Improving growth through genetics
Growth is a trait of economic importance, is moderately heritable, and can be measured with reasonable accuracy. In general, with all other things being equal, higher growth rates will lead to higher profitability and consequently it a key breeding objective for most herds.
BREEDPLAN calculates three growth EBVs – 200 Day Growth, 400 Day Weight and 600 Day Weight. These EBVs are the best genetic prediction of the animal’s ability to grow to weaning (200 day), yearling (400 day) and later ages (600 day). 200 Day Growth EBVs are therefore important to vealer breeders, 400 Day Weight EBVs for yearling breeders and 600 Day Weight EBVs for breeders of heavy steers. These EBVs are closely linked genetically but there is some scope to select for them individually. When selecting bulls for growth EBVs it is also important to check Birth Weight EBVs, as there is a positive correlation with growth. Small or moderate Birth Weight EBVs are desirable.
(i) 200 Day Growth
200 Day Growth EBVs are estimates of the genetic differences between animals in live weight at 200 days of age due to their genetics for growth. Expressed in kilograms (kg) it is a measure of an animal’s early growth until weaning. This trait is measured on the weight of calves between 80-300 days of age.
It is an important trait for breeders turning off animals as vealers or weaners. Larger, more positive, 200 Day Growth EBVs are generally more favourable.
(ii) 400 Day Weight
400 Day Weight EBVs are estimates of the genetic differences between animals in live weight at 400 days of age. Expressed in kilograms (kg) and calculated from the weights of calves taken between 301 and 500 days of age.
This EBV is an important trait for breeders turning off animals as yearlings. Larger, more positive, 400 Day Weight EBVs are generally more favourable.
(iii) 600 Day Weight
600 Day Weight EBVs are estimates of the genetic differences between animals in live weight at 600 days of age. Expressed in kilograms (kg) and calculated from the weights of calves taken between 501 and 900 days of age.
This EBV is an important trait for breeders targeting the production of animals suited for heavy weight grass or grain fed markets. Larger, more positive, 600 Day Weight EBVs are generally more favourable.
Mature Cow Weight
Mature Cow Weight EBVs are estimates of the genetic differences between cows in live weight at 5 years of age. Expressed in kilograms (kg) and calculated from weights taken on the cow when her calf’s 200 day (weaning) weight is being measured. A cow with a higher, more positive Mature Cow Weight EBV would usually produce progeny with a higher mature weight than animals with lower Mature Cow Weight EBVs.
Mature Cow Weight EBVs are an indicator of:
- cow feed requirements – in general, lighter cows will tend to eat less and consequently have lower feed requirements and be less expensive to maintain.
- cull cow values – the major determinant in the value of cull cows in a commercial herd will be live weight. Consequently, heavier cows may provide higher returns from the sale of cull cows.
What level of Mature Cow Weight EBV is optional and depends on your herd and breeding objective, although a balance between the cow feed requirements and cull cow values should be considered for commercial producers.
It is important to remember that selection on increasing growth alone may also result in changes to other economically important traits that may affect profitability of your herd. For example there may be higher instances of calving difficulty by selection of animals with increased growth and therefore increased birth weight.
Adapted from Understanding Growth EBVs (121 KB), Understanding Mature Cow Weight EBVs (190KB), BREEDPLAN International Beef Recording Scheme 2012.