A new herd of elite dairy cows was established in 2012 to evaluate the use of genomic selection. This herd achieved a 5% empty rate and produced 430kg of milk solids per cow in 2014, with only first- and second-lactation cows.

During 2012, a research team based at Moorepark began genotyping maiden heifers from around the country that could be suitable for the experiment. In total, 160 maiden and in-calf heifers were purchased.

The purchased animals had to pass a number of tests: firstly, they had to be high EBI Holstein Friesian; secondly, they had to pass a rigorous health screening programme; and finally, they had to be genetically diverse.

“To put genetic diversity in context, of the heifers that we purchased in 2012, there were 42 different sires represented and no more than eight heifers had the same sire. Since then, we have introduced more sire lines through our own breeding programme. This is important as it helps to keep the study diverse and to avoid over reliance on any one particular sire or grand sire,” explained project leader Frank Buckley.

The herd is based at the Dairygold research farm in Kilworth. The high-EBI cows (Elite) are being compared against lower EBI cows (National Average). In 2014, the Elite herd, of which there are 90 cows, had an EBI of €244, with €67 for milk and €139 for fertility.

The National Average herd had an EBI of €133 with €48 for milk and €63 for fertility.

Frank explained that there is more to the experiment than just comparing Elite and National Average cows;

“We are running the cows across three feeding systems. System one is our control group. These cows graze to 4.5cm post-grazing height and consume about 500kg of concentrate in a typical year. The next group is our low grass allowance group. These cows graze tighter, down to 3.5cm post-grazing height, but get the same concentrate level as the control herd. The third group is the high concentrate group. These graze to the same height as the control cows, but consume over 1t of concentrate feed per year.”

Measurements

The researchers are then comparing the performance of the Elite and National Average animals across the three feed systems. According to Frank, production and fertility are the main measurements, but other measurements are also being taken.

“The Elite herd is effectively two generations ahead of the National Average herd at the moment. This allows us a unique opportunity to measure all aspects of their performance and behaviour to better understand what makes them elite.”

These measurements include: grazing behaviour studies, dry matter intake, feed conversion efficiency, locomotion scoring and greenhouse gas emissions, among others.

“This is important as if there was some trait appearing that we didn’t like, or some other health issue affecting the Elite herd, at least we will be aware of it before it affects the national herd.”

So, after two full years of production, how is the Next Generation herd performing? Looking at fertility results, substantial differences have emerged between the two groups.

“When comparing 2013 and 2014 together, the Elite herd is hitting all our fertility targets, achieving a 95% submission rate in three weeks, a 71% six-week in-calf rate and a 10% empty rate after 12 weeks of breeding.”

“The lower EBI National Average herd had an 89% submission rate, a 55% six week in-calf rate and a 24% empty rate after 12 weeks of breeding,” Frank said. There was no difference in the fertility between the feeding systems. Frank says the better fertility with the Elite animals will have long-term consequences.

“The differences between the herds are substantial and hugely positive. For me, the most important measure of fertility is the six week in-calf rate and the higher this is the better. This means more cows will be calving earlier in the season, in line with the grass growth curve and following on from this there will be longer lactations for the majority of the herd.

Difference

“There is a huge difference in the empty rate between the two herds, with the Elites averaging 10% between 2013 and 2014, versus 24% for the National Average herd. From a practical point of view, this means less replacements are required and more milk is produced from a more mature herd.”

When it comes to milk solids production, small differences emerged between the two groups. The Elite herd produced 391kg MS and the National Average herd produced 390kg MS on average between 2013 and 2014. Remember, these were all first lactation cows in 2013, so production is going to be less than with a mature herd.

There was also a 30% replacement rate in 2014. This is the same for both herds – Frank says this is to ensure there is no bias, but it means that the Elite herd has an artificially high replacement rate which reduces the average yield per cow as first lactation animals yield less than mature cows.

There was a notable difference in the way the milk was produced with the Elite cows producing less volume but with a higher fat and protein percentage whereas the National Average herd produced more volume but with less solids.

“In an A+B-C payment system, the value of the milk from the Elite herd is greater by about €34 per cow when milk is at 30 cent per litre.” Frank said.