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Carcass and non-carcass characteristics of Suffolk-sired lambs from South Australian Merino, Poll Dorset X Merino and Border Leicester X Merino ewes
Small Ruminant Research, 3 (1990) 283-290 Elsevier Scier~ce Publishers B.V., Amsterdam - - Printed in The Netherlands
283
Carcass and N o n - C a r c a s s Characteristics of S u f f o l k - S i r e d Lambs from South Australian Merino, Poll D o r s e t X Merino and Border Leicester X Merino E w e s D.O. KLEEMANN, C.H.S. DOLLING 1 and R.W. PONZONI 2
South Australian Department of Agriculture, Turretfield Research Centre, Rosedale, S.A. 5350 (Australia) 1Box 74, McLaren Vale, S.A. 5171 (Australia) 2South Australian Department of Agriculture, G.P.O. Box 1671, Adelaide, S.A. 5001 (Australia) (Accepted 23 March 1989 )
ABSTRACT Kleemann, D.O., Dolling, C.H.S. and Ponzoni, R.W., 1990. Carcass and non-carcass characteristics of Suffolk-sired lambs from South Australian Merino, Poll Dorset × Merino and Border Leicester X: Merino ewes. Small Rumin. Res., 3: 283-290. The carcass and non-carcass characteristics of 121 Suffolk-sired lambs from South Australian Merino (M), Poll Dorset × South Australian Merino (PD × M) and Border Leicester × South Australian l~[erino (BL × M) ewes were compared in two pen experiments (PE1, PE2) at Turretfield Research Centre, South Australia. When lambs were slaughtered at the same liveweight and carcass characteristics adjusted to constant carcass weight (15.6 and 15.7 kg; PE1 and PE2, respectively) there were no significant differences between breeds of dam for fat depth C, or for percentages ,~f chemical fat (ether extract), protein, moisture and ash. At constant liveweight (e.g. 36.4 kg, PE2) dressing percentage was higher for BL × M and PD × M compared with M progeny (44.6 and 44.5% vs. 39.9%, respectively). Differences due to breed of dam were detected for some of the non-carcass characteristics, adjusted for slaughter weight in either PE1 or PE2, but on no occasion were the differences significant in both experiments. Greasy fleece weight, measured in PE2 only, was heavier for M compared with B L × M progeny which in turn was heavier compared with PD × M progeny (1.60, 1.29 and 1.11 kg, respectively). We conclcLded that differences between Suffolk-sired lambs from South Australian Merino, PD × M and BL × M ewes were small for most carcass and non-carcass characteristics when compared at the same carcass weight and slaughter weight, respectively. The relative economic merit of the breech,, therefore, is more likely to be determined by factors other than those examined in the present experiments.
INTRODUCTION
The Australian lamb-meat industry has developed a two-tier cross-breeding structure in which Merino ewes, surplus to wool-growing requirements are 0921-4488/90/$03.50
© 1990 Elsevier Science Publishers B.V.
284
D.O. KLEEMANN ET AL.
mated to long-wool British-breed sires, the Border Leicester being the most popular. The resultant first-cross ewe progeny are mated to terminal meat-sire breeds like the Dorset or Suffolk. In South Australia, Merino strains have been developed that are larger-framed than their Peppin and non-Peppin counterparts in the Eastern states of Australia. They are used extensively in Australia for wool growing and to a lesser extent for meat-growing purposes. Some South Australian Merino ewes are mated directly to a terminal breed such as the Dorset. A proportion of the resultant Dorset X Merino ewes are kept as breeders in areas favoured for 'out of season' lamb production because of their ability to conceive in the spring (McGuirk, 1967; Kajons, 1972; Fogarty, 1978). Most research in Australia on the Dorset has been concentrated on the Dorset Horn but in the last 1-2 decades the Poll Dorset has become the predominant breed used in the lamb-meat industry (Australian Bureau of Statistics, 1986). Biological efficiency of the South Australian Merino ewe and its crosses with the Border Leicester and Poll Dorset have been described in terms of the amount and quality of wool grown per unit intake and amount of carcass grown per unit intake (Kleemann et al., 1984). Other biological components that could be important in determining economic efficiency, such as carcass composition, skin weight and offal weight have not been described for the foregoing ewe genotypes. Some comparative information is available for other Merino strains and the Border Leicester X Peppin Merino (e.g. Atkins and Thompson, 1979; Cotterill and Roberts, 1979). This paper reports the effect of breed of dam on carcass and non-carcass characters of Suffolk-sired lambs from South Australian Merino, Poll Dorset X South Australian Merino and Border Leicester X South Australian Merino ewes. The results of two pen experiments are reported. MATERIALSAND METHODS Lambs were slaughtered in each of two pen experiments described by Kleemann et al. (1984). The number of lambs involved in each experiment is given in Tables 1 and 2. In pen experiment 1 (PE1), South Australian Merino ewes of the Bungaree strain (M) and Border Leicester X Bungaree Merino ( BL X M ) ewes, pregnant to Suffolk rams (S) (n= 16), were penned in an animal house 6-7 weeks before parturition. Experimental feeding began on 10 July (day 0). Ewes lambed between days 34 and 46, the first lamb being slaughtered on day 118 and the last lamb on day 209. All ewes and lambs were fed lucerne pellets to appetite. All lambs were tailed and male lambs castrated at 3-5 days of age. Single-born lambs weighing 32 kg or more and twin-born lambs weighing a total of 64 kg or more at a weekly weighing were fasted overnight. They were weighed and slaughtered on the following afternoon at Turretfield Research Centre, and were dressed according to commercial practice.
CHARACTERIS~ICS OF SEVERAL BREEDS OF SHEEP
285
In pen experiment 2 (PE2) M, B L × M ewes and Poll Dorset×Bungaree Merino ( P D x M ) ewes, pregnant to Suffolk rams (S) ( n = 1 6 ) , were penned in an animal house 6-7 weeks before parturition. Details of feeding were the same as those of PE1. The first lamb was slaughtered on day 145 after experimental feeding began, and the last lamb on day 225. Single-born lambs weighing 35 kg or more and twin-born lambs weighing a total of 70 kg or more at a two-weekly weighing were shorn, the fleeces weighed and the lambs then fasted overnight. On the following morning they were weighed, slaughtered and dressed. The following components of the Iambs were weighed at slaughter and were defined as the non-carcass components: head (severed between occipital bone and first cervical vertebra, with ears and most of the skin removed), feet (distal to tarsus and carpus, with skin on), skin, wool (PE2 only), heart plus lungs (including trachea), liver (minus gall bladder), omental fat, stomachs plus digesta (including oesophagus), small intestines plus digesta, and large intestine plus digesta. Hot carcass weight (including kidneys and kidney knob and channel fat) was recorded. On the morning following slaughter, fat depth C (Palsson, 1939) was measured on the left side of the carcass between the 12th and 13th rib. A sample of lambs in PE2 was chosen at random from within type of birth × sex of lamb categories for determination of chemical composition of the carcass.; all single-reared lambs were analysed in PEa. The right side of each carcass was minced according to the description of Walker et al. (1971) and the mince sampled and stored at - 1 5 ° C . The percentage of moisture, ether extract (chemical fat), protein and ash were determined using the following methods. A 100 g sub-sample of mince was macerated with 20 ml of water in a homogenizer. The same 5 g of homogenized sample and its container were used for the determination of moisture, ether extract and ash. The sample was dried at 70°C for 7 h in a vacuum oven (20 mm Hg). The dried sample was extracted with diethyl ether for 5 h, dried for 1 h at 100°C, cooled and weighed. The sample was heated in a muffle furnace overnight, or for a minim u m of 5 h, cooled and weighed. Crude protein (N × 6.25) was determined on 2 g of homogenized sample using the Kjeldahl method with selenium as the catalyst. All characteristics were analysed by least-squares analysis of variance (Harvey, 1975), within experiments. The basic model fitted was:
Yijkl = / l + b i + t i +Sk + (bt)ij + (bs)ik + (ts)ih + eiikz where Yiiht is the/th observation in the ith breed of dam, jth
type of birth, and k th sex of lamb, p is the common mean and eijkl is the random error. Breed of dam (b), type of birth (t) and sex of lamb (s) were treated as fixed effects. The pen experiments were designed such that single-born lambs were slaughtered at approximately the same weight and twin-born lambs when their combined weight averaged that of the singles. Since not all lambs were slaughtered at the
286
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same weight, the slaughter and carcass characteristics were adjusted to constant slaughter weight and carcass weight, respectively, using the latter two characteristics as linear covariates in the basic model. RESULTS
Results of the characteristics measured at slaughter, adjusted to a constant slaughter weight, are given for PE2 (Table 1 ) because all three breeds of ewes were represented in this experiment. Results for PE1 are not given, but are commented on when appropriate. Heads of lambs from the M and PD × M ewes were :heavier than those from the BL × M in PE2; the difference between M and BL X M breeds in PE1 was not significant. Lamb skin weight, including wool, was heavier for the M than the BL X M breed of dam in PE~. However, skin weight minus wool did not differ between breeds (PE2; Table 1). Lambs from M ewes grew more greasy wool than those from BL × M ewes, which in turn grew more than those from PD X M ewes. In PEx, heart plus lungs of lambs from BL × M ewes were heavier than those of lambs from M ewes. There was no significant difference between breeds of dam for the weights of the components of the abdominal contents, except that in PE, stomach weight of lambs from the M breed was heavier than that of TABLE1
Least-squares means and standard errors for slaughter characteristics adjusted to 36.4 kg nonfasted slaughter weight in pen experiment 2 Breed of ewe 1
N u m b e r of observations:
M
BLXM
PDXM
11
27
212
1.52 a3 _+0.04 0.76 a _+0.03 3.13 a_+ 0.14 1.60 a _+0.11 0.80 a +_0.04 0.59 ~_+ 0.03 0.38 ~_+ 0.06 4.35 a _+0.33 1.07 a_+ 0.07 1.17 ~ _+0.07
1.40 b _+0.02 0.77 ~ _+0.02 2.76 a_+ 0.06 1.29 b _+0.05 0.90 a_+ 0.02 0.62 ~___0.01 0.42 ~ + 0.03 3.88 a _+0.15 1.18 ~_+ 0.03 1.08 a _+0.03
1.49 a +_0.02 0.75 ~ _ 0.02 2.77 ~___0.07 1.11 c _+0.05 0.89 ~_+ 0.02 0.59 ~_+ 0.02 0.41 ~ +---0.03 4.31 ~ _+0.16 1.11 ~ +_0.03 1.13 ~ +_0.03
S l a u g h t e r c h a r a c t e r i s t i c s (kg)
Head F o u r feet Skin
Wool Heart plus lungs Liver Omental fELt Stomachs ]31usdigesta Small intestines plus digesta
Large intestines plus digesta IM=South
Australian
Merino;
BL×M--Border
Leicester×South
Australian
Merino;
P D × M = Poll Dorset × South Australian Merino. 2Data were not collected for 2 lambs. 3Within each variable,means followed by a c o m m o n letterare not significantlydifferent ( P > 0.05 ).
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D.O. KLEEMANN ET AL.
lambs from BL X M ewes. There were significant breed X type of birth interactions for heart plus lungs (PE1), and small ruminant intestinal weight (PE2). However, inspection of the least-squares means indicated that changes in the magnitude of the differences rather than changes in the ranking of the breeds were responsible. Carcass characters measured in PE1 and PE2 (Table 2) were adjusted to either constant slaughter weight or carcass weight since not all lambs were slaughtered at exactly the same weight (co-twins were slaughtered when their combined weight averaged that of singles). Dressing percentage was significantly higher for BL X M and PD X M breeds compared with the M breed. There were no significant differences between breeds for fat depth over the eye muscle, chemical fat, protein, moisture and ash. There were no significant breed X other main effect interactions for the carcass characteristics. DISCUSSION Differences between breeds of ewe in the value of lambs, independent of differences due to growth rate, would be determined by variation in carcass composition and conformation at the same carcass weight and variation in non-carcass components at the same slaughter weight. Neither fat depth nor carcass composition of lambs from South Australian Merino, PD X M and BL X M ewes varied significantly in our study. This result is the first report for the PD X M and is important because of the Poll Dorset's current numeric predominance in the Australian lamb-meat industry (Australian Bureau of Statistics, 1986). Our observations on the BL X M and M breeds are consistent with those of Atkins and Thompson (1979) where the Peppin Merino was used as the base Merino strain. Extrapolation of our results to carcass weights much greater than 16 kg is not justified since Atkins and Thompson (1979) have reported that as carcass weight increased from 15 kg to 26 kg the rate of increase in fat depth of lambs from BL X M ewes was greater than in those from M ewes. Since the average yearly carcass weight of lambs slaughtered in Australia has varied between 16 and 17 kg over the last 10 years (Australian Bureau of Statistics, 1987) results of the present study would be relevant to an appreciable section of the lamb-meat industry. Thompson and Atkins (1980) indicated that carcass conformation should not be considered as an important component in a classification scheme because it added little additional information above that of carcass weight and measures of fatness as predictors of percentage carcass composition. However, they suggested that shape per se may affect appearance and hence improve retail value of joints. Comparative data for breeds were not available from the present experiments; however, results of Kleemann et al. (unpublished) indicated that Suffolk-sired carcasses from PD X M ewes were more compact than those from M and B L x M breeds. Carcass lengths (measured according to
CHARACTERISTICS OF SEVERAL BREEDS OF SHEEP
289
Moxham and Brownlie, 1976) were 91.1 cm vs 94.4 and 93.3 cm, respectively, at 16.3 kg constant carcass weight. Some differences were observed between breeds for the various non-carcass components when comparisons were made at the same slaughter weight. Differences between breeds for skin weight were due to differences in fleece weight; lambs from PD × M ewes had the lightest fleeces. Skin weight, staple length and visual count are the main characters used in classing lamb skins (Dunne, 1976). The latter two characters were not measured in our study, however, results of Kleemann et al. (unpublished) have shown that neither staple length nor visual count differed between M and PD × M breeds. Variation between M and BL × M breeds for these characters may be expected as Atkins and Gilmour (1981) have indicated that lambs from M ewes had shorter staples and higher visual counts. However, until the relative economic importance of skin weight, staple length and visual count are known, the monetary consequences of changes in these characters cannot be determined. Since breed differences for other non-carcass characters were small and not consistent between experiments, we consider they would have little influence on commercial value. There are no other comparative studies on this matter. Some of the non-carcass components have value in their own right as components of fresh or processed foods and other by-products. The present results give an indication of the yields to be expected in commercial lambs slaughtered at about the average yearly weight common for lambs in Australia. CONCLUSIONS
We concluded that differences between progeny from South Australian Merino, Poll Dorset × South Australian Merino and Border Leicester × South Australian Merino ewes were small for most carcass and non-carcass characters, when compared at the same carcass weight and slaughter weight, respectively. The relative economic worth of the breeds, therefore, is more likely to be determined by factors other than those associated with the carcass and its by products, and include growth rate of the lamb and reproductive performance, wool growth and feed intake of the ewe. Breed differences between these latter biological components, with the exception of reproductive performance, have been reported elsewhere (Kleemann et al., 1984). ACKNOWLEDGEMENTS
We thank the staff at Turretfield Research Centre, in particular Messrs. R.E. Holloway, D.H. Smith and A.O. Uppill, for skilled technical assistance; Mr. R. Hel~herington, Department of Chemistry, Adelaide, for analysis of meat samples; Mr. R.V. Kenyon for statistical analysis. The study was supported by
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the Australian Meat Research Committee, now the Australian Meat and Livestock Research and Development Corporation.
REFERENCES Atkins, K.D. and Thompson, J.M., 1979. Carcass characteristics of heavyweight crossbed lambs. I. Growth and carcass measurements. Aust. J. Agric. Res., 30:1197-1205. Atkins, K.D. and Gilmour, A.R., 1981. The comparative productivity of five ewe breeds. 4. Growth and carcass characteristics of purebred and crossbred lambs. Aust. J. Exp. Agric. Anim. Husb., 21: 172-178. Australian Bureau of Statistics, 1986. Livestock and Livestock products, Australia, March. Canberra Catalogue No. 7221.0, p. 93. Australian Bureau of Statistics, 1987. Livestock and Livestock Products, Australia, June. Canberra Catalogue No. 7221.0, p. 5. Cotterill, P.P. and Roberts, E.M., 1979. Crossbred lamb growth and carcass characteristics of some Australian sheep breeds. Aust. J. Exp. Agric. Anim. Husb., 19: 407-413. Dunne, A.J., 1976. The sheep skin industry. New South Wales Department of Agriculture, Sydney, Economic and Technical Bulletin, No. 12, p. 21. Fogarty, N.M., 1978. Development of the ideal prime lamb dam. Wool Technol. Sheep. Breed., 26: 31-36. Harvey, W.R., 1975. Least-squares analysis of data with unequal subclass numbers. United States Department of Agriculture, Agriculture Research Service, ARS H-4, Washington, DC, pp. 85112. Kajons, A., 1972. Dorset X Merino ewes for reliable spring joining. Agric. Gaz. N.S.W., 83: 87-88. Kleemann, D.O., Dolling, C.H.S. and Ponzoni, R.W., 1984. Effect of breed of dam, type of birth and sex of lamb on efficiency of conversion of food to lamb and wool in Merino, Poll Dorset X Merino and Border Leicester X Merino ewes. Aust. J. Agric. Res., 35: 579-594. McGuirk, B.J., 1967. Breeding for lamb production. Wool Technol. Sheep Breed., 14: 73-75. Moxham, R.W. and Brownlie, L.E., 1976. Sheep carcase grading and classification in Australia. Wool Technol. Sheep Breed., 13." 17-25. Palsson, H.M., 1979. Meat qualities in the sheep with special reference to Scottish breeds and crosses. J. Agric. Sci. Camb., 29: 544-625. Thompson, J.M. and Atkins, K.D., 1980. Use of carcase measurements to predict percentage carcase composition in crossbred lambs. Aust. J. Exp. Agric. Anim. Husb., 20: 144-150. Walker, D.J., Potter, B.J. and Jones, G.B., 1971. Modification of carcass characteristics in sheep maintained on a saline water regime. Aust. J. Exp. Agric. Anim. Husb., 11: 14-17.
283
Carcass and N o n - C a r c a s s Characteristics of S u f f o l k - S i r e d Lambs from South Australian Merino, Poll D o r s e t X Merino and Border Leicester X Merino E w e s D.O. KLEEMANN, C.H.S. DOLLING 1 and R.W. PONZONI 2
South Australian Department of Agriculture, Turretfield Research Centre, Rosedale, S.A. 5350 (Australia) 1Box 74, McLaren Vale, S.A. 5171 (Australia) 2South Australian Department of Agriculture, G.P.O. Box 1671, Adelaide, S.A. 5001 (Australia) (Accepted 23 March 1989 )
ABSTRACT Kleemann, D.O., Dolling, C.H.S. and Ponzoni, R.W., 1990. Carcass and non-carcass characteristics of Suffolk-sired lambs from South Australian Merino, Poll Dorset × Merino and Border Leicester X: Merino ewes. Small Rumin. Res., 3: 283-290. The carcass and non-carcass characteristics of 121 Suffolk-sired lambs from South Australian Merino (M), Poll Dorset × South Australian Merino (PD × M) and Border Leicester × South Australian l~[erino (BL × M) ewes were compared in two pen experiments (PE1, PE2) at Turretfield Research Centre, South Australia. When lambs were slaughtered at the same liveweight and carcass characteristics adjusted to constant carcass weight (15.6 and 15.7 kg; PE1 and PE2, respectively) there were no significant differences between breeds of dam for fat depth C, or for percentages ,~f chemical fat (ether extract), protein, moisture and ash. At constant liveweight (e.g. 36.4 kg, PE2) dressing percentage was higher for BL × M and PD × M compared with M progeny (44.6 and 44.5% vs. 39.9%, respectively). Differences due to breed of dam were detected for some of the non-carcass characteristics, adjusted for slaughter weight in either PE1 or PE2, but on no occasion were the differences significant in both experiments. Greasy fleece weight, measured in PE2 only, was heavier for M compared with B L × M progeny which in turn was heavier compared with PD × M progeny (1.60, 1.29 and 1.11 kg, respectively). We conclcLded that differences between Suffolk-sired lambs from South Australian Merino, PD × M and BL × M ewes were small for most carcass and non-carcass characteristics when compared at the same carcass weight and slaughter weight, respectively. The relative economic merit of the breech,, therefore, is more likely to be determined by factors other than those examined in the present experiments.
INTRODUCTION
The Australian lamb-meat industry has developed a two-tier cross-breeding structure in which Merino ewes, surplus to wool-growing requirements are 0921-4488/90/$03.50
© 1990 Elsevier Science Publishers B.V.
284
D.O. KLEEMANN ET AL.
mated to long-wool British-breed sires, the Border Leicester being the most popular. The resultant first-cross ewe progeny are mated to terminal meat-sire breeds like the Dorset or Suffolk. In South Australia, Merino strains have been developed that are larger-framed than their Peppin and non-Peppin counterparts in the Eastern states of Australia. They are used extensively in Australia for wool growing and to a lesser extent for meat-growing purposes. Some South Australian Merino ewes are mated directly to a terminal breed such as the Dorset. A proportion of the resultant Dorset X Merino ewes are kept as breeders in areas favoured for 'out of season' lamb production because of their ability to conceive in the spring (McGuirk, 1967; Kajons, 1972; Fogarty, 1978). Most research in Australia on the Dorset has been concentrated on the Dorset Horn but in the last 1-2 decades the Poll Dorset has become the predominant breed used in the lamb-meat industry (Australian Bureau of Statistics, 1986). Biological efficiency of the South Australian Merino ewe and its crosses with the Border Leicester and Poll Dorset have been described in terms of the amount and quality of wool grown per unit intake and amount of carcass grown per unit intake (Kleemann et al., 1984). Other biological components that could be important in determining economic efficiency, such as carcass composition, skin weight and offal weight have not been described for the foregoing ewe genotypes. Some comparative information is available for other Merino strains and the Border Leicester X Peppin Merino (e.g. Atkins and Thompson, 1979; Cotterill and Roberts, 1979). This paper reports the effect of breed of dam on carcass and non-carcass characters of Suffolk-sired lambs from South Australian Merino, Poll Dorset X South Australian Merino and Border Leicester X South Australian Merino ewes. The results of two pen experiments are reported. MATERIALSAND METHODS Lambs were slaughtered in each of two pen experiments described by Kleemann et al. (1984). The number of lambs involved in each experiment is given in Tables 1 and 2. In pen experiment 1 (PE1), South Australian Merino ewes of the Bungaree strain (M) and Border Leicester X Bungaree Merino ( BL X M ) ewes, pregnant to Suffolk rams (S) (n= 16), were penned in an animal house 6-7 weeks before parturition. Experimental feeding began on 10 July (day 0). Ewes lambed between days 34 and 46, the first lamb being slaughtered on day 118 and the last lamb on day 209. All ewes and lambs were fed lucerne pellets to appetite. All lambs were tailed and male lambs castrated at 3-5 days of age. Single-born lambs weighing 32 kg or more and twin-born lambs weighing a total of 64 kg or more at a weekly weighing were fasted overnight. They were weighed and slaughtered on the following afternoon at Turretfield Research Centre, and were dressed according to commercial practice.
CHARACTERIS~ICS OF SEVERAL BREEDS OF SHEEP
285
In pen experiment 2 (PE2) M, B L × M ewes and Poll Dorset×Bungaree Merino ( P D x M ) ewes, pregnant to Suffolk rams (S) ( n = 1 6 ) , were penned in an animal house 6-7 weeks before parturition. Details of feeding were the same as those of PE1. The first lamb was slaughtered on day 145 after experimental feeding began, and the last lamb on day 225. Single-born lambs weighing 35 kg or more and twin-born lambs weighing a total of 70 kg or more at a two-weekly weighing were shorn, the fleeces weighed and the lambs then fasted overnight. On the following morning they were weighed, slaughtered and dressed. The following components of the Iambs were weighed at slaughter and were defined as the non-carcass components: head (severed between occipital bone and first cervical vertebra, with ears and most of the skin removed), feet (distal to tarsus and carpus, with skin on), skin, wool (PE2 only), heart plus lungs (including trachea), liver (minus gall bladder), omental fat, stomachs plus digesta (including oesophagus), small intestines plus digesta, and large intestine plus digesta. Hot carcass weight (including kidneys and kidney knob and channel fat) was recorded. On the morning following slaughter, fat depth C (Palsson, 1939) was measured on the left side of the carcass between the 12th and 13th rib. A sample of lambs in PE2 was chosen at random from within type of birth × sex of lamb categories for determination of chemical composition of the carcass.; all single-reared lambs were analysed in PEa. The right side of each carcass was minced according to the description of Walker et al. (1971) and the mince sampled and stored at - 1 5 ° C . The percentage of moisture, ether extract (chemical fat), protein and ash were determined using the following methods. A 100 g sub-sample of mince was macerated with 20 ml of water in a homogenizer. The same 5 g of homogenized sample and its container were used for the determination of moisture, ether extract and ash. The sample was dried at 70°C for 7 h in a vacuum oven (20 mm Hg). The dried sample was extracted with diethyl ether for 5 h, dried for 1 h at 100°C, cooled and weighed. The sample was heated in a muffle furnace overnight, or for a minim u m of 5 h, cooled and weighed. Crude protein (N × 6.25) was determined on 2 g of homogenized sample using the Kjeldahl method with selenium as the catalyst. All characteristics were analysed by least-squares analysis of variance (Harvey, 1975), within experiments. The basic model fitted was:
Yijkl = / l + b i + t i +Sk + (bt)ij + (bs)ik + (ts)ih + eiikz where Yiiht is the/th observation in the ith breed of dam, jth
type of birth, and k th sex of lamb, p is the common mean and eijkl is the random error. Breed of dam (b), type of birth (t) and sex of lamb (s) were treated as fixed effects. The pen experiments were designed such that single-born lambs were slaughtered at approximately the same weight and twin-born lambs when their combined weight averaged that of the singles. Since not all lambs were slaughtered at the
286
D.O. KLEEMANN ET AL
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same weight, the slaughter and carcass characteristics were adjusted to constant slaughter weight and carcass weight, respectively, using the latter two characteristics as linear covariates in the basic model. RESULTS
Results of the characteristics measured at slaughter, adjusted to a constant slaughter weight, are given for PE2 (Table 1 ) because all three breeds of ewes were represented in this experiment. Results for PE1 are not given, but are commented on when appropriate. Heads of lambs from the M and PD × M ewes were :heavier than those from the BL × M in PE2; the difference between M and BL X M breeds in PE1 was not significant. Lamb skin weight, including wool, was heavier for the M than the BL X M breed of dam in PE~. However, skin weight minus wool did not differ between breeds (PE2; Table 1). Lambs from M ewes grew more greasy wool than those from BL × M ewes, which in turn grew more than those from PD X M ewes. In PEx, heart plus lungs of lambs from BL × M ewes were heavier than those of lambs from M ewes. There was no significant difference between breeds of dam for the weights of the components of the abdominal contents, except that in PE, stomach weight of lambs from the M breed was heavier than that of TABLE1
Least-squares means and standard errors for slaughter characteristics adjusted to 36.4 kg nonfasted slaughter weight in pen experiment 2 Breed of ewe 1
N u m b e r of observations:
M
BLXM
PDXM
11
27
212
1.52 a3 _+0.04 0.76 a _+0.03 3.13 a_+ 0.14 1.60 a _+0.11 0.80 a +_0.04 0.59 ~_+ 0.03 0.38 ~_+ 0.06 4.35 a _+0.33 1.07 a_+ 0.07 1.17 ~ _+0.07
1.40 b _+0.02 0.77 ~ _+0.02 2.76 a_+ 0.06 1.29 b _+0.05 0.90 a_+ 0.02 0.62 ~___0.01 0.42 ~ + 0.03 3.88 a _+0.15 1.18 ~_+ 0.03 1.08 a _+0.03
1.49 a +_0.02 0.75 ~ _ 0.02 2.77 ~___0.07 1.11 c _+0.05 0.89 ~_+ 0.02 0.59 ~_+ 0.02 0.41 ~ +---0.03 4.31 ~ _+0.16 1.11 ~ +_0.03 1.13 ~ +_0.03
S l a u g h t e r c h a r a c t e r i s t i c s (kg)
Head F o u r feet Skin
Wool Heart plus lungs Liver Omental fELt Stomachs ]31usdigesta Small intestines plus digesta
Large intestines plus digesta IM=South
Australian
Merino;
BL×M--Border
Leicester×South
Australian
Merino;
P D × M = Poll Dorset × South Australian Merino. 2Data were not collected for 2 lambs. 3Within each variable,means followed by a c o m m o n letterare not significantlydifferent ( P > 0.05 ).
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lambs from BL X M ewes. There were significant breed X type of birth interactions for heart plus lungs (PE1), and small ruminant intestinal weight (PE2). However, inspection of the least-squares means indicated that changes in the magnitude of the differences rather than changes in the ranking of the breeds were responsible. Carcass characters measured in PE1 and PE2 (Table 2) were adjusted to either constant slaughter weight or carcass weight since not all lambs were slaughtered at exactly the same weight (co-twins were slaughtered when their combined weight averaged that of singles). Dressing percentage was significantly higher for BL X M and PD X M breeds compared with the M breed. There were no significant differences between breeds for fat depth over the eye muscle, chemical fat, protein, moisture and ash. There were no significant breed X other main effect interactions for the carcass characteristics. DISCUSSION Differences between breeds of ewe in the value of lambs, independent of differences due to growth rate, would be determined by variation in carcass composition and conformation at the same carcass weight and variation in non-carcass components at the same slaughter weight. Neither fat depth nor carcass composition of lambs from South Australian Merino, PD X M and BL X M ewes varied significantly in our study. This result is the first report for the PD X M and is important because of the Poll Dorset's current numeric predominance in the Australian lamb-meat industry (Australian Bureau of Statistics, 1986). Our observations on the BL X M and M breeds are consistent with those of Atkins and Thompson (1979) where the Peppin Merino was used as the base Merino strain. Extrapolation of our results to carcass weights much greater than 16 kg is not justified since Atkins and Thompson (1979) have reported that as carcass weight increased from 15 kg to 26 kg the rate of increase in fat depth of lambs from BL X M ewes was greater than in those from M ewes. Since the average yearly carcass weight of lambs slaughtered in Australia has varied between 16 and 17 kg over the last 10 years (Australian Bureau of Statistics, 1987) results of the present study would be relevant to an appreciable section of the lamb-meat industry. Thompson and Atkins (1980) indicated that carcass conformation should not be considered as an important component in a classification scheme because it added little additional information above that of carcass weight and measures of fatness as predictors of percentage carcass composition. However, they suggested that shape per se may affect appearance and hence improve retail value of joints. Comparative data for breeds were not available from the present experiments; however, results of Kleemann et al. (unpublished) indicated that Suffolk-sired carcasses from PD X M ewes were more compact than those from M and B L x M breeds. Carcass lengths (measured according to
CHARACTERISTICS OF SEVERAL BREEDS OF SHEEP
289
Moxham and Brownlie, 1976) were 91.1 cm vs 94.4 and 93.3 cm, respectively, at 16.3 kg constant carcass weight. Some differences were observed between breeds for the various non-carcass components when comparisons were made at the same slaughter weight. Differences between breeds for skin weight were due to differences in fleece weight; lambs from PD × M ewes had the lightest fleeces. Skin weight, staple length and visual count are the main characters used in classing lamb skins (Dunne, 1976). The latter two characters were not measured in our study, however, results of Kleemann et al. (unpublished) have shown that neither staple length nor visual count differed between M and PD × M breeds. Variation between M and BL × M breeds for these characters may be expected as Atkins and Gilmour (1981) have indicated that lambs from M ewes had shorter staples and higher visual counts. However, until the relative economic importance of skin weight, staple length and visual count are known, the monetary consequences of changes in these characters cannot be determined. Since breed differences for other non-carcass characters were small and not consistent between experiments, we consider they would have little influence on commercial value. There are no other comparative studies on this matter. Some of the non-carcass components have value in their own right as components of fresh or processed foods and other by-products. The present results give an indication of the yields to be expected in commercial lambs slaughtered at about the average yearly weight common for lambs in Australia. CONCLUSIONS
We concluded that differences between progeny from South Australian Merino, Poll Dorset × South Australian Merino and Border Leicester × South Australian Merino ewes were small for most carcass and non-carcass characters, when compared at the same carcass weight and slaughter weight, respectively. The relative economic worth of the breeds, therefore, is more likely to be determined by factors other than those associated with the carcass and its by products, and include growth rate of the lamb and reproductive performance, wool growth and feed intake of the ewe. Breed differences between these latter biological components, with the exception of reproductive performance, have been reported elsewhere (Kleemann et al., 1984). ACKNOWLEDGEMENTS
We thank the staff at Turretfield Research Centre, in particular Messrs. R.E. Holloway, D.H. Smith and A.O. Uppill, for skilled technical assistance; Mr. R. Hel~herington, Department of Chemistry, Adelaide, for analysis of meat samples; Mr. R.V. Kenyon for statistical analysis. The study was supported by
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D.O.KLEEMANNET AL.
the Australian Meat Research Committee, now the Australian Meat and Livestock Research and Development Corporation.
REFERENCES Atkins, K.D. and Thompson, J.M., 1979. Carcass characteristics of heavyweight crossbed lambs. I. Growth and carcass measurements. Aust. J. Agric. Res., 30:1197-1205. Atkins, K.D. and Gilmour, A.R., 1981. The comparative productivity of five ewe breeds. 4. Growth and carcass characteristics of purebred and crossbred lambs. Aust. J. Exp. Agric. Anim. Husb., 21: 172-178. Australian Bureau of Statistics, 1986. Livestock and Livestock products, Australia, March. Canberra Catalogue No. 7221.0, p. 93. Australian Bureau of Statistics, 1987. Livestock and Livestock Products, Australia, June. Canberra Catalogue No. 7221.0, p. 5. Cotterill, P.P. and Roberts, E.M., 1979. Crossbred lamb growth and carcass characteristics of some Australian sheep breeds. Aust. J. Exp. Agric. Anim. Husb., 19: 407-413. Dunne, A.J., 1976. The sheep skin industry. New South Wales Department of Agriculture, Sydney, Economic and Technical Bulletin, No. 12, p. 21. Fogarty, N.M., 1978. Development of the ideal prime lamb dam. Wool Technol. Sheep. Breed., 26: 31-36. Harvey, W.R., 1975. Least-squares analysis of data with unequal subclass numbers. United States Department of Agriculture, Agriculture Research Service, ARS H-4, Washington, DC, pp. 85112. Kajons, A., 1972. Dorset X Merino ewes for reliable spring joining. Agric. Gaz. N.S.W., 83: 87-88. Kleemann, D.O., Dolling, C.H.S. and Ponzoni, R.W., 1984. Effect of breed of dam, type of birth and sex of lamb on efficiency of conversion of food to lamb and wool in Merino, Poll Dorset X Merino and Border Leicester X Merino ewes. Aust. J. Agric. Res., 35: 579-594. McGuirk, B.J., 1967. Breeding for lamb production. Wool Technol. Sheep Breed., 14: 73-75. Moxham, R.W. and Brownlie, L.E., 1976. Sheep carcase grading and classification in Australia. Wool Technol. Sheep Breed., 13." 17-25. Palsson, H.M., 1979. Meat qualities in the sheep with special reference to Scottish breeds and crosses. J. Agric. Sci. Camb., 29: 544-625. Thompson, J.M. and Atkins, K.D., 1980. Use of carcase measurements to predict percentage carcase composition in crossbred lambs. Aust. J. Exp. Agric. Anim. Husb., 20: 144-150. Walker, D.J., Potter, B.J. and Jones, G.B., 1971. Modification of carcass characteristics in sheep maintained on a saline water regime. Aust. J. Exp. Agric. Anim. Husb., 11: 14-17.