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Accuracy, repeatability and reproducibility of the anal fold measurement for predicting carcass backfat depth in cattle
Livestock Production Science, 15 (1986) 103--106 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
103
Short Communication ACCURACY, REPEATABILITY AND REPRODUCIBILITY OF THE ANAL FOLD MEASUREMENT FOR PREDICTING CARCASS BACKFAT DEPTH IN CATTLE
A.J. SOMERVAILLE, C.S. EVELEIGH and C.J. THWAITES Department of Animal Science, University of New England, Armidale, New South Wales (Australia)
(Accepted 14 January 1986)
ABSTRACT
Somervaille, A.J., Eveleigh, C.S. and Thwaites, C.J., 1986. Accuracy, repeatability and reproducibility of the anal fold measurement for predicting carcass backfat depth in cattle. Livest. Prod. Sci., 15: 103--106. Anal fold thickness as measured by inexperienced assessors was poorly related to carcass backfat depth (r from 0.05 to 0.59) in studies on 296 cattle. Anal fold measurements were not highly repeatable within assessors nor reproducible between assessors. Residual standard deviations for backfat depth estimated from anal fold measurements ranged from 2.2 to 4.2 mm.
INTRODUCTION S i g h t - u n s e e n selling m e t h o d s r e q u i r e r e p e a t a b l e a n d a c c u r a t e m e a n s f o r e s t i m a t i n g b a c k f a t d e p t h in c a t t l e u n d e r f a r m c o n d i t i o n s . A n u m b e r o f a p p r o a c h e s are available (Daley et al., 1983), a n d o f t h e s e t h e anal fold m e a s u r e m e n t (Charles, 1 9 7 4 ) is a t t r a c t i v e since it is quick, s e m i - o b j e c t i v e and r e q u i r e s o n l y simple, r o b u s t calipers. H o w e v e r , while Charles ( 1 9 7 4 ) r e p o r t e d a highly significant regression b e t w e e n anal fold t h i c k n e s s and carcass b a c k f a t d e p t h , D e n n e s et al. ( 1 9 7 5 ) f o u n d t h a t t h e s a m e m e a s u r e m e n t a c c o u n t e d f o r o n l y 31% o f t h e v a r i a t i o n in b a c k f a t d e p t h . MATERIALS AND METHODS T h e skin a n d s u b c u t a n e o u s f a t at a p o s i t i o n m i d w a y b e t w e e n t h e p o i n t o f t h e i s c h i u m a n d t h e b a s e o f t h e tail (the " a n a l f o l d " ) w a s m e a s u r e d w i t h calipers f i t t e d w i t h 2 X 2 c m j a w s (Charles, 1974). T h e assessors w e r e inexp e r i e n c e d w i t h t h e t e c h n i q u e , b u t received i n s t r u c t i o n a n d p r a c t i c e o n unr e l a t e d c a t t l e d u r i n g t h e w e e k b e f o r e t h e trials began. T w o - h u n d r e d and n i n e t y - s i x slaughter-age cattle w i t h liveweights ranging
0301-6226/86/$03.50
© 1986 Elsevier Science Publishers B.V.
104 TABLE I D e t a i l s o f t h e c a t t l e s t u d i e d in G r o u p s 1 - - 6 and o f the c o r r e l a t i o n (r) b e t w e e n anal f o l d and c a r c a s s b a c k f a t m e a s u r e m e n t s ( m e a n -+ s . d . ) Group
Number
1 2 3 4 5
107 25 60 39 55
6
10
Liveweight (kg)
475 398 395 386 317
+ + + + +
61 28 46 92 72
4 0 3 + 12
10/11 rib b a c k f a t thickness (mm)
9.6 2.5 8.4 9.5 8.6
-+ 3 . 3 + 1.3 + 2.7 +- 4 . 8 -+ 4 . 2
9 . 2 -+ 1.6
Anal fold thickness (mm)
33.8 32.4 35.5 35.7 (A) 1 32.3 (B) 2 9 . 4 31.3
+ 4.0 -+ 2.9 +- 3 . 0 + 4.2 -+ 4 . 8 +- 4 . 4 + 2.5
10/11 rib
1 2 / 1 3 rib
0.09 0.34 0.32** 0.55*** 0.24 0.16 0.24
0.11 -0.12 0.35** 0.59*** 0.27* 0.05 0.31
*P <~ 0 . 0 5 ; * * P ( 0 . 0 1 ; * * * P <~ 0 . 0 0 1 . A s s e s s o r s A a n d B.
from 252 to 538 kg were available for study in 6 groups (Table I). All animals were evaluated randomly and in Group 5 were re-randomized before being measured a second time. Following slaughter, carcass backfat depths 13 cm from the midline were measured at the 10/11 and 12/13 rib positions after 24 h at 4°C. Data were subjected to analysis of variance and regression analysis, with repeatability and reproducibility being estimated by the methods of Evans (1978). RESULTS
AND
DISCUSSION
A ccuracy
Simple correlations between anal fold thickness and backfat depth were in general low and non-significant (Table I). The fact that between-animal variation was relatively low in the current groups explains in part why our correlations were lower and less significant than those reported by Charles (1974). Thus an overall analysis o f our data yielded a highly significant correlation between anal fold and backfat depth at the 12/13 rib site (r = 0.38; P < 0.001). Errors associated with measurement of carcass fat thickness, and dehiding damage to the subcutaneous fat layer, no d o u b t contributed in part to the low magnitude of the observed correlations. With variability associated with liveweight removed, partial correlation analysis revealed t h a t a significant correlation remained only for Group 3 at the 12/13 rib (r' = 0.27; P < 0.01). Liveweight alone accounted for a significant proportion of the variation in carcass backfat depth at both the 10/11 (4.6 -- 35.9%) and 12/13 (15.1 -- 69.8%) rib sites in Groups 1, 3 and 4, but not in Group 2. Inclusion of anal fold measurements with liveweight in multiple regression increased the proportion of variation accounted for by a m a x i m u m o f 5.4% (not significant, N.S.). With respect to predicting backfat depth, it is apparent t h a t the use o f the anal fold technique added
105 little to the accuracy o f the estimates available from the use of liveweight alone. Viewed overall, the results in Table I indicate considerable variability in the anal folds o f animals o f similar carcass fat depth. Breed and age (Tulloh, 1961), as well as nutritional history and between-assessor differences contribute to such variation, and all such factors are likely to complicate the field use of the anal fold technique. Residual standard deviations for backfat depth as estimated from anal fold measurements in the current study ranged from 2.2 to 4.2 mm, with an overall value of 2.9 mm which corresponds closely with the value reported by Charles (1974), but which is rather too high for predictions to be useful in a marketing sense.
Reproducibility Two inexperienced assessors made independent observations on the 55 cattle o f Group 5, and on this basis the between-animal reproducibility was f o u n d to be only 55%. This figure would be expected to improve with experience, but out aim was to approximate conditions where inexperienced farmers would use the technique infrequently.
Repeatability Two estimates were made. In Group 5, two assessors measured each animal and their repeatabilities, expressed as intra-class correlations, were 0.37 and 0.51 (both N.S.). The anal folds of 20 additional Hereford cows (Group 7), weighing 456.2 -+ 42.4 kg, were measured twice by each o f two assessors. Repeatabilities, estimated from the components of variance (Evans, 1978), were 0.47 and 0.63 (both N.S.). One factor determining both reproducibility and repeatability is tlae pressure applied to the calipers when measuring the anal fold. Experience would presumably help standardize this factor, as would use o f constantpressure calipers. Thus, for skin thickness, 'Haltain' constant-pressure calipers have subsequently been found to produce more repeatable (r = 0.85 -0.98) and reproducible (r = 0.57 -- 0.68) results than the manual instrument used in the current work (r = 0.80--0.92 and 0.35--0.74, respectively). Viewed overall, the current results suggest that in the hands of inexperienced assessors the anal fold technique is unlikely to improve the accuracy o f the backfat estimates available from a knowledge of liveweight and from the application of established visual/tactile (Daley et al., 1983) and ultrasonic (Simm, 1983)techniques. REFERENCES Charles, D.D., 1974. A method of estimating carcase components in cattle. Res. Vet. Sci., 16: 94--98.
106 Daley, D.A., Tatum, J.D. and Taylor, R.E., 1983. Accuracy of subjective and objective pre-slaughter estimates of beef carcass fat thickness. J. Anita. Sci., 56: 1--5. Dennes, D.J., Parsons, S.A. and Campbell, D.J., 1975. Objective measurement of fat on hot unquartered beef carcasses. Quart. Rev. Agric. Econ., 28: 25--37. Evans, D.G., 1978. The interpretation and analysis of subjective body condition scores. Anita. Prod., 26: 119--125. Simm, G., 1983. The use of ultrasound to predict the carcass composition of live cattle-A review. Anim. Breed Abstr., 51: 853--875. Tulloh, N.M., 1961. Variations in the skin and skin-fold thickness of beef cattle. Aust. J. Agric. Res., 12: 992--1004.
RESUME Sommervaille, A.J., Eveleigh, C.S. et Thwaites, C.J., 1986. Precision, r~p~tabilit~ et reproductibilitd du pli cutan6 caudal pour pr6dire l'~paisseur du gras dorsal chez les bovins. Livest. Prod. Sci., 1 5 : 1 0 3 - - 1 0 6 (en anglais). L'~paisseur du pli cutan~ caudal, mesur~e par des notateurs inexp~riment6s, n'a 6t~ que faiblement reli~e ~ l'~paisseur du gras dorsal (r de 0.05 d 0.59) dans des ~tudes sur 296 bovins. Cette mesure n'a pas 6t$ fortement r~p~table pour un m ~ m e notateur, ni reproductible d'un notateur ~ l'autre. L'erreur r~siduelle de l'~paisseur du gras dorsal calcul~e d partir du pli cutan6 caudala vari~ de 2.2 ~ 4.2 ram.
KURZFASSUNG Somervaille, A.J., Eveleigh, C.S. und Thwaites, C.J., 1986. Genauigkeit, Wiederholbarkeit und Reproduzierbarkeit des Griffes a m Schwanzansatz zur Vorhersage der Fettabdeckung a m SchlachtkSrper yon Rindem. Livest. Prod. Sci., 15:103--106 (auf englisch). In einer Untersuchung mit 296 R i n d e m konnte fastgesteUt werden, da~ der Griff a m Schwanzansatz, w e n n er von unerfahrenen Technikem angewendet wurde, nur geringfiigig mit der Fettabdeckung a m Schlachtk~rper korreliert war (r: 0.05 -- 0.59). Der FettgTiff a m Schwanzansatz war weder hochwiederholbar innerhalb Techniker noch reproduzierbar zwischen Technikern. Die Standardabweichungen des Sch~itzfehlers fiirdie Fettabdeckung -- gesch~tzt anhand des Griffes a m Schwanzansatz -- bewegten sich zwischen 2.2 und 4.2 m m .
103
Short Communication ACCURACY, REPEATABILITY AND REPRODUCIBILITY OF THE ANAL FOLD MEASUREMENT FOR PREDICTING CARCASS BACKFAT DEPTH IN CATTLE
A.J. SOMERVAILLE, C.S. EVELEIGH and C.J. THWAITES Department of Animal Science, University of New England, Armidale, New South Wales (Australia)
(Accepted 14 January 1986)
ABSTRACT
Somervaille, A.J., Eveleigh, C.S. and Thwaites, C.J., 1986. Accuracy, repeatability and reproducibility of the anal fold measurement for predicting carcass backfat depth in cattle. Livest. Prod. Sci., 15: 103--106. Anal fold thickness as measured by inexperienced assessors was poorly related to carcass backfat depth (r from 0.05 to 0.59) in studies on 296 cattle. Anal fold measurements were not highly repeatable within assessors nor reproducible between assessors. Residual standard deviations for backfat depth estimated from anal fold measurements ranged from 2.2 to 4.2 mm.
INTRODUCTION S i g h t - u n s e e n selling m e t h o d s r e q u i r e r e p e a t a b l e a n d a c c u r a t e m e a n s f o r e s t i m a t i n g b a c k f a t d e p t h in c a t t l e u n d e r f a r m c o n d i t i o n s . A n u m b e r o f a p p r o a c h e s are available (Daley et al., 1983), a n d o f t h e s e t h e anal fold m e a s u r e m e n t (Charles, 1 9 7 4 ) is a t t r a c t i v e since it is quick, s e m i - o b j e c t i v e and r e q u i r e s o n l y simple, r o b u s t calipers. H o w e v e r , while Charles ( 1 9 7 4 ) r e p o r t e d a highly significant regression b e t w e e n anal fold t h i c k n e s s and carcass b a c k f a t d e p t h , D e n n e s et al. ( 1 9 7 5 ) f o u n d t h a t t h e s a m e m e a s u r e m e n t a c c o u n t e d f o r o n l y 31% o f t h e v a r i a t i o n in b a c k f a t d e p t h . MATERIALS AND METHODS T h e skin a n d s u b c u t a n e o u s f a t at a p o s i t i o n m i d w a y b e t w e e n t h e p o i n t o f t h e i s c h i u m a n d t h e b a s e o f t h e tail (the " a n a l f o l d " ) w a s m e a s u r e d w i t h calipers f i t t e d w i t h 2 X 2 c m j a w s (Charles, 1974). T h e assessors w e r e inexp e r i e n c e d w i t h t h e t e c h n i q u e , b u t received i n s t r u c t i o n a n d p r a c t i c e o n unr e l a t e d c a t t l e d u r i n g t h e w e e k b e f o r e t h e trials began. T w o - h u n d r e d and n i n e t y - s i x slaughter-age cattle w i t h liveweights ranging
0301-6226/86/$03.50
© 1986 Elsevier Science Publishers B.V.
104 TABLE I D e t a i l s o f t h e c a t t l e s t u d i e d in G r o u p s 1 - - 6 and o f the c o r r e l a t i o n (r) b e t w e e n anal f o l d and c a r c a s s b a c k f a t m e a s u r e m e n t s ( m e a n -+ s . d . ) Group
Number
1 2 3 4 5
107 25 60 39 55
6
10
Liveweight (kg)
475 398 395 386 317
+ + + + +
61 28 46 92 72
4 0 3 + 12
10/11 rib b a c k f a t thickness (mm)
9.6 2.5 8.4 9.5 8.6
-+ 3 . 3 + 1.3 + 2.7 +- 4 . 8 -+ 4 . 2
9 . 2 -+ 1.6
Anal fold thickness (mm)
33.8 32.4 35.5 35.7 (A) 1 32.3 (B) 2 9 . 4 31.3
+ 4.0 -+ 2.9 +- 3 . 0 + 4.2 -+ 4 . 8 +- 4 . 4 + 2.5
10/11 rib
1 2 / 1 3 rib
0.09 0.34 0.32** 0.55*** 0.24 0.16 0.24
0.11 -0.12 0.35** 0.59*** 0.27* 0.05 0.31
*P <~ 0 . 0 5 ; * * P ( 0 . 0 1 ; * * * P <~ 0 . 0 0 1 . A s s e s s o r s A a n d B.
from 252 to 538 kg were available for study in 6 groups (Table I). All animals were evaluated randomly and in Group 5 were re-randomized before being measured a second time. Following slaughter, carcass backfat depths 13 cm from the midline were measured at the 10/11 and 12/13 rib positions after 24 h at 4°C. Data were subjected to analysis of variance and regression analysis, with repeatability and reproducibility being estimated by the methods of Evans (1978). RESULTS
AND
DISCUSSION
A ccuracy
Simple correlations between anal fold thickness and backfat depth were in general low and non-significant (Table I). The fact that between-animal variation was relatively low in the current groups explains in part why our correlations were lower and less significant than those reported by Charles (1974). Thus an overall analysis o f our data yielded a highly significant correlation between anal fold and backfat depth at the 12/13 rib site (r = 0.38; P < 0.001). Errors associated with measurement of carcass fat thickness, and dehiding damage to the subcutaneous fat layer, no d o u b t contributed in part to the low magnitude of the observed correlations. With variability associated with liveweight removed, partial correlation analysis revealed t h a t a significant correlation remained only for Group 3 at the 12/13 rib (r' = 0.27; P < 0.01). Liveweight alone accounted for a significant proportion of the variation in carcass backfat depth at both the 10/11 (4.6 -- 35.9%) and 12/13 (15.1 -- 69.8%) rib sites in Groups 1, 3 and 4, but not in Group 2. Inclusion of anal fold measurements with liveweight in multiple regression increased the proportion of variation accounted for by a m a x i m u m o f 5.4% (not significant, N.S.). With respect to predicting backfat depth, it is apparent t h a t the use o f the anal fold technique added
105 little to the accuracy o f the estimates available from the use of liveweight alone. Viewed overall, the results in Table I indicate considerable variability in the anal folds o f animals o f similar carcass fat depth. Breed and age (Tulloh, 1961), as well as nutritional history and between-assessor differences contribute to such variation, and all such factors are likely to complicate the field use of the anal fold technique. Residual standard deviations for backfat depth as estimated from anal fold measurements in the current study ranged from 2.2 to 4.2 mm, with an overall value of 2.9 mm which corresponds closely with the value reported by Charles (1974), but which is rather too high for predictions to be useful in a marketing sense.
Reproducibility Two inexperienced assessors made independent observations on the 55 cattle o f Group 5, and on this basis the between-animal reproducibility was f o u n d to be only 55%. This figure would be expected to improve with experience, but out aim was to approximate conditions where inexperienced farmers would use the technique infrequently.
Repeatability Two estimates were made. In Group 5, two assessors measured each animal and their repeatabilities, expressed as intra-class correlations, were 0.37 and 0.51 (both N.S.). The anal folds of 20 additional Hereford cows (Group 7), weighing 456.2 -+ 42.4 kg, were measured twice by each o f two assessors. Repeatabilities, estimated from the components of variance (Evans, 1978), were 0.47 and 0.63 (both N.S.). One factor determining both reproducibility and repeatability is tlae pressure applied to the calipers when measuring the anal fold. Experience would presumably help standardize this factor, as would use o f constantpressure calipers. Thus, for skin thickness, 'Haltain' constant-pressure calipers have subsequently been found to produce more repeatable (r = 0.85 -0.98) and reproducible (r = 0.57 -- 0.68) results than the manual instrument used in the current work (r = 0.80--0.92 and 0.35--0.74, respectively). Viewed overall, the current results suggest that in the hands of inexperienced assessors the anal fold technique is unlikely to improve the accuracy o f the backfat estimates available from a knowledge of liveweight and from the application of established visual/tactile (Daley et al., 1983) and ultrasonic (Simm, 1983)techniques. REFERENCES Charles, D.D., 1974. A method of estimating carcase components in cattle. Res. Vet. Sci., 16: 94--98.
106 Daley, D.A., Tatum, J.D. and Taylor, R.E., 1983. Accuracy of subjective and objective pre-slaughter estimates of beef carcass fat thickness. J. Anita. Sci., 56: 1--5. Dennes, D.J., Parsons, S.A. and Campbell, D.J., 1975. Objective measurement of fat on hot unquartered beef carcasses. Quart. Rev. Agric. Econ., 28: 25--37. Evans, D.G., 1978. The interpretation and analysis of subjective body condition scores. Anita. Prod., 26: 119--125. Simm, G., 1983. The use of ultrasound to predict the carcass composition of live cattle-A review. Anim. Breed Abstr., 51: 853--875. Tulloh, N.M., 1961. Variations in the skin and skin-fold thickness of beef cattle. Aust. J. Agric. Res., 12: 992--1004.
RESUME Sommervaille, A.J., Eveleigh, C.S. et Thwaites, C.J., 1986. Precision, r~p~tabilit~ et reproductibilitd du pli cutan6 caudal pour pr6dire l'~paisseur du gras dorsal chez les bovins. Livest. Prod. Sci., 1 5 : 1 0 3 - - 1 0 6 (en anglais). L'~paisseur du pli cutan~ caudal, mesur~e par des notateurs inexp~riment6s, n'a 6t~ que faiblement reli~e ~ l'~paisseur du gras dorsal (r de 0.05 d 0.59) dans des ~tudes sur 296 bovins. Cette mesure n'a pas 6t$ fortement r~p~table pour un m ~ m e notateur, ni reproductible d'un notateur ~ l'autre. L'erreur r~siduelle de l'~paisseur du gras dorsal calcul~e d partir du pli cutan6 caudala vari~ de 2.2 ~ 4.2 ram.
KURZFASSUNG Somervaille, A.J., Eveleigh, C.S. und Thwaites, C.J., 1986. Genauigkeit, Wiederholbarkeit und Reproduzierbarkeit des Griffes a m Schwanzansatz zur Vorhersage der Fettabdeckung a m SchlachtkSrper yon Rindem. Livest. Prod. Sci., 15:103--106 (auf englisch). In einer Untersuchung mit 296 R i n d e m konnte fastgesteUt werden, da~ der Griff a m Schwanzansatz, w e n n er von unerfahrenen Technikem angewendet wurde, nur geringfiigig mit der Fettabdeckung a m Schlachtk~rper korreliert war (r: 0.05 -- 0.59). Der FettgTiff a m Schwanzansatz war weder hochwiederholbar innerhalb Techniker noch reproduzierbar zwischen Technikern. Die Standardabweichungen des Sch~itzfehlers fiirdie Fettabdeckung -- gesch~tzt anhand des Griffes a m Schwanzansatz -- bewegten sich zwischen 2.2 und 4.2 m m .