Selection for high and low ratio and high and low primary density in Merino sheep

1978 ◽  
Vol 29 (5) ◽  
pp. 1077 ◽  
Author(s):  
JM Rendel ◽  
T Nay
Keyword(s):  
Point Of View ◽  
Primary Follicle ◽  
Merino Sheep ◽  
Selection For ◽  
Fleece Weight

The result of selecting sheep up and down for secondary to primary follicle ratio (S/P) and up and down for the number of primary follicles to the square millimetre is examined from the point of view of Fraser's theory of competition between follicles. The possibility of finding other characters in which variation will cause variation in fleece weight has also been investigated. It is concluded that selection which increased the S/P ratio and primary density did not increase fleece weight; follicle depth is possibly one skin character which, when changed, causes changes in fleece weight but this requires confirmation.

Genetic studies of South Australian Merino sheep. 4. Genetic, phenotypic and environmental correlations between various wool and body traits

1982 ◽  
Vol 33 (2) ◽  
pp. 363 ◽  
Author(s):  
IP Gregory
Keyword(s):  
Great Increase ◽  
Fibre Diameter ◽  
Skin Thickness ◽  
Primary Follicle ◽  
Genetic Studies ◽  
Environmental Correlations ◽  
Merino Sheep ◽  
Selection For ◽  
Fleece Weight ◽  
Australian Merino

Genetic, phenotypic and environmental correlations were estimated between 23 quantitative and qualitative wool and body traits of South Australian Merino sheep. Clean fleece weight was significantly correlated genetically with greasy fleece weight (0.62), yield (0.47), staple length (0.41), crimps per inch (-0.34), secondary/primary follicle ratio (0.37) and skin thickness (0.39). No significant half-sib genetic correlation was found between clean fleece weight and fibre diameter and the dam-offspring correlation was quite low, although significant (0.16, P < 0.05). This indicates that selection for clean fleece weight should not lead to any great increase in fibre diameter. Skin thickness is discussed as a possible early indicator of clean fleece weight.

Selection for economic characters in Australian Merino sheep. V. Further estimates of phenotypic and genetic parameters.

1955 ◽  
Vol 6 (1) ◽  
pp. 77 ◽  
Author(s):  
FHW Morley
Keyword(s):  
Genetic Correlations ◽  
Minor Importance ◽  
Agricultural Experiment Station ◽  
Genetic Progress ◽  
Sheep Population ◽  
Merino Sheep ◽  
Agricultural Experiment ◽  
Selection For ◽  
Fleece Weight ◽  
Genetic Homeostasis

Estimates of heritability, genetic correlations, phenotypic correlations, and other parameters among eight characteristics were obtained from Merino sheep at Trangie Agricultural Experiment Station. One set of estimates was obtained by parent-offspring regressions from data obtained between 1943 and 1952. Another set was obtained by half-sib analyses from data from sheep with first adult shearings in 1953. Estimates of heritability were: greasy fleece weight, 0.40 ± 0.06; yield (per cent.), 0.39 ± 0.07; clean fleece weight, 0.47 ± 0.07; staple length, 0.56 � 0.07; crimps per inch, 0.47 ± 0.11; folds, 0.50 ± 0.07; body weight, 0.36 ± 0.08; birthcoat, 0.80 ± 0.10. The most important genetic correlation limiting genetic improvement in clean fleece weight is that between this trait and crimps per inch. Because of this the rate of improvement in fleece weight could be reduced by about 30 per cent. whenever crimps per inch is also selected. Other genetic correlations indicate antagonisms between characteristics, but these antagonisms appear to be of minor importance except that between clean fleece weight and crimps per inch. This sheep population does not appear to have reached a state of genetic homeostasis, a t least with respect to the characteristics studied. However, the findings emphasize the necessity for careful evaluation of the economic importance of different traits, and for accurate measurement, if maximum genetic progress is to be achieved.

Corrigendum - Response to partial selection on clean fleece weight in South Australian strong-wool Merino sheep

1969 ◽  
Vol 20 (1) ◽  
pp. 151
Author(s):  
O Mayo ◽  
JC Potter ◽  
RE Brady ◽  
CW Hooper
Keyword(s):  
Fibre Diameter ◽  
Index Method ◽  
Visual Method ◽  
Merino Sheep ◽  
Index Group ◽  
Agricultural College ◽  
Selection For ◽  
The Difference ◽  
Fleece Weight ◽  
Selection Of

This paper reports the results of an experiment carried out at Roseworthy Agricultural College from 1953 to 1966 comparing two bases of selection of rams: (1) visual appraisal (the "visual" method); (2) visual culling of 70% of rams followed by selection of breeding animals from the remaining 30% on the basis of clean fleece weight (the "index" method). No selection for fleece weight was practiced on ewes. Seven rams were used in each of the two flocks, and six of the seven were replaced each year by 16-month-old animals from the succeeding drop, the seventh being a year older. Rams used for breeding in the Index flock were significantly higher in clean fleece weight than those of the Visual flock, and were higher, though not always significantly so, in greasy fleece weight. This led to a divergence between the flocks for clean fleece weight (P < 0.05), with an increase of c. 0.05 lb per year per head for the Index animals over the Visual animals. The Index rams were more wrinkly and lighter, on the whole, than the Visual rams, and the wrinkly effect carried over into their offspring with a slight divergence apparent, the Index animals becoming more wrinkled than the Visual (P < 0.05). In fibre diameter there were no differences between selected animals or between flocks. Visual rams tended to have more crimps per inch in their wool, and this was observed in the flocks also, but the divergence was not significant (P > 0.05). Index rams had longer wool than Visual rams, with the difference generally significant within years, and this tendency carried over in a lesser manner to the flocks. Fleece density was generally greater in the Index group, though not usually significantly so. This experiment did not include a randomly bred control flock, but was rather designed to compare two practical methods of selecting rams. Merits of this scheme are discussed in the light of both groups' failure to show increases in fleece weight over the course of the experiment

Selection for weaning weight in Merino sheep. 2. Correlated responses in other production characters

1965 ◽  
Vol 5 (19) ◽  
pp. 361 ◽  
Author(s):  
WA Pattie
Keyword(s):  
Milk Protein ◽  
Survival Rates ◽  
Genetic Correlations ◽  
Negative Relationship ◽  
Weaning Weight ◽  
Merino Sheep ◽  
Selection For ◽  
The Difference ◽  
Fleece Weight ◽  
Lamb Growth

The heritabilities of seven production characters of Merino Sheep and their phenotypic and genetic correlations with corrected weaning weight have been calculated using half-sib and dam-daughter correlations. Realized genetic correlations calculated from responses in Weight Plus and Weight Minus selection flocks, which showed broad agreement with these correlations, were : 17-month body weight, 0.72 ; yield, 0.22 ; clean fleece weight, 0.24 ; and staple length, 0.17. There was zero relationship with greasy fleece weight and crimps per inch, and a large negative relationship between folds and high weaning weight. There were strong phenotypic correlations between lamb growth and milk production through the total weight of milk protein produced. The lamb's genotype was the most important contributor to the difference in weaning weight between the flocks. There were no differences in reproductive performance or survival rates between the flocks but twice as many twin rams and 20 per cent more twin ewes were mated in the Weight Minus flock over the selection period.

Selection for economic characters in Australian Merino sheep. VI. Inheritance and interrelationships of some subjectively graded characteristics

1955 ◽  
Vol 6 (6) ◽  
pp. 873 ◽  
Author(s):  
FHW Morley
Keyword(s):  
Genetic Correlation ◽  
Reproductive Efficiency ◽  
Agricultural Experiment Station ◽  
Merino Sheep ◽  
Experiment Station ◽  
Agricultural Experiment ◽  
Selection For ◽  
Fleece Weight ◽  
Australian Merino

Genetic and phenotypic relationships among subjectively graded characteristics were examined in a flock of Merino sheep a t Trangie Agricultural Experiment Station. Estimates of heritability were: wool handle, 0.30; wool colour, 0.63; wool character, 0.38; back wool, 0.00; hocks, 0.14; face cover, 0.38. The genetic correlation between face cover and fleece weights suggested that selection for fleece weight would increase "wool-blindness", with possible diminution of reproductive efficiency. Selection for wools of good character (well-defined crimp) would improve softness and would not decrease fleece weight. The conclusion emerging from this and previous studies is that intense selection for high fleece weight will be rewarded by substantial increases, and will be offset only partly by adverse changes in a few of the several characters investigated.

Genetic studies of South Australian Merino sheep. 3. Heritabilities of various wool and body traits

1982 ◽  
Vol 33 (2) ◽  
pp. 355 ◽  
Author(s):  
IP Gregory
Keyword(s):  
Body Weight ◽  
Fibre Diameter ◽  
Skin Thickness ◽  
Production Traits ◽  
Primary Follicle ◽  
Merino Sheep ◽  
Main Production ◽  
Fleece Weight ◽  
Australian Merino ◽  
Staple Length

Heritabilities have been estimated for a large number of quantitative and qualitative wool and body traits recorded on two flocks of South Australian Merino sheep over a 12-year period. Data were unadjusted for fixed environmental effects and so the estimates are applicable to the heterogeneous populations found in most practical situations. Dam-offspring heritabilities of quantitative traits ranged from 0.15 for primary follicle number to 0.63 for body weight. Greasy and clean fleece weights, percentage clean yield, staple length, crimps per inch, fibre diameter, secondary and total follicle number, skin thickness, coefficient of variation of fibre diameter and secondary/primary follicle ratio had moderate to high heritabilities. Dam-offspring heritabilities of qualitative traits ranged from 0.12 for weather damage of the fleece to 0.75 for birthcoat. Total folds, face cover and hocks had high heritabilities, and wool character, type of staple formation and wool quality had moderate heritabilities. The main production traits (body weight, greasy fleece weight, yield, clean fleece weight, staple length, fibre diameter and total follicle number) were corrected for variation due to type of birth and age of dam and their heritabilities re-estimated. No change occurred in the half-sib heritabilities; dam-offspring heritabilities increased by an average of 0.05.

Response to partial selection on clean fleece weight in South Australian strong-wool Merino sheep

1969 ◽  
Vol 20 (1) ◽  
pp. 151
Author(s):  
O Mayo ◽  
JC Potter ◽  
RE Brady ◽  
CW Hooper
Keyword(s):  
Fibre Diameter ◽  
Index Method ◽  
Visual Method ◽  
Merino Sheep ◽  
Index Group ◽  
Agricultural College ◽  
Selection For ◽  
The Difference ◽  
Fleece Weight ◽  
Selection Of

This paper reports the results of an experiment carried out at Roseworthy Agricultural College from 1953 to 1966 comparing two bases of selection of rams: (1) visual appraisal (the "visual" method); (2) visual culling of 70% of rams followed by selection of breeding animals from the remaining 30% on the basis of clean fleece weight (the "index" method). No selection for fleece weight was practiced on ewes. Seven rams were used in each of the two flocks, and six of the seven were replaced each year by 16-month-old animals from the succeeding drop, the seventh being a year older. Rams used for breeding in the Index flock were significantly higher in clean fleece weight than those of the Visual flock, and were higher, though not always significantly so, in greasy fleece weight. This led to a divergence between the flocks for clean fleece weight (P < 0.05), with an increase of c. 0.05 lb per year per head for the Index animals over the Visual animals. The Index rams were more wrinkly and lighter, on the whole, than the Visual rams, and the wrinkly effect carried over into their offspring with a slight divergence apparent, the Index animals becoming more wrinkled than the Visual (P < 0.05). In fibre diameter there were no differences between selected animals or between flocks. Visual rams tended to have more crimps per inch in their wool, and this was observed in the flocks also, but the divergence was not significant (P > 0.05). Index rams had longer wool than Visual rams, with the difference generally significant within years, and this tendency carried over in a lesser manner to the flocks. Fleece density was generally greater in the Index group, though not usually significantly so. This experiment did not include a randomly bred control flock, but was rather designed to compare two practical methods of selecting rams. Merits of this scheme are discussed in the light of both groups' failure to show increases in fleece weight over the course of the experiment

Fleece characteristics and postnatal fleece development in Finnish Landrace × Merino sheep

1972 ◽  
Vol 15 (1) ◽  
pp. 75-84 ◽  
Author(s):  
M. L. Ryder ◽  
D. T. Wilson
Keyword(s):  
Fibre Diameter ◽  
Variable Length ◽  
Primary Follicle ◽  
Merino Sheep ◽  
Fibre Development ◽  
The Mean ◽  
Commercial Value ◽  
Fleece Weight ◽  
Staple Length

SUMMARY1. Fleece characteristics in Finnish Landrace × Merino and Merino × Finnish Landrace sheep were compared with those of the parental breeds, and although most characters in the crossbreds showed no significant departure from the parental mean, they had similarities to the Merino which imparted commercial value.2. The wool was mostly of 60s quality compared with 58s in the Finnish Landrace, and 64s and over in the Merino parents. Crimp number showed heterosis, being 5 to 6 per cm in the crossbreds compared with 2 in the Finnish sheep and 7 in the Merino.3. The mean fleece weight was 3-5 kg, compared with 2-2 kg in the Finnish sheep and 4-2 kg in the Merino.4. The mean staple length was 13 cm compared with a very variable length around a mean of 16 cm in the Finnish Landrace, and 10 cm in the Merino.5. The fibre diameter was nearer to that of the Merino, but not significantly so (primary mean 29·2 μ, secondary mean 26·6 μ).6. The greater fleece weight of the crossbreds would be expected to be associated with a greater skin follicle density, but they had a secondary/primary follicle ratio of about 10 (compared with 5 in the Finnish Landrace and 20 in the Merino), which did not differ significantly from the parental mean.7. There was some evidence that fibre development was initially more rapid in the crossbred lambs.

Genetic parameters for bodyweight, wool, and disease resistance and reproduction traits in Merino sheep. 2. Genetic relationships between bodyweight traits and other traits

2008 ◽  
Vol 48 (9) ◽  
pp. 1186 ◽  
Author(s):  
A. E. Huisman ◽  
D. J. Brown
Keyword(s):  
Coefficient Of Variation ◽  
Genetic Relationships ◽  
Fibre Diameter ◽  
Eye Muscle ◽  
Merino Sheep ◽  
Scrotal Circumference ◽  
Reproduction Traits ◽  
Negative Effect ◽  
Selection For ◽  
Fleece Weight

The Australian Merino is the predominant genetic resource for both the prime lamb and sheep meat industries of Australia. There are very few studies that provide good information on the relationships between wool and non-wool traits. The objective of this paper was to describe genetic relationships within bodyweight traits and between bodyweight and other traits recorded in Merino sheep. The genetic correlation between bodyweight, fleece weight and fibre diameter was positive (0.1 to 0.2). While fibre diameter coefficient of variation, staple length, staple strength, mean fibre curvature, and faecal egg count were not correlated with bodyweight. Scrotal circumference (0.4), number of lambs born (0.1), and number of lambs weaned (0.1) were positively correlated with bodyweight. Results indicate that selection for an increase in bodyweight will have a positive effect on eye muscle depth, fleece weight, and reproduction traits, while selection for an increase in bodyweight will have a negative effect on fibre diameter and fibre diameter coefficient of variation.

Sign in / Sign up

Export Citation Format

Share Document