Australia's breeding indices work in identifying sires that produce more profitable herds, Professor Ben Hayes told the Herd 17 conference in March.
Prof Hayes presented an analysis based on research from two projects - Feeding the Genes and ImProving Herds Genetics - to provide an insight into the workings of Australia's breeding indices on farms.
Three new breeding indices were launched in 2015:
Balanced Performance Index (BPI): designed to improve farm profit by identifying bulls and heifers for selection with a balance of longevity, health, type, production and feed efficiency.
Type Weighted index (TWI): designed for farmers who wished to fast track improvements in type traits.
Health Weighted index (HWI): designed for farmers who wished to fast track improvements in fertility and mastitis resistance.
Prof Hayes said his analysis showed that selecting sires with higher BPI Australian Breeding Value (ABV) resulted in cows that:
Produced more milk and milk solids than daughters of lower BPI sires, regardless of feeding system.
Were more likely to last in the herd, in all feeding systems except in total mixed ration (TMR) herds, where they were just as likely to last.
Had higher fertility. These results were also observed for sires with higher HWI and TWI ABVs.
As a result of these differences, these sires made a greater contribution to farm profit, he said.
Irish genetics research scientist Dr Donagh Berry, from the Irish Agriculture and Food Development Authority Teagasc, told the conference that having proof genetic indices worked was vital in getting farmers to trust and use them. He said Ireland, and now Australia, were the only countries that had excellent scientific proof that their breeding indices did in fact lift farm profit.
Prof Hayes said his analysis looked at three key questions:
What were differences actually observed on farm between cows sired by high and low index bulls? This included traits such as fertility, longevity and production.
Australia had the world's most diverse range of dairy feeding systems, from almost 100 per cent pasture feeding to 100 per cent TMR feeding. Did the selection indices select bulls that had daughters with higher fertility and performance across the production systems, or in only one or two production systems?
Was it possible to demonstrate that cows with a higher BPI ABV contributed more to farm profit than cows with a low BPI ABV?
Prof Hayes said the Feeding the Genes research completed by Dr John Morton in 2016 assessed the difference on farm between cows sired by low and high index ABVs bulls on milk production, survival and reproductive performance across different feeding systems. Dr Morton collected as much data as possible from as many herds as possible to do the analysis.
For survival, he looked at records from 64 Holstein herds and 27 Jersey herds showing the proportion of cows that had recalved by 20 months.
The results showed a good relationship, with probability of recalving by 20 months increasing with sire BPI ABV in all feeding systems except TMR herds where no effect was evident. The relationship was stronger for sires with high HWI ABV.
For milk production by feeding system, he used data from 203,746 lactations from 100,702 Holstein cows in 437 herds and from 36,357 lactations from 17,414 Jersey cows in 171 herds.
The relationship between protein yield, and other milk production traits, and the sire's BPI ABV was strong, across all production systems. A similar result was observed for HWI and TWI.
For fertility, the effects of the sire's BPI, HWI and TWI ABVs were assessed using the InCalf Fertility Data Project 2011 dataset. This comprised 74 commercial seasonal and split calving herds, selected because they had high-quality reproductive data in some or all mating periods from 1996 to 2010.
There was a significant relationship between six-week-in-calf rate and the sire's BPI, with the six-week-in-calf rate increasing as the sire's BPI ABV increased. Results were similar across all feed systems, and the relationship was stronger for the HWI.
Prof Hayes said the results from Dr Morton's study were:
In all feeding systems the daughters of higher BPI ABV sires produced more milk and milk solids than daughters of lower BPI ABV sires.
In all feeding systems, other than TMR herds, daughters of higher BPI ABV sires were more likely to last in the herd. (In TMR herds, daughters of higher BPI sires were just as likely to last).
Continued selection of high BPI ABV sires would result in small but ongoing increases in herd reproductive performance.
Prof Hayes said the next question to answer was did these differences actually lead to more profit on farm. He used research from Dr Jo Newton as part of the ImProving Herds project, which is a large-scale project that brings together a rigorous economic evaluation of farm profitability for 25 herds that cover the range of feeding systems and breeds used in Australia, and evaluation of genetic merit for cows in the same herd.
Dr Newton studied three Victorian dairy farms using information from the Dairy Farm Monitor (DFM) database, which collects and analyses detailed financial and farm production data from dairy farms on an annual basis, and DataGene, the national database of cow production, pedigree and ABV records.
Each herd also had additional cow lactation, health and mating records and at least two-thirds of cows had ABVs.
Dr Newton then used the information to work out how much farm profit each cow made across its lifetime. This was calculated by looking at the income from the cow's milk production, calves produced and cull value less the cost for feed, artificial insemination and mastitis treatments.
The feed cost calculation took into account the energy requirements for each cow, based on its age, breed, lactation and pregnancy records and herd level information about distance walked each day, farm topography, liveweight and condition score loss during lactation.
Within each herd, the cows were compared as two groups - a high BPI group and a low BPI group. The average contribution to profit of each group was then calculated.
The three herds included Holstein, Jersey and mixed Jersey and Holstein cows. So ABVs across breeds were scaled to a single base to enable comparison among all cows.
In all three herds, the higher BPI group of cows were significantly more profitable than the lower BPI cows. The average difference in cow contribution to profit ranged from $150 to $235 per cow per year.
The main source of this difference was milk income, with cows in high BPI groups generating on average between $185 and $258 more income from milk sales each year. Although feed costs were higher in the high BPI groups, the extra cost of feed ranged from $30 to $42, which was more than compensated for by additional milk income.
On all three farms, the high BPI cows contributed more profit than was expected. This might be because all three were Victorian herds, which had cheaper feed costs than the national average, Prof Hayes said.
A wider study with 25 herds is now underway as part of the ImProving Herds project.
Prof Hayes said Dr Newton's research showed in the three herds the cows with a higher index value contributed more to farm profit than cows with a low index value.D