BRAHMAN NEWS SEPTEMBER 2007 Issue #156
More than fifty Brahman bulls sourced from some of Australia’s leading seedstock producers as well as overseas have been evaluated as part of a large research project to help pinpoint the best ways of breeding productive and profitable progeny in northern Australian environments.
The Beef Cooperative Research Centre (CRC) research project is using purebred Brahman bulls from a number of seedstock herds identified in conjunction with the Australian Brahman Breeders’ Association as being representative of the range of Brahman genetics available in Australia over the past decade.
The project used leading bloodlines from Australia, South America, Brazil and the United States and were joined in industry herds to Brahman cows contributed by Belmont Research Station, Cona Creek, Consolidated Pastoral Company, McDonald Holdings, Stanbroke Pastoral Company and Tartrus.
The bulls, including well known sires like Lancefield Ambition and Mr International, were joined over four years (shown in figure 1 as Generation 0) and their progeny (Generation 1) have since been involved in an intense evaluation program spanning the past seven years.
During this time the progeny have been data recorded over diverse environments for a wide range of productive and adaptive traits, including complete carcase and beef quality, feed efficiency, resistance to stressors such as ticks, worms, buffalo flies, heat and seasonally poor nutrition, age at puberty in heifers, days to calving in breeding females and scrotal size in male offspring.
One project sire is able to breed progeny with the ability to add an extra 26 kilograms in carcase weight ... using recently quoted figures ... this equates to an extra $90 dollars a head, achieved simply by carrying out some genetic homework
To further value add the research the Generation 1 female progeny are now also being recorded for traits associated with lifetime reproductive performance, taking into account environmental stressors and lactation. Their male offspring (Generation 2) are being evaluated for male reproductive traits to identify traits in males that will improve the reproductive performance of their daughters and other female relatives.
Early results are already showing large differences between the sires in the project, indicating there are significant economic gains for breeders willing to base joinings on genetics and producers purchasing bulls proven to be genetically superior based on measured performance.
Estimated Breeding Values (EBVs) of the Generation 0 sires evaluated in the project have been calculated for some of the project traits. Table 1 shows the range of Brahman BREEDPLAN EBVs between the best and worst Brahman sires for a number of different attributes.
Using current market prices, the results show that that basing selection of breeding cattle on measured performance will generate increased economic returns. For example, research found one sire is able to breed progeny with the ability to add an extra 26 kilograms in carcase weight. Using a price of 345 cents a kilo, this equates to an extra $90 dollars a head, achieved simply by carrying out some genetic homework.
Similarly significant economic gains have also been identified in regard to saleable meat yield.
The bull with the best EBVs for the saleable meat yield trait was able to increase meat yield in his progeny by an extra 7.4 kilograms.
Multiply this by the average of $10 per kg and an extra $74 a head is achievable.
Another trait identified from Beef CRC research as having a major impact on productivity in the research project is days to calving.
One bull in the research project is able to reduce the days to calving of his daughters by nearly 15 days.
This equates to more than a 15 percent difference in calving rate with the added benefit of steers that are born early in the calving period and all at the same time of the year provides a significant advantage when preparing and managing sale progeny.
Table 2 shows the range of performance for Generation 1 Brahman heifer progeny for traits associated with reproduction. Whilst the average age at puberty (measured by the CRC as the age that a first corpus luteum (CL) was detected on the ovary during regular ovarian ultrasound scanning) was slightly more than two years of age in the CRC environments (Toorak, Swans Lagoon and Belmont Research Stations near Julia Creek, Ayr and Rockhampton respectively), some heifers achieved puberty at about 13 months, whilst others did not achieve puberty until >39 months.
Weight and fat depth at the time the heifers achieved puberty varied enormously. One aim of the CRC study is to identify those sire lines which reached puberty early and determine whether they are also the same sire lines that have best lifetime fertility.
Another aim is to identify indicator traits of lifetime fertility (e.g. growth rate and body composition traits) that could be modified using non-genetic approaches, to determine the economic feasibility of managerial interventions to improve reproductive performance.
Age at first CL was strongly genetically correlated with days to calving and calving success following first joining in Brahmans, indicating that females that were younger at puberty had genetically shorter days to calving and increased calving success when mated for the first time at approximately 25 months.
All data collected from the Beef CRC project goes into BREEDPLAN and EBVs are readily available on the web at http://breedplan.une.edu.au/
To date the research project has yielded two significant findings: the first that the difference in the age of puberty for the bulls’ daughters could vary by as much as six months, and secondly there is an overall difference of 25 percent in the calving rate between the daughters of the project, a trait which is estimated to have an 18 percent heritability.
In Brahmans, age of first CL could be used as an indirect selection criterion to improve subsequent reproductive performance, provided it can be measured cost effectively in industry and providing the associations with lifetime reproductive performance indicate the approach would be economically important for industry.
Table 1. Highest and lowest EBVs for project Brahman sires for a range of traits
|Trait||Lowest EBV||Highest EBV||Range||Estimated difference in progeny|
|Carcase Weight||-8||+44||52kg at 650 days of age||26kg carcase weight|
|Retail Beef Yield %||-1.2||+3.6||4.8% at 300kg carcase||2.4% saleable meat yield at a 300kg carcase = 7.2kg saleable yield|
|Days to Calving||+16.6||-12.9||30 days||15 days|
|Jap Ox $ Index||-23||+54||$77 per cow joined/year||$38.50 per cow joined/year|
Table 2. Trait means and ranges of performance for Brahman heifer progeny
|Age at puberty* (days)||751||394||1211|
|Weight at puberty (kg)||334||196||485|
|P8 Rump fat depth at puberty* (mm)||4.5||1.0||15.0|
|Heifers achieving puberty* by commencement of first joining at 2 years (%)||0.51||0.||1.0|
|Days to calving following first joining (days)||346||279||423|
|Calving success following first joining (%)||0.71||0.0||1.0|