do I stop here and sell. One thing that many producers still can't seem to swallow is the cost of their building (if owned or paid for by the space, rather than the lb of gain) is not considered in this decision. If you are one of those who pays $X/pig space and divide this out by the number of days in a year and add it into the decision here along with feed cost, you flunk economics and will be selling too light to maximize profits.
Choosing the optimal selling weight of individual pigs and a distribution of pigs is not overly complicated (as long as you are willing to make some reasonable assumptions). When you add the issue of optimal "dumping" time for the finisher, i.e., should you set up a strategy that says sort off the first two loads and then empty the building, the issue takes on a little bit of added complexity. The basic idea however, is the same as the first two optimizations we have talked about. The question is, "Shall I leave the remaining pigs in this building another day (what is the added cost of another day, what is the added value created) or shall I dump them? The complication is we have to look at the alternative use of the building (the next pigs coming) when we assess the basic economic decision. More to come.
