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Assessment of a probe to measure fat depth of lamb carcases
Meat Science 159 (2020) 107937
Contents lists available at ScienceDirect
Meat Science journal homepage: www.elsevier.com/locate/meatsci
Assessment of a probe to measure fat depth of lamb carcases a,b,c,⁎
Stephanie M. Fowler
d
, Stephen Morris , David L. Hopkins
T
b,c
a
Cooperative Research Centre for Sheep Innovation, Armidale, NSW 2350, Australia NSW Department of Primary Industries, Centre for Red Meat and Sheep Development, Cowra, NSW 2794, Australia Graham Centre for Agricultural Innovation (NSW Department of Primary Industries and Charles Sturt University), Wagga Wagga, NSW 2650, Australia d Wollongbar Primary Industries Institute, NSW Department of Primary Industries, Wollongbar, NSW 2477, Australia b c
A B S T R A C T
Despite the research to ensure Australian prime lamb carcases remain a premium meat, there are no objective carcase assessment tools which enable economic incentives to be translated to producers of high meat yielding lambs. Consequently, a probe developed in Iceland, the Icemeat probe, was investigated as a tool for measuring the tissue depth at the Greville (GR) site. To this end, 1087 lambs were measured at two abattoirs over a period of 4 months using the device and a GR knife on every lamb. Agreement was assessed by linear regression and by graphical analysis for systematic patterns of disagreement. Overall, these results highlighted increasing variability of the Icemeat probe measurements with increasing GR tissue depth. Therefore, further developments are required prior to industry adoption.
1. Introduction Changing consumer preferences have been an ongoing challenge for the Australian prime lamb industry as genetic and on-farm practices have improved, resulting in larger lamb carcases. Consequently, much research has been conducted to develop the lamb supply chain as a value based chain where prices are determined by the carcases meeting market specifications (Fowler et al., 2018). However, the adoption of a value based trading system for lamb carcases is limited by the scarcity of objective carcase assessment tools as many processors still pay a flat price per carcase or on a carcase weight basis (Pearce, 2016). While carcase weight is a poor predictor of yield, this also inhibits the adoption of economic incentives for producers, as increasing weight may reflect increasing fat depths. Therefore, an objective measurement of fat depth is required by industry to facilitate the evolution of lamb payment schemes to ensure producers who sell carcases which yield high amounts of saleable meat are rewarded within the supply chain. The GR (named after Mr. Greville) tissue depth (110 mm from the midline on the 12th rib; Anonymous, 2005) is the current measure for fat depth of lamb carcases used in Australia as it is easily measured on hot carcases and is indicative of overall fatness of the carcase (Pearce, 2016). Despite the adoption of the AUS-Meat Sheep Probe (ASP) in the 1990's (Hopkins, Anderson, Morgan, & Hall, 1995), it is no longer available to industry. Furthermore the use of a GR knife, the gold standard (Pearce, 2016), is not suitable for use in commercial processing plants due to the high chain speeds, of up to 15 animals per minute, used by lamb processors. Therefore, the aim of this research was to determine the suitability of a probe capable of measuring GR at chain
⁎
speeds, which was developed in Iceland (the Icemeat probe) for commercially produced lambs in Australia. 2. Materials and methods One thousand and eighty seven (1087) lambs were measured at 2 abattoirs during 8 data collection periods over 4 months. Measured carcases were of varying fat depths, from different consignments and different abattoirs within two states to represent the variety of prime lambs typically processed within Australia. Lamb carcases were first measured at the GR tissue depth location with a GR knife prior to measurement with the Icemeat probe (Einarsdóttir, 1998). Thus, the Icemeat probe was measured in the same location, using the mark from the GR knife as a guide. The probe works via displacement, where the distance between the end of several forks which are inserted into the carcase to sit on the 12th rib and a metal plate which remains on the subcutaneous fat of the carcase is digitally measured and recorded as a measurement in millimeters (mm). Measurement occurred as the lambs entered the chillers off the processing chain approximately 25 min post slaughter. Sample date and location were also recorded. The relationship between the measurements taken using the GR probe and the GR knife was estimated by a linear model. Sample date was included as a random effect to account for any effects associated with the batch of carcases measured on each day. Measurements of 25 mm or more on the GR knife were excluded as this is the upper limit of detection (resulting in 945 observations being analysed). The model fitting was conducted in the R environment (R Core Team, 2017) using the lme4 package (Bates, Maechler, & Bolker,
Corresponding author at: NSW Department of Primary Industries, Centre for Red Meat and Sheep Development, Cowra, NSW 2794, Australia E-mail address: [email protected] (S.M. Fowler).
https://doi.org/10.1016/j.meatsci.2019.107937 Received 14 May 2019; Received in revised form 2 September 2019; Accepted 2 September 2019 Available online 02 September 2019 0309-1740/ Crown Copyright © 2019 Published by Elsevier Ltd. All rights reserved.
Meat Science 159 (2020) 107937
S.M. Fowler, et al.
Fig. 1. The relationship between the GR Tissue depth using the GR Knife and the Icemeat Probe where the solid line represents the linear model, the dashed line represents the 1:1 line and the dotted lines show fat scores 1–5.
differ from the old method, the GR knife. As highlighted by Fig. 2, consideration of the differences between the measurements over increasing fat depth demonstrated some areas of concern. For leaner carcasses (GR fat depth < 12 mm) there was systematic over estimation of GR knife by the Icemeat probe. As the GR knife fat depth measurements increased there was also an increase in the variability of measurement using the Icemeat probe. It is hypothesised that over estimation of leaner carcases is due to the differences in the size of the plate on the Icemeat probe which measures a larger surface area than the GR knife. As described by Fowler et al. (2017) this results in discrepancies between the measurements as the larger plate does not sit flat with the curvature of the ribs. Furthermore, carcases with less subcutaneous fat may be more prone to damage from the hide puller and poor dressing resulting in an uneven surface under the probe which artificially increases the measurement, but which does not affect the area of the GR knife measurement. Thus, it is suggested the size of the plate on the front of the probe is reduced to match the size of the GR knife. Under estimation of the higher GR tissue depth is a challenge for the adoption of the Icemeat probe in its current form given this error would result in the carcase being given a premium grade under a value based trading system rather than being penalised for having excess carcase fat. However, the processor would still need to pay labour to have the
2011). The error of the measurement using the Icemeat probe was calculated as the GR knife measurement (mm) minus the Icemeat probe measurement (mm) and assessed graphically for systematic patterns. 3. Results and discussion GR tissue depths ranged from 1 to 24 mm with a mean of 14.0 ( ± s.d 5.4 mm). Linear modelling indicated that most of the variation in Icemeat probe data was accounted for by regression on the corresponding GR knife measurements R2 = 0.88 (Fig. 1), which yielded the equation:
Predicted (GR Knife) = 1.18 (± s. e. 0.23) + 0.89 (± s. e. 0.01) Icemeat probe Although this model suggests the Icemeat probe has a higher correlation with the GR knife than the GR/Impedence probe previously trialed (Fowler et al., 2017), it is important to consider the agreement between the methods along with the linear association. Bland and Altman (1986) demonstrated that regression modelling can be misleading in method comparison studies and proposed study of the difference between methods to check for systematic change in the level of disagreement. Consequently, an analysis was conducted which highlights how much the new method, the Icemeat probe, was observed to
Fig. 2. Boxplot showing the distribution of measurement error of GR Tissue depth with the Icemeat probe (GR knife – Icemeat probe) with increasing GR knife depths where the vertical dotted lines represent each fat score (1–5; (Anonymous, 2005)) and the horizontal line represents 0 error. 2
Meat Science 159 (2020) 107937
S.M. Fowler, et al.
measurement in commercial lamb processing plants. However the variability in the error of the measurements by the Icemeat probe as GR knife measurements increase indicates that further development is required to modify the force of the plate on the subcutaneous fat during measurement. Furthermore, this study indicated the size of the plate on the front of the Icemeat probe also needs to be modified to reduce the over estimation of leaner carcases.
fat removed to meet the cut specifications and ultimately the carcase would have a lower saleable meat yield than predicted using the measurement. In a worst case scenario, this difference could be up to 5 mm for a carcase with a GR knife tissue depth of 20–24+ mm (fat score 5), resulting in a Icemeat probe measurement of a fat score lower than the GR knife. Thus, despite showing promise based on the variance explained, further development is required prior to the adoption of the probe by industry. The observer experience during measurement suggested that this increased variability of measurement by the Icemeat probe at high GR tissue depth may be the result of the mechanism pushing the fat of the carcase in during the measurement of fatter carcases. Indeed, a similar phenomenon was observed during the development of the ASP (Hopkins et al., 1995) and the trial of a GR/Impedance probe (Fowler et al., 2017). Consequently, further development of the probe is suggested to determine the force which is required to push through the tissue over the rib without exerting excess force on the subcutaneous fat of the carcase. A comparison of these results with the ASP indicates that the Icemeat probe yielded a higher coefficient of determination compared to the estimation of GR knife using the ASP (R2 = 0.77), however Hopkins et al. (1995) do not provide any data to indicate the agreement between the two methods. Thus, it is difficult to compare the performance of the ASP with the results reported in this study in terms of agreement. However, the study conducted by Hopkins et al. (1995) does highlight other factors, including operator and chain speed, which can contribute to spurious measurements. As this study was conducted by a sole operator who was proficient in the measurement of GR tissue depth, it is expected that the variability would increase if less trained operators were using the Icemeat probe at chain speeds of up to 15 carcases per minute. Thus, further development is needed before industry adoption.
Declaration of Competing Interest Authors declare that there is no conflict of interest. References Anonymous (2005). Handbook of Australian meat. Brisbane, Australia: AUS-MEAT Limited. Bates, D., Maechler, M., & Bolker, B. (2011). lme4: Linear mixed-effects models using S4 classes. http://CRAN.R-project.org/package=lme4. Bland, J. M., & Altman, D. G. (1986). Statistical methods for assessing agreement between two methods of clinical measurement. The Lancet, 327, 307–310. Einarsdóttir, Ó. (1998). The use of probes to predict the composition of Icelandic lamb carcasses. MSc thesisSwedish University of Agricultural Sciences. Fowler, S. M., Hoban, J. M., Melville, G., Pethick, D. W., Morris, S., & Hopkins, D. L. (2018). Maintaining the appeal of Australian lamb to the modern consumer. Animal Production Science, 58, 1392–1398. Fowler, S. M., Hoban, J. M., van de Ven, R., Boyce, M., Williams, A., Pethick, D. W., & Hopkins, D. L. (2017). A GR/impedance probe proves unsuitable for measuring GR depth in Australian lamb carcases. Meat Science, 129, 71–73. Hopkins, D. L., Anderson, M. A., Morgan, J. E., & Hall, D. G. (1995). A probe to measure GR in lamb carcasses at chain speed. Meat Science, 39, 159–165. Pearce, K. (2016). Improving lamb lean meat yield - a technical guide for the Australian lamb and sheep meat supply chain. Sheep CRC. Available: http://www.sheepcrc.org.au/ files/pages/information/publications/publications-meat/Lean_Meat_Yield_Manual___ Web_Feb16.pdf. R Core Team (2017). R: A language and environment for statistical computing. http:// www.R-project.org.
4. Conclusion The Icemeat probe has potential to substitute for the GR knife
3
Contents lists available at ScienceDirect
Meat Science journal homepage: www.elsevier.com/locate/meatsci
Assessment of a probe to measure fat depth of lamb carcases a,b,c,⁎
Stephanie M. Fowler
d
, Stephen Morris , David L. Hopkins
T
b,c
a
Cooperative Research Centre for Sheep Innovation, Armidale, NSW 2350, Australia NSW Department of Primary Industries, Centre for Red Meat and Sheep Development, Cowra, NSW 2794, Australia Graham Centre for Agricultural Innovation (NSW Department of Primary Industries and Charles Sturt University), Wagga Wagga, NSW 2650, Australia d Wollongbar Primary Industries Institute, NSW Department of Primary Industries, Wollongbar, NSW 2477, Australia b c
A B S T R A C T
Despite the research to ensure Australian prime lamb carcases remain a premium meat, there are no objective carcase assessment tools which enable economic incentives to be translated to producers of high meat yielding lambs. Consequently, a probe developed in Iceland, the Icemeat probe, was investigated as a tool for measuring the tissue depth at the Greville (GR) site. To this end, 1087 lambs were measured at two abattoirs over a period of 4 months using the device and a GR knife on every lamb. Agreement was assessed by linear regression and by graphical analysis for systematic patterns of disagreement. Overall, these results highlighted increasing variability of the Icemeat probe measurements with increasing GR tissue depth. Therefore, further developments are required prior to industry adoption.
1. Introduction Changing consumer preferences have been an ongoing challenge for the Australian prime lamb industry as genetic and on-farm practices have improved, resulting in larger lamb carcases. Consequently, much research has been conducted to develop the lamb supply chain as a value based chain where prices are determined by the carcases meeting market specifications (Fowler et al., 2018). However, the adoption of a value based trading system for lamb carcases is limited by the scarcity of objective carcase assessment tools as many processors still pay a flat price per carcase or on a carcase weight basis (Pearce, 2016). While carcase weight is a poor predictor of yield, this also inhibits the adoption of economic incentives for producers, as increasing weight may reflect increasing fat depths. Therefore, an objective measurement of fat depth is required by industry to facilitate the evolution of lamb payment schemes to ensure producers who sell carcases which yield high amounts of saleable meat are rewarded within the supply chain. The GR (named after Mr. Greville) tissue depth (110 mm from the midline on the 12th rib; Anonymous, 2005) is the current measure for fat depth of lamb carcases used in Australia as it is easily measured on hot carcases and is indicative of overall fatness of the carcase (Pearce, 2016). Despite the adoption of the AUS-Meat Sheep Probe (ASP) in the 1990's (Hopkins, Anderson, Morgan, & Hall, 1995), it is no longer available to industry. Furthermore the use of a GR knife, the gold standard (Pearce, 2016), is not suitable for use in commercial processing plants due to the high chain speeds, of up to 15 animals per minute, used by lamb processors. Therefore, the aim of this research was to determine the suitability of a probe capable of measuring GR at chain
⁎
speeds, which was developed in Iceland (the Icemeat probe) for commercially produced lambs in Australia. 2. Materials and methods One thousand and eighty seven (1087) lambs were measured at 2 abattoirs during 8 data collection periods over 4 months. Measured carcases were of varying fat depths, from different consignments and different abattoirs within two states to represent the variety of prime lambs typically processed within Australia. Lamb carcases were first measured at the GR tissue depth location with a GR knife prior to measurement with the Icemeat probe (Einarsdóttir, 1998). Thus, the Icemeat probe was measured in the same location, using the mark from the GR knife as a guide. The probe works via displacement, where the distance between the end of several forks which are inserted into the carcase to sit on the 12th rib and a metal plate which remains on the subcutaneous fat of the carcase is digitally measured and recorded as a measurement in millimeters (mm). Measurement occurred as the lambs entered the chillers off the processing chain approximately 25 min post slaughter. Sample date and location were also recorded. The relationship between the measurements taken using the GR probe and the GR knife was estimated by a linear model. Sample date was included as a random effect to account for any effects associated with the batch of carcases measured on each day. Measurements of 25 mm or more on the GR knife were excluded as this is the upper limit of detection (resulting in 945 observations being analysed). The model fitting was conducted in the R environment (R Core Team, 2017) using the lme4 package (Bates, Maechler, & Bolker,
Corresponding author at: NSW Department of Primary Industries, Centre for Red Meat and Sheep Development, Cowra, NSW 2794, Australia E-mail address: [email protected] (S.M. Fowler).
https://doi.org/10.1016/j.meatsci.2019.107937 Received 14 May 2019; Received in revised form 2 September 2019; Accepted 2 September 2019 Available online 02 September 2019 0309-1740/ Crown Copyright © 2019 Published by Elsevier Ltd. All rights reserved.
Meat Science 159 (2020) 107937
S.M. Fowler, et al.
Fig. 1. The relationship between the GR Tissue depth using the GR Knife and the Icemeat Probe where the solid line represents the linear model, the dashed line represents the 1:1 line and the dotted lines show fat scores 1–5.
differ from the old method, the GR knife. As highlighted by Fig. 2, consideration of the differences between the measurements over increasing fat depth demonstrated some areas of concern. For leaner carcasses (GR fat depth < 12 mm) there was systematic over estimation of GR knife by the Icemeat probe. As the GR knife fat depth measurements increased there was also an increase in the variability of measurement using the Icemeat probe. It is hypothesised that over estimation of leaner carcases is due to the differences in the size of the plate on the Icemeat probe which measures a larger surface area than the GR knife. As described by Fowler et al. (2017) this results in discrepancies between the measurements as the larger plate does not sit flat with the curvature of the ribs. Furthermore, carcases with less subcutaneous fat may be more prone to damage from the hide puller and poor dressing resulting in an uneven surface under the probe which artificially increases the measurement, but which does not affect the area of the GR knife measurement. Thus, it is suggested the size of the plate on the front of the probe is reduced to match the size of the GR knife. Under estimation of the higher GR tissue depth is a challenge for the adoption of the Icemeat probe in its current form given this error would result in the carcase being given a premium grade under a value based trading system rather than being penalised for having excess carcase fat. However, the processor would still need to pay labour to have the
2011). The error of the measurement using the Icemeat probe was calculated as the GR knife measurement (mm) minus the Icemeat probe measurement (mm) and assessed graphically for systematic patterns. 3. Results and discussion GR tissue depths ranged from 1 to 24 mm with a mean of 14.0 ( ± s.d 5.4 mm). Linear modelling indicated that most of the variation in Icemeat probe data was accounted for by regression on the corresponding GR knife measurements R2 = 0.88 (Fig. 1), which yielded the equation:
Predicted (GR Knife) = 1.18 (± s. e. 0.23) + 0.89 (± s. e. 0.01) Icemeat probe Although this model suggests the Icemeat probe has a higher correlation with the GR knife than the GR/Impedence probe previously trialed (Fowler et al., 2017), it is important to consider the agreement between the methods along with the linear association. Bland and Altman (1986) demonstrated that regression modelling can be misleading in method comparison studies and proposed study of the difference between methods to check for systematic change in the level of disagreement. Consequently, an analysis was conducted which highlights how much the new method, the Icemeat probe, was observed to
Fig. 2. Boxplot showing the distribution of measurement error of GR Tissue depth with the Icemeat probe (GR knife – Icemeat probe) with increasing GR knife depths where the vertical dotted lines represent each fat score (1–5; (Anonymous, 2005)) and the horizontal line represents 0 error. 2
Meat Science 159 (2020) 107937
S.M. Fowler, et al.
measurement in commercial lamb processing plants. However the variability in the error of the measurements by the Icemeat probe as GR knife measurements increase indicates that further development is required to modify the force of the plate on the subcutaneous fat during measurement. Furthermore, this study indicated the size of the plate on the front of the Icemeat probe also needs to be modified to reduce the over estimation of leaner carcases.
fat removed to meet the cut specifications and ultimately the carcase would have a lower saleable meat yield than predicted using the measurement. In a worst case scenario, this difference could be up to 5 mm for a carcase with a GR knife tissue depth of 20–24+ mm (fat score 5), resulting in a Icemeat probe measurement of a fat score lower than the GR knife. Thus, despite showing promise based on the variance explained, further development is required prior to the adoption of the probe by industry. The observer experience during measurement suggested that this increased variability of measurement by the Icemeat probe at high GR tissue depth may be the result of the mechanism pushing the fat of the carcase in during the measurement of fatter carcases. Indeed, a similar phenomenon was observed during the development of the ASP (Hopkins et al., 1995) and the trial of a GR/Impedance probe (Fowler et al., 2017). Consequently, further development of the probe is suggested to determine the force which is required to push through the tissue over the rib without exerting excess force on the subcutaneous fat of the carcase. A comparison of these results with the ASP indicates that the Icemeat probe yielded a higher coefficient of determination compared to the estimation of GR knife using the ASP (R2 = 0.77), however Hopkins et al. (1995) do not provide any data to indicate the agreement between the two methods. Thus, it is difficult to compare the performance of the ASP with the results reported in this study in terms of agreement. However, the study conducted by Hopkins et al. (1995) does highlight other factors, including operator and chain speed, which can contribute to spurious measurements. As this study was conducted by a sole operator who was proficient in the measurement of GR tissue depth, it is expected that the variability would increase if less trained operators were using the Icemeat probe at chain speeds of up to 15 carcases per minute. Thus, further development is needed before industry adoption.
Declaration of Competing Interest Authors declare that there is no conflict of interest. References Anonymous (2005). Handbook of Australian meat. Brisbane, Australia: AUS-MEAT Limited. Bates, D., Maechler, M., & Bolker, B. (2011). lme4: Linear mixed-effects models using S4 classes. http://CRAN.R-project.org/package=lme4. Bland, J. M., & Altman, D. G. (1986). Statistical methods for assessing agreement between two methods of clinical measurement. The Lancet, 327, 307–310. Einarsdóttir, Ó. (1998). The use of probes to predict the composition of Icelandic lamb carcasses. MSc thesisSwedish University of Agricultural Sciences. Fowler, S. M., Hoban, J. M., Melville, G., Pethick, D. W., Morris, S., & Hopkins, D. L. (2018). Maintaining the appeal of Australian lamb to the modern consumer. Animal Production Science, 58, 1392–1398. Fowler, S. M., Hoban, J. M., van de Ven, R., Boyce, M., Williams, A., Pethick, D. W., & Hopkins, D. L. (2017). A GR/impedance probe proves unsuitable for measuring GR depth in Australian lamb carcases. Meat Science, 129, 71–73. Hopkins, D. L., Anderson, M. A., Morgan, J. E., & Hall, D. G. (1995). A probe to measure GR in lamb carcasses at chain speed. Meat Science, 39, 159–165. Pearce, K. (2016). Improving lamb lean meat yield - a technical guide for the Australian lamb and sheep meat supply chain. Sheep CRC. Available: http://www.sheepcrc.org.au/ files/pages/information/publications/publications-meat/Lean_Meat_Yield_Manual___ Web_Feb16.pdf. R Core Team (2017). R: A language and environment for statistical computing. http:// www.R-project.org.
4. Conclusion The Icemeat probe has potential to substitute for the GR knife
3