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PRODUCTION NORMS OF THE GROOTFONTEIN DOHNE MERINO FLOCK


 W.J Olivier, M.J. Herselman & M. Van Heerden

 

Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg (EC), 5900

Email: Willem Olivier

 


INTRODUCTION

The demand for finer wool (<20 µm) increased during the 1980’s and 1990’s and this resulted in price premiums being paid for the finer wool types. This shift in the demand for finer wool led to more emphasis being placed on the production of fine wool (Olivier, 2009). Consequently, the number of flocks in South Africa where selection for decreased fibre diameter was practiced increased markedly.

 

Therefore, it may be profitable to produce finer wool over the long-term and that breeding and selection decisions should reflect this. The wool industry and particularly producers in Australia took cognisance of this and significantly reduce the fibre diameter of their clip (Greeff, 1999).

 

This price premium for finer wool led to the initiation of several fine wool projects by the Department of Agriculture, Forestry and Fisheries at Grootfontein Agriculture Development Institute. The first was the establishment of the Cradock fine wool Merino stud in 1988 at the Cradock Experimental station on irrigated pastures (Olivier et al., 2006). The Grootfontein fine wool Merino flock was also developed at the same time to evaluate the fine wool Merino genetic material under veld conditions (Olivier & Roux, 2007). In 2000 it was decided to evaluate animals from the Grootfontein fine wool Merino flock under veld conditions in four traditional strong wool areas of South Africa (Olivier & Olivier, 2007). The most important conclusions from all three these studies were that it is possible to breed fine wool animals without adverse effects on the other economically important traits and that it can be done under natural grazing conditions.

 

Certain aspects and questions around fine wool production remain unresolved. The first aspect is the fact that the fibre diameter in dual purpose sheep has not received much attention despite the important contribution of these sheep to the South African wool clip and consequently, the current status of and variation in fibre diameter of dual purpose sheep is not well defined. It has to be determined to what extent selection for fineness would impact on the meat quality and growth performance of dual purpose sheep which are the most economically important traits. Furthermore, it is necessary to determine to what extent the income potential of dual purpose sheep could be improved by increased wool quality, decreased fibre diameter and increased meat quality.

 

Wool income from a dual purpose breed such as the Dohne Merino contributes approximately 20 percent to total income and therefore has an important impact on profitability. Nonetheless, the wool production function of the dual purpose sheep is an aspect that can be exploited to increase the profitability further through selection for better quality. Decreasing fibre diameter from 22 µm to 18 µm could theoretically double the wool income if all other production traits were maintained.

 

The aim of this study was to establish a genetic pool of dual purpose sheep with premium quality meat and super fine wool under extensive conditions to investigate the above mentioned issues.

 

MATERIALS AND METHODS

The Grootfontein Dohne Merino stud was established in 2001 after a request made by the wool industry of South Africa to Grootfontein. The Dohne Merino Breed Society identified Dohne Merino breeders during 2001 to 2002, who had non-pregnant ewes available for inclusion into the Grootfontein Dohne Merino genetic pool during the first phase of the project.  The objective was to screen the breed and find baseline values with regard to fibre diameter and body weight and then to identify ewes for the establishment of the genetic pool at Grootfontein.

 

The screening at farm level was done as follows:

 

The combined results obtained for the individual farmers screened from 2001 to 2002 are summarised in Table 1. The body weight and fibre diameter, corrected for breeder and age structure of the 2479 Dohne Merino ewes screened were 53.5 kg and 21.2 mm respectively. The selection differentials for body weight and fibre diameter of the 217 Dohne Merino ewes bought for the genetic pool were +1.6 kg and –1.95 mm respectively.

 

Table 1. Mean body weight and fleece traits for the Dohne Merino ewes sampled randomly amongst breeders and for the ewes that were selected and bought for the genetic pool at Grootfontein

 

Traits

Randomly sampled ewes

Selected ewes

Number

2479

217

Body weight (kg)

53.5

55.1

Fibre diameter (mm)

21.2

19.1

Clean yield (%)

70.6

69.6

Coefficient of variation of fibre diameter (%)

18.6

18.4

Comfort factor (%)

97.7

99.6

Crimps/25 mm

13.6

14.2

Duerden

108

99

 

The first breeding season was in May 2001 and 137 Dohne Merino ewes were mated to three rams from the Dohne Merino industry. During April 2002, 171 Dohne Merino ewes were mated to three rams from the industry and during April 2003, 215 Dohne Merino ewes were mated. The first offspring were used as sires during the 2003 breeding season.

 

Ewe numbers in the nucleus flock at Grootfontein declined considerably during the 2005-season due to the fact that a large proportion of the ewes initially bought from breeders had to be culled due to age (worn teeth). During 2006 and 2007 a further 28 Dohne Merino ewes with estimated breeding values higher than 0 kg for body weight and -0.1 kg for clean fleece weight and lower than -1.2 µm for fibre diameter were obtained from stud breeders. These ewes, together with 12 ewes from the Grootfontein Dohne Merino stud were used in an embryo transfer program. The semen from the best rams in the industry with regard to the selection objectives for body weight and fibre diameter of this stud were used as sires. During 2006, 287 embryos were recovered and implanted into 136 recipients and during 2007, 778 embryos were collected during two separate flushings. These embryos were implanted into 462 recipients. This procedure was again repeated during 2008 when 348 embryos were collected from 40 Dohne Merino stud ewes and implanted into 215 recipients. The remainder of the Dohne Merino ewe flock was mated to own bred rams and rams from the industry during these three years.

 

Data recorded from 2431 ram and ewe lambs born from 2001 to 2008 were used for the analysis of the body weight at different ages and wool characteristics. The least-squares means and standard errors for the respective traits were obtained with the PROC GLM-procedure of SAS, and significance levels for the fixed effects were obtained with the PDIFF-option under the PROC GLM-procedure of SAS (SAS, 2004). Only effects and interactions which had a significant effect (P<0.01) on a specific trait were included in the final operational model.

 

The traits analysed included birth weight, 42-day body weight, weaning weight, 6-month body weight, 8-month body weight, 12-month body weight, greasy fleece weight, clean yield, clean fleece weight, staple length, fibre diameter, crimps per 25mm, Duerden, standard deviation of fibre diameter, coefficient of variation of fibre diameter, comfort factor, creeping belly and staple strength. The wool quality and conformation of the Dohne Merino lambs were annually subjectively assessed at 13 months of age. The assessment was done on a scale from 1 – 9 where, 1 – 2 = poor, 3 – 4 = below average, 5 = average, 6 – 7 = above average and 8 – 9 = excellent wool quality or conformation.

 

The estimation of the genetic parameters and breeding values were done with ASREML (Gilmour et al., 2002). Log likelihood ratio tests were done to determine the most suitable model for the estimation of (co)variance components for each trait. The most suitable model for all traits only included the direct additive genetic variance. The genetic trends for the respective traits were obtained from univariate analyses.

 

RESULTS AND DISCUSSION

The number of records, mean, coefficient of variation, minimum and maximum for each of the respective traits are summarised in Table 2. Body weights of the lambs born from 2001 to 2008 in this stud at different ages are summarised in Table 3, while the wool production data at the age of 13 months are summarised in Table 4. The body weight at mating and wool production of the adult ewes in 2002 and 2008 are summarised in Table 5. It is evident from this table that the body weight of the ewes at mating was higher in 2008 than in 2002. The 2008 adult ewe flock produced less, but finer wool with shorter staples compared to the 2002 ewes. Furthermore, the tensile strength of the 2008 adult ewe flock was also better than the 2002 adult ewe flock.

 

Table 2. The number of records, mean, coefficient of variation, minimum and maximum for the body weights and wool traits

Trait

N

Mean

Coefficient of

variation (%)

Minimum

Maximum

Birth weight (kg)

2431

4.7

21.8

1.0

8.2

42-Day body weight (kg)

2215

16.2

25.3

5.6

41.0

Weaning weight (kg)

2130

26.4

20.2

10.6

44.2

6-Month body weight (kg)

1998

33.5

19.9

10.2

85.2

8-Month body weight (kg)

1958

39.2

20.4

19.4

84.8

12-Month body weight (kg)

1625

48.1

22.1

22.5

86.0

Greasy fleece weight (kg)

1609

3.8

29.8

1.4

8.3

Clean fleece weight (kg)

1598

2.5

27.8

0.3

5.4

Clean yield (%)

1611

65.5

9.1

6.3

81.6

Staple length (mm)

1615

83.5

18.6

40.0

134.6

Fibre diameter (µm)

1611

17.0

9.1

13.0

22.4

Crimps per 25 mm

1615

13.9

21.3

9.6

99.9

Duerden

1610

87.1

10.0

61.0

123.0

Standard deviation of  fibre diameter (µm)

1611

3.4

12.8

2.4

5.4

Coefficient of variation of fibre diameter (%)

1611

20.1

11.8

14.5

30.3

Comfort factor (%)

1611

99.7

0.4

94.9

100.0

Creeping belly score

1137

4.2

28.6

1.0

8.

Staple strength (N/Ktex)

1405

32.4

26.4

9.0

66.0

 

Table 3. Body weights (± s.e.) of the progeny born in the stud over the experimental period

Trait

Ram lambs

Ewe Lambs

Birth weight

4.1±0.1 (n = 1182)

3.9±0.1 (n = 1249)

42 Days body weight

14.6±0.4 (n = 1087)

13.7±0.4 (n = 1128)

Weaning weight

26.9±0.1 (n = 1048)

25.7±0.1 (n = 1082)

6 Months body weight

34.3±0.2 (n = 988)

31.4±0.2 (n = 1010)

8 Months body weight

39.9±0.2 (n = 967)

36.0±0.2 (n = 990)

12 Months body weight

50.7±0.2 (n = 824)

43.5±0.2 (n = 801)

 

Table 4. Wool production data (± s.e.) of progeny born in the stud over the experimental period at selection age (13 months of age)

Trait

Rams

(n = 794)

Ewes

(n = 815)

Greasy fleece weight (kg)

3.8±0.2

3.6±0.2

Clean yield (%)

66.3±1.4

66.7±1.4

Clean fleece weight (kg)

2.6±0.1

2.4±0.1

Staple length (mm)

78.1±3.6

79.2±3.3

Fibre diameter (µm)

16.1±0.3

19.6±0.3

Crimps / 25mm

14.3±0.8

14.1±0.8

Duerden

84.1±2.1

87.2±2.1

Standard deviation of  fibre diameter (µm)

3.3±0.1

3.6±0.1

Coefficient of variation of fibre diameter (%)

20.5±0.6

21.2±0.6

Comfort factor (%)

99.9±0.1

99.7±0.1

Creeping belly

4.3±0.3

4.6±0.3

Staple strength (N/Ktex)

34.7±2.1

34.1±2.1

 

Table 5. Production data of adult ewes in 2002 and 2008

Trait

2002

2008

Body weight at mating  (kg)

58.8±0.7

64.9±0.5

Greasy wool (kg)

4.9±0.1

4.3±0.1

Clean yield (%)

65.3±0.4

71.7±0.3

Clean wool (kg)

3.2±0.1

3.1±0.1

Fibre diameter (µm)

20.2±0.2

19.3±0.1

Staple length (mm)

100.1±2.5

78.6±1.3

CV (%)

18.5±0.2

17.5±0.1

Comfort factor (%)

98.7±0.1

99.3±0.0

Crimps per 25 mm

14.2±0.1

13.5±0.1

Duerden

104±0.7

98.0±0.6

Staple strength (N/Ktex)

32.7±0.8

39.8±0.8

 

The slope and intercept for the genetic trends of the Dohne Merino stud for weaning weight, body weight at 12 months of age, fleece weight and wool characteristics are summarised in Table 6. It is evident from Table 6 and the respective genetic trends that the stud increased in body weight from 2001, while the fleece weight remained constant. The fibre diameter of the Dohne Merino stud decreased and the length of the staples increased.

 

Table 6. The slope and intercept for the genetic trends of weaning weight, body weight at 12 months of age, fleece weight and wool characteristics

Trait

Linear trend

R2

Weaning weight (kg)

y = 0.0934x + 0.5437

0.29

12 month Body weight (kg)

y = 0.3372x + 0.0669

0.457

Clean fleece weight (kg)

y = 0.018x + 0.2115

0.16

Clean yield (%)

y = 0.1044x + 0.9556

0.08

Staple length (mm)

y = 0.9576x - 3.5377

0.79

Fibre diameter (µm)

y = -0.0971x + 0.2219

0.53

Number of crimps per 25 mm

y = 0.1357x - 1.417

0.75

Duerden

y = -0.3279x - 1.0969

0.44

Coefficient of variation of fibre diameter (%)

y = -0.0133x + 0.5421

0.00

Creeping belly score

y = -0.0149x + 0.352

0.03

Staple strength (N/Ktex)

y = 0.3633x - 0.8546

0.10

 

The distribution of staple strength and creeping belly scores of the Dohne Merino progeny are illustrated in Figures 1 and 2 respectively. The staple strength (N/Ktex) distribution of the progeny was grouped into 9 classes, where 1 = <15, 2 = 15.1 – 20, 3 = 20.1 – 25, 4 = 25.1 – 30, 5 = 30.1 – 35, 6 = 35.1 – 40, 7 = 40.1 – 45, 8 = 45.1 – 50 and 9 => 50.1. Despite the fact that the genetic trend for tensile strength in the stud was improving, it is evident from Figure 1 that 44 % of the Dohne Merino progeny had a tensile strength of below 30 N/Ktex. The same tendency was observed in the adult Dohne Merino ewe flock with 32 % of the tensile strength measurements being below 30 N/Ktex. This problem with tensile strength is of great concern, as it has a big influence on the income derived from wool. It is also evident from Figure 2 that of the 1137 Dohne Merino progeny scored for creeping belly, 87 % had a score of 5 and lower. Creeping belly was scored subjectively from 1 to 10, with 10 being no creeping belly present. This is of great concern due to the fact that more of the fleece type wool will be classed as belly type wool as the incidence of creeping belly increases.

Figure 1. The distribution of staple strength of the Dohne Merino progeny

 

Figure 2. The distribution of the creeping belly score of the Dohne Merino progeny

The wool quality and conformation scores of the Dohne Merino progeny are illustrated in Figures 3 and 4. It is evident from Figure 3 that approximately 21 % of the Dohne Merino progeny had subjective wool quality scores of  more than six. The phenotypic correlation between fibre diameter and subjective wool score is 0.18, meaning that lower fibre diameter is associated with poorer wool score. The corresponding correlation between fibre diameter and conformation score is 0.27. Furthermore, from Figure 4 it is evident that approximately 25 % of the Dohne Merino progeny had conformation scores of  more than six.

 

Figure 3. The wool quality scores of the Dohne Merino progeny

 

Figure 4. The conformation scores of the Dohne Merino progeny

 

The genetic trends in body weight (EBV-BW), clean fleece weight (EBV-CFW) and fibre diameter (EBV-FD) of the Grootfontein Dohne Merino stud and the Dohne Merino breed averages are illustrated in Figures 5 to 7.

Figure 5. Genetic trends for body weight of the National versus Grootfontein Dohne Merino stud

It is evident from these graphs that the genetic trend for body weight is in the same order as that of the National Dohne Merino database. Furthermore, the progeny of this stud also produced genetically more and finer wool than the National average. The large change in genetic trends observed in the Dohne Merino stud for 2006 is a reflection of the impact of the rams selected as sires and embryo transfer program with ewes selected for high body weight and fleece weight and low fibre diameter.

Figure 6. Genetic trends for clean fleece weight of the National versus Grootfontein Dohne Merino stud

 

Figure 7. Genetic trends for fibre diameter of the National versus Grootfontein Dohne Merino stud

CONCLUSION 

It is evident from the results of this study that the objectives of the project with regard to establishing a genetic pool of dual purpose sheep with superior fibre diameter were achieved. The body weight, as well as staple length of the stud improved since 2001. Furthermore, it is seems that the threshold with regard to the selection for decreased fibre diameter within this flock has been reached, due to the high incidence of creeping belly and the low staple strength. Therefore, the relationship between the selection for decreased fibre diameter, wool quality characteristics and tensile strength needs to be further investigated.

 

ACKNOWLEDGEMENTS

Cape Wools SA is acknowledged for their financial support of the project.

 

REFERENCES

Gilmour, A.R., Gogel, B.J., Cullis, B.R., Welham, S.J. & Thompson, R., 2002. ASREML User’s Guide Release 1.0. VSN International Ltd, Hemel, Hempstead, HP11es, UK.

Greeff, J.C., 1999. Relationship between staple strength and coefficient of variation of fibre diameter within and between flocks. Proc. Assoc. Advmt. Anim. Breed. Genet. 13, 54 – 57.

Littell, R.C., Freud, R.J. & Struop, W.W., 2002. SAS-system for linear models, 4th Ed. SAS Institute. Inc. Cary, N.C., USA.

Olivier, W.J., 2009. Is selection for decreased fibre diameter in a Merino flock with overstrong wool viable? Grootfontein Agric, 9, 1, 27 – 33.

Olivier, W.J. & Olivier, J.J., 2007. Evaluation of genetic fine wool animals under natural conditions in the non-traditional fine wool producing areas of the RSA. Grootfontein Agric, 7, 1, 35 – 38.

Olivier, W.J., Olivier, J.J., Cloete, S.W.P. & Van Wyk, J.B., 2006. Genetic analysis of the Cradock fine wool Merino stud. Proc. 8th WCGALP, Belo Horizonte, 13 -18 August.

Olivier, W.J. & Roux, J.A., 2007. Production and reproduction norms of fine woolled Merino sheep on natural pastures in the Karoo. S. Afr. J. Anim. Sci., 37, 1, 31 – 34.

 

Published

Grootfontein Agric 10 (1)