Selection for carcass lean content in a terminal sire breed of sheep

1992 ◽  
Vol 54 (3) ◽  
pp. 367-377 ◽  
Author(s):  
N. D. Cameron ◽  
J. Bracken
Keyword(s):  
Selection Index ◽  
Selection Criterion ◽  
Live Weight ◽  
Residual Maximum Likelihood ◽  
Cumulative Response ◽  
Cumulative Selection ◽  
Selection For ◽  
The Difference ◽  
Terminal Sire ◽  
Sire Breed

AbstractA divergent selection experiment for carcass leanness in Texel-Oxford sheep was established to examine the differences between genetically lean and fat animals derived from the same base population. The selection criterion was designed to change body composition without a corresponding change in live weight, using an index of ultrasonic backfat depth and live weight at 20 weeks of age. The index was constructed using estimates of genetic and phenotypic parameters, which were available at the start of the experiment in 1985. The difference between the high and low lines, after 3 years of selection, for the selection index, live weight at 20 weeks of age, ultrasonic backfat and muscle depths was 0·59,1·30 kg, -0·76 mm and 0·88 mm respectively. The estimated difference for carcass lean and fat weight was 0·72 kg and -0·04 kg respectively with 13·5 g/kg and -13·8 g/kg for carcass lean and fat proportion. The realized heritability for the selection index, estimated from the regression of cumulative response on cumulative selection differential was 0·42, with a standard error of 0·25, after taking account of genetic drift. The selection index heritability, estimated with residual maximum likelihood (REML) methodology, was 0·46 (s.e. 0·14). REML heritability estimates for live weight at 20 weeks of age, ultrasonic backfat and muscle depths were 0·20 (s.e. 0·13), 0·35 (s.e. 0·14) and 0·43 (s.e. 0·14) respectively.

Physiological responses to selection for carcass lean content in a terminal sire breed of sheep

1991 ◽  
Vol 1991 ◽  
pp. 25-25
Author(s):  
N.D. Cameron
Keyword(s):  
Lipid Metabolism ◽  
Genetic Improvement ◽  
Selection Index ◽  
Carcass Composition ◽  
Physiological Traits ◽  
Esterified Fatty Acids ◽  
Breeding Programmes ◽  
Selection For ◽  
Terminal Sire ◽  
Sire Breed

Sheep breeding programmes for genetic improvement in carcass composition of terminal sires measure livewelght and ultrasonic backfat and muscle depths for inclusion in a selection index to predict genetic merit. Physiological traits which were genetically correlated with carcass traits could be incorporated into the selection index to increase the accuracy of selection and the rate of genetic improvement.This study examined differences in physiological traits between lines selected for high or low carcass lean content. The measured physiological traits were chosen according to their role in protein and lipid metabolism : b-hydroxybutyrate (BHB) and glucose (GLUC) : indicators of energy balance; triglyceride (TRIG) and non-esterified fatty acids (NEFA) : intermediaries of lipid metabolism; UREA and creatinine (CREA) : indicators of nitrogen / amino acid metabolism and insulin-like growth factor-1 (IGF-1): an Indicator of growth hormone status.

Genetic parameters for live weight, ultrasonic measurements and conformation in Bluefaced Leicester sheep

1999 ◽  
Vol 1999 ◽  
pp. 122-122 ◽  
Author(s):  
A.M. van Heelsum ◽  
R.M. Lewis ◽  
D.W. Jones ◽  
W. Haresign ◽  
M.H. Davies
Keyword(s):  
Selection Index ◽  
Live Weight ◽  
Carcass Quality ◽  
Export Markets ◽  
Acceptable Quality ◽  
Breeding Programmes ◽  
The Uk ◽  
Terminal Sire ◽  
Sire Breed

Currently fewer than 50% of UK lambs produce carcasses of acceptable quality for the domestic and export markets, which compromises the competitiveness of sheep farming. Carcass quality can be changed by selection, and this is now being taken advantage of in terminal sire breeds and, to a lesser extent, in hill breeds. However, little attention has yet been focused on the crossing breeds, which have relatively poor carcass quality, in spite of the large impact such breeds have on the slaughter generation. Recently, a long-term project began to develop breeding programmes relevant to crossing sire (‘longwool’) breeds. Its objective is to produce a selection index to improve carcass quality without compromising the reproductive performance or maternal ability of these breeds. The Bluefaced Leicester is the most prevalent crossing sire breed with its crossbred (‘Mule’) daughters out of draft hill ewes accounting for 89% of crossbred (longwool x hill) ewes in the UK (Pollot, 1998).

Correlated responses in slaughter and carcass traits of crossbred progeny to selection for carcass lean content in sheep

1992 ◽  
Vol 1992 ◽  
pp. 27-27
Author(s):  
N.D. Cameron
Keyword(s):  
Selection Index ◽  
Carcass Traits ◽  
Selection Differential ◽  
Population Responses ◽  
Ewe Lambs ◽  
High Line ◽  
Fixed Weight ◽  
Selection For ◽  
Terminal Sire ◽  
Sire Breed

A divergent selection experiment in a terminal sire breed of sheep was started in 1985 to examine the differences between genetically lean and fat animals, which were derived from the same population. Responses in performance and physiological traits measured on the selection lines were reported at the BSAP 1991 Winter Meeting. Responses In slaughter and carcass traits, measured on crossbred progeny of the terminal sires, are presented in this study.The ram selection index was -0.995 FATD + 0.206 WT20, where FATD and WT20 are the ultrasonic backfat depth and liveweight at 20 weeks of age, with both traits standardised to have zero mean and unit phenotyplc variance. A total of 32 and 34 rams from the high (lean) and low (fat) selection lines were performance tested in 1988, and 11 rams were selected from the high line and 12 rams from the low line for mating to crossbred ewes for the progeny test, with a selection differential of 0.85 Index units. There were 8 and 11 rams from the high and low lines with progeny slaughtered at fixed weight, such that the selection differential was 1.0 Index units. A total of 329 crossbred lambs were slaughtered at 16 weeks of age and 250 lambs were slaughtered at fixed weight, 39±1 kg for castrates and 37±1 kg for ewe lambs.

An economic selection index for lean meat production in New Zealand sheep

1987 ◽  
Vol 45 (3) ◽  
pp. 465-475 ◽  
Author(s):  
G. Simm ◽  
M. J. Young ◽  
P. R. Beatson
Keyword(s):  
New Zealand ◽  
Selection Index ◽  
Live Weight ◽  
Breeding Value ◽  
Index Selection ◽  
Meat Production ◽  
Total Fat ◽  
Terminal Sire ◽  
Economic Selection ◽  
Lean Weight

ABSTRACTAn economic selection index was derived for terminal sire sheep breeds or strains, using physical and financial results from New Zealand export lamb-producing flocks. The aggregate breeding value of the index comprised carcass lean weight and carcass total fat weight. Index measurements were live weight, ultrasonic fat depth and ultrasonic muscle depth. Economic values used for lean and fat weights (NZ$5·65 and NZ$–1·2 per kg, respectively) were the change in profit per kg increase in lean or fat weight from that in the average carcass of lambs slaughtered in 1984/85. The s.d. of the aggregate breeding value was NZS3·20, and the correlation between the full index and the aggregate breeding value was 0·23. This correlation fell to 0·18, 0·15 and 0·07, respectively, when muscle depth or fat depth or muscle and fat depths were omitted from the index. Selection on the full index, or on the index omitting muscle depth was expected to lead to an increase in carcass lean weight and a slight decrease in carcass fat weight. Selection on the index omitting fat depth, or selection on live weight alone, was expected to lead to an increase in both fat and lean weights.

Effects of selection for low backfat thickness in pigs on the sites of tissue deposition in the body

1983 ◽  
Vol 36 (3) ◽  
pp. 389-397 ◽  
Author(s):  
J. D. Wood ◽  
O. P. Whelehan ◽  
M. Ellis ◽  
W. C. Smith ◽  
R. Laird
Keyword(s):  
Selection Index ◽  
Subcutaneous Fat ◽  
Live Weight ◽  
Carcass Composition ◽  
The Body ◽  
Backfat Thickness ◽  
Selection For ◽  
The University ◽  
And Control ◽  
The Relationship

ABSTRACTThe effects of selection for low backfat thickness on tissue deposition in different body sites has been investigated in pigs. Eight castrated male and eight female pigs from each of the selection and control lines maintained at the University of Newcastle upon Tyne were used. One castrated male and one female from each line was killed at 15, 30, 45, 60, 75, 90, 105 and 120 kg live weight following ad libitum food consumption and fully dissected.There were only small effects of line on carcass composition, selected pigs having 120 g/kg more bone than controls at the mean side weight (P < 0·001) and 40 g/kg more lean (NS). At the same mean weight of subcutaneous fat, selected pigs had thinner backfat than controls (approximately 3 mm) over m. longissimus at the last rib and over the shoulder but not at the mid-rump or mid-back positions. There appears to have been a slight shift in the sites of fat deposition from above m. longissimus in the loin towards the mid-line and rump as a result of selection, even though mid-rump, C and K measurements were all included in the selection index. However, there was no difference between the lines in the weight distribution of subcutaneous fat between six regions and so these shifts must have been very localized. There was no difference between lines in the relationship between P2 fat thickness and proportion of lean in the side.The effects of selection on the sites of deposition within tissues other than subcutaneous fat were small. In particular there was no evidence that selection has caused relocation of body fat from subcutaneous to the other sites.

The consequences of index selection on carcass composition in Suffolk sheep

1999 ◽  
Vol 1999 ◽  
pp. 46-46 ◽  
Author(s):  
R. M. Lewis ◽  
G. C. Emmans ◽  
G. Simm ◽  
W. S. Dingwall ◽  
J. FitzSimons ◽  
...  
Keyword(s):  
Performance Test ◽  
Selection Index ◽  
Live Weight ◽  
Growth Index ◽  
Carcass Composition ◽  
Control Line ◽  
Lean Growth ◽  
Selection Decisions ◽  
Terminal Sire ◽  
And Control

Early in the 1980s a selection index was designed at SAC to improve the rate of lean growth in terminal sire sheep which combined ultrasound measurements of fat and muscle depth, and live weight at 150 days of age (Simm and Dingwall, 1989). Beginning in 1985, this index was applied in the SAC Suffolk flock in a performance test. In 1994, rams from a line selected on this index weighed on average 12% more (8 kg) and had 12% lower fat depth (– 0.9 mm) and 10% higher muscle depth (2.9 mm) than rams from an unselected Control line. Comparison of Selection and Control line animals has thus far been based on live predictors of carcass composition at weights substantially heavier than typical market lamb weights. The aims of this study were to test whether selection decisions based on the lean growth index produced an improvement in actual carcass composition in purebred terminal sire sheep and whether these changes persisted at live weights different from those under which selection was carried out.

Comparative evaluation of beef cattle breeds of African, European and Indian origins. 1. Live weights and heterosis at birth, weaning and 18 months

1998 ◽  
Vol 67 (1) ◽  
pp. 27-38 ◽  
Author(s):  
J. E. Frisch ◽  
C. J. O'Neill
Keyword(s):  
Birth Weight ◽  
Growth Rates ◽  
Comparative Evaluation ◽  
Live Weight ◽  
Growth Potential ◽  
Northern Australia ◽  
Cattle Breeds ◽  
Beef Cattle Breeds ◽  
The Difference ◽  
Sire Breed

AbstractCattle breeds of African, European and Indian origins are being evaluated at Rockhampton for their suitability for beef production in northern Australia. In the current study, Belmont Adaptaur (HS), Belmont Red (AX) and Belmont BX (BX) dams were mated to produce straightbreds and crossbred progeny by Brahman (B), Boran (Bo) and Tuli (Tu) sires. B dams were mated to produce straightbreds and crossbred progeny by AX, BX, Bo, Charolais (Ch), HS and Tu sires. This paper reports values for heterosis for some crosses and live weights on pasture for some straightbred and crossbred genotypes at birth, at weaning and at 18 months.Heterosis for birth weights was greatest for taurine dam breed × indicine sire breed, generally negative for the reciprocal cross and markedly less for Tu-sired than for B- or Bo-sired progeny. Heterosis was not estimated for Bo and Tu crosses at weaning or at 18 months. At these ages, heterosis for growth includes a component related to resistance to environmental stresses. Thus, heterosis was then greater for B crossbreds derived from the less resistant HS than from the more resistant AX.There were significant differences between genotypes in live weights at each age. Progeny by B sires from taurine dams had higher live weights than progeny by Bo or Tu sires. Evidence is presented that strongly indicates that the difference in growth rates between the B- and Bo-sired progeny arose entirely from differences in mature live weights of the B and Bo, not from differences in efficiency of growth of their crossbred progeny. Similarly, live weights of progeny by taurine sires from B dams ranked according to the mature live weights of the sire breeds. Thus, the Ch- and Tu-sired progeny had the highest and lowest live weights at all ages respectively. Comparative growth potentials of the indicine sire breeds were estimated by comparing 18-month live weights of progeny from HS dams. Relative to Bo = 100, growth potential of B = 205. Similarly, growth potentials of the taurine sire breeds were estimated from progeny from B dams. Relative to Tu = 100, the estimates were HS = 104, AX = 111 and Ch = 117. Crossbred progeny by B and Bo sires were generally significantly heavier at all ages than the corresponding straightbreds. However, Tu-sired progeny had similar birth weights too, but generally higher weaning and 18-month live weights than, the corresponding straightbreds. Relatively low birth weight and low heterosis for birth weight identify the Tu as a potentially useful sire breed when an increase in birth weight of crossbreds is undesirable.Within each dam breed, no straightbred could match the growth rate of the best crossbred. At 18 months this advantage was proportionately 0·21, 0·09, 0·05 and 0·16 over that of the straightbred HS, AX, BX and B respectively. Live weight of every crossbred based on B dams exceeded that of the straightbred B, the most populous breed in northern Australia. Thus, increases in growth rates could be achieved by crossbreeding irrespective of the base breed. Live weights at 18 month for progeny of Bo, Tu and AX sires from B dams, all of which exceeded those of the straightbred B, suggest that the African breeds can be used to complement the B in crossbreeding programmes in northern Australia.

A selection index for lean meat production in sheep

1993 ◽  
Vol 1987 ◽  
pp. 59-59
Author(s):  
G. Simm ◽  
W.S. Dingwall
Keyword(s):  
Selection Index ◽  
Live Weight ◽  
High Energy ◽  
Carcass Composition ◽  
Meat Production ◽  
Lean Meat ◽  
In Vivo Measurements ◽  
Terminal Sire ◽  
Protein Feed

It is generally accepted that leanness of terminal sire sheep breeds should be increased. However, it is very difficult to define formally a selection goal for these breeds. Put loosely, at a given age, we probably require terminal sires with as much extra lean meat as possible, whilst minimising any increase in fat weight. In the past, selection has been mainly on weight for age, but this may actually increase fatness at the age of selection.Intuitively we expect some in vivo measurements of carcass composition to help in achieving the selection goal. In practice, in vivo measurements of carcass composition in sheep are often imprecise, though the treatment of the animals can affect the relative precision. Ad libitum feeding on a high energy, high protein feed appears to increase the variation in carcass composition of ram lambs compared to those on a lower plane of nutrition (Simm et al, 1985 compared to Cuthbertson et al, 1983). Under these conditions we were able to predict carcass composition reasonably precisely from live weight and ultrasonic measurements (means and original and residual s.d.s for carcass lean weight: 18.30, 1.60 and l.00 kg and for fat weight 13.74, 2.70 and 0.96 kg).

A note on short term selection for birth weight in mice

1976 ◽  
Vol 22 (1) ◽  
pp. 127-130 ◽  
Author(s):  
J. Eklund ◽  
G. E. Bradford
Keyword(s):  
Birth Weight ◽  
Realized Heritability ◽  
Base Population ◽  
Short Term ◽  
Individual Values ◽  
Term Selection ◽  
Cumulative Response ◽  
Cumulative Selection ◽  
Line Selection ◽  
Selection For

SummaryA short-term selection experiment was undertaken to estimate the realized heritability for birth weight in mice.A cross of two strains was used as a base population, from which heaviest and lightest birth weight individuals were selected to initiate an up (JU) and a down (JD) selected line. Selection was applied on a within-litter basis for six generations. By the end of the experiment, the two lines differed by 0·20 ± 0·01 g. The heritability, estimated from the regression of cumulative response on cumulative selection differentials and adjusted to that of individual values, was 0·14 ± 0·02. Six-week body weight, averaged over both sexes, was higher in line JU than in JD by 1·0 ± 0·3 g at generation 6. Litter size was higher in line JU in every generation, the regression of the divergence between JU and JD on generation number being 0·13 ± 0·03.

Prediction of selection index coefficient for birth weight and three month weight in Baluchi breed of sheep

2005 ◽  
Vol 2005 ◽  
pp. 132-132
Author(s):  
M. Hosseinpour Mashhadi ◽  
F. Eftekhari Shahroudi ◽  
R. Valizadeh
Keyword(s):  
Birth Weight ◽  
Selection Index ◽  
Selection Criterion ◽  
Phenotypic Correlations ◽  
Different Ages ◽  
Genetic And Phenotypic Correlations ◽  
Selection For

The method for establishing a selection criterion for a given selection objective is referred to as selection index methodology. Usually in the flock sheep, The first selection for lambs that substitution ewes and rams, is at three month of age. Genetic and phenotypic correlations for weight traits at different ages are high and range of those were from 0.42 to 0.94 and from 0.06 to 0.56 respectively. Thus, the aim of this study was to predict the coefficient of selection index.

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