semen straw© FLPA/REX/Shutterstock

US bull semen fertility data used routinely in American to aid breeding decisions has been made available to British farmers.

Californian AI company World Wide Sires has published Sire Conception Rate (SCR) figures for all its eligible American bulls available to UK farmers.

SCRs, which are calculated by the US Council on Dairy Cattle Breeding (CDCB) and published for the American AI industry three times a year, are an indication of a bull’s semen fertility.

See also: Dairy semen specialists World Wide Sires to split from Cogent

The SCR average for each breed is zero, and values are expressed as either plus or minus the average.

  • Sires with a score a point either way of zero are considered average
  • While those scoring +2.0 or more are considered outstanding fertility sires
  • A bull with a SCR value of +2.0 is expected to improve conception rates by 2% compared with an average sire
  • The average for SCR in December 2015 was +0.53

In the UK herd, each percentage point is worth £2 to the farmer per semen dose, says World Wide Sires.

“Between the highest and lowest ranking sires in the population there may be a difference of up to 12% in conception rate which combined with the estimated value of £2 per point underlines the significant of considering SCRs as part of sire selection,” says Mark Evington, general manager at World Wide Sires.

How it works

The SCR evaluation model takes into account factors including:

  • Age of the bull
  • Year the semen was used
  • Inbreeding percentage of the service sire
  • Resulting offspring

The model uses data on more than 57 million breedings, collected from across the US.

Ole Meland, former chair of the CSCB, says the size of the database contributes to the precision of the model.

“The December 2015 SCR lists were calculated using over 18 million breedings from over five million cows, only data collected within 48 months of the inseminations being included. To keep SCRs current, the last 24 months of data receives more weighting in the calculations than those from 25-48 months earlier,” he says.