Feed efficiency: What to know

Previously, genetic improvement has been aimed mainly at output traits such as fertility and liveweight, however little direct emphasis has been placed on reducing inputs to improve efficiency of production. Selection for livestock which is more efficient when it comes to feed intake and production is however not a new concept; this has long been recognized in the pig and poultry industries, in which cost of feed is easily quantified. These industries have made significant improvement by improving both genetic and non-genetic factors effecting feed efficiency.

Profitability depends on keeping cost to a minimum without sacrificing production or quality. Producers have no or little control over the market price for their products; therefore, they should focus on producing their products more efficiently. Various factors contribute to feed efficiency becoming more and more important in the beef cattle industry. These include factors such as frequent droughts, increasing feed cost, decreasing weaner prices, etc. Feed is a major expense for cattle producers, second only to fixed costs. Numerous studies have shown that feed cost account for 60-65 % of the total cost of production. Maintenance in breeding cows account for 75 % of the total feed cost. Improved feed efficiency can therefore have a big economic effect on a farming enterprise. In other words, improving feed efficiency in a beef cow herd, can lead to substantial savings for producers.

The adoption of this technology in the beef cattle industry has been slow despite its known economic value. This is due to various factors, that includes for example:

• It is costly to test animals for Net Feed Intake (NFI).
• The long investment period from the implementation of the technology until economic returns are realised.
• Producers do not realize the importance of feed cost in the profitability of their farming enterprises. This is especially important in the grazing industries, since most producers tend to underestimate the true cost of pasture.

In beef cattle, attempts at genetic improvement of feed utilization in the past have been based on feed conversion ratio (FCR), which is the amount of feed consumed divided by liveweight gain. A typical range of feed conversion ratio is 4.5 -7.5, with a lower value being more desirable as it would indicate that a bull required less feed per kilogram of weight gain. Feed conversion ratio is a good measure for monitoring feedlot cattle performance. However, it is not a great measure to select for in a breeding enterprise. Feed conversion ratio is correlated to growth rate. Selection for improved FCR will result in an increase in the genetic merit for growth, which will lead to increased mature cow size and in turn will ultimately increase the feed cost of the cow herd.

Recent interest in feed efficiency in livestock has been focused on net feed intake (NFI), which unlike FCR, is phenotypically independent of growth. It is defined as the difference between an animal’s actual feed intake and its expected feed requirements for maintenance and growth. NFI is the variation in feed intake that remains after the requirements for maintenance and growth have been met. It is independent of the level of production. Because it is independent of growth, research has investigated selection based on NFI with great success. Efficient animals eat less than expected for their body weight and ADG, and have a negative or low NFI, while inefficient animals eat more than expected and have a positive or high NFI.  Residual feed intake (RFI) is exactly the same measurement/trait as Net feed intake (NFI). NFI is used by Australia and RFI in other parts of the world.

Net feed intake is the best available measure of efficiency because it is independent of the level of production.

Recent advances in computing and electronics and the availability of reliable automatic feed intake recorders have made it easier to measure feed intake. Animals can currently be tested at any of the ARC’s feed testing stations in South Africa and at the private testing station at Sernick. In Namibia animals can be tested at the private test station, GenTecSol.

Which Animals Should Be Tested for Feed Intake?

• For the NFI-P (post wean) tests (at ARC’s Calan Gate testing stations) animals should be between 180 and 280 days of age at the start of the adaptation period.
• For NFI-F (finishing) tests at a GrowSafe station animals should be between 300 and 400 days of age at the start of the adaptation period.
• Bulls, steers or heifers can be tested.
• Animals should be tested in contemporary groups (i.e. animals of the same sex which are born within an individual herd in a 60-day period) to ensure that comparisons are made between animals run under identical conditions, both before and during the feed intake test.
• Animals must be recorded with the breed society/BREEDPLAN prior to the start of the test and it is strongly recommended that they have at least a 200-day weight recorded.
• Animals that are in small or single animal contemporary groups prior to the test (e.g. twins, sick animals) should not be included.
• For effective sire comparisons it is recommended to have a minimum of five progeny per sire with at least two sires represented.
• The largest practical number of animals in a contemporary group representing the progeny of more than one sire is recommended as it will provide more comparative information per animal.

Measurement of NFI in cattle probably has the most value when recorded during growth and development. Cattle tested as efficient (low NFI) during the post weaning period, remain efficient throughout their lives. Studies have shown that a 5% improvement in feed efficiency has an economic impact 4x greater than a 5% improvement in ADG. Improving feed efficiency will influence the unit cost of production and the value of breeding stock, embryos, semen and weaner animals. For the grazing animal industries, it translates to the utilization of less pasture per cattle unit. This gives a farmer the flexibility to keep more animals on his farm or have more spare pasture available for times of draught, as we experienced recently.

Most of the anticipated benefits of selection for RFI are economic in nature, but recent assessments also indicate benefits in environmental sustainability. The agricultural sector is a global source of greenhouse emissions with the magnitude of its contribution differing from country to country. A recent FAO report estimates that globally livestock are responsible for 18% of greenhouse gas emissions. Selection for low RFI has an additional benefit of reducing greenhouse gas emissions by cattle. Research in Alberta (USA) and Australia shows that selection for low RFI can have significant results:

• lower maintenance requirements of the cow herd by 9% to 10%
• reduce feed intake by 10% to 12%
• have no effect on ADG or mature size
• improve FCR by 9% to 15%
• improve calf-weight-per-cow feed intake by 15%
• lower methane emissions by 25% to 30%
• lower manure production by 15% to 20%
• lower heat production by 9% to 10%

It is fortunate that NFI selection is not associated with any negative effects on reproduction or growth. Considerable variation in NFI exists among individual animals within a specific breed. This variation suggests that substantial genetic progress can be made. It is fair to moderately (h² = 0.29 – 0.46) heritable, so it is worth selecting for. NFI is believed to represent the inherent variation in the basic metabolic processes which determine efficiency.

The fastest way to improve feed efficiency in your herd is to select breeding bulls that are naturally feed-efficient, since 80 to 90 % of the genetic improvement in a herd comes from the sires. An efficient bull will pass on superior genetics for feed efficiency to his progeny, which will be realized as feed savings for calves in the feedlot and for replacement heifers entering the cow herd. Studies have shown that selection for low NFI will result in progeny that consume less feed for the same level of production as progeny of high NFI cattle.

Where are we at with feed efficiency in the Brahman breed in Southern Africa

BREEDPLAN recently conducted a test run for NFI in Brahman cattle in Southern Africa. This run included the NFI records of 2665 bulls tested over the years. Most of these records were historic phase C test data. Approximately, 30% of these records were in single bull contemporary groups (CGs). Of the remaining records, 21% were in CGs of 2 bulls, 21% in CGs of 3-5 bulls and 29% in CGs of 6+ bulls. Contemporary groups of less than 5 animals are not that informative and are normally excluded from the analysis. The contemporary groups of 6 and more animals suggest some potentially useful data. The majority of historic data is lost in the analysis due to single or very small contemporary groups. Thus, the 2665 NFI records that exist for Brahman is an over-estimation of the amount of potentially useful data for the analysis. Going forward it is very important that when animals are sent to be tested for NFI, breeders should make 100% sure that they send animals in contemporary groups of no less than 5 animals per group. Preferably groups should be 10 animals and more with the progeny of at least 2 sires. If Brahman breeders continue testing of their animals for NFI, BREEDPLAN will soon be able to estimate breeding values for their animals to be published. This will be a significant benefit for the Brahman breed.