Genetics and Breeding
Over the past decade, about one third of productivity improvements achieved by Australian dairy farmers can be credited to better genetics.
While the impact of genetics is gradual, it is permanent and compounds year after year. Therefore, it is worth making every breeding decision count.
Opportunity exists for Australian dairy farmers to significantly improve the genetic basis of their herds to achieving higher productivity, longer lasting cows, better fertility, and improvements in health and welfare.
The two most important ways in which farmers can accelerate the rate of genetic improvement in their herd is by:
- Consistently selecting AI sires from the Good Bulls Guide/App
- Genomic testing of replacement heifers.
Consistently selecting Good Bulls and the right replacement heifers accelerates the rate of genetic improvement in a herd. Conversely, making a poor selection decision will lock in small losses for many years to come as their poor genes are passed down. It takes the same amount of time and effort to choose a good AI sire as it does to select a poor AI sire.
Australian Breeding Values (ABVs)
Australian Breeding Values (ABVs) are an estimate of a heifer, cow, or bull's genetic merit for a particular trait. Traits for which ABVs are available include production, health, management, or type traits. Examples include:
- Milk (L)
- Fat (kg and %)
- Protein (kg and %)
- Mastitis resistance
- Survival (longevity)
- Daughter fertility
- Calving ease
- Gestation length
- Milking speed
- Feed saved
- Heat tolerance
- Overall type.
ABVs are relative measures, meaning they make more sense when compared to each other or to an average. The average, also known as the ‘base’ is a clearly defined group of animals to which all others are compared. It is updated periodically so it reflects the cows that are milking in today’s herds.
For production traits, feed saved and gestation length, the average is set at 0.
For type, health and management traits, the average is set at 100.
To illustrate this, cows with a Daughter Fertility ABV of 110 have a 10% higher 6-week in-calf rate compared to cows with an ABV of 100 (John Morton; unpublished).
Download the Pocket Guide to Australian Breeding Values (ABVs) for more information.
The Balanced Performance Index (BPI) and Health Weighted Index (HWI)
There are now over 45 different traits to choose from. Traits that have been identified as influencing a cow’s lifetime contribution to the dairy business (production, health and fertility, longevity, workability, type, and feed efficiency) have produced two multi-trait indices, the Balanced Performance Index (BPI) and the Health Weighted Index (HWI).
The BPI and HWI are designed take the hard work out of breeding for more than one trait at once. Choose the index that best suits your breeding goals.
If you are most interested in:
a balance of traits to deliver maximum profit:
Balanced Performance Index (BPI)
fast-tracking genetic improvement for traits, such as fertility, mastitis resistance and feed saved.
Health Weighted Index (HWI)
Both indices have a base of zero and there is a difference in the emphasis given to specific traits within each index. AI sires that rank highly within the BPI and HWI are listed in the Good Bulls Guide and Good Bulls App. Select Good bulls that meet your breeding goals.
The Balanced Performance Index (BPI) is an economic index that reflects most Australian farmers’ preferences as identified in the National Breeding Objective review. The BPI combines milk, fat, protein, survival, cell count and mastitis, fertility, workability, type and feed saved ABVs. The BPI is measured in dollars ($), compared with the breed average (or ‘base’) which is set at zero.
The Health Weighted Index (HWI) allows farmers to fast-track genetic improvement for traits such as fertility, mastitis resistance and feed saved. The HWI places greater weighting on these traits than the BPI. Breeding for HWI is expected to reduce cow size and show minimal production improvements because it places less emphasis on milk yield per cow. The HWI is modelled on a strictly seasonal calving system.
Do Australian Breeding Values (ABVs) and the Balanced Performance Index (BPI) work?
The Australian genetic evaluation system, which produces Australian Breeding Values (ABVs), the Balanced Performance Index (BPI) and Heath Weighted Index (HWI) is the only system which has been validated in Australia. The results of two independent validation studies are described below.
Feeding the Genes Project (2016)
In 2016, DataGene commissioned independent veterinary epidemiologist Dr John Morton to investigate the effect of sire genetics in different feeding systems in real Australian herds. The study included both Holstein and Jersey cows from 505 commercial Australian dairy herds with a wide range of feeding systems. The dataset included 240,000 lactations and almost 118,000 cows.
The five feeding systems included in Feeding the Genes (2016):
Grazed pasture plus other forages and up to one tonne of grain or concentrates fed in the bail
Grazed pasture plus other forages and more than one tonne of grain or concentrate fed in the bail.
Partial mixed ration (PMR)
Pasture is grazed for most or all the year plus a mixed ration is fed on feed pad with or without grain or concentrates fed in the bail.
Pasture is grazed for less than nine months per year plus a mixed ration is fed on feed pad with or without grain or concentrates fed in the bail.
Total mixed ration (TMR)
Cows are fed a total mixed ration with zero grazing.
The results showed that in all feeding systems, the daughters of high BPI sires produced more milk solids than daughters of low BPI sires (Figure 1). The size of the response to using high BPI sires varied between feeding systems and the benefits were greatest in herds using more intensive feeding systems (hybrid and TMR). Despite low levels of concentrate feeding, the daughters of high BPI sires also produced significantly more than the daughters of low BPI sires in low bail feeding systems.
The results also showed that in all pasture-based feeding systems (i.e., all systems other than TMR), the daughters of high BPI sires are more likely than other cows to last in the herd (Figure 2). For cows in TMR herds, there is no marked effect of the sire’s BPI on their longevity in the herd. Daughters of high and low BPI sires lasted about the same. The reason for the difference is not known but may be due to different culling priorities in TMR herds.
An additional finding of the study was that daughters of higher Daughter Fertility ABV bulls are more fertile for both Holstein and Jersey breeds (Figure 3).
Download the Feeding the Genes factsheet for more information.
ImProving Herds (2018)
The ImProving Herds project was a three-year project to explore and demonstrate the value of genetics and herd improvement in 34 Australian farms.
One of the key findings from the study was that, on average, high BPI cows produced more milk solids and last as long or longer than their low BPI herd-mates. Cows in both groups had similar numbers of artificial inseminations and mastitis treatments.
Average difference between high and low BPI cows for milk production in 27 Genetic Focus Farms.
Compared to their lower BPI herd mates, high BPI cows lasted eight months longer in productive life and produced:
- 649 L/cow/year more milk
- 50 kg/cow/year more fat
- 38 kg/cow/year more protein
- 0.29% higher fat percentage
- 0.19% higher protein percentage.
Genetic Progress Report
At a herd level, herd recording and genomic testing farms can measure and monitor genetic improvement using the Genetic Progress Report. This tool enables farmers to track progress for BPI and several traits of interest.
The Genetic Progress Report is a within-breed analysis of a herd over a ten-year period and illustrates genetic improvement for overall profitability (BPI), production, type, longevity, fertility and mastitis resistance.
Farmers can request a report from their herd test centre or contact DataGene.
The Genetic Progress Report offers farmers their own herd’s genetic picture with little extra effort.
Herd information which is collected through regular herd recording or genomic testing is routinely used to produce the cow ABVs upon which this report is based.
Download a sample Genetic Progress Report.
Breeding for improved fertility
The Daughter Fertility ABV reflects the percentage of an animal’s daughters pregnant by six weeks after mating start date, compared to the average. For year-round calving herds, this is equivalent to the percentage of daughters pregnant by 100 days after calving.
The Daughter Fertility ABV is expressed relative to an average of 100 with higher breeding values indicating more fertile daughters.
To breed a more fertile herd, choose Good Bulls or genomic tested heifers with a Daughter Fertility ABV of at least 100. In the Holstein breed, if you want to make faster gains, consider increasing the cut off to 105 or 110, as there is now a wide range of bulls available with high Daughter Fertility ABVs.
Download the Breeding for Fertility factsheet for more information.
DataGene is an independent and industry-owned organisation that is responsible for developing modern tools and resources to drive genetic gain and herd improvement in the Australian dairy industry, through research, development, and extension activities.
For more information about genomics, visit the DataGene website.