Hybrid Vigour for Fertility in Tropical Beef Herds, by Greg Popplewell
As rising input costs and weather events continue to eat away at the profits of Northern Australian beef production, the topic of fertility has received much more air time in the rural media and around the cattle yards, kitchen and board room tables of beef producers. There are several elements to a successful fertility improvement strategy including bull selection, bull fertility testing, pregnancy testing, and nutrition, however, have we forgotten about hybrid vigour?
When most people think of hybrid vigour (heterosis) they think of increased growth rates and thrifty calves, however increased breeder fertility is the biggest gain you will get from hybrid vigour and hybrid vigour is currently for most cattle breeders, the biggest opportunity to genetically improve their herd’s fertility.
So, it’s obvious that hybrid vigour has a massive role to play in animal production systems that see big economic improvements per unit of fertility increase, be it eggs, piglets or calves. How we apply the proven success of hybrid vigour to the Northern Australian beef industry however needs a more simple practical solution than the strategies currently employed by the white meat industry.
To make lots of first cross females in laying chooks is easy; run some purebred hens with a few purebred roosters and hatch lots of crossbred chickens to use the females as commercial layers. A single purebred hen can produce around 100 crossbred daughters a year. This F1 female production strategy of the layer industry however is not so practical in tropical beef cattle production where a cow on average has less than one calf per year. In a well run Northern Australian herd you are likely to need to run about 5 purebred breeders for every 1 crossbred breeder in order to maintain a static herd size of each.
To avoid having to run a one herd of purebred cows to supply another smaller herd of crossbreds, composite breeding can be chosen to maximize total system hybrid vigour. Providing inbreeding is controlled, a four breed composite can maintain around 75% of first cross (F1) hybrid vigour. Once established, the logistics of a composite program is much simpler than that of F1 breeding and two breed rotational strategies. On average composite breeding offers more hybrid vigour per breeder.
Another advantage of running composites is that you also get hybrid vigour in your bulls, meaning improved bull fertility, which is great because it takes two to tango!
Fertility can also be slowly genetically improved by selection, involving careful measurement and evaluation of animals and their relatives. For this reason it important to source bulls from a composite program that also includes selection for fertility within a multi-trait selection policy. That being, a policy that incorporates selection for fertility, growth and carcass and in addition to this has used foundation breeds and animals that are inherently fertile.
*levels may vary depending on base breeds, design and herd dynamics.