Optimal selling weight

Recently I spent a week in London and everywhere I went I noticed how cars were getting smaller and smaller as Londoners faced the skyrocketing cost of fuel. The typical public service worker in London makes about 26k (pound sterling) and the typical private sector worker makes about 35k (pound sterling). They buy their gasoline by the liter and it costs about 4.5 pound sterling a gallon. As I have mentioned, if you are a tourist from the U.S. that's about $9/gallon if you rent a car.

There were a lot of very strange looking conveyances which I suppose classify as cars including the so-called Smart Car. You can check one of these out at www.smartcarpictures.com.

     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.

     Let's take another crack at this optimal selling weight idea.  In general, for a single pig (to get the theory down), you want to add weight as long as the next lb added returns a profit.  That is, the cost of adding that pound is less than the return it receives.  Somewhere in late finishing, a pig will start receiving less and less for each pound added.  This is because feed efficiency is deteriorating and the packer matrix will at some point discount the lb because the pig is too heavy.  Even though all lbs are discounted when the sort matrix indicates a penalty, as long as the last pound was at a profit, it should be added.