|Practice tip||Peer reviewed|
Cite as: Gonçalves MAD, Dritz SS, Tokach MD, et al. Fact sheet – Feed efficiency adjustments to compare group close-outs in finishing pigs. J Swine Health Prod. 2017;25(2):73–75.
Also available as a PDF.
Keywords: swine, feed efficiency, production, management
Search the AASV web site for pages with similar keywords.
Received: July 24, 2015
Accepted: February 9, 2016
This practice tip includes a fact sheet on feed efficiency adjustments to compare group close-outs in finishing pigs
Conflict of interest
Scientific manuscripts published in the Journal of Swine Health and Production are peer reviewed. However, information on medications, feed, and management techniques may be specific to the research or commercial situation presented in the manuscript. It is the responsibility of the reader to use information responsibly and in accordance with the rules and regulations governing research or the practice of veterinary medicine in their country or region.
Fact Sheet: Feed efficiency adjustments to compare group close-outs in finishing pigs
Feed efficiency of group close-outs can be compared after adjusting for known factors that can influence it.
Body weight, dietary energy and lysine, grain particle size, immunocastration, mortality, pelleting, ractopamine, and gender are major factors affecting feed efficiency, and thus adjusting for them can produce more meaningful benchmark comparisons.
Feed efficiency is typically defined as feed-to-gain ratio (F:G). Feed-to-gain is not always related to profit, but is a useful metric in benchmarking group close-outs, especially within a production system. In order to evaluate F:G across group close-outs, adjustment factors can be used to account for known sources of variation.
Feed efficiency adjustments in finishing close-outs
Initial and final body weight (BW) are major factors affecting feed-to-gain ratio (F:G), because fat deposition is less efficient than protein deposition, and the rate of fat deposition increases relative to protein deposition as BW increases.1 A 1% increase in dietary net energy (NE) results in a 1% improvement in feed efficiency as long as NE loading values of the ingredients in the diet are correct.2 This assumes dietary lysine is not limiting, according to NRC requirements.1
Equations accounting for factors affecting F:G
Equation (1)3 accounts for initial and final BW:
Adjusted F:G = observed F:G + [standardized initial BW (kg) – actual initial BW (kg)] × slope estimate + [standardized final BW (kg) – actual final BW (kg)] × slope estimate
Equation (2)4 accounts for initial and final BW and energy level of the diet:
Adjusted F:G = observed F:G + [standardized initial BW (kg) – actual initial BW (kg)] × slope estimate + [standardized final BW (kg) – actual final BW (kg)] × slope estimate – [(standardized energy level – actual energy level) ÷ standardized energy level) × observed F:G]
The slope estimate varies with energy level of the diet and genetic line,5,6 and slope estimates per kg BW range from 0.007 to 0.011.5,6 Use caution when applying these slope estimates to other genetic lines that have different body composition or growth curves.
Equation (3)7 accounts for NE, average BW, and standardized ileal digestible (SID) lysine (Lys). This equation predicts F:G and then is modified to calculate an adjusted F:G that is based on the observed F:G.
F:G prediction = 1 ÷ [(0.000004365 × NE) – (0.00162 × average BW) – (0.08023 × SID Lys) + (0.000094 × NE × SID Lys) + 0.3496]
Adjusted F:G = (F:G from Equation 3 using standardized values) ÷ (F:G from Equation 3 using actual values) × observed F:G
where NE is the weighted average kcal of NE per kg. Average BW (kg) is the average of initial and final BW, and SID Lys (%) is the weighted average SID Lys. The NE and SID Lys are weighted on the basis of the amount of feed in each phase during the finishing period. This equation encompasses a range of BW from 20.8 to 138.2 kg. Information regarding NE of ingredients can be found in NRC’s Nutrient Requirements of Swine.1
Other factors to consider when adjusting for F:G. The impact of mortality on F:G can be calculated by using the average day in which the mortality occurred in the close-out. If mortality is assumed to occur at the mid-point of the finishing phase, for every 1% increase in mortality, F:G will be poorer by 0.5% to 0.8%.8 Pelleting improves F:G by about 4% to 6% for pelleted diets with less than 20% fines.4 Feed efficiency will be poorer by 0.002857 for each 1% fines in the pelleted diet.9 Grain particle size improves F:G by 1.0% to 1.2%10 for each 100-micron reduction from 900 to 500 microns. Gilts have approximately 1.7% better F:G than mixed gender, whereas barrows have 1.7% poorer F:G than mixed gender.1 Ractopamine fed for 21 days prior to market decreases finisher F:G by 1.8% for 5 ppm (5 g per tonne) inclusion and 3.4% for 10 ppm (10 g per tonne) inclusion, in a summary of 12 experiments.11 In a meta-analysis of 10 studies,12 F:G in immunocastrated barrows was 4% lower than in surgically castrated barrows for the whole finishing phase. The meta-analyses included only data from studies with animals slaughtered between 4 and 6 weeks after the second immunization (market weight, 107 to 110 kg). The F:G advantage would be expected to be less if animals were slaughtered more than 6 weeks after the second immunization.
Examples of differences in F:G adjustment that are based on the change of a single factor from the baseline system values are shown in Table 1, using a feed efficiency adjustment calculator. For example, when comparing two close-outs with similar observed F:G, if one was fed a diet with higher energy, the adjusted F:G would be poorer than the observed F:G, reflecting the way that group would have performed if the pigs had received diets containing the same amount of dietary energy as the lower energy group.
Table 1: Feed efficiency adjustment simulations for different factors in a barn close-out, accounting for mortality and pelleting7
|Parameters||Baseline||Entry weight||Final weight||Dietary energy||Mortality||Pelleting||Gender|
|Initial weight (kg)||22||25||22||22||22||22||22|
|Final weight (kg)||130||130||135||130||130||130||130|
|Weighted SID Lys (%)||0.78||0.78||0.78||0.78||0.78||0.78||0.78|
|Weighted energy (kcal) NE/kg||2527||2527||2527||2653||2527||2527||2527|
|Average mortality (dpp)||60||60||60||60||60||60||60|
|Pelleting (Yes or No)†||No||No||No||No||No||Yes||No|
|If pelleted (% fines)†||0||0||0||0||0||20||0|
* Assumed impact of mortality over the baseline F:G.
† Assumed to reduce F:G by 5% when diets were in pellet form, increase F:G by 0.002857 for each 1% fines in the pelleted diet.
‡ Assumed that F:G in barrows is approximately 1.7% lower than mixed gender based on NRC1 model.
§ Developed using Equation 3: 1 ÷ [(0.000004365 × NE) – (0.00162 × Average BW) – (0.08023 × SID Lys) + (0.000094 × NE × SID Lys) + 0.3496]. Then, adjusted F:G = (F:G from Equation 3 using standardized values) ÷ (F:G from Equation 3 using actual values) × observed F:G. The range of BW that this equation encompasses is 20.8 to 138.2 kg.
F:G = feed-to-gain ratio; SID Lys = standardized ileal digestible lysine; NE = net energy; dpp = days post placement; NA = not applicable.
These adjustments are useful because they account for the various known factors that affect F:G and that are normally present in production systems. A feed efficiency adjustment calculator that accounts for these factors can be found at http://www.asi.k-state.edu/research-and-extension/swine/calculators.html.
Contribution no. 16-010-J from the Kansas Agricultural Experimental Station, Manhattan, KS 66506-0210.
1. National Research Council. Models for estimating nutrient requirements of swine. In: Nutrient Requirements of Swine. 11th rev ed. Washington, DC: National Academy Press; 2012:127–156.
*2. Euken RM. Swine feed efficiency: Effect of dietary energy on feed efficiency. Kansas State Research and Extension. 2012. Available at http://www.swinefeedefficiency.com/factsheets/IPIC25i%20SFE%20effect%20of%20dietary%20energy%20on%20efficiency.pdf. Accessed 5 December 2016.
*3. Goodband RD, Tokach MD, Dritz SS, DeRouchey JM, Nelssen JL. Feeding and feeder management influences on feed efficiency. Proc Allen D. Leman Swine Conf, Nutrition Workshop: Focus on Feeding Efficiency. St Paul, Minnesota. 2008;20–27.
4. Gaines AM, Peterson BA, Mendoza OF. Herd management factors that influence whole herd feed efficiency. In: Patience J, ed. Feed Efficiency in Swine. Wageningen, The Netherlands: Wageningen Academic Publishers; 2012:15–39.
*5. Jungst S, Matthews N, Booher C, Fields B, Dreadin T, Tabor S, Anderson J, Martin J, Williams A, Jobin M, Sosnicki A, Wilson E. Growth curves for PIC327L sired pigs fed diets with differing energy levels. PIC Tech Memo. Hendersonville, Tennessee. 2010;ES50–344. Available at http://www.pic.com/Images/Users/1/SalesPortal/ExcecutiveSummaries/ES050.pdf. Accessed 14 December 2016.
*6. Jungst S, Matthews N, Booher C, Fields B, Dreadin T, Tabor S, Anderson J, Martin J, Williams A, Jobin M, Sosnicki A, Wilson E. Growth curves for commercial PIC337RG pigs fed high and low energy diets. PIC Tech Memo. Hendersonville, Tennessee. 2010;ES51–344. Available at http://www.pic.com/Images/Users/1/SalesPortal/ExcecutiveSummaries/ES051.pdf. Accessed 14 December 2016.
7. Nitikanchana S, Dritz SS, Tokach MD, DeRouchey JM, Goodband RD, White BJ. Regression analysis to predict growth performance from dietary net energy in growing-finishing pigs. J Anim Sci. 2015;93:2826–2839.
8. Tokach MD, Goodband RD, DeRouchey JM, Dritz SS, Nelssen JL. Feeding and barn management strategies that maximize feed efficiency. In: Patience J, ed. Feed Efficiency in Swine. Wageningen, The Netherlands: Wageningen Academic Publishers; 2012:41–62.
9. De Jong J. Swine. Calculators. Feed efficiency evaluator for finishing pigs. Available at www.ksuswine.org. Accessed 5 December 2016.
*10. Steinhart TL. Swine feed efficiency: Influence of particle size. 2012. Available at http://www.swinefeedefficiency.com/factsheets/IPIC25d%20SFE%20Influence%20of%20Particle%20Size.pdf. Accessed 5 December 2016.
*11. Kelly JA, Tokach MD, Dritz SS. Weekly growth and carcass response to feeding ractopamine (Paylean). Proc AASV. Orlando, Florida. 2003:51–58.
12. Dunshea FR, Allison JRD, Bertram M, Boler DD, Brossard L, Campbell R, Crane JP, Hennessy DP, Huber L, de Lange C, Ferguson N, Matzat P, McKeith F, Moraes PJU, Noblet J, Quiniou N, Tokach M. The effect of immunization against GnRF on nutrient requirements of male pigs: A review. Animal. 2013;7:1769–1778.
* Non-refereed references.