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What is Net Feed Efficiency?

Net Feed Efficiency (NFE) is a biological measure of efficiency that seeks to disentangle the underlying effects of improved metabolic efficiency from the apparent improvement in efficiency that can be associated with animals simply getting bigger. The traditional Feed Conversion Ratio (FCR) value is highly correlated with higher growth rates and bigger animals so that better FCR figures does not necessarily mean real improvements in underlying biological feed efficiency or profitability.

The mathematical derivation of NFE from daily feed intake and live weight gain figures identifies the underlying biological efficiency of the animal at a metabolic level but does it in such a way that is independent of both daily growth rate and mature body size. Using NFE rather than FCR as the measure of true biological efficiency and basing selection procedures on this measure will achieve the optimum rate of genetic improvement in the shortest time possible.

NFE is heritable (0.34) so the benefits of superior animals captured in a breeding programme are cumulative and sustainable.

What have Stabiliser done?

The Stabiliser NFE EBV has been developed from data a collected at the Wold Farm Feed Unit from over 1000 stabiliser bulls and steers.

Signet will routinely calculate the EBV for NFE based on data supplied from the Wold unit and processed by the BIG team.

At present the range of NFE EBVs is from +1.00 (poor) to -1.00 (excellent). The description of NFE is kg of DM consumed for a constant rate of growth, so larger negative numbers identify better preforming cattle.

Top 1% -0.45
Top 10% -0.17
Top 25% -0.8
Average 0
Bottom 25% 0.07
Bottom 10% 0.14
Bottom 1% 0.3

At present NFE is a “stand alone EBV” which means it does not contribute to the calculation of Beef Value or Maternal production Value indexes.

As with all EBVs, NFE is part of the overall jigsaw so single trait selection is not a good idea! A bull with good EBVs all round and a poorer that average NFE may have a significant contribution to the breeding programme.

The EBV behaves in the same way as the others on the BASCO site so you can search for animals based on NFE rating.   The accuracy figures are an important indicator of how much data is contributing to the NFE EBV.  Bulls with several sons tested will typically have accuracy figures over 75%.   Bulls not tested themselves but from a tested bull will have accuracy figures in the 40% area.

Table 1. Means, standard deviations (SD), and minimum (Min) and maximum (Max) values of dry matter intake (DMI), estimated DMI (EDMI),  liveweight gain (LWG), feed conversion ratio (FCR), net feed efficiency (NFE) and fat depth (FD)  of the first 627 tested bulls.

Trait N Mean SD Min Max
DMI (kg/day) 627 11.21 1.48 6.83 15.45
EDMI (kg/day) 627 11.23 1.27 7.95 14.82
LWG (kg/day) 627 1.707 0.299 0.786 2.824
FCR (kg DMI/kg LWG) 627 6.696 1.095 4.182 14.463
NFE (kg) 627 -0.018 0.726 -2.334 2.695
FD (mm) 627 5.13 1.54 1.75 12.75

Bulls were tested at 9-11 months of age and a summary of the range in performance is shown below. In practical terms the average of the top third bulls will eat 13% less feed than the average of the bottom third bulls for the same level of growth.

For more information contact Duncan Pullar at: [email protected]