BETTER BULLS TO BREED BETTER COWS
As well as Estimated Breeding Values (EBVs) for the traditional production traits such as growth and muscling, breeders and buyers of Limousin cattle can take advantage of a range of Maternal trait EBVs developed in recent years.
Extensive research by SAC, DEFRA, SEERAD, MLC and supported by the British Limousin Cattle Society identified the following as the major maternal factors contributing to UK beef profitability:
- age at first calving
- reproductive success
- replacement rate, and
- cow size
In response, so that breeders can effectively select animals with high genetic merit for traits that contribute to these, the Estimated Breeding Values (EBVs) available are as follows:
- Longevity (years)
- Age at First Calving (%)
- Calving Interval (days)
- Maternal Calving Ease (%)
The table below shows what each EBV indicates and how to interpret it when using or buying bulls and replacement females:
| Trait | Predicts | Interpretation |
|---|---|---|
| Longevity (years) | Predicts the length of a cow’s breeding life. For bulls it predicts the breeding life of his female offspring. | +ve values = longer breeding life |
| Age at First Calving (%) | Predicting the ability to first calve at a young age, given the opportunity. For bulls, it predicts their female offspring’s’ ability to first calve at a young age, given the opportunity. | -ve values = a higher proportion of females reaching puberty at an early age |
| Calving Interval (days) | Predicts reproductive success. For bulls, it predicts the reproductive success of female offspring. | -ve values = cows that will get back in calf more quickly |
| Maternal Calving Ease (%) | Predicts the ease with which a cow will calve. For bulls it predicts how easy calving his female offspring will be. Not to be confused with Calving Ease Direct (the ease with which a bull’s progeny will be born). | +ve values = more unassisted calvings |
Together with the existing 200 Day Milk EBV, the Beef Value and the Calving Value, these EBVs have also been used to produce two new Indexes, as follows:
Maternal Value
An index predicting the overall economic value of an animal’s genetic ability to produce breeding females.
As with all other breeding indexes, the Maternal Value is calculated from the relative economic values of the contributing EBVs.
A bull with a Maternal Value of LM12V, for example, will be worth £12 more per cow mated than a bull with a value of LM0V, half of which will be realised in his progeny by merit of their maternal characteristics.
Maternal Production Value
The economic value of an animal in terms of its overall genetic potential to produce female replacements for breeding and males for finishing.
This Index is calculated from Maternal Value, Beef Value and Calving Value, while also taking into account Maintenance Value (the costs associated with feeding mature cows within the herd).
A bull with a Maternal Production Value of LM10P, for example, will be worth £10 more per cow mated than a bull with a value of LM0P, half of which will be realised in his progeny by merit of their maternal and carcase characteristics.
In addition to this, five further EBVs are at various stages of development and will be produced as herd data becomes available. Scrotal Circumference EBV: an indicator of fertility in related females
- Scrotal Circumference EBV: an indicator of fertility in related females
- Cow Weight EBV: an indicator of mature size of cows
- Udder Score EBV: an indicator of udder size and shape
- Teat Score EBV: an indicator of teat size
- Docility EBV: an indicator of animal temperament
All these new EBVs and Indexes have been created using data from purebred and cross bred herds in the UK and are unique to our beef industry. Simulated herd exercises (SAC, 2004) show that the difference between selecting a bull to breed replacement heifers on the basis of Maternal Production Value can be worth up to £42/cow mated more than if the bull were selected on Beef Value alone. As more and more producers are retaining their own suckler herd replacements each year, these tailor-made EBVs and Indexes will help find the most cost-efficient animals for the job.
