Last update: November 18, 2010 07:20:59 AM E-mail Print

PRODUCTIVE PERFORMANCE OF HAIR AND WOOL TYPE DORPER SHEEP

UNDER EXTENSIVE CONDITIONS

 

1M. A. Snyman, W. J. Olivier, P.J. Griessel, 2J.A.N. Cloete

 

1Grootfontein ADI, Private Bag X529, Middelburg EC, 5900

2Carnarvon Experimental Station, Carnarvon, 8995

 


1.    Introduction 

Mutton production is an important component of the agricultural sector in the extensive north-western sheep grazing areas of the Republic of South Africa. Due to the limited natural resources in these areas, it is important to increase the efficiency of mutton production within the limits of these resources. It is therefore essential that the most suitable type of sheep for these areas, in terms of adaptability and efficiency, be identified.

Dorper sheep constitute a large proportion of the small stock numbers in these areas, and it is therefore obvious that the most efficient type within this breed should be identified. Animals within the Dorper breed are classified into different types, mainly according to their coat cover, conformation or fat distribution. Several perceptions as to the productive and reproductive potential of these types exist among breeders and farmers. One of these is that the hair type Dorper is more hardy and better adapted and produces better than the  woolly type under extensive conditions. Results of two studies, in which growth and carcass traits of hair / wool type and compact / larger frame type Dorper lambs were evaluated under intensive conditions, are available (Van Niekerk & Steenkamp, 1995; Strydom et al., 1995). There is, however, no information available on the relative performance of hair and wool type Dorper sheep under extensive veld conditions, especially with regard to reproductive performance

This study was therefore conducted to evaluate reproductive performance, growth and slaughter traits, as well as several conformation traits in hair and wool type Dorper sheep under extensive conditions at the Klerefontein Experimental Station in the north-western Karoo region..

 

2.   Material and Methods

2.1  Description of the experimental location

The study was conducted under natural conditions at the Klerefontein Ex­perimental Station near Carnarvon (30E 59'S, 22E 9'E) in the north‑western Karoo region of the Republic of South Africa. The experimental station is representative of the extensive low potential areas of the Karoo region. The natural pasture varies from mixed grass and shrub veld to karoo shrub veld and is described by Acocks (1988) as arid karoo. The official graz­ing capacity norm is estimated at 36.7 ha per large stock unit. The climate is characterised by severe winters and hot summers. The average annual rainfall is 209 mm, occurs mainly during the autumn months and is very erratic.

 

2.2  Experimental animals

During July 1993, animals of the existing experimental Dorper flock at the Klerefontein Ex­perimental Station were classed into two groups on the basis of their coat cover, i.e. either hair or wool type. Furthermore, 20 hair and 20 wool type young ewes were bought from the industry during 1994. These ewes formed the basis of the two experimental flocks. Flock size was kept at 110 ewes each for the hair and wool types. During the 1993 and 1994 breeding seasons, seven hair and wool type rams from other experimental flocks were used as sires, together with wool and hair type rams from the existing flock at Klerefontein. Since 1995, only rams bred within the hair and wool flocks, were used as sires.

 

2.3  Management practices and data recorded

The hair and wool ewes were managed as one flock for the duration of the study. Lambs were also run together and managed as one flock. Animals were kept under natural veld conditions and received no supplementary feeding or any licks at any stage. The normal inoculation, drenching and tick control program was followed.

The ewes were hand mated once a year during April. Young replacement ewes were mated for the first time at seven months of age. Young replacement rams were used for the first time at 18 months of age. An age structure of five ewe and two ram age groups was followed, where 20 % of old ewes and all but one or two rams were replaced with young ones each year. Only ewes with udder defects were culled; ewes were not culled on poor reproductive performance.

During the lambing season in September, the following data were recorded for each lamb : Lamb ID, Dam ID, Sire ID, date of birth, birth weight, sex and birth status of the lamb and coat cover score. Body weight at 42 days and weaning weight, condition score and coat cover score at 100 days of age were also recorded.

At six months of age, various conformation traits were measured or subjectively assessed on a linear scale ranging from one to 50 for all lambs. The subjectively assessed traits, as well as the scale of assessment are summarised in Table 1. All subjective assessments were done by the same person, in order to eliminate possible differences due to the assessor.

 

Table 1. Linear scale of assessment for conformation traits and coat cover

Trait

Scale a

1

 25

 50

 Coat cover

Hairy

Mixture

Woolly

Condition score

Emaciated

Average

Fat

General conformation of the head

Poor

Average

Ideal

Chest width and depth 

Narrow

Average

Wide & deep

Protrusion of chest between front legs

None

Average

Much

Shoulders

Loose

Average

Ideal

Hind quarters

Narrow

Average

Well filled

Hocks

Poor

Average

Ideal

Front pasterns

Poor

Average

Ideal

Hind pasterns

Poor

Average

Ideal

Top line

Poor

Average

Straight

Slope of rump

Sloped

Average

Straight

 1 - 10 = Poor; 11 - 20 = Below average; 21 - 30 = Average; 31 - 40 = Above average;  41 - 50 = Excellent

 

During the subjective assessment at six months of age, ewe and ram lambs were classed and ewe lambs for replacement purposes were selected, while 40-50 ram lambs each of the hair and wool type were kept for future selection purposes. Lambs with weaning weight indices below 85, conformation defects or definite cull faults, or lambs that were either too hairy or too woolly for their group, were earmarked to be slaughtered. These surplus lambs, as well as the ram lambs kept for future selection purposes, were weighed monthly until 12 months of age.

Surplus ram and ewe lambs were slaughtered as soon as they reached a body weight of approximately 40 kg. Upon reaching slaughter weight, lambs were fasted over night and fasted body weight was recorded before slaughtering the next morning. Carcass weight, dressing percentage and all carcass measurements, as recorded for the national lamb carcass competition (Bruwer, 1984), were taken.

 

2.4  Statistical analysis

2.4.1  Data of lambs

Data from lambs born from 1993 to 2000 in the hair (n=1070) and wool (n=1044) flocks were available. The number of records for each of the growth traits are given in Table 2. For body weight from 42-days till seven months of age, body weights of all lambs were included, i.e. surplus as well as selected lambs. From 8 months of age, body weight data for surplus ram and ewe lambs not yet slaughtered, as well as the selected ram lambs, were included. Data from 1708 and 816 lambs were analysed for the conformation traits and slaughter traits respectively. Least‑squares procedures (SAS) were used to analyse data for all growth, conformation and slaughter traits (Littell et al., 1991).

 

2.4.2  Reproduction data

Data collected on the ewe flock from 1993 to 2000 include records on body weight before mating, number of ewes mated, number of ewes that lambed, number of lambs born, and number of lambs weaned. A total of 872 and 874 reproductive records were available for the hair and wool flocks respectively.

Differences between the hair and wool flocks with regard to the percentage of ewes that lambed, percentage of lambs born per ewe mated or lambed, survival rate of lambs from birth till weaning and percentage of lambs weaned per ewe mated, were tested for significance employing the CHI-SQUARE-procedure of SAS (SAS, 1990).

Total weight of lamb produced per ewe per year (kg) was calculated as follows (Snyman et al., 1997) : Firstly, within each lambing season, 42-day body weight and weaning weight for all lambs were corrected to 42 and 120 days respectively, followed by least-squares corrections for sex of the lamb. No corrections were made for birth status. Secondly, the corrected weights of all the lambs produced by each ewe in each lambing season were added together, in order to obtain total weight of lamb at 42 days and total weight of lamb weaned. For the analyses of variance for body weight before mating and total weight of lamb produced per ewe per year, fixed effects for flock, year and age of the ewe were included in the models. Least‑squares means for these traits were obtained with the PROC GLM-procedure of SAS (Littell et al., 1991).

 

3.    Results and discussion 

3.1   Growth traits

Least-square means of growth traits and coat cover score of hair and wool type Dorper lambs are summarised in Table 2.

 

Table 2. Least-square means ("SE) of growth traits and coat cover score of hair and wool type Dorper lambs

Trait

 n

 Hair

 Wool

 P

 Birth weight (kg)

2114

4.06"0.03

4.12"0.03

*

Coat cover at birth

1887

9.7"0.2

23.1"0.2

**

42-Day body weight (kg)

2036

17.6"0.1

17.5"0.1

ns

100-day Weaning weight (kg)

1985

30.1"0.3

30.0"0.3

ns

Coat cover score at weaning

1438

14.2"0.6

35.9"0.6

**

Condition score at weaning

1438

24.9"0.5

28.3"0.5

**

Daily gain from birth to weaning (g/day)

1985

246.6"3.4

245.5"2.4

ns

5 Month body weight (kg)

1730

33.6"0.3

33.6"0.3

ns

6 Month body weight (kg)

1693

36.9"0.3

36.7"0.3

ns

7 Month body weight (kg)

1570

38.5"0.3

38.3"0.3

ns

Daily gain from weaning to 7 months of age (g/day)

1547

105.1"1.9

103.3"1.9

ns

8 Month body weight (kg)

784

44.3"0.7

44.2"0.7

ns

9 Month body weight (kg)

636

48.2"0.8

47.8"0.8

ns

10 Month body weight (kg)

575

54.8"1.1

54.0"1.1

ns

11 Month body weight (kg)

514

58.9"1.1

58.0"1.1

ns

12 Month body weight (kg)

421

64.4"1.1

63.5"1.1

ns

P = ns : no significant differences between groups

P = ** : significant differences between groups

 

Birth weight of wool lambs was significantly higher (P<0.05) than that of the hair lambs.

From Table 2 it is evident that no differences between hair and wool lambs were found for body weight recorded from 42 days till 12 months of age, nor for pre- or post-weaning growth rate.

Coat cover score at birth and weaning differed significantly between hair and wool lambs (P<0.01). Wool lambs also had a higher condition score at weaning ( 28.3 " 0.5 vs. 24.9 " 0.5). Testis circumference of hair ram lambs measured at six months of age was larger (P<0.05) than that for the wool type ram lambs (28.1"0.4 cm vs. 27.6"0.4 cm).

 

3.2  Conformation traits

Least-square means of conformation traits of hair and wool type Dorper lambs are summarised in Table 3.

 

Table 3. Averages ("SE) for conformation traits of hair and wool type Dorper lambs at six month of age

Trait

 Hair

Wool

 P

 General conformation of the head

34.0"0.3

33.9"0.3

ns

Chest width and depth

33.8"0.4

33.3"0.4

ns

Protrusion of chest between front legs

31.5"0.4

30.9"0.4

*

Shoulders

30.7"0.4

29.9"0.4

**

Hind quarters

28.6"0.4

27.8"0.4

**

Width of rump (cm)

14.2"0.1

13.9"0.1

**

Width of hind leg from the side (cm)

14.8"0.1

14.7"0.1

ns

Length of hind leg from the side (cm)

27.9"0.2

28.2"0.2

**

Body length (cm)

63.5"0.3

63.6"0.3

ns

Body depth (cm)

28.6"0.2

28.5"0.2

ns

Body height (cm)

56.7"0.2

57.7"0.2

**

Hocks

39.5"0.1

40.3"0.1

**

Front pasterns

42.7"0.2

42.7"0.2

ns

Hind pasterns

42.8"0.1

42.5"0.1

ns

Top line

36.2"0.3

36.1"0.3

ns

Slope of rump

36.4"0.1

37.0"0.1

**

P = ns : no significant differences between groups

P = ** : significant differences between groups

 

Hair lambs had a better conformation than wool lambs when considering the traits such as chest width and depth, protrusion of the chest between the front legs, shoulders, hind quarters and width of the rump. Wool lambs had a higher body height and length of hind leg, as well as better hocks and less sloped rumps, compared to the hair lambs. No differences in general conformation of the head, width of hind leg, body length, body depth, front or hind pasterns or top line were evident between hair and wool lambs.

From these it seems as if the hair lambs were bulkier with shorter legs, compared to the leggier appearance of the wool lambs. This is supported by the results of a study conducted by Van Niekerk & Steenkamp (1995), comparing carcass traits of hair, wool and hair/wool Dorper lambs, that hair type Dorpers appear to be smaller animals, compared to their woolly counterparts.

 

3.3  Slaughter traits

Least-square means of slaughter traits of hair and wool type Dorper lambs are summarised in Table 4.

 

Table 4. Averages ("SE) for slaughter traits of hair and wool type Dorper lambs

Trait

 Hair

 Wool

 P

 Fasted body weight (kg)

40.1"0.3

39.8"0.3

ns

Carcass weight (kg)

19.2"0.1

19.6"0.1

**

Age at slaughter (days)

264.1"3.4

266.3"3.6

ns

Dressing percentage

49.0"0.1

49.9"0.2

**

Length of leg B1 (cm)

37.8"0.1

38.6"0.1

**

Length of leg B2 (cm)

49.2"0.2

49.8"0.2

**

Circumference of leg (cm)

72.7"0.1

73.0"0.1

*

Carcass length (K2) (cm)

107.2"0.1

108.5"0.1

**

V1-fat depth (mm)

6.5"0.3

6.7"0.3

ns

V2-fat depth (mm)

4.9"0.2

5.2"0.3

ns

V3-fat depth (mm)

5.6"0.3

5.8"0.3

ns

V4-fat depth (mm)

3.0"0.1

3.0"0.1

ns

V5-fat depth (mm)

1.3"0.1

1.3"0.1

ns

P = ns : no significant differences between groups

P = ** : significant differences between groups

V1 = Fat depth measured between 3rd and 4th sacral vertebrae, 25 mm off the midline

V2 = Fat depth measured between 3rd and 4th sacral vertebrae, 50 mm off the midline

V3 = Fat depth measured between 3rd and 4th lumbar vertebrae, 25 mm off the midline

V4 = Fat depth measured between 9th and 10th rib, 25 mm off the midline

V5 = Fat depth measured between 5th and 6th rib, 25 mm off the midline

 

Hair and wool lambs were slaughtered at a live body weight of 40.1"0.3 kg and 39.8"0.3 kg respectively. There was no difference in the age when hair and wool lambs reached slaughter weight, as is also evident from the growth performance in Table 2.

In a study done by Van Niekerk & Steenkamp (1995), carcass traits of hair, wool and hair/wool type lambs, kept under intensive feedlot conditions from weaning and slaughtered at either 25, 30, 35 or 40 kg live weight, were compared. The results of the latter study compare well with those obtained in the present study. While dressing percentage of wool lambs was higher (P<0.01) than for hair lambs in the current study, the opposite trend, albeit non-significant, was observed in the study of Van Niekerk & Steenkamp (1995). The higher dressing percentage recorded for wool lambs in the current study, resulted in their higher carcass weights (19.6"0.1 kg vs. 19.2"0.1 kg). The lower dressing percentage of hair lambs was most probably due to the heavier coat cover of the hair lambs.

Carcass length and length of hind leg (B1 and B2) were longer in wool than hair lambs in the current study, which concur with the other study as far as B1 measurements are concerned. With regard to fat measurements, no significant differences were observed among groups in both the studies. It therefore follows that there should be no difference in carcass grading between types, as grading is based primarily on V3 fat measurements. The distribution of hair and wool slaughter lamb carcasses over the various grades is presented in Figure 1. From this figure it is evident that there was no difference in grading between hair and wool lamb carcasses.

 

Figure 1. Distribution of hair and wool type lamb carcasses over the different grades

 

3.4   Reproduction of the ewe flock

Reproductive performance of hair and wool type Dorper ewes is summarised in Table 5. Reproductive parameters for the first parity for the ewe lambs mated at seven months of age are summarised in Table 6 for all young ewes mated, as well as for only those young ewes that weaned a lamb/s.

 

Table 5. Reproductive performance of hair and wool Dorper ewes

 

Hair ewes

n=872

Wool ewes

n=874

P

Body weight at mating (kg)

57.4"0.3

56.4"0.3

**

Ewes lambed / ewes mated (%)

85.9

82.5

ns

Lambs born / ewe mated (%)

128.6

124.0

ns

Lambs born / ewe lambing (%)

149.7

150.4

ns

Survival rate from birth till weaning (%)

96.9

95.79

ns

Lambs weaned / ewe mated (%)

116.2

111.3

ns

kg Lamb weaned / ewe/ annum

35.3"0.8

33.9"0.8

ns

P = ns : no significant differences between groups

P = ** : significant differences between groups


 

Table 6. Reproductive performance of young hair and wool Dorper ewes at their first parity

 

 

Hair ewes

Wool ewes

P

All young ewes mated :

n=237

 n=245

 

Body weight at mating (kg)

40.3"0.3

39.6"0.3

ns

Ewes lambed / ewes mated (%)

67.1

63.3

ns

Lambs born / ewe mated (%)

76.8

 70.2

ns

Lambs born / ewe lambing (%)

114.5

111.0

ns

Survival rate from birth till weaning (%)

95.1

93.6

ns

Lambs weaned / ewe mated (%)

 63.3

 57.1

ns

kg Lamb weaned / ewe/ annum

17.1"1.1

15.8"1.1

ns

Young ewes that weaned a lamb/s :

n=133

 n=128

 

Body weight at mating (kg)

40.8"0.4

40.3"0.4

ns

kg Lamb weaned / ewe/ annum

31.1"0.6

30.4"0.6

ns

P = ns : no significant differences between groups

 

Body weight at mating was higher for hair ewes than for wool ewes (57.4 " 0.3 kg vs. 56.4 "0.3 kg). No differences were, however, observed for percentage of ewes lambed, lambs born, lambs weaned, survival rate of lambs or kg lamb produced per ewe per year. The same applied for the young ewes, where no differences in reproductive performance were observed between hair and wool type ewes.

 

4.   Conclusion

With regard to growth and slaughter traits and reproduction, the performance of the two experimental flocks was well within the ranges reported in a literature review on productive performance of Dorper sheep (Cloete et al., 2000). Unfortunately, no other studies on the relative performance of hair and wool type Dorper sheep are available in this regard, with which to compare the present findings. However, the present findings are based on data collected over eight years and a large number of records, therefore the findings of this study can be regarded as reliable.

Claims or perceptions in the industry as to the superior performance of hair type Dorper sheep under extensive conditions are not supported by the results of this study. In terms of the economically important reproduction and growth traits, there are no differences between hair and wool Dorpers. Differences that do occur, such as some conformation and carcass traits, will not have any effect on the economic realisation from the different types.

 

5.   References

Acocks, J.P.H., 1988. Veld types of South Africa.  Memoirs of the botanical survey of South Africa, No 57. Botanical Research Institute, Dept. of Agric. and Water Supply, Pretoria, South Africa. pp.

Bruwer, G.G., 1984. Objective evaluation of the carcass grading system for lambs and sheep in R.S.A. M.Sc. treatise, University of Stellenbosch, Stellenbosch, South Africa.

Cloete, S.W.P., Snyman, M.A., Herselman, M.J., 2000. The South African Dorper sheep : A review of productive performance. Small Rum. Res. 36, 119-135

Littell, R.C., Freud, R.J., Spector, P.C., 1991. SAS-system for linear models, 3rd  Ed., Cary, NC : SAS Institute. Inc. pp. 137-198

SAS Institute. Inc., SAS Procedures Guide, Version 6, 3rd Ed., Cary, NC : SAS Institute. Inc., 1990. pp. 325-340

Snyman, M.A., Olivier, J.J., Erasmus, G.J., Van Wyk, J.B., 1997. Genetic parameter estimates for total weight of lamb weaned in Afrino and Merino sheep.  Livest. Prod. Sci. 48(2), 111-116

Strydom, P.E., Vermeulen, J.H., Nel, E., De Bruyn, J.F., 1995. Production and reproduction of two types of Dorper sheep (in Afrikaans). Research report available at the Dorper Sheep Breeders= Society of South Africa, P.O. Box 26, Middelburg, 5900, South Africa. 20 pages

Van Niekerk, W.A., Steenkamp, K., 1995. Comparison of three types of Dorper lambs (wool-, hair- and intermediate type) with regard to growth, feed and water intake, protein and fat metabolism (in Afrikaans).  Research report available at the Dorper Sheep Breeders Society of South Africa, P.O. Box 26, Middelburg, 5900, South Africa. 25 pages

 

Published

Karoo Agric Vol 4 (1)