There are seven existing breeding values published by NZAEL that assess udder strength and teat placement. Udder overall is the summary score for overall udder conformation.

The economic value of udder overall considers three main costs to the farm system due to poor udder conformation. These are:

1. increased risk of developing mastitis
2. increased cost of wintering a cow whose udder deteriorates early in the season
3. increased cost of rearing a heifer to replace a cow whose udder has failed

The economic benefit of udder quality is not linear. That is, the difference in the profitability of a cow with an average udder vs a cow with very poor udder is much more than the difference in profitability between a cow with an average udder and a cow with a really good udder. Due to these diminishing returns as udder overall improves, the EV for udders in the BW index is a non-linear value. This means unlike the other eight traits; each animal has a slightly different EV for udder depending on their udder overall BV.

Read more on how udder overall is incorporated into breeding worth

There are three main changes to the liveweight evaluation:

• Firstly, only weights measured from electronic scales will be included, this means that weight scores from Traits other than Production (TOP) will no longer be used.
• The second change is the heritability for mature liveweight is higher than previously thought. This represents that more of the variation in liveweight is due to genetics than the environment.
• Lastly, instead of a pre-adjustment of two-year-old weights to a mature equivalent weight, the evaluation accounts for the greater spread of weight in mature cows than in younger cows.

Combined, these changes have resulted in breeding values that are more reflective of mature liveweight than the previous model.

Why are TOP weight scores no longer used to estimate liveweight breeding values?

The liveweight breeding value included in BW represents mature liveweight, while weight scores from TOP are only available on two-year-old heifers. Through extensive research and validation of the liveweight evaluation, NZAEL has determined that breeding values generated by using the TOP scores were not good predictors of mature liveweight breeding values, especially in an across breed evaluation system. The majority of progeny-testing herds have both scale and TOP scores available, therefore even after dropping the TOP weight scores, most of the progeny tested bulls will still have a significant number of daughters with weight records.