The provision of feed is the single largest cost in beef production in temperate environments, making feed efficiency one of the most economically important traits in beef production. Selection to genetically improve feed efficiency of cattle therefore has significant economic benefits by reducing feed costs. This fact sheet reports on the potential for genetic improvement in Net Feed Intake.

_________________________________________________Net Feed Intake explained

Net feed intake measures whether an animal eats more or less than expected for its weight and growth rate over a test period. Low NFI animals eat less than expected and are therefore more efficient. The growth and economic advantages of efficient (low NFI) over inefficient (high NFI) steers in feedlots has been shown to be consistent and heritable in both paddock and feedlot trials.

Selection for Net Feed Intake and improved young animal performance

Several comparisons of high and low NFI lines developed from a single Angus beef herd at Trangie, NSW, have shown a considerable range in efficiency (Table 1) and that breeding to change feed efficiency is possible.

For example, after 5 years of divergent selection for NFI in a post-weaning feed test, the low NFI line (better efficiency) when compared with the high NFI line had a:• 1.25kg/day lower NFI, • 1.2kg lower daily feed intake (9.4kg/d vs. 10.6

kg/day) • 15% better feed conversion (6.6kg vs. 7.8 kg

feed eaten per kilogram of live weight gain)

Daily gain and weight at the end of the feed test did

FAST FACTS• The major British breeds of cattle in Australia are using Net Feed Intake (NFI) as their measure of feed efficiency for the

purpose of genetic improvement • There are differences in feed efficiency, as NFI, among growing and mature cattle that are both measurable and heritable• Some variation in feed efficiency between animals is due to body tissue partitioning, with efficient animals tending to be

leaner and slightly heavier • Efficient (low NFI) cows may also be leaner and conceive later than inefficient cows, though differences in overall

reproductive rate are small and inconsistent

Opportunities for Improvement in Feed Efficiency

Opportunities for Improvement in Feed Efficiency Fact Sheet CRC FOR BEEF GENETIC TECHNOLOGIES

FACT SHEETCRC FOR BEEF GENETIC TECHNOLOGIES

not differ between the NFI lines.

When measured at pasture, low NFI steers (better efficiency) when compared with the high NFI line had: • similar feed intake (3.0 vs. 3.2kg/day) • a trend towards higher daily weight gain (0.50kg/day vs. 0.42kg/day) • a trend towards better food conversion (6.4kg vs. 8.5kg feed eaten per

kilogram live weight gain).

Low NFI (efficient)

High NFI (inefficient)

Steer performance at pasture

Feed intake (kg/day) 3.0 3.2

Average daily gain (kg/day) 0.50 0.42

Feed conversion ratio (kg feed/kg gain) 6.4 8.5

Steer performance in the feedlot

Feed intake (kg/day) 12.3 12.5

Average daily gain (kg/day) 1.53 1.49

Net feed intake (kg/day)* -0.12 +0.10

Feed conversion ratio (kg/kg) 7.6 8.2

Pre-slaughter rib fat depth (mm)* 10.2 11.6

Pre-slaughter P8 fat depth (mm)* 13.1 14.8

Table 1: Live animal measurements and carcass attributes of Angus steers from Low and High NFI selection lines

* indicates a significant difference between lines

Opportunities for Improvement in Feed Efficiency Fact Sheet CRC FOR BEEF GENETIC TECHNOLOGIES

Further readingFurther information is available in RM Herd and WS Pitchford, ‘Recent Advances in Animal Nutrition – Australia’ 2011 Vol. 18 pages 45-58. University of New England: Armidale NSW

Contact DetailsTodd AndrewsNSW Department of Primary IndustriesPh: 0429 987 405Email: todd.andrews@industry.nsw.gov.au

Research LeaderDr Robert Herd NSW Department of Primary IndustriesBeef Industry Centre University of New EnglandArmidale, NSW, 2351Ph: 02 6770 1808Email: robert.herd@dpi.nsw.gov.au

Fact Sheet Prepared: April 2012

Net Feed Intake and further considerations

There are likely to be many reasons for the measured variation in efficiency. However, cattle with high NFI (low efficiency) deposit more fat and are genetically fatter based on BREEDPLAN Rib and Rump Fat EBVs.

Though increased efficiency in pasture or lot-fed young animals is desirable, the tendency for low NFI (more efficient) cows to be leaner could result in reduced female fertility. For example, breeding for low NFI has been linked to delays in reaching puberty and delayed calving compared with high NFI cows. However, differences tend to be small and inconsistent.

Research has also shown that differences between high and low efficiency lines are most pronounced when feed is readily available. When diets approach maintenance levels, there is minimal variation in the efficiency of feed use for basal metabolism. This indicates there is no difference in the energy required to maintain cow body weight when feed availability is low. The implication for producers is that during drought or other situations where nutrition is limiting, and when the benefits of reduced feed requirements would be maximised, there is little difference in NFI between animals.

Summary

Any genetic improvement in feed efficiency in the breeding herd, and in backgrounding and pasture- or feedlot-finished cattle would be welcomed by the beef industry. Although this is achievable, there can be associated changes to body composition that could impact the ability to meet market specifications for fatness and cow maternal performance. However, antagonisms between traits in breeding programs are common. Having balanced breeding objectives and multiple trait selection allows for animals with the best combination of all traits to be identified. In this case, that means identifying and selecting animals with low (favourable) NFI but also favourable fertility and carcass quality.

Figure 1: High NFI cow with calf

Figure 3: Low NFI herd in the yards

Figure 2: High NFI cows