Abstract:
Animal Production in Australia A TACTILE METHOD MODIFIED TO ASSESS THE FINISH OF BEEF CATTLE IN MARKETABLE CONDITION IN NORTH QUEENSLAND I.D. LOXTON*, J.A. LINDSAY* and M.A. TOLEMAN** SUMMARY Three methods of assessing the fat finish of marketable beef cattle were compared using Bos indicus crossbred cattle. The methods were: the Queensland Livestock Market Reporting Service, the National Beef Recording Scheme and a modified tactile method (MT) of the Meat and Livestock Commission. None of the three methods was able to predict accurately the fat depth at the 13th rib of the carcass. The highest correlation between finish score and fat depth was r = 0.568 for one operator using the MT method. However, when data from the MT method were examined it was found that mean fat depth at the 13th rib increased (P < 0.05) with increasing finish score in two of the three liveweight categories studied. It is suggested that scoring individual animals on finish is no more accurate than weighing and allocating them to finish categories on the basis of liveweight. INTRODUCTION Assessment of fat depth or finish in the live animal is generally subjectively based. Two methods of visual appraisal in common use are the National Beef Recording Scheme method (NBRS) and the Livestock Market Reporting Scheme method (LMRS). The tactile method of the Meat and Livestock Commission of Great Britain and Northern Ireland (MLC) employs some element of objectivity. Four key locations, namely, the tail head, loin, ribs and chine, are palpated and an assessment of finish made. A modified MLC method (MT) has been developed for use with Brahman cross cattle in north Queensland. Only the loin and ribs are palpated. There is little documented evidence on how accurately assessments of finish in live animals using the above techniques relate to actual depth of fat over the rib-eye on the carcasses at slaughter. We examined this relationship in beef animals in north Queensland. PATERIALS AND METHODS Seventy-eight (+ SE) and aged 2.5 different methods; various methods, as Bos indicus crossbred steers of mean liveweight 452.2 + 7.1 kg to 4.5 years were assessed for fat finish by each of three the MT,LMRS and NBRS. A total of seven operators used the shown in' Table 2. Description of the three body condition methods The LMRS method standard visual guide is very lean and 5 is emaciated being 1 and ranks animals into one of five categories on the basis of a and description of five key sites on the body. A score of 1 very fat. The NBRS method uses a scale of eight points with very fat being 8. The MT method is described in Table 1. Finish at each handling point is assessed by varying pressure on the twc points on the left side of each animal. * Qld Dept Primary Industries, Swan's Lagoon Beef Cattle Research Station, via Ayr, 4807. ** Qld Dept Primary Industries, P.O. Box 1085, Townsville, 4810. 265 Animal Production in Australia TABLE 1 Description of classes for the two handling points of the modified tactile method Procedure Animals were yarded, weighed unfasted and their finish assessed by each method on day 1. They were transported to the meatworks on day 2, slaughtered on day 3 and carcass weights collected. Subcutaneous fat depth was measured 24 h post-slaughter between the 12013th ribs oneach side of the carcass using the Australian Beef Carcass Appraisal System. Statistical analysis Serial Snedecor and measurements tested using and partial correlations were calculated using the formulae of Cochran (1967). Analysis of variance was carried out on fat depth for each liveweight range. Differences between score means were the least significant difference method. RESULTS The mean carcass fat depth at the 12th rib was 4.49 + 0.30 mm (+ SE) with a range of l-14 mm. Correlations between finish score and subcutaneous fat depth were moderate to low in this observation (Table 2). When partial correlation was adjusted for breed as well as final liveweight, this gave similar results to those in Table 2. A simple correlation coefficient of r = 0.539 (P < 0.01) was found between final liveweight and fat depth. 266 Animal Production in Australia TABLE 2 Partial correlations (r), adjusted for full liveweight before slaughter of 12th/13th rib subcutaneous fat depth with finish score using three methods and a number of operators When r 9 0.222, then P < 0.05 When r 9 0.289, then P < 0.01 As the MT method gave slightly better correlations between finish score and fat depth, the mean fat depth for a given score over three liveweight ranges is given in Table 3. Mean fat depth increased as the score increased and the difference between scores was significant (P < 0.05) in the two heavier liveweight ranges. There were small differences between operators, but these were not significant. TABLE 3 Finish assessed by three operators using the MT method for four categories compared with the mean subcutaneous fat depth for three final liveweight ranges -I- Means within a row without the same superscript differ significantly (P < 0.05). L + Number of animals. DISCUSSION In our study, none of the operators using any of the methods of assessing finish in the live animal was able to predict accurately the carcass fat depth of individual animals. They were no more accurate with any one method than with any other. There was considerable variation between operators in their ability to assess animals, with the range in correlations between finish and carcass fat depth being 0.37 to 0.56. This result agrees closely with Holland (1979) who reported low correlations of 0.20 to 0.52. The inaccuracy in our assessments was possibly due to lack of experience of the operators rather than any inherent flaws in the three methods. This conclusion is supported by previous wcrk of Lewis et al. (1968). They found that experienced operators were able to detect 75% of the variation in fat depth whereas inexperienced personnel were only half as effective. Alternatively, our cattle had too narrow a range of fat depths for differences to be detected between animals. 267 Animal Production in Australia Merely weighing animals was as accurate as scoring them on finish. Thus allocating animals on the basis Iof liveweight may be as accurate as the use of any of these scoring methods. Under commercial conditions it is easier to weigh animals than to appraise them individually, particularly using the MT method. It is noteworthy that while carcass fat depth is highly correlated with carcass composition (Ramsey et al. 1962; Butterfield 1965), it was only moderately related to liveweight. Furthermore our #value of 0.54 tends to be higher than most, with reported correlations varying frlom 0.23 (McReynold and Arthaud 1970) through 0.31 (Shelby et al. 1963) to 0.52 (Wood et al. 1979). Recent work using the MLC tactile method indicated that body condition scoring of cows was a useful adj'unct to their nutritional management (Frood and Croxton 1978). As our MT method has not been investigated in cows,further research would seem warranted. ACKNOWLEDGEMENTS The assistance of the staff at Swan's Lagoon Beef Cattle Research Station and the co-operation of Mr. Bob Garbiutt, Livestock Market Reporting Service reporter, Townsville, in this study is gratefully acknowledged. REFERENCES BUTTERFIELD, R.M. (1965). Res. 'Vet. Sci. 6: 24. FROOD, M.J., and CROXTON, D. (1978). Anim: Prod. 27: 285. HOLLAND, B.J.M. (1979). Proc. Aust. Assoc. Anim. Breed. Genet. 1: 177. LEWIS, T.R., SUESS, G.G., and KAUFFMAN, R.G. (1968). J. Anim. STi. 27: 1134. McREYNOLD, W.E., and ARTHAUD, V.:H. (1970). 3. 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