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. 200 Day Growth EBVs are expressed in kilograms (kg) and are calculated from the weights of calves taken between 80 and 300 days of age. This EBV is a measure of an animal’s early growth to weaning. 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. 400 Day Weight EBVs are expressed in kilograms (kg) and are 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. 600 Day Weight EBVs are expressed in kilograms (kg) and are 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. Mature Cow Weight EBVs are expressed in kilograms (kg) and are calculated from weights taken on the cow when her calf’s 200 day (weaning) weight is being measured.

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.

For more information see BREEDPLAN EBVs.