The Economic Breeding Index (EBI) has transformed dairy breeding in Ireland since its introduction in 2001. EBI is a tool used to evaluate the genetic merit of dairy animals, helping farmers make more informed breeding decisions. Selecting animals with higher genetic merit improves performance and profitability in grass-based dairy systems. The analysis of farm financial data (E-profit monitor) and EBI data from 2012-2016 in spring calving herds has shown that every €1 increase in herd EBI was associated with €1.96 net profit per cow.
The EBI comprises of eight sub-indexes, each with an emphasis percentage, representing the average contribution of each sub-index to the overall breeding index. Milk production and fertility are the two most valuable indexes. For example, the milk sub-index constitutes 32% of the EBI. Different traits measure each sub-index, and these traits are multiplied by economic values to generate a Euro value. These Euro values are then summed to generate an overall EBI figure. Details of the eight sub-indexes and all the traits in the EBI are presented in Graph 1.
The traits in the EBI are expressed as PTAs (Predicted Transmitting Abilities). This indicates the amount of a particular trait an animal is expected to pass on to its progeny, relative to the base cow. The PTA is equal to half of its own breeding value since a cow only passes on half her genes to her offspring. The genetic base cow is a benchmark or reference point from which the EBI is measured. All dairy animals are compared to the base cow, which has an EBI of €0. For example, if an animal has an EBI of €100, this indicates that its genetic merit is higher than the base cow. Additionally, the same animal has the potential to breed replacements that will be €100 more profitable than the base cow.
The PTA for the base group is zero, so all other animals compared to this group are either plus or minus depending on their performance. The base cow is calculated using a group of over 60,000 well-recorded cows born in 2005 and subsequently milk recorded for the first time in 2007. The performance of the base cow is presented in Table 1 below. For example, a cow with a milk kg PTA of 120kg is genetically capable of producing 240kg more milk than the base cow. This group of animals is also used as the base for fertility, using their calving interval and survival percentages, which are 398.8 days and 85.3%, respectively.
What do the different sub-indexes select for?
The milk sub-index allows for the direct genetic selection for increased milk solids and yield. The milk sub-index of the EBI selects animals using the A+B-C milk payment system. The fertility sub-index selects for more fertile cows that will go in calf easily and last longer in the herd. This will lower the number of replacements required and provide a more mature herd. Fertility remains a key driver of improving milk solids through cows calving earlier and surviving longer, which explains the large emphasis on fertility within the EBI. The calving interval trends along with the milk solids and survival trends over the last 10 years are presented below in Graph 2 and Graph 3, respectively.
The calving sub-index helps identify short gestation, easy calving bulls, and lower mortality rates. As cows start to live longer, animal health becomes even more important. The health sub-index can be used to identify bulls that will breed healthier cows. Selecting sires with better genetic merit for health traits will improve the health status of your herd. The maintenance sub-index indicates the cost of growing and maintaining the progeny of an animal differing in size. A higher maintenance sub-index equates to a smaller cow, typically with a lower maintenance cost. This is displayed in Graph 4 below.
The beef sub-index ensures the genetics for beef traits in dairy cows are improved or maintained as they contribute to 50% of their offspring’s genes. This is extremely important with the increasing focus on improving the quality of beef cattle from the dairy herd due to growing concerns around live exports. The management sub-index indicates the milking speed and milking temperament of a bull’s daughter, with negative and positive values desired, respectively. The carbon sub-index will speed up genetic progress in reducing GHG emissions from the dairy herd. This is the first breeding tool in the world to include the cost of carbon. Agriculture must reduce carbon emissions by 25% by 2030, and the carbon sub-index will help farmers breed animals with a lower carbon footprint.
National Ranking of Herds
The data in Table 2 shows dairy herds ranked by EBI, the milk sub-index, and the fertility sub-index. On average, for over 12,400 dairy herds, the average herd EBI is €181. However, substantial variation exists between herds, with the top 5% averaging €36 higher EBI than the top 25%. Similarly, the variation between herds for milk and fertility sub-indexes is €11 and €24, respectively. Such variation implies that the choice of AI sires selected for an individual herd depends on the genetic merit for the main traits of importance. Research studies from Teagasc have demonstrated that higher EBI translates into more profit per cow.
This analysis further supports the results from the Next Generation Herd that EBI is delivering for Irish farmers. The Next Generation Herd compares the performance of a group of elite high EBI cows (top 1%) to a group of national average EBI cows across various key performance indicators. Both groups are managed together under the same environmental conditions. The results show the elite EBI cows consistently produce higher milk solids, have significantly better fertility performance, and produce fewer GHG emissions compared to the national average EBI cows.
Summary
Research has shown that the Economic Breeding Index (EBI) is delivering more profitable dairy genetics while also lowering GHG emissions from dairy cows. Breeding contributes to half of the performance gains in dairy herds. Genetic improvement is cumulative and permanent; therefore, breeding high genetic merit animals into a herd will have lasting effects for several generations and can be built upon.