Canada acts to iron out RIPdips in bull proofs
Canada acts to iron out RIPdips in bull proofs
By Jessica Buss
CANADA has taken steps to minimise the effects of records-in-progress – RIP – dips between bulls first and final proofs with a new production evaluation method used in its February proof run.
The UKs Animal Data Centre also hopes to begin using the technique soon.
Currently, each milker included in a bulls proof has a predicted 305-day lactation based on a standard lactation curve. Each time she is milk recorded this prediction is updated.
However, it is generally accepted that a bull can affect the shape of its daughters lactation curve. A bulls daughters may have a lower peak yield and milk more persistently compared with another bulls daughters, but could produce the same lactation yield.
This has lead to the development of the Test Day Model (TDM) at Guelph University, Canada, which doesnt use a standard lactation curve, explains Sefax geneticist Jo Bellamy.
TDM plots a point on a graph from each weighing of each daughter to produce a lactation curve specific to that sire. Before data from a bulls progeny is available the curve is predicted from his parents proofs. Milk weights are compared with those of their herd mates to account for management differences.
"TDM will allow producers to make better breeding decisions based on more precise genetic information," she says.
Germany has also begun using a TDM system but it is calculated using a different method which she believes is less able to prevent the RIP-dip effect than the Canadian TDM calculation.
"Research has found that accuracy of indexes for production traits will improve using TDM. Expected improvements are 12% for cows and 9% for newly proven bulls with fewer that 50 daughters.
"Greater accuracy significantly increases the rate of genetic progress and results in more profitable cows that produce milk more efficiently.
"It is hoped that TDM will reduce, or remove, the records-in-progress dip effect seen in the proofs of some bulls whose daughters have flatter lactation curves than the average for that breed."
TDM will also cause some re-ranking of Canadian bulls on its Lifetime Profitability Index (LPI).
Other benefits of using TDM include more accurate somatic cell count predictions and a new evaluation for lactation persistency. Milk yield persistency ratings based on lactation curve slope will help producers select sires to suit their management.
It may also be possible to include records of animals officially milk recorded less frequently in bull evaluations, she adds. This would allow producers to have fewer supervised recordings, saving costs and still providing data for bull proofs. Currently Canadian herds must have 10 tests a year, of which five must be supervised.
The ADCs Gordon Swanson says that he hopes to begin using the TDM to calculate UK proofs soon because of the massive benefits it offers for genetic progress. It will also help companies testing bulls because of increased accuracy of a sires first proofs.
Milk recording can also be more flexible, potentially allowing those animals recorded just four times a year to be included in bull evaluation, he says.
SAC has reseached TDM for three years and hopes to report its results soon, but more development is needed which needs funding, he adds.
TEST DAY MODEL
Young bull proofs more accurate.
Prevents RIP-dip.
Faster genetic progress.
TESTDAYMODEL
• Young bull proofs more accurate.
• Prevents RIP-dip.
• Faster genetic progress.