Feed into beef – a new applied feeding system for beef cattle

Tianhai Yan (1), Francis Lively (1), Richard Dewhurst (2) and Gemma Miller (3)

(1) Sustainable Livestock Systems Branch, Agri-Food and Biosciences Institute, Hillsborough, County Down BT26 6DR. (2) Agriculture & Business Management, Biorefining and Advanced Materials Research Centre, Scotland’s Rural College, Parkgate, Barony Campus, Dumfries DG1 3NE. (3) Agriculture Horticulture and Engineering Sciences, Beef & Sheep Research Centre, Scotland’s Rural College, Easter Bush, Roslin Institute Building, Midlothian EH25 9RG.

Background

During recent decades, beef production in the UK has been improved significantly, with increased growth rates and carcase quality. These improvements, together with associated changes in feeding management, merited a review and evaluation of the beef feed rationing system recommended by Agricultural and Food Research Council (AFRC, 1993) for use in the UK for rationing beef cattle. Indeed, in a Defra-funded project (Feed into Beef and Sheep) over 15 years ago, a review of the available scientific literature indicated that rationing beef cattle using AFRC (1993) could underestimate their energy and protein requirements (Cottrill et al., 2009). Subsequently, new evidence showed that AFRC (1993) underpredicted metabolizable energy (ME) requirement for maintenance (MEm) by over 20% for Holstein heifers and steers (Jiao et al., 2015) and suckler cows (Zou et al., 2016). Therefore, the present Feed into Beef (FiB) project aimed to review the impact of the above-mentioned changes and to develop updated feed-rationing models for modern beef cattle.

This FiB project was funded by Agriculture and Horticulture Development Board (AHDB). Scientists at Agri-Food and Biosciences Institute (AFBI) in Northern Ireland and Scotland’s Rural College (SRUC) led the research (coordinated by Francis Lively of AFBI) in partnership with the Centre for Innovation Excellence in Livestock (CIEL), who helped manage the project and produce information for use in knowledge exchange with industry through AHDB and other networks.

Research for updating beef feed rationing models

The research aimed to update the tools available for predicting the nutritional requirements of beef cattle or their performance on given rations, as well as ration formulation to achieve a defined level of performance. The research programme was undertaken in the following areas.

Updating feed intake models

The prediction of feed intake requires the nutritive value of the feed. The measurement of nutritive values of conserved forages (e.g., grass silage) was made breakthrough over 20 years ago with the development of the Near Infra-Red Spectroscopy technique (NIRS). This technique has now been widely adopted in the UK for rapid and robust prediction of the feed intake potential and nutritive value of grass silage. The NIRS silage intake potential (SIP) was used in this FiB project to develop new updated feed intake models for grass silage-based beef feeding systems. The dataset used for the modelling was collected from long-term feeding studies undertaken in AFBI over last 10 years. The new models are more applicable to the commercial farms when compared to the silage intake models of AFRC (1993) which are based on silage toluene dry matter (DM) and ammonia concentrations and digestible organic matter in total DM. A comparison example in total feed intake (grass silage and concentrate) presented in Figure 1 reported a similar feed intake prediction between FiB (2024) and AFRC (1993) for beef cattle with live weight from 200 to 600kg offered an average UK grass silage and 2kg DM/d of concentrate feed. Because there were little data available for maize silage intake of growing/finishing beef cattle or feed intake data for suckler cows, we suggested to retain the models of AFRC (1993) for prediction feed intake for maize silage-fed beef cattle and suckler cows.

Updating metabolizable energy requirement and supply models

Based on the available data, we updated: (1) prediction models of MEm, (2) adjustment factors for correction of the effect of sex (bull vs heifer vs steers) and maturity (early vs medium vs late) on energy concentration in live weight gain, and (3) the adjustment factor for correction of the effect of the level of feeding on dietary ME concentration from maintenance feeding level to production feeding level. However, we suggested to retain the models of AFRC (1993) for prediction of (1) ME requirement for live weight gain for growing/finishing beef cattle, (2) ME requirement for pregnancy and lactation for suckler cows and (3) ME requirement for live weight gain or ME support from live weight loss for suckler cows.

The MEm accounts for a significant proportion of total ME requirement in beef cattle. The model for prediction of MEm for beef cattle was updated in the FiB project with data used collected from respiration calorimeter studies with heifers, steers and suckler cows undertaken at AFBI and the University of Reading from 1993 to 2015. The output indicated that the new FiB models increased MEm by 24% when compared to that calculated from the models of AFRC (1993). The increase might reflect the high metabolic rate of modern beef cattle with increased growth rates and carcase quality (more lean tissue).

Another major work was the revision of adjustment factors for correction of the effect of sex (bull vs heifer vs steers) and maturity (early vs medium vs late) on energy concentration in live weight gain of growing and finishing beef cattle. This was based on the research of Dewhurst and Miller (2023) who used the statistical modelling technique of extrapolating data back for 40 years and found that carcase fat contents for modern British breeds (Aberdeen Angus, Hereford, Beef Shorthorn) were reduced, while for large continental breeds (Charolais and British Blue) it increased, with little change for some breeds (Limousin, Simmental and Stabiliser).

The FiB models increased total ME requirements of beef cattle when compared to those of AFRC (1993). An example of comparison is presented in Table 1 below. For a given live weight of 400kg steer of late maturity breed, with live weight gains from 0 to 1.5kg/d, FiB models increased total ME requirement by 24% to 16%.

Table 1: The comparison of prediction of ME requirement for late maturity steers between FiB (2024) and AFRC (1993).

The FiB ME requirement models were validated using data collected from long-term feeding studies with growing/finishing beef cattle undertaken in AFBI over the last 10 years. The outputs are presented in Figure 2.

The FiB models had a marginal underprediction of ME intake (2%), while AFRC (1993) underestimated ME intake by 13%. Most predicted ME intake data using AFRC (1993) are below the x=y line (underprediction), while FiB predictions are clustered around the x=y line. AFRC (1993) had a much higher prediction error than the FiB model in terms of mean square prediction error (MSPE) and mean prediction error. The majority of MSPE for FiB models was from the random error (72%), while this value was smaller for AFRC (1993) (28%). This validation indicates that the FiB models can predict ME requirements of beef cattle more accurately than the models of AFRC (1993).

Updating metabolizable protein requirement and supply models

The metabolizable protein (MP) rationing system used in the UK for feeding beef cattle was lastly updated in 1993 by AFRC (1992 and 1993). Sixteen years later, Cottrill et al. (2009) reviewed international MP systems and observed that MP requirement for maintenance (MPm) in AFRC (1993) was significantly lower than in other MP systems. Since there were little published data available for us to validate and update MP requirement and supply models of AFRC (1993), we conducted a number of activities to review these models, including: literature review of published information, consultation with industrial consortium of this FiB project and comparison of MP requirement and supply models of AFRC (1993) with those published by Feed into Milk (2004), National Academies of Science, Engineering and Medicine in USA (NASEM, 2016) and Institut National de la Recherche Agronomique in France (INRA, 2018). Based on the output of these activities, we proposed the following approaches to ration modern beef cattle in the UK.

MP requirement

We suggested to (1) adopt the model of NASEM (2016) to calculate MPm, and (2) reduce the adjustment factors of AFRC (1993) for correction of the effect of sex (bull, heifer and steer) and maturity (early, medium and late) on net protein (NP) requirement of live weight gain for growing/finishing beef cattle. However, we proposed to remain MP requirement models of AFRC (1993) to predict: (1) NP requirement of live weight gain for growing/finishing beef cattle and the efficiency of utilization of NP for live weight gain, (2) MP requirements for pregnancy and lactation of suckler cows, (3) MP requirement for live weight gain or MP supply from live weight loss of suckler cows.

An example of comparison is presented in Table 2 below. For a given live weight of 400kg steer of late maturity breed, with live weight gains from 0 to 1.5kg/d, FiB models increased total MP requirement by 90% to 36%.

Table 2: The comparison of prediction of MP requirement for late maturity steers between FiB (2024) and AFRC (1993).

MP supply from feed intake

We recommended to use models of Feed into Milk (2004) to estimate the supply of (1) digestible undegradable rumen protein (DUP), and (2) digestible microbial true protein through calculating rumen fractional outflow rates of liquid, forage and concentrate, and then effective rumen degradable protein and adenosine triphosphate (ATP) supply.

Other works

The quality of beef feed ingredients has been changed considerably during the last 3 decades. For example, the implementation of the Nitrate Directive programme over 10 years ago restricts the nitrogen input for grassland production which could reduce grass protein concentration, while the improvement in ensiling techniques during the last 3 decades could improve silage quality. Therefore, we reviewed the literature and feed databases of AFRC (1993) and Feed into Milk (2024) and updated feed composition tables.

The project also delivered predictions of methane production for beef cattle fed different rations. It can be used to inform carbon foot-printing and allow farmers to choose feeds that deliver a lower carbon footprint for the beef that is produced.

Verification and adoption of Feed into Beef models

A key role in this FiB project was played by an Industry Advisory Group, which was presented with preliminary findings during development and had the final set of equations for field testing for one year before they were released to the wider industry. This provided a means to gain feedback on how the equations worked together in real rationing scenarios. In addition, an industry prediction tool, Ultramix (AGM Systems Ltd), was used to optimise the equations when they are used together, based on advice from experienced industry nutritionists.

This last step was needed because no one dataset could inform the development of all equations of interest. Some were better suited to energy requirement, protein requirement, growth rate and carcase or body composition or feed intake. There was also the need to update feed composition tables due to advances in the feeds available for beef rations. Equations were therefore based on different, often overlapping sets of data, necessitating the optimisation of these equations through use of a tool designed for doing this, in this case Ultramix.

This project provides new information to the UK beef industry, with which it can increase the efficiency of beef production, reduce its carbon footprint and better meet market requirements through more precise feeding of beef cattle and better knowledge of feed quality.

Acknowledgements

The work to update beef feed equations was funded by AHDB and carried out by AFBI, SRUC and CIEL. We would also like to acknowledge and thank the Industry Advisory Group for their time and support in the direction of this project. In particular, we would like to thank David Wilde and Michael Marsden for their valuable contributions and expertise.

We would also like to thank CAB International publishers for granting kind permission to reproduce existing equations that were not updated by the FiB models. This has enabled the provision of a comprehensive source of the latest nutrition equations for beef cattle in one document.

Feed into Beef project management and delivery

Industry Advisory Group – Chaired by Malcolm Crabtree.

Contractors: AFBI – Dr Francis Lively and Professor Tianhai Yan; SRUC – Professor Richard Dewhurst, Dr Jenna Bowen and Dr Gemma Miller; CIEL – Dr Mark Young and Nikki Dalby.

References

Agricultural and Food Research Council, AFRC. (1992) Nutritive Requirements of Ruminant Animals: Protein. Nutrition Abstracts and Reviews (Series B) 62, 787-835.

Agricultural and Food Research Council (1993) Energy and protein requirements of ruminants. An advisory manual prepared by the AFRC Technical Committee on Responses to Nutrients. CAB International, Wallingford, UK.

Cottrill, B.R., Dawson, L.E.R., Yan, T. and Xue, B. (2009) Energy feeding systems for beef cattle and sheep. In: A Review of the Energy, Protein and Phosphorus Requirements of Beef Cattle and Sheep. Project WQ 0133, Department for Environment Food & Rural Affairs, London, UK.

Dewhurst R.J. and G. Miller. (2023) Modelling the composition of liveweight gain in beef cattle. In: Proceedings of the British Society of Animal Science; p 164, Birmingham, UK.

Feed into Milk (FiM) (2004) A New Applied Feeding System for Dairy Cows. Nottingham University Press, Nottingham, UK.

Institut National de la Recherche Agronomique (INRA; 2018). INRA Feeding System for Ruminants. Wageningen Academic Publishers, Wageningen, The Netherlands.

Jiao, H.P., Yan, T., Wills, D.A., Carson, A.F. and McDowell, D.A. (2015) Development of the maintenance energy requirement for young Holstein cattle from calorimeter data measured at 6, 12, 18 and 22 months of age. Livestock Science, 178: 150-157.

National Academies of Science, Engineering and Medicine (NASEM) (2016) Nutrient Requirements of Beef Cattle, 8th Edition. National Academy Press, Washington DC, USA.

Zou, C.X., Lively, F.J., Wylie, A.R.G. and Yan, T. (2016) Estimation of the maintenance energy requirements, methane emissions and nitrogen utilisation efficiency of two suckler cow genotypes. Animal, 10(4): 616-622.

The figures referred to in this paper can be found in the full Digest PDF, available to members in the Members area.