One of the popular myths presented at this time of the year is that proofs for young genomic AI bulls don’t stack up and that, as a result, farmers would be better to stick to using daughter-proven or even stock bulls when breeding dairy female replacements. Is there evidence to support this assertion or should farmers continue to use teams of young genomic AI bulls?
To answer the question, the ICBF undertook an analysis of 2019 co-op performance report data from 10,553 spring-calving dairy herds. A total of 1.06m cows were included in the analysis, with the herds categorised into three groupings as follows:
(i) Young genomically selected (GS) AI bulls to breed their heifer replacements;(ii) Daughter-proven (DP) AI bulls (for milk traits), to breed their heifer replacements;(iii) Stock bulls (SB) to breed their heifer replacements. The results were remarkably consistent across the three groups and clearly highlighted that herds using higher levels of young GS bulls had higher herd EBI values and were therefore more profitable and sustainable in terms of milk solids and female fertility performance (see Table 1).
Differences in milk solids/cow amounted to some 30kg fat and protein between the herds using GS bulls, compared with DP bulls and a further 29kg difference between herds using GS bulls and those using mainly stock bulls.
These results were further supported by an additional analysis undertaken by the ICBF, wherein heifers calving into the national dairy herd for the first time in 2020 were categorised into one of three categories, whether they were the progeny of:
(i) A genomically selected (GS) bull at the time of conception.(ii) A daughter proven (DP) bull (for milk traits) at the time of conception or (iii) A stock bull (SB). This exercise was then repeated for each previous year up to 2015, resulting in almost two million animals being included in the analysis.
Plots of the genetic trend for each of these three groups were then generated (see Figure 1) and indicated that, in EBI terms, progeny of young GS bulls were €30 ahead of daughter-proven bulls and €70 ahead of stock bulls, across all of the six years of data.
These EBI differences reflect closely the differences in actual performance observed in Table 1 and confirm without question that if you want to maximise the profitability and sustainability of your dairy herd this spring, then use teams of high-EBI GS bulls.
Getting rid of the dairy stock bull
The data presented in Table 1 clearly shows that cows bred from stock bulls lag behind both classes of AI-bred animals. Milk yield is over 530l/cow behind herds that use genomic bulls, milk solids is 59kg/cow behind and milk value is €269 behind.
That milk value figure is shocking. It stems from the fact that stock bull-bred cows have lower milk fat and protein constituents and have significantly poorer fertility traits, meaning they don’t get the same days in milk as their AI-bred cohorts.
Faced with this unequivocal data, why do farmers persist with using a stock bull to breed dairy replacements? And let’s be clear, the number of replacements bred by stock bulls is not small, with about 50% of all replacements entering the national herd bred by stock bulls. Based on the data in Table 1, the cumulative opportunity cost of using stock bulls is as much as €215m in lost milk sales across the whole sector.
The only rationale I can think of for using a dairy stock bull is that it is less effort than carrying out AI. It’s hard to argue against this point, but, at the same time, the return on investment from putting in this effort is huge. However, the good news is that it’s not as though farmers who currently use stock bulls and who don’t want to use AI don’t have an alternative. The alternative is to buy in high-EBI AI-bred replacements either as calves or as older heifers. Instead of using a dairy stock bull, they can use a beef stock bull which will increase the value of all their calves born and offset the cost of purchasing the dairy replacement heifers.
Aidan Brennan
One of the popular myths presented at this time of the year is that proofs for young genomic AI bulls don’t stack up and that, as a result, farmers would be better to stick to using daughter-proven or even stock bulls when breeding dairy female replacements. Is there evidence to support this assertion or should farmers continue to use teams of young genomic AI bulls?
To answer the question, the ICBF undertook an analysis of 2019 co-op performance report data from 10,553 spring-calving dairy herds. A total of 1.06m cows were included in the analysis, with the herds categorised into three groupings as follows:
(i) Young genomically selected (GS) AI bulls to breed their heifer replacements;(ii) Daughter-proven (DP) AI bulls (for milk traits), to breed their heifer replacements;(iii) Stock bulls (SB) to breed their heifer replacements. The results were remarkably consistent across the three groups and clearly highlighted that herds using higher levels of young GS bulls had higher herd EBI values and were therefore more profitable and sustainable in terms of milk solids and female fertility performance (see Table 1).
Differences in milk solids/cow amounted to some 30kg fat and protein between the herds using GS bulls, compared with DP bulls and a further 29kg difference between herds using GS bulls and those using mainly stock bulls.
These results were further supported by an additional analysis undertaken by the ICBF, wherein heifers calving into the national dairy herd for the first time in 2020 were categorised into one of three categories, whether they were the progeny of:
(i) A genomically selected (GS) bull at the time of conception.(ii) A daughter proven (DP) bull (for milk traits) at the time of conception or (iii) A stock bull (SB). This exercise was then repeated for each previous year up to 2015, resulting in almost two million animals being included in the analysis.
Plots of the genetic trend for each of these three groups were then generated (see Figure 1) and indicated that, in EBI terms, progeny of young GS bulls were €30 ahead of daughter-proven bulls and €70 ahead of stock bulls, across all of the six years of data.
These EBI differences reflect closely the differences in actual performance observed in Table 1 and confirm without question that if you want to maximise the profitability and sustainability of your dairy herd this spring, then use teams of high-EBI GS bulls.
Getting rid of the dairy stock bull
The data presented in Table 1 clearly shows that cows bred from stock bulls lag behind both classes of AI-bred animals. Milk yield is over 530l/cow behind herds that use genomic bulls, milk solids is 59kg/cow behind and milk value is €269 behind.
That milk value figure is shocking. It stems from the fact that stock bull-bred cows have lower milk fat and protein constituents and have significantly poorer fertility traits, meaning they don’t get the same days in milk as their AI-bred cohorts.
Faced with this unequivocal data, why do farmers persist with using a stock bull to breed dairy replacements? And let’s be clear, the number of replacements bred by stock bulls is not small, with about 50% of all replacements entering the national herd bred by stock bulls. Based on the data in Table 1, the cumulative opportunity cost of using stock bulls is as much as €215m in lost milk sales across the whole sector.
The only rationale I can think of for using a dairy stock bull is that it is less effort than carrying out AI. It’s hard to argue against this point, but, at the same time, the return on investment from putting in this effort is huge. However, the good news is that it’s not as though farmers who currently use stock bulls and who don’t want to use AI don’t have an alternative. The alternative is to buy in high-EBI AI-bred replacements either as calves or as older heifers. Instead of using a dairy stock bull, they can use a beef stock bull which will increase the value of all their calves born and offset the cost of purchasing the dairy replacement heifers.
Aidan Brennan
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