BREEDING cattle that can utilise feed more efficiently allows producers greater opportunity to offset the cost of feed in a commercial cattle program.

As noted in tonight’s separate article, feed cost is the greatest costs incurred within a commercial breeding program. Often these costs are not so much seen as line items, but are manifested in restrictions on production, fertility or market compliance.

Many producers often consider offsetting the lower levels of production that are a result of feed costs, by selecting for higher growth rates. However, the impact of selection for higher growth and its impact on the feed efficiency of a breeding herd is something that many producers have yet to truly consider.

A recent paper written by Robert Herd, Hutton Oddy, Paul Arthur and Matt McDonagh has been published in the CSIRO Journal of Animal Production Science.

This paper outlines research conducted with Angus cattle selected based on growth rates over five generations. The trial cattle came from three different lines: A fast growth to yearling age (High Line), slow growth to yearling age (Low Line) and from an unselected control line.

Single trait selection

Over the five generations, the cattle in the project had been selected for the single trait of growth rate on pasture. As a result of this process, there was a 34 percent difference in yearling weight between the Fast (High) and Slow (Low) lines.

The experiment described in this recent paper was conducted over sequential years, where steers and heifers were measured for feedlot performance over a 70-day period and following slaughter were assessed for carcase and eating quality traits.

Results

The results of the experiment offer some interesting insights into the impact selection for a single trait such as growth rate had on feedlot performance.

The steers from the High Line where 42pc heavier than the Low line steers when they were entered into the feeding period. These steers grew 49pc faster and at the end of 70 days were 43pc heavier.

While on the surface this does appear to offer some encouragement to producers wanting to achieve faster growth, there were some other results worth noting.

The amount of feed the High Line steers consumed over the 70-day period was higher per day (51pc greater than the low line steers). More significantly, the Feed Conversion Ratio (FCR – a measure of daily feed intake divided by average daily gain), was no different between the two lines.

In practical terms this meant that while the High Line (fast growth) steers would be expected to gain 100kg in a shorter time than the slow growth steers (86 days vs 129 days), both lines would eat about the same amount of feed to put on this amount of weight.

Feed intake vs feed efficiency

The experiment demonstrated that while selection for growth rate on pasture did achieve consistent changes in feed intake and growth rate of steers in a feedlot finishing program, while the fast group of cattle (High Line) were more than 40pc heavier at the end of the feeding period, their feed intake was proportionally higher, and there was no improvement in the feed conversion ratio of those animals.

As the paper noted “In other words, after more than five generations of genetic selection, the superior growth was driven by increased feed intake rather than increased efficiency of feed use.”

The value of this work for producers is in demonstrating that focussing on a single trait may not actually achieve the results that were intended.

Faster-growing cattle may be of value in a feedlot program. However, it is likely this value would be captured through either faster throughput or having more cattle moving through the feedlot infrastructure. On a feed cost, it is likely the benefits would be more marginal.

Performance records

In selecting for both increased growth and greater feed efficiency, producers should access and consider performance records (EBVs) and particularly consider the accuracies presented with this data.

It is possible to change the genetics of a herd to achieve both a more feed efficient herd as well as capturing higher growth, which will have a positive impact within the breeding herd and in the performance of sale progeny.

Alastair Rayner is the General Manager of Extension & Operations with Cibo Labs and Principal of RaynerAg.  Alastair has over 28 years’ experience advising beef producers & graziers across Australia.   He can be contacted here or through his website www.raynerag.com.au