The NFE unit in Yorkshire
The Net Feed Efficiency (NFE) unit was established by the Beef Improvement Group to identify the most feed efficient future generations of Stabiliser sires. Both young breeding bulls and finishing steers have been evaluated through the unit over the last two years and the NFE unit is focussed on improving the efficiency of nutrient use for maintenance as well as growth across the entire suckler beef production system. The NFE project (called IMPROBEEF) is funded by the Technology Strategy Board under its Sustainable Agriculture and Food Innovation Platform and seeks to improve prosperity for beef farmers but also to reduce the Greenhouse gases associated with UK beef supply chains.
The NFE unit is based at Givendale on the Yorkshire Wolds and consists of four dedicated finishing pens each of which can hold approximately 20 young breeding bulls or finishing steers to give a capacity of approximately 80 animals per batch with an annual throughput of 3 batches per year. Animals within each pen are fed through four ‘Growsafe’ feed intake bins that have been imported from Canada especially for this purpose. The bins work using EID ear tags located in each animal, tag readers within the rim of each bin and continuous recording of feed disappearance using two weight cells which are used as mountings for the feed bins and their associated computer software.
Following an adaptation period of approximately four weeks on the unit, collation of these records across a 56 day recording period allows the actual feed intake during every meal for every animal to be accurately recorded and related to animal productivity measures. Each week, animal LW is recorded so that average LW and DLWG can be accurately derived by linear regression over the 56 day period. In addition, the backfat depths of the breeding bulls or finishing steers are determined by ultra-sound scanning at the end of the 56 day period in the normal way. Finally these values for dry matter intake (DMI), average metabolic size (LW0.75), DLWG and backfat depth are used to calculate the individual animal NFE value.
Why use NFE for the suckler beef industry?
NFE is one of the measures of feed efficiency that goes beyond simple feed conversion ratio (FCR) to take other important biological factors into account when seeking fundamental improvements in the underlying efficiency of entire suckler beef production systems. Within scientific institutions NFE can also be called Net Feed Intake (NFI) or Residual Feed Intake (RFI). Provided that they have been calculated in the same way, they all mean the same thing.
Going beyond FCR is necessary since most of the nutrient use across the entire suckler beef system is actually used for maintenance rather than growth. The entire suckler system of course, includes the breeding cows, replacement heifers, breeding bulls, suckling calves up to weaning as well as the weaned calves that have entered a beef finishing programme. Using only FCR as the efficiency measure of choice can only focus on the relationship between dry matter intake (DMI) and daily liveweight gain (DLWG) since FCR=DMI / DLWG.
For a maternal cow breed such as the Stabiliser, focussing on an efficiency measure that seeks to improve the efficiency of nutrient use for maintenance across all the animals within the suckler system should be seen as a high priority. NFE achieves this focus whilst FCR does not since NFE scales DMI to animal size, growth rate and carcass fatness rather than DLWG alone. In addition, the widely established correlations between FCR and animal size are likely to result in animals getting larger rather than focussing on greater efficiency should FCR be used as a method to select future breeding sires for improved efficiency within suckler beef systems.
NFE is expressed in terms of kg DMI/day and can be either a positive or negative number for each individual animal. Negative values are preferable since these are animals which eat less on a daily basis for any given level of animal productivity.
Results from the project so far
We are now 2 years into the project so 6 batches of cattle have been through the unit and five datasets of approximately 80 animals each have been calculated such that NFE values for 241 young Stabiliser breeding bulls, 198 Stabiliser finishing steers and 39 Beef Shorthorn young breeding bulls have been determined. Rations for both young breeding bulls and finishing steers have been based on approximately 50:50 forage: concentrate diets on a DM basis with mainly wholecrop wheat being the basal forage and simple mixes of barley, sugarbeet pulp and distillers gains making up the concentrate portions of the complete diets.
Results from one of the batches of young Stabiliser breeding bulls where NFE was determined at approximately 10–13 months of age are shown in Table 1. The general format of presenting results is to split the batch of animals into three groups on the basis of the standard deviation of the NFE values so that we can statistically compare the low NFE animals (more efficient) with the mid or average NFE animals and the high NFE animals (less efficient animals) in much the same way as enterprise gross and net margin data is presented as bottom, average and top third data in survey reports from EBLEX, QMS and HCC.
The results show that DMI figures are significantly lower for the low NFE groups compared with either the mid or high NFE groups regardless of the way the results are expressed on either a kg/day, g/kg LW or g/kg metabolic (LW0.75) basis. As the NFE calculation mechanism requires there are no significant differences in either animal size, (LW0.75), DLWG or backfat depth confirming that these differences in DMI have been identified that are independent of how big the animal is, how fast it is growing or how much backfat depth it has. Consequently, the average NFE values for the low NFE group is -ve at -0.77 kg/d compared with the average NFE value of 0 kg/d for the mid group and +0.80 kg/d for the high NFE group.
In other words we have identified animals that are more efficient without correlation with size, growth rate or body composition. In the long term, it is these more efficient animals that eat less for any given unit of size and productivity that we are seeking to identify and select as potential parents for future generations of Stabiliser beef cattle.
The full graphical presentation of all 82 Stabiliser breeding bull NFE values for this batch is shown in Figure 1.
Whilst the most efficient individual bull is approximately 25% more efficient than the least efficient individual bull this batch of bulls has demonstrated that on average, low NFE bulls consumed 13% less feed, were 14% more efficient and cost £25 less to feed over the 12 week period (at £155/t DM) on the NFE unit compared with high NFE bulls without significant differences in LW0.75, DLWG or carcass fat depth (more of the finances later).
Similar results and ranges in NFE values can be seen when finishing steers are evaluated through the NFE unit in Yorkshire. Results from one of the batches of Stabiliser finishing steers where NFE was determined at approximately 13–18 months of age are shown in Table 2 with the corresponding individual NFE values for all steers shown in Figure 2.
In much the same way as the breeding bulls above, no significant differences between the three groups were seen in mean LW0.75, LWG, or fat depth parameters as expected in NFE derivation studies. However, low NFE steers ate significantly less and were significantly more efficient (P<0.05) in terms of NFE compared to the high NFE group of steers.
Since the steers were slaughtered at the end of the NFE study in this case, the killing out proportion (g/kg) could also be determined and was also used in the derivation of the NFE value so as to ensure that NFE was also independent of body composition in terms of overall KO proportion. This may well be important since we do not want to inadvertently select for animals with poorer KO proportions over time just as we do not want to select for animals that have lower backfat depths.
Low NFE steers consumed 16% less feed, were 14% more efficient and cost £28 less to feed over the 12 week period on the NFE unit (at 165/t DM) compared with high NFE steers without significant differences in animal performance characteristics.
Similar differences in NFE values across the low, mid and high NFE groups were seen in all 5 batches of cattle where NFE values have been derived so far. Average improvement in NFE was 13.6% between the low and high NFE groups. The long term aim of the project is to develop an EBV for NFE so that more efficient Stabiliser cattle can be selected as parents of future generations. Selecting more efficient breeding animals which make up the future cow base will go a long way to ensuring more efficient and lower cost beef production in the years ahead.
Financial consequences of differences in NFE
Substantial savings in feed costs can be achieved by identifying and breeding future Stabiliser generations from these efficient animals within the suckler beef population. Given the actual feed costs used during the 12 weeks that animals were in the NFE unit (4 weeks adaptation plus 56 days NFE measurement period) it is possible to calculate the actual feed cost savings obtained within each batch of cattle through the unit. Feed costs across the 5 batches calculated so far have ranged from £155–£165 per tonne DM. The feed cost divergence between the low and high NFE groups in each of the 5 animal batches are shown in Table 3 and averaged £23.20 per animal in the low NFE groups compared with animals in the high NFE group.
Within a typical beef finishing unit where 4 batches of animals could be put through a finishing period of approximately 3 months per annum this saving would represent a feed cost saving of £92.80 per animal place per year within the unit without significant difference in animal size, growth rate or backfat depth where top third animals could be sourced compared with bottom third animals.
Similarly within the context of an entire suckler beef herd production system, assuming that similar improvements in NFE could be bred into the entire cow base and progeny population using an appropriate EBV over the longer term allows some estimation of potential cost savings from efficiency gains. Table 4 details the total feed and forage costs associated with various beef production systems from a recent survey of Scottish suckler beef farms (QMS, 2013). Assuming either a 13.6% or a 6.8% cost saving from long term NFE selection allows the scope for monetary savings to be made for each of these systems.
To estimate the cost saving potential across an entire suckler beef system including the cow herd system as well as the finishing unit it is necessary to add together the savings from the respective cow herd and cattle finishing systems. For example, adding together the figure for upland herds with the forage based finishing system at >22 months gives potential savings of £71.26 or £35.63 at either 13.6% or 6.8% efficiency gains actually realised. Currently, suckler beef production systems are mostly to be found in the upland areas of the UK with average finishing ages of slaughter cattle at approximately 23 months suggesting these potential savings would be applicable to a reasonably large number of UK suckler beef systems.
Additional issues highlighted within the IMPROBEEF project
GHG emissions – it is well recognised that lower feed intakes lead to lower methane emissions since it is the fermentation of feeds within the rumen that primarily generates methane output from ruminant animals. Figure 3 outlines the methane emissions from one batch of Stabiliser bulls and steers from the NFE unit where outputs are based on actual feed intakes and predicted methane yields (litres/kg DMI) from the low (efficient) mid and high (less efficient) animals in the study. It can be seen that due to the lower feed intakes of low NFE animals projected methane emissions are lower compared with either mid or high NFE animals (average emissions were 445, 461 and 489 litres/day for the combined low, mid and high NFE bull and steer groups respectively).
In addition to the daily outputs described in Figure 3, it has been calculated that the total greenhouse gas (GHG) emissions emitted over the time period to grow the final 150 kg of animal liveweight (500 to 650 kg) is actually 24% higher from steers due to the fact that bulls take only 82 days to achieve this, compared to steers who take 102 days. More efficient animals that emit lower levels of greenhouse gases are a distinct bonus from both an economic and environmental point of view.
Meat Eating Quality
Initial results from some of the steers put through the NFE unit also indicate that selecting for improved NFE should not result in any adverse effects on the eating quality of beef. Figure 4 outlines the tenderness measured as slice shear force (N) against the NFE value of 33 steers that have been evaluated through the NFE unit. Essentially there is no relationship between slice shear force and NFE suggesting that selecting for more efficient animals would have no effect on meat tenderness. Further samples will be obtained to augment this database.
Interestingly, slice shear values for Stabiliser bulls finished at 13–15 months of age (139.5 N) were not statistically significantly different from slice shear values for Stabiliser steers finished at 16–18 months of age (160.1 N).
Bull vs steer production systems
During 2012, approximately half of one batch was young bulls at 10–12 months of age; whilst the other half was finishing steers at approximately 15–17 months of age. Both groups were offered the same 50:50 forage:concentrate finishing quality diet ad libitum over the same 56 day growth and feed intake study. The results (Table 5) show that whilst both bulls and steers ate exactly the same amount at 12.8 kg of dry matter per day, liveweight gain for bulls was 1.84 kg/d whilst steers grew at 1.47 kg/d confirming the greater feed efficiency of bulls compared to steers.
On a feed cost basis it was also clear that each kg of LWG cost 20% less when bulls were fed compared to steers. It is well known that steers sell for higher p/kg carcass weight when marketed compared with bulls. However, it would take a hefty price premium for steers to counteract a 20% lower feed cost per kg LWG over the animals lifetime if finishing steers were to compete with the economic efficiency of finishing bulls at much younger ages compared to typical steer finishing systems.
These results focus on the need to consider total feed costs (and its associated GHG emissions) as well as sale price/kg to produce a finished carcass when comparing the overall merits of finishing bulls vs steers on both an economic and environmental basis.
Conclusions
Modern, dedicated and reliable feed intake equipment is required to measure feed intake and performance in beef cattle if valid NFE figures are to be obtained. Fortunately, such equipment has now been developed and is working successfully in the UK. Substantial savings in feed costs are evident where efficient animals are being identified using this equipment and an added bonus is that greenhouse gas emissions are also lower from these efficient animals. Ongoing work will concentrate on generating more NFE data and developing an EBV for NFE so that future generations of efficient beef animals can be bred to enhance the profitability of UK Stabiliser suckler beef systems.
Acknowledgements
The partners in the IMPROBEEF project are:– Beef Improvement Group, JSR Farming Ltd, Keenan Ltd, SAC Consulting Ltd with additional in-kind support from Morrisons and Eblex. Funding was provided by the Technology Strategy Board.
References
QMS, 2013. Cattle and Sheep Enterprise Profitability in Scotland. 2013 edition.
QMS, The Rural Centre, West Mains, Ingliston, Newbridge EH28 8NZ.