Live weights taken on animals when the average age of the contemporary group is between 501 and 900 days of age are used to calculate 600 Day Weight EBVs within the TransTasman Angus Cattle Evaluation (TACE).
Recording 600 day weights
All weights should be recorded using appropriate (and accurate) scales. Do not guess/estimate weight or use measuring tapes to calculate weight. Either weigh the animals using appropriate scales or don’t record weights. Weights should be recorded to the nearest kilogram.
When should 600 day weights be collected?
The 600 day weight for an animal needs to be recorded when the average age of their contemporary group is between 501 and 900 days of age. Within this age range, a date should be chosen that fits in with normal, routine management practices (e.g. pregnancy testing heifers) and is reasonably close to when the average age of the group of animals is 600 days of age. TACE provides suggested weigh dates to assist you when making this decision. Animals do not need to be weighed when they are all individually 600 days of age on the day of weighing, but rather the whole contemporary group
weighed when the average age of the group is approximately 600 days (i.e. 20 months).
Important considerations when collecting 600 day weights for heifers
Recording 600 day weights on heifers that are in the later stages of pregnancy can cause significant bias to the 600 Day Weight EBVs that are calculated due to variation in live weight being incorrectly attributed to differences in growth genetics.
The additional weight at each stage of pregnancy in an Angus heifer resulting from a 39kg calf (at birth) is outlined in the table below.
If heifers are being calved down at 2 years of age, as is usually the case in Angus breeding enterprises, consideration can be given to collecting 600 day weights for heifers at an earlier age (e.g. 550 days of age, or commonly pregnancy testing) when the effect of pregnancy status on weight is minimal.