EBVs…
Calving ease is one of three new
EBVs…
By John Burns
SIGNET has added three new estimated breeding values to the six already used for beef bulls.
New calving values will allow producers to compare calving ability of sires within breeds, while muscle depth will allow selection for meatier animals.
Speaking at a meeting in Tiverton, Devon, Signet consultant Rob Shields explained that the new EBVs were calving ease, where a more positive score is better; gestation length, where a more negative score is desirable; and muscle depth, where a positive score is wanted.
The new calving EBVs have enabled bulls to be given a Calving Value in £, calculated from the economic effect of the components. Each day below breed average gestation length is considered to be worth £1, and differences in EBV for calving ease are priced at £22.40 for each standard deviation from breed average. The third component of calving value is birth weight, though it is not given an economic weighting. Calving values can only be compared within breeds.
All breed societies agreed calving ease should be given top priority, said Mr Shields.
The information used to calculate values comes from breeders own records. This puts calving difficulty on a scale from 1 to 5, with 1 referring to a unassisted production of a live calf, and 5 meaning a caesarian was necessary. The economic weighting given to the scores is: Score 1, nil; 2, £7; 3, £56; 4, £95; 5, £281.
For statistical and presentational reasons the data are converted from the calving difficulty scale where the highest scores and costs refer to the greatest difficulty, to a calving ease EBV where the higher the score the easier the calvings and on to a calving value where the highest cash value is linked to the easiest calving.
Gestation length records are collected only from AI users, though pressure is growing for herds using closely recorded natural service to be allowed to contribute.
The Calving Value is for bulls and refers strictly to the ease with which his progeny will be born. It does not follow that his daughters will have their own calves easily. In fact it is possible that the reverse will be true because the progeny of a bull with a high calving value might have achieved that because they were narrow-hipped.
That would not be a good conformation for an easy-calving cow. An EBV for the ease with which cows calve will be developed later, said Mr Shields.
A bull with an EBV of 6 for his progenys ease of calving would, on average, sire 3% more calves which were born easily than would a bull with an EBV of 0.
Mr Shields countered criticism that the system was too dependent on breeders assessments by saying that there were so many records that a few cheats would have minimal effect.
Although the muscle depth EBV is a new development it includes records going back to the 1970s. It is 26% heritable and so it is hoped its inclusion will increase the rate of progress towards meatier cattle.
The beef value for a bull now includes EBVs for birth weight, 200-day and 400-day weights, muscling score (assessed visually on a scale of 1 to 15), muscle depth, and fat depth.
The latest beef values for the majority of bulls in most breeds had fallen, said Mr Shields. That was partly because the EBV for muscle depth were now included, and partly because more UK data had replaced foreign data in the calculations.
NEW Ebvs
• Identifies bull with easily born progeny.
• May not follow that progeny easy calving.
• Muscle depth now included in beef value.
The new calving value score will reflect how easily a bulls progeny is born.
NEW EBVS
• Identifies bull with easily born progeny.
• May not follow that progeny are easy calving.
• Muscle depth now included in beef value.