Adding to BW boosts genetic gain

Shane Campbell.

Body condition score (BCS) is soon to be incorporated into Breeding Worth (BW). The move, which follows 10 years of research and comes into effect in February, recognises the value of a cow's ability to hold on to body condition into late lactation.

New Zealand Animal Evaluation Limited (NZAEL), a wholly owned subsidiary of DairyNZ, carried out research in late 2014 which determined this value to be $107 per late lactation BCS.

This research project followed the 2013 review of the national breeding objective (NBO) where farmers indicated that they saw a cow's BCS in late lactation as an important trait.

The economic value is driven by the remedial actions that a farmer needs to take with lighter cows through autumn and winter to get them up to a BCS 5 before calving.

Achieving BCS targets is very important, as cows who calve in poor condition will be compromised for the subsequent season.

This change to BW is estimated to result in only minimal shifts for most herds and bulls ($0-$15).

It is predicted that the new eight trait BW index will lead to faster genetic gain in the national herd.

BCS value recognised

Waikato lower order sharemilkers Shane and Lynda Campbell have been ahead of the curve in recognising the value of BCS within the 450-cow herd they milk north of Matamata.

The couple have local veterinarian and accredited BCS assessor Katrina Roberts visit once a month. Ms Roberts provides a comprehensive report on the spread of cow BCS, the changes since her last visit and her recommendations for the coming months.

The couple run almost half the herd as a separate mob, which contains the heifers and thinner cows.

When cows' BCS is recorded as falling to 4 or below, they will be drafted out of the main herd.

In the second mob they will receive an additional 2-3kg DM per day.

Mr Campbell is looking forward to seeing the BCS trait incorporated into BW and believes it will confirm much of what he has witnessed in past years of recording BCS in their $132 BW herd.

"The top cows' condition seems to fall off a lot quicker over lactation. By putting the BCS trait into BW, that puts a value on their ability to hold that condition, especially later in lactation. If you can get a cow that can milk well, and hold BCS, it has to be a worthwhile trait to consider."

Drying off early costs money

The couple aim to get 300 days in milk, but Mr Campbell says they also want to be realistic about the cows being up to BCS 5 for the start of following season.

Mr Campbell needs no convincing about the cost of drying off early, or getting a lighter cow up to condition through winter.

Last season, they had 20 cows at less than BCS 4 in February that required drying off.

"We have established that those 20 cows cost us around $12,500 in lost production and extra feed."

His calculation is based on a milk price of $5.50kg MS and a feed cost of $250/t of dry matter.

With several years of BCS history behind his herd now, Mr Campbell is also interested in the heritability of BCS from mother to daughter.

He has noticed how cows who lose their weight quickly tend to produce heifers that do the same.

"It will be good to see the BCS numbers in the BW backing up what we are observing in the herd every season."

* First published in Inside Dairy