Much like the dog that didn’t bark in the Sherlock Holmes story, the letters to the editor in last week’s paper were notable for what they didn’t mention.
The dairy article (17 April 2021) to which the letters from Bernard Eivers of NCBC and Andrew Cromie of ICBF refer, has four key points:
None of these issues were raised in the responses from the aforementioned. Bernard Eivers says it is an error to compare EBI in 2018 with EBI in 2021. Why is that considering there was no base change in 2020? The changes that took place in 2020 were to reduce the weighting of genomics in the proof – done so because the 2018 proof was considered inaccurate with too much genomics present.
In his response, Andrew Cromie says the suggestion that the breeding programme is “breeding tall, milky cows” is not factually correct but then goes on to say why milk volume is increasing in high-EBI bulls.
He is correct to say that there is no evidence that the bulls mentioned will breed taller cows.
They will, however, breed heavier cows as their EBI for maintenance is over €4 lower than the national average. I cannot with any certainty say whether these cows will be taller, wider or indeed longer but they will be heavier.
Genetic improvement (or disimprovement) is permanent and cumulative. While a €4 difference in maintenance sub-index may not seem that large, in five generations the progeny will be at least 50kg heavier than they are today.
It’s always important to know the direction of travel.
As for achieving higher milk solids without increasing milk volume, surely if the percentage of fat and protein is higher in the milk then the total solids will also be higher?
The original article highlighted the fact that this is a more advantageous way of increasing output rather than using high-volume bulls, which also adds to peak milk supply management problems.
However, I will admit that it may not be the fastest way to make gains in milk solids output, but I will argue that it is a more sustainable and profitable way to do so.
Perhaps the -9c/l penalty in EBI on milk volume is insufficient, particularly in light of new environmental and peak milk constraints and that this is something which should be reviewed?
The EBI is a brilliant tool that puts an economic value on all important traits.
My original point remains: farmers need to look closely at the bulls being used, whether on fresh semen panels or not. In my view, bulls with a high predicted transmitting ability (PTA) for milk volume and a low maintenance sub-index should be avoided.
In relation to the milk sub-index, bulls within plus or minus 100kg milk PTA, but highly positive for fat and protein percentage, will be a far superior choice than bulls with low percentages but high overall solids because they produce a lot of water.