All criticism should be constructive, so let us start by deconstructing BW: identifying what we have and don't have; what we like or consider inappropriate; then make genuine suggestions of what we would make BW more commercially acceptable.
Firstly, in breeding plants or animals the more traits we try to select for, the less overall progress we make. BW is a composite of seven indices bound together by separate economic weightings eg fat BV x economic value. Simarly protein, etc. Are there too many traits? Individual trait Breeding Values are computer generated in a statistical methodology that has been peer – endorsed, and outside the expertise of most.
Economic values are a little more nebulous, and I believe DairyNZ's Sire Summary explanation (May 2011 edition) is misleading. We should be consulted as to what is financially relevant to us.
Milk BV, expressed in litres, has a negative economic value recognising volume is expensive in terms of feed cost, especially in producing lactose, and in storing, transporting, and removing water. The present AEU weighting on volume is –$0.09. It "costs" top Friesian bull 'Mint Condition' 98 BW points. Meanwhile an average Jersey bull gains + 57 BW points through lower volume (-637 litres). Is this reasonable, or should we opt for the Fonterra multiple of 4c?
Fat & Protein BV's
Measured in Kilogrammes, the concern here is not so much the Economic Values of each, but rather the ratio between them.
Fonterra has, over the years, paid 2.5 to 2.7 time as much for protein as fat yet the BW ratio over the past five years averaged 5P:1F.
With fat now returning as much as protein in our overseas markets the BW is clearly sending the wrong signals. It favours Friesian. The Jersey fraternity should be screaming 'Blue Murder'. We are entitled to an explanation.
Somatic Cell Count BV
Originally Fonterra wanted the penalty level at BSC200. It would have penalised 75% of suppliers, so they settled at 400. Nevertheless, a high BV and highly negative Economic Value can make SCC BV's influence on BW negative. A change to the EV weighting, made in 2007, from -25 to -30, correctly sends the market signals.
Liveweight BV, in kilogrammes, ostensibly recognises bigger cows use more feed on maintenance. It ignores the fact three big cows may well produce as much as four small cows, saving a maintenance ration with potential for big 'per-cow' related cost cuts. The negative economomic weighting has risen from -1.06 in 2007 to -1.398 this year. Consequently liveweight can distort BW considerably, yet may be totally irrelevant to farmers.
The fertility BV is very important, and controversial. No calf, no milk, no cow!
I've left the best 'til last:
Residual Survival BV
Another composite index produced from the Longevity index with or without portions of all of the other six BW component indices. While allegations it represents "Double Dipping" have been denied, how else can you describe it when the BW contains seven parts, one of which includes the other six parts, held together by two different sets of Economic Values? Why not simply use the Longevity BV, though personally I would scrap it entirely: the Longevity BV has its own idiosyncrasies, not all of which are obvious from its definition.
In conclusion, I believe BW should be based on the four production traits. I am ambivalent about Liveweight: its Economic Value needs moderation. Fertility BV should be kept as a separate stand-alone index and scrap Residual Survival BV.
Type Index is also 'out' and I would be loathe to include a "Management" Index in the BW because there is too much variation in the subjective farmer assessments.
• Don Blumhardt is a member for five dairy breed societies, and was until two years ago an LIC Shareholders Councillor in Northland. He invited feedback on this issue either to him on telephone/fax 09 433 0468, or by way of letters to the editor: This email address is being protected from spambots. You need JavaScript enabled to view it.
