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The estimation of the age of cattle by the measurement of thermal stability of tendon collagen
Meat Science 29 (1991) 243-249
The Estimation of the Age of Cattle by the Measurement of Thermal Stability of Tendon Collagen Douglas J. H o r g a n CSIRO Division of Food Processing, Meat Research Laboratory, P.O. Box 12, Cannon Hill, Queensland 4170, Australia
(Received 16 February 1990; revised version received 4 June 1990; accepted 5 June 1990)
A BS TRA C T Two measures of the thermal stability o f tendon collagen (thermal transition temperature and isometric tension) have been studied as a fimction of age o f cattle. The aim was to assess their potential for estimating the age of an animal from which a sample of meat originated. The variation in thermal transition temperature between animals was too large for reliable estimation o f animal age by this method. The maximum isometric force generated during heating of strips of tendon from the longissimus dorsi muscle was f o u n d to increase linearly with age. Measurements of isometric tension at p H 6"0 had the least variation between animals from 2 to 16 years o f age, but were not suitable for younger animals. A t p H 7.5, the entire age range could be measured, and although the variation between animals was increased, the accuracy o f the age determination still compared favourably with that o f dentition.
INTRODUCTION Many contracts for the purchase of meat specify that it should originate from animals within a certain age range. Furthermore, animal age is an important parameter in marketing systems such as classification or sale by description. Traditionally, animal age is estimated by dentition (e.g. Franklin, 1950) when birth dates are not known. However, this method is unreliable, as in beef animals the eighth tooth may erupt at any time from 39 months to 57 m o n t h s (Dodt & O'Rourke, 1988). Moreover, the 243
Meat Science 0309-1740/91/$03"50 © 1991 Elsevier Science Publishers Ltd, England. Printed in Great Britain
244
Douglas J. Horgan
better the pasture, the earlier the eruption (Tulloh, 1962; Weiner & Purser, 1957), i.e. prime animals appear by dentition to be older than their true age. Once meat has been removed from a carcass, alternative methods are required so that purchasers of meat cuts may check for compliance with their specifications. Although most intracellular proteins are turned over rapidly, some of the collagen appears to be long-lived (Neuberger & Slack, 1953). Furthermore, slow chemical reactions gradually increase the number and alter the structure of cross-links between collagen polypeptide chains during the life of an animal (for recent review see Bailey, 1988). One effect of changes in cross-linking is greater thermal stability of collagen in older animals. This has formed the basis for earlier studies relating animal age to measurements such as isometric tension of rat-tail and frog-finger tendons (Brocas & Verzfir, 1961a, b) and solubilization of hydroxyproline on heating cattle corium (Verzfir, 1960), rat-tail tendon (Verzfir & Meyer, 1961), human skin (Verzfir, 1962) and rat muscle (Schaub, 1963). Recently, we reported on the use of isometric tension, thermal transition temperature and hydroxyproline solubilization to estimate the age of goats (Horgan et al., 1988). The most satisfactory method tested was the measurement of the m a x i m u m hydrothermal isometric tension (HITm) of the tendons from longissimus dorsi (LD) muscle. The relationship with age was linear over the age range 0"2-14 years and the precision of this method compared favourably with that of dentition. In this study isometric tension and thermal transition temperature (Tin) measurements were applied to the tendons from the LD muscles of cattle with known birth dates. Correlations with age were measured and results compared to those previously found with goat tendons.
MATERIALS AND METHODS
Samples LD muscles with attached tendons from 70 cattle of mixed breed and sexes ranging in age from 0-7 to 15-8 years were obtained from research stations in southern Queensland and northern New South Wales. They were stored at -30°C until required. Samples of tendon were obtained by dissection from the surface of the muscle and suspended overnight in either 50mM sodium citrate, 10mM ethylene diamine tetra-acetic acid, pH 6-0 (buffer A) or 0"15M sodium chloride, 50 mM sodium phosphate, pH 7.5 (buffer B), before measurement of thermal properties.
Estimation of age of cattle by thermal stability of tendon collagen
245
Thermal transition temperature
The endothermal transition of collagen was measured in either buffer A or buffer B using a differential scanning calorimeter as described previously by King (1987). Although other workers use the extrapolated onset temperature (To), Tm, the m a x i m u m differential heating rate, was used here as it reflects 'average stability' whereas T Oarises from the least stable collagen in a sample (Ledward et al., 1975). Isometric tension measurements
Maximum hydrothermal isometric tension (HITm) was measured essentially as described by Snowden et al. (1977) but modified as follows: Strips of tendon approximately 3 c m long and 2 - 6 r a m wide were immersed overnight in buffer in a refrigerator (approximately 5°C). In preparation for a measurement, excess liquid was removed from each strip by blotting between paper towels. The length and weight of each strip were recorded. The strip was then immersed in buffer and held taut between two clamps on an Instron Model TM-M. The distance between the clamps was 10 ram. After immersion for approximately 10 min the clamps were moved 0-3 m m further apart to apply a slight tension (30-50 g) to the sample. A circulating water bath was used to raise the temperature (measured by a CuConstantin thermocouple) at a rate o f 2°C/min until the force began to decline after reaching a maximum. The mean cross-sectional area of collagen in each sample was estimated from the weight per unit length by assuming a collagen content of 30% of the wet weight and a density of 1-4 g/cm 2 for collagen (Snowden et al., 1977). Each tendon was measured in triplicate.
RESULTS Thermal transition temperature
Figure 1 shows that the T m of bovine LD tendon appeared to increase linearly with increasing age. However, the variation in T m between animals of similar age was large. Although not shown, the 95% confidence limits for estimating age by this m e t h o d are approximately _ 4 years. Also shown in Fig. 1 is the regression line previously found for goat LD tendons (Horgan et al., 1988).
Douglas J. Horgan
246
G
64
/ l
~63 /
/
/
62 2
,/
•
s
o
•
~
•
~ 60
g
//sl
~"
'-- 59
~ 57 ..:.'.
w
,,
o. ~
°
'-- 56 i
i
2
4
i
J
G 8 10 ANIMAL AGE {years)
J
i
i
12
14
18
Fig. 1. Thermal transition t e m p e r a t u r e (Tm) as a function o f animal age; O , each point is the m e a n o f two d e t e r m i n a t i o n s with bovine L D t e n d o n in buffer A, p H 6"0 (n = 55. r = 0"89), .... , regression line previously f o u n d for goat L D tendons.
Isometric tension measurements The maximum isometric tension developed during heating (HITm) is shown in Fig. 2 as a function of age. In this experiment the tendons were equilibrated in buffer A, pH 6.0, the same conditions as previously used for goat tendons (Horgan et al., 1988). 200 180: 160 _.~E140
-
°
J"
120' --
100
c~_ 8O
z" ~"
60 -
"
°
//'~
40
20
i
.." 2
•
, t 4
8
8
t0
12
14
18
ANIMAL AGE {years) Fig. 2.
Maximum isometric tension (HIT,.) as a function of animal age; ©, bovine LD
t e n d o n was i m m e r s e d in buffer A, p H 6-0 a n d the t e m p e r a t u r e raised at 2°C/min. Each p o i n t is the m e a n o f three d e t e r m i n a t i o n s (n = 32, r = 0"99), - . . . . , regression line previously f o u n d for g o a t L D tendons.
Estimation of age of cattle by thermal stability of tendon collagen
247
2O0 • °"
180~ 180'
I
120
@
100 L~
~- 80
6o .
- - 40
~ 15'
,,'"
20
~
,.'"
/" ,Y""
i
i
2
4
i
i
8 8 10 ANIMAL AtE (years)
i
i
12
14
18
Fig. 3. Maximum isometric tension (HITm) as a function of animal age. Bovine LD tendon was immersed in buffered saline, pH 7-5 and the temperature raised at 2:C/min. Each point is the mean of three determinations (n = 68, r = 0-98).......... 95% confidence limits obtained from a plot of x/(HITm) versus ,/(animal age). The scatter o f points a r o u n d the fitted line does not appear to vary much with age and the 9 5 % confidence limits for estimating age by this m e t h o d are approximately __ 1.4 years. The broken line in Fig. 2 is the regression line previously found for goat L D tendons (Horgan et al., 1988). As the regression line for measurements at p H 6-0 intercepts the age axis some distance from the origin this m e t h o d was not suitable for animals less than two years old. Figure 3 shows the results when H I T m was measured at p H 7.5. The H I T m values again increase linearly with age and can be measured satisfactorily in y o u n g animals. Regression analysis shows that the slopes of the lines measured at p H 6-0 (Fig. 2) and p H 7.5 (Fig. 3) are significantly different ( P < 0-01). The scatter o f experimental points a r o u n d the fitted line at p H 7-5, increases with increasing age and so the confidence limits shown in Fig. 3 were calculated from a plot o f x/(HITm) against x/(animal age). The confidence limits are approximately _+ 1 year, +_ 1-5 years and __ 2 years at mean ages o f 2, 4 and 8 years.
DISCUSSION Although the thermal transition temperature of L D tendon collagen increased linearly with increasing animal age (Fig. 1) the scatter o f experimental results was too large for this to be a practical m e t h o d for
248
Douglas J. Horgan
estimating the age of cattle. This agrees with previous findings for goats (Horgan et al., 1988). Figure 1 also shows that, except for the very young, bovine LD tendon collagen has a much lower Tmthan goat LD tendon of the same age. As the Tm of collagen depends on the heat stability of the crosslinks (Flandin et al., 1984) this suggests that bovine LD tendons have fewer heat-stable cross-links than goat tendons of the same age. As was found previously for goats (Horgan et al., 1988) isometric tension measurements were more suitable for estimating animal age than thermal transition temperatures. Figure 2 shows that, at pH 6-0, the regression line with bovine LD tendons did not pass through the origin but instead intercepted the age axis at approximately 1-2 years. This makes any age estimation for animals less than 2 years old very uncertain. Figure 2 also shows that the regression line for goat LD tendons (broken line) was higher at all ages and intercepted the age axis much closer to the origin than did the bovine line. As it is well established that the isometric tension generated by collagen fibres during heating depends on the type of cross-link involved (for a recent review, see Kopp & Bonnet, 1987) this result supports the conclusion from the Tm results, i.e. that bovine LD tendons contain fewer heat-stable cross-links than goat tendons of the same age. It is of interest that the species difference in the HIT m results (Fig. 2) was almost constant throughout the age range in contrast to the Tm results (Fig. 1) where the difference increased with age. It would appear that the higher content of heat-labile (aldimine) bonds in the bovine LD tendons has different quantitative effects on the two measures of heat stability, i.e. HIT m and Tm. Apparently these bonds, although labile at high temperatures, can generate quite high tensions at the more moderate temperatures where the maxima occur, before relaxing at the higher temperatures. When the HIT m measurements of bovine LD tendons were made at pH 7.5 (Fig. 3), higher values were found at young ages which caused the gradient of the regression line to be significantly different to that found at pH 6"0 (Fig. 2). This was, presumably, because soaking in the pH 6-0 buffer destroyed some of the labile aldimine bonds. At pH 7.5, the age of young animals could be estimated more accurately thai1 at pH 6-0 but, overall, the variation of HIT m values for animals with similar ages was greater and increased with age. The 95% confidence limits for estimating the age of cattle at pH 7-5 and 6"0 were respectively ___24 months and + 18 months compared to the previously found value of 4- 14 months for goats at a mean animal age of 6 years. In conclusion, the age of cattle can be estimated from isometric tension measurements of the tendon from the LD muscle. Measurements at pH 6.0 have less scatter but are not suitable for very young animals. At pH 7.5 the whole age range can be measured with an accuracy that, although less than
Estimation of age of cattle by thermal stability of tendon collagen
249
for both cattle and goats at pH 6-0, is still comparable to that obtained from dentition.
A C K N O W L E D G E M ENTS The skilled technical assistance o f Miss Anita Sikes is gratefully acknowledged, as is the cooperation o f Dr Helen Hearnshaw, Agricultural Research Station, Grafton, NSW. This w o r k was supported in part by the Australian Meat and Live-stock Research and Development Corporation.
REFERENCES Bailey, A. J. (1988). Proc. 34th Int. Cong. Meat Sci. Technol., Brisbane, p. 152. Brocas, J. & Verzfir, F. (1961a). Gerontologia, 5, 223. Brocas, J. & Verz~tr, F. (1961b). Gerontologia, 5, 228. Dodt, R. M. & O'Rourke, P. K. (1988). Queensland J. Agric. Anita. Sci., 45, 53. Flandin, F., Buffevant, C. & Herbage, D. (1984). Biochim. Biophys. Acta., 791, 205. Franklin, M. C. (1950). Influence of diet on dental development in the sheep. CSIRO Bulletin No. 252. Horgan, D. J., King, N. L. & Kurth, L. B. (1988). Proc. 34th Int. Cong. Meat SeL Technol., Brisbane, p. 197. King, N. L. (1987). Meat Sei., 20, 25. Kopp, J. & Bonnet, M. (1987). In Advances in Meat Research, Volume 4, Collagen as a food, ed. A. M. Pearson, T. R. Dutson & A. J. Bailey. AVI, New York, p. 163. Ledward, D. A., Chizzolini, R. & Lawrie, R. A. (1975). J. Food TechnoL, 10, 349. Neuberger, A. & Slack, H. G. B. (1953). Biochem. J., 53, 47. Schaub, M. C. (1963). Gerontologia, 8, 16. Snowden, J. M., Bouton, P. E. & Harris, P. V. (1977). J. Food Sci., 42, 890. Tulloh, N. M. (1962). Aust. J. Agrie. Res., 13, 350. Verzfir, F. (1960). Gerontologia, 4, 104. Verz~r, F. (1962). Experientia, 18, 473. Verzfir, F. & Meyer, A. (1961). Gerontologia, 5, 163. Weiner, G. & Purser, A. F. (1957). J. Agrie. Sei., 49, 51.
The Estimation of the Age of Cattle by the Measurement of Thermal Stability of Tendon Collagen Douglas J. H o r g a n CSIRO Division of Food Processing, Meat Research Laboratory, P.O. Box 12, Cannon Hill, Queensland 4170, Australia
(Received 16 February 1990; revised version received 4 June 1990; accepted 5 June 1990)
A BS TRA C T Two measures of the thermal stability o f tendon collagen (thermal transition temperature and isometric tension) have been studied as a fimction of age o f cattle. The aim was to assess their potential for estimating the age of an animal from which a sample of meat originated. The variation in thermal transition temperature between animals was too large for reliable estimation o f animal age by this method. The maximum isometric force generated during heating of strips of tendon from the longissimus dorsi muscle was f o u n d to increase linearly with age. Measurements of isometric tension at p H 6"0 had the least variation between animals from 2 to 16 years o f age, but were not suitable for younger animals. A t p H 7.5, the entire age range could be measured, and although the variation between animals was increased, the accuracy o f the age determination still compared favourably with that o f dentition.
INTRODUCTION Many contracts for the purchase of meat specify that it should originate from animals within a certain age range. Furthermore, animal age is an important parameter in marketing systems such as classification or sale by description. Traditionally, animal age is estimated by dentition (e.g. Franklin, 1950) when birth dates are not known. However, this method is unreliable, as in beef animals the eighth tooth may erupt at any time from 39 months to 57 m o n t h s (Dodt & O'Rourke, 1988). Moreover, the 243
Meat Science 0309-1740/91/$03"50 © 1991 Elsevier Science Publishers Ltd, England. Printed in Great Britain
244
Douglas J. Horgan
better the pasture, the earlier the eruption (Tulloh, 1962; Weiner & Purser, 1957), i.e. prime animals appear by dentition to be older than their true age. Once meat has been removed from a carcass, alternative methods are required so that purchasers of meat cuts may check for compliance with their specifications. Although most intracellular proteins are turned over rapidly, some of the collagen appears to be long-lived (Neuberger & Slack, 1953). Furthermore, slow chemical reactions gradually increase the number and alter the structure of cross-links between collagen polypeptide chains during the life of an animal (for recent review see Bailey, 1988). One effect of changes in cross-linking is greater thermal stability of collagen in older animals. This has formed the basis for earlier studies relating animal age to measurements such as isometric tension of rat-tail and frog-finger tendons (Brocas & Verzfir, 1961a, b) and solubilization of hydroxyproline on heating cattle corium (Verzfir, 1960), rat-tail tendon (Verzfir & Meyer, 1961), human skin (Verzfir, 1962) and rat muscle (Schaub, 1963). Recently, we reported on the use of isometric tension, thermal transition temperature and hydroxyproline solubilization to estimate the age of goats (Horgan et al., 1988). The most satisfactory method tested was the measurement of the m a x i m u m hydrothermal isometric tension (HITm) of the tendons from longissimus dorsi (LD) muscle. The relationship with age was linear over the age range 0"2-14 years and the precision of this method compared favourably with that of dentition. In this study isometric tension and thermal transition temperature (Tin) measurements were applied to the tendons from the LD muscles of cattle with known birth dates. Correlations with age were measured and results compared to those previously found with goat tendons.
MATERIALS AND METHODS
Samples LD muscles with attached tendons from 70 cattle of mixed breed and sexes ranging in age from 0-7 to 15-8 years were obtained from research stations in southern Queensland and northern New South Wales. They were stored at -30°C until required. Samples of tendon were obtained by dissection from the surface of the muscle and suspended overnight in either 50mM sodium citrate, 10mM ethylene diamine tetra-acetic acid, pH 6-0 (buffer A) or 0"15M sodium chloride, 50 mM sodium phosphate, pH 7.5 (buffer B), before measurement of thermal properties.
Estimation of age of cattle by thermal stability of tendon collagen
245
Thermal transition temperature
The endothermal transition of collagen was measured in either buffer A or buffer B using a differential scanning calorimeter as described previously by King (1987). Although other workers use the extrapolated onset temperature (To), Tm, the m a x i m u m differential heating rate, was used here as it reflects 'average stability' whereas T Oarises from the least stable collagen in a sample (Ledward et al., 1975). Isometric tension measurements
Maximum hydrothermal isometric tension (HITm) was measured essentially as described by Snowden et al. (1977) but modified as follows: Strips of tendon approximately 3 c m long and 2 - 6 r a m wide were immersed overnight in buffer in a refrigerator (approximately 5°C). In preparation for a measurement, excess liquid was removed from each strip by blotting between paper towels. The length and weight of each strip were recorded. The strip was then immersed in buffer and held taut between two clamps on an Instron Model TM-M. The distance between the clamps was 10 ram. After immersion for approximately 10 min the clamps were moved 0-3 m m further apart to apply a slight tension (30-50 g) to the sample. A circulating water bath was used to raise the temperature (measured by a CuConstantin thermocouple) at a rate o f 2°C/min until the force began to decline after reaching a maximum. The mean cross-sectional area of collagen in each sample was estimated from the weight per unit length by assuming a collagen content of 30% of the wet weight and a density of 1-4 g/cm 2 for collagen (Snowden et al., 1977). Each tendon was measured in triplicate.
RESULTS Thermal transition temperature
Figure 1 shows that the T m of bovine LD tendon appeared to increase linearly with increasing age. However, the variation in T m between animals of similar age was large. Although not shown, the 95% confidence limits for estimating age by this m e t h o d are approximately _ 4 years. Also shown in Fig. 1 is the regression line previously found for goat LD tendons (Horgan et al., 1988).
Douglas J. Horgan
246
G
64
/ l
~63 /
/
/
62 2
,/
•
s
o
•
~
•
~ 60
g
//sl
~"
'-- 59
~ 57 ..:.'.
w
,,
o. ~
°
'-- 56 i
i
2
4
i
J
G 8 10 ANIMAL AGE {years)
J
i
i
12
14
18
Fig. 1. Thermal transition t e m p e r a t u r e (Tm) as a function o f animal age; O , each point is the m e a n o f two d e t e r m i n a t i o n s with bovine L D t e n d o n in buffer A, p H 6"0 (n = 55. r = 0"89), .... , regression line previously f o u n d for goat L D tendons.
Isometric tension measurements The maximum isometric tension developed during heating (HITm) is shown in Fig. 2 as a function of age. In this experiment the tendons were equilibrated in buffer A, pH 6.0, the same conditions as previously used for goat tendons (Horgan et al., 1988). 200 180: 160 _.~E140
-
°
J"
120' --
100
c~_ 8O
z" ~"
60 -
"
°
//'~
40
20
i
.." 2
•
, t 4
8
8
t0
12
14
18
ANIMAL AGE {years) Fig. 2.
Maximum isometric tension (HIT,.) as a function of animal age; ©, bovine LD
t e n d o n was i m m e r s e d in buffer A, p H 6-0 a n d the t e m p e r a t u r e raised at 2°C/min. Each p o i n t is the m e a n o f three d e t e r m i n a t i o n s (n = 32, r = 0"99), - . . . . , regression line previously f o u n d for g o a t L D tendons.
Estimation of age of cattle by thermal stability of tendon collagen
247
2O0 • °"
180~ 180'
I
120
@
100 L~
~- 80
6o .
- - 40
~ 15'
,,'"
20
~
,.'"
/" ,Y""
i
i
2
4
i
i
8 8 10 ANIMAL AtE (years)
i
i
12
14
18
Fig. 3. Maximum isometric tension (HITm) as a function of animal age. Bovine LD tendon was immersed in buffered saline, pH 7-5 and the temperature raised at 2:C/min. Each point is the mean of three determinations (n = 68, r = 0-98).......... 95% confidence limits obtained from a plot of x/(HITm) versus ,/(animal age). The scatter o f points a r o u n d the fitted line does not appear to vary much with age and the 9 5 % confidence limits for estimating age by this m e t h o d are approximately __ 1.4 years. The broken line in Fig. 2 is the regression line previously found for goat L D tendons (Horgan et al., 1988). As the regression line for measurements at p H 6-0 intercepts the age axis some distance from the origin this m e t h o d was not suitable for animals less than two years old. Figure 3 shows the results when H I T m was measured at p H 7.5. The H I T m values again increase linearly with age and can be measured satisfactorily in y o u n g animals. Regression analysis shows that the slopes of the lines measured at p H 6-0 (Fig. 2) and p H 7.5 (Fig. 3) are significantly different ( P < 0-01). The scatter o f experimental points a r o u n d the fitted line at p H 7-5, increases with increasing age and so the confidence limits shown in Fig. 3 were calculated from a plot o f x/(HITm) against x/(animal age). The confidence limits are approximately _+ 1 year, +_ 1-5 years and __ 2 years at mean ages o f 2, 4 and 8 years.
DISCUSSION Although the thermal transition temperature of L D tendon collagen increased linearly with increasing animal age (Fig. 1) the scatter o f experimental results was too large for this to be a practical m e t h o d for
248
Douglas J. Horgan
estimating the age of cattle. This agrees with previous findings for goats (Horgan et al., 1988). Figure 1 also shows that, except for the very young, bovine LD tendon collagen has a much lower Tmthan goat LD tendon of the same age. As the Tm of collagen depends on the heat stability of the crosslinks (Flandin et al., 1984) this suggests that bovine LD tendons have fewer heat-stable cross-links than goat tendons of the same age. As was found previously for goats (Horgan et al., 1988) isometric tension measurements were more suitable for estimating animal age than thermal transition temperatures. Figure 2 shows that, at pH 6-0, the regression line with bovine LD tendons did not pass through the origin but instead intercepted the age axis at approximately 1-2 years. This makes any age estimation for animals less than 2 years old very uncertain. Figure 2 also shows that the regression line for goat LD tendons (broken line) was higher at all ages and intercepted the age axis much closer to the origin than did the bovine line. As it is well established that the isometric tension generated by collagen fibres during heating depends on the type of cross-link involved (for a recent review, see Kopp & Bonnet, 1987) this result supports the conclusion from the Tm results, i.e. that bovine LD tendons contain fewer heat-stable cross-links than goat tendons of the same age. It is of interest that the species difference in the HIT m results (Fig. 2) was almost constant throughout the age range in contrast to the Tm results (Fig. 1) where the difference increased with age. It would appear that the higher content of heat-labile (aldimine) bonds in the bovine LD tendons has different quantitative effects on the two measures of heat stability, i.e. HIT m and Tm. Apparently these bonds, although labile at high temperatures, can generate quite high tensions at the more moderate temperatures where the maxima occur, before relaxing at the higher temperatures. When the HIT m measurements of bovine LD tendons were made at pH 7.5 (Fig. 3), higher values were found at young ages which caused the gradient of the regression line to be significantly different to that found at pH 6"0 (Fig. 2). This was, presumably, because soaking in the pH 6-0 buffer destroyed some of the labile aldimine bonds. At pH 7.5, the age of young animals could be estimated more accurately thai1 at pH 6-0 but, overall, the variation of HIT m values for animals with similar ages was greater and increased with age. The 95% confidence limits for estimating the age of cattle at pH 7-5 and 6"0 were respectively ___24 months and + 18 months compared to the previously found value of 4- 14 months for goats at a mean animal age of 6 years. In conclusion, the age of cattle can be estimated from isometric tension measurements of the tendon from the LD muscle. Measurements at pH 6.0 have less scatter but are not suitable for very young animals. At pH 7.5 the whole age range can be measured with an accuracy that, although less than
Estimation of age of cattle by thermal stability of tendon collagen
249
for both cattle and goats at pH 6-0, is still comparable to that obtained from dentition.
A C K N O W L E D G E M ENTS The skilled technical assistance o f Miss Anita Sikes is gratefully acknowledged, as is the cooperation o f Dr Helen Hearnshaw, Agricultural Research Station, Grafton, NSW. This w o r k was supported in part by the Australian Meat and Live-stock Research and Development Corporation.
REFERENCES Bailey, A. J. (1988). Proc. 34th Int. Cong. Meat Sci. Technol., Brisbane, p. 152. Brocas, J. & Verzfir, F. (1961a). Gerontologia, 5, 223. Brocas, J. & Verz~tr, F. (1961b). Gerontologia, 5, 228. Dodt, R. M. & O'Rourke, P. K. (1988). Queensland J. Agric. Anita. Sci., 45, 53. Flandin, F., Buffevant, C. & Herbage, D. (1984). Biochim. Biophys. Acta., 791, 205. Franklin, M. C. (1950). Influence of diet on dental development in the sheep. CSIRO Bulletin No. 252. Horgan, D. J., King, N. L. & Kurth, L. B. (1988). Proc. 34th Int. Cong. Meat SeL Technol., Brisbane, p. 197. King, N. L. (1987). Meat Sei., 20, 25. Kopp, J. & Bonnet, M. (1987). In Advances in Meat Research, Volume 4, Collagen as a food, ed. A. M. Pearson, T. R. Dutson & A. J. Bailey. AVI, New York, p. 163. Ledward, D. A., Chizzolini, R. & Lawrie, R. A. (1975). J. Food TechnoL, 10, 349. Neuberger, A. & Slack, H. G. B. (1953). Biochem. J., 53, 47. Schaub, M. C. (1963). Gerontologia, 8, 16. Snowden, J. M., Bouton, P. E. & Harris, P. V. (1977). J. Food Sci., 42, 890. Tulloh, N. M. (1962). Aust. J. Agrie. Res., 13, 350. Verzfir, F. (1960). Gerontologia, 4, 104. Verz~r, F. (1962). Experientia, 18, 473. Verzfir, F. & Meyer, A. (1961). Gerontologia, 5, 163. Weiner, G. & Purser, A. F. (1957). J. Agrie. Sei., 49, 51.