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TRACE MINERAL SUPPLEMENTATION OF SHEEP AND ANGORA GOATS

IN THE DIFFERENT GRAZING AREAS OF SOUTH AFRICA

 

J.H. Hoon# & M.J. Herselman


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

# Corresponding author: E-mail: Jan Hoon

 


INTRODUCTION

Trace minerals are normally of practical and economical importance only when a deficiency or excess manifested itself in terms of deviating animal behaviour, lower production and reproduction rate, a specific disease syndrome and/or an increase in the mortality rate. Twenty-one inorganic minerals are essential in animal nutrition, of which seven are required in reasonably large quantities and are known as the macro minerals, while the other 14 are required in very small quantities and are known as the micro or trace minerals. However, in farm animal nutrition the six most important trace minerals are zinc (Zn), manganese (Mn), copper (Cu), cobalt (Co), selenium (Se) and iodine (I). These trace minerals play an important role in optimal growth, production, reproduction and general health (Underwood & Suttle, 1999).

The problem that normally exists is that trace mineral deficiencies occur in different grades and that it is difficult to diagnose a moderate deficiency.  There is furthermore a move away from supplementing to prevent possible deficiencies towards supplementing for optimal animal production. Trace mineral supplements are used on a large scale in the small stock industry, but there are still many questions regarding animal response with and the cost efficiency of trace mineral supplementation. For this reasons, the role players in the small stock industry requested an investigation into the economic advantages of trace mineral supplementation for small stock.

In this study, the supplementation of Angora goats and sheep with Zn, Mn and Se was investigated. Deficiencies of Zn, Mn and Se in small stock are associated with a variety of symptoms, but in this study only the effect of supplementing these three trace minerals on the reproduction of ewes and the growth rate of lambs/kids were investigated.

The aim of the project was to determine the effect of supplementation of sheep and Angora goats with a commercial trace mineral supplement on the reproduction rate of ewes and the growth rate of lambs/kids in order to establish guidelines and make recommendations that will benefit producers financially.

 

 

MATERIAL AND METHODS

This project was conducted at 20 localities in the small stock producing areas of South Africa. At seven of the localities data were collected on Angora goats, while sheep were used at the other 13 localities. At each locality, a flock of the farmer’s own ewes was mated as one group. The flock was randomly divided into two groups (control and treatment) and the groups were individually tagged and numbered with two different colour ear tags. The ewes of the treatment group received a 1 ml subcutaneous injection of a commercial trace mineral supplement 4-6 weeks prior to mating and again 4-6 weeks before lambing/kidding. The commercial product Multimin® (Virbac) was used, consisting of a combination of chelated Zn and Mn, as well as Se in the form of sodium selenite.  A minimum of 70 ewes per group was used and all the ewes were managed as one group for the duration of the study. However, where necessary, the two groups of ewes were placed in two comparable camps at the onset of lambing for accurate lamb identification. The procedures were repeated for two to three years in order to minimize year effects. Due to various practical and logistical reasons, it was not possible to repeat the procedures in consecutive years at all the localities.

The following data were collected at all the localities: body weight of lambs/kids at 42-day age, body weight of lambs/kids at weaning and weaning percentages of ewes. Where possible, ewes were also scanned for pregnancy to determine conception and/or scanning percentages. Blood samples of 10 animals per group were collected approximately four weeks after the first supplementation, i.e. with the onset of the mating period. The full blood samples were analysed for selenium (Se) to determine the effect of supplementation on the levels of Se in the blood.

Economic analyses, using the SM2000 computer simulation model (Herselman, 2002), were done on the combined data of all the localities over the two to three year period to determine the economic viability of trace mineral supplementation of Angora goats and sheep. The average weaning weight of kids/lambs and weaning percentages over the three year period were used in the analyses. Body weight of ewes, fleece weight, etc., were kept the same for the two groups. Average meat and mohair/wool prices over the trial period, as well as a cost of R2.00/ewe for the trace mineral supplement in the treatment group, were used in the calculation.

Statistical analysis was done by using the GLM procedures of SAS (Littell et al., 1991).

 

RESULTS AND DISCUSSION

Angora goats

The conception and scanning percentages of the Angora ewes, body weight of kids at 42-day age and at weaning and the weaning percentages at the different localities for Year 1, 2 and 3, are presented in Table 1 to Table 4. In Year 2 and 3, the ewes at the different localities were not scanned due to the non-availability of skillful operators and the high cost associated with the long distances that the operators had to travel.

Table 1. Conception and scanning percentages of the ewes

 

CONTROL

SUPPLEMENTATION

 

Conception %

Scanning %

Conception %

Scanning %

Year 1





Middelburg      

87.0

100.0

90.0

100.0

Willowmore        

98.0

100.0

97.0

110.0

Steytlerville    

94.8

102.0

94.9

101.0

Jansenville     

91.0

94.0

85.0

90.0

Murraysburg  

96.0

100.0

97.0

103.0

Conception percentage = Number of ewes pregnant/Number of ewes mated

Scanning percentage = Number of kids scanned/Number of ewes mated

The results indicated relatively small differences in the reproduction data (conception rate and scanning percentages) between the control and supplementation groups, with some data favouring the supplementation and other the control groups.

 

Table 2. Body weight (± s.e.) of kids at 42-day age

 

CONTROL (kg)

SUPPLEMENTATION (kg)

Year 1

 

 

Middelburg

16.0 ± 0.3a

17.0 ± 0.3b

Willowmore

12.8 ± 0.2

13.3 ± 0.3

Steytlerville

8.1 ± 0.2

8.1 ± 0.2

Jansenville

8.2 ± 0.2

8.0 ± 0.2

Murraysburg

10.4 ± 0.2

11.0 ± 0.3

Year 2

 

 

Middelburg

14.7 ± 0.2

14.7 ± 0.2

Cradock

12.0 ± 0.3a

13.1 ± 0.3b

Beaufort West

11.2 ± 0.2

10.9 ± 0.2

Murraysburg

10.8 ± 0.2

11.0 ± 0.2

Year 3

 

 

Middelburg

13.5 ± 0.2

13.7 ± 0.2

Cradock

15.7 ± 0.3

15.4 ± 0.3

ab Values with different superscripts in rows differ significantly (P<0.05)

With regard to the body weight of kids at 42-day age, the trend was generally in favour of the supplementation groups, although it was only significantly higher (P<0.05) for the supplementation groups at Middelburg (Year 1) and Cradock (Year 2). At all the other localities, differences between the control and supplementation groups were very small.

The large differences in body weight that were observed among the different localities, can be attributed to differences in environmental and grazing conditions, as well as the fact that the kids were not weighed at exactly the same age.

 

Table 3. Body weight (± s.e.) of kids at weaning

 

CONTROL (kg)

SUPPLEMENTATION (kg)

Year 1

 

 

Middelburg

16.0 ± 0.3a

17.0 ± 0.3b

Willowmore

12.8 ± 0.2

13.3 ± 0.3

Steytlerville

8.1 ± 0.2

8.1 ± 0.2

Jansenville

8.2 ± 0.2

8.0 ± 0.2

Murraysburg

10.4 ± 0.2

11.0 ± 0.3

Year 2

 

 

Middelburg

14.7 ± 0.2

14.7 ± 0.2

Cradock

12.0 ± 0.3a

13.1 ± 0.3b

Beaufort West

11.2 ± 0.2

10.9 ± 0.2

Murraysburg

10.8 ± 0.2

11.0 ± 0.2

Year 3

 

 

Middelburg

13.5 ± 0.2

13.7 ± 0.2

Cradock

15.7 ± 0.3

15.4 ± 0.3

ab Values with different superscripts in rows differ significantly (P<0.05)

The body weight of the kids at weaning followed more or less the same pattern than their corresponding 42-day weights, with only the kids of supplementation groups at Middelburg (Year 1) and Cradock (Year 2) having significantly higher (P<0.05) body weights than their respective control groups. At all the other localities, differences between the control and supplementation groups were very small.

 

Table 4. Weaning percentages of the ewes

 

CONTROL (%)

SUPPLEMENTATION (%)

Year 1

 

 

Middelburg

81.0

82.0

Willowmore

65.0

70.0

Steytlerville

78.0

87.0

Jansenville

71.0

62.0

Murraysburg

81.0

85.0

Year 2

 

 

Middelburg

97.0

100.0

Cradock

72.0

72.0

Beaufort West

60.0

69.0

Murraysburg

70.4

73.2

Year 3

 

 

Middelburg

88.0

90.0

Cradock

58.0

59.0

With the exception of Jansenville, the number of kids weaned/ewes mated (weaning percentage) was equal or higher for the supplementation groups, compared to the control groups, at all the localities. At most of the localities the differences were, however, relatively small.

 

Sheep

The conception and scanning percentages of the ewes, body weight of lambs at 42-day age and at weaning and the weaning percentages at the different localities, are presented in Table 5 to Table 8. At some localities the ewes were not scanned due to the non-availability of skillful operators and the high cost associated with the long distances scan operators had to travel.

Table 5. Conception and scanning percentages of the ewes

 

CONTROL

SUPPLEMENTATION

 

Conception %

Scanning %

Conception %

Scanning %

Year 1

 

 

 

 

Adelaide           

77.0

 

87.3

 

Britstown                   

97.0

107.0

95.0

105.0

Kareedouw(1)         

93.8

120.8

95.1

129.1

Kareedouw(2)  

70.5

81.0

89.0

92.5

Fraserburg                  

87.0

110.0

93.0

113.0

Cradock           

96.3

 

96.3

 

Year 2

 

 

 

 

Dewetsdorp      

83.0

94.0

88.0

100.0

Springbok         

94.0

116.0

96.0

136.0

Koopmansfontein       

68.1

 

72.2

 

Adelaide           

94.0

99.0

92.0

96.0

Moorreesburg  

91.0

104.0

83.0

92.0

Riversdale      

79.1

93.6

72.0

81.3

Laingsburg     

93.2

115.9

93.3

117.8

Upington         

86.8

 

89.0

 

Kareedouw(1) 

95.3

 

97.3

 

Kareedouw(2) 

78.0

 

92.0

 

Britstown         

96.0

122.0

92.6

127.7

Fraserburg      

86.7

113.3

100.0

118.3

Cradock         

95.1

 

97.6

 

Year 3

 

 

 

 

Fraserburg     

100.0

113.3

100.0

115.0

Conception percentage = Number of ewes pregnant/Number of ewes mated

Scanning percentage = Number of kids scanned/Number of ewes mated

The conception and scanning percentages of the ewes varied between localities and over years, with the general tendency in favour of the supplementation groups. At some localities, such as Adelaide and Kareedouw(2) in Year 1 and Kareedouw(2) and Fraserburg in Year 2, a marked increase in the conception percentage of the ewes of the supplementation group was observed. There were, however, also localities where the control groups performed better than the supplementation groups.

 

Table 6. Body weight (± s.e.) of lambs at 42-day age

 

CONTROL (kg)

SUPPLEMENTATION (kg)

Year 1

 

 

Britstown

15.2 ± 0.2

15.4 ± 0.2

Fraserburg

20.4 ± 0.4a

21.7 ± 0.4b

Kareedouw(1)

15.9  ± 0.2

16.7 ± 0.3

Kareedouw(2)

16.2 ± 0.3a

19.8 ± 0.4b

Year 2

 

 

Dewetsdorp

16.5 ± 0.3

16.8 ± 0.3

Riversdale

16.1 ± 0.3

15.4 ± 0.3

Upington

16.7 ± 0.3

17.0 ± 0.3

Koopmansfontein

17.4 ± 0.4

18.2 ± 0.4

Fraserburg

10.9 ± 0.2a

13.8 ± 0.3b

Kareedouw (1)

17.4 ± 0.3a

19.5 ± 0.3b

Cradock

22.9 ± 0.4

22.0 ± 0.4

Year 3

 

 

Fraserburg

14.7 ± 0.3

14.6 ± 0.3

Cradock

18.5 ± 0.3a

19.7 ± 0.4b

ab Values with different superscripts in rows differ significantly (P<0.05)

With regard to 42-day body weight of lambs, significant differences in favour of the supplementation groups were observed at Fraserburg and Kareedouw(2) in Year 1, Fraserburg and Kareedouw(1) in Year 2 and Cradock in Year 3.

The large differences in body weight that were observed among the different localities, can be attributed to differences in environmental and grazing conditions, as well as the fact that the lambs were not weighed at exactly the same age.

 

Table 7. Body weight (± s.e.) of lambs at weaning

 

CONTROL (kg)

SUPPLEMENTATION (kg)

Year 1

 

 

Britstown

26.9 ± 0.3

27.5 ± 0.3

Fraserburg

36.1 ± 0.4a

38.4 ± 0.4b

Kareedouw(1)

27.8 ± 0.3a

29.9 ± 0.4b

Kareedouw(2)

26.8 ± 0.4a

29.8 ± 0.4b

Year 2

 

 

Dewetsdorp

27.8 ± 0.4

28.8 ± 0.4

Riversdale

29.9 ± 0.3

30.6 ± 0.4

Upington

26.2 ± 0.3

26.4 ±0.3

Koopmansfontein

24.9 ± 0.5

25.6 ± 0.6

Fraserburg

28.8 ± 0.5

29.9 ± 0.5

Springbok

19.6 ± 0.3

20.6 ± 0.4

Kareedouw(1)

26.7 ± 0.4a

29.4 ± 0.4b

Cradock

27.7 ± 0.4

26.1 ± 0.4

Year 3

 

 

Fraserburg

30.7 ± 0.5

31.0 ± 0.5

Cradock

29.0 ± 0.4

29.8 ± 0.4

ab Values with different superscripts in rows differ significantly (P<0.05)

The weaning weight of the lambs was higher (P<0.05) for the supplementation groups at Fraserburg, Kareedouw(1), Kareedouw(2) in Year 1 and Kareedouw(1) in Year 2 With the exception of a few localities, the general tendency with regard to the growth rate of lambs until weaning was in favour of the supplementation groups.

 

Table 8. Weaning percentages of the ewes

 

CONTROL (%)

SUPPLEMENTATION (%)

Year 1

 

 

Britstown

85.0

92.0

Fraserburg

73.3

75.0

Kareedouw(1)

78.0

87.0

Kareedouw(2)

73.5

86.5

Year 2

 

 

Dewetsdorp

85.0

86.0

Riversdale

71.8

73.8

Koopmansfontein

64.6

69.8

Fraserburg

85.0

98.3

Springbok

88.2

84.3

Kareedouw(1)

116.5

115.8

Cradock

73.4

84.6

Year 3

 

 

Fraserburg

106.7

110.0

Cradock

81.7

81.5

With regard to the weaning percentages of the ewes, the results were in favour of the supplementation groups at most of the sheep localities.

 

Blood analysis

The mean blood Se values in the full blood samples of the control and treatment groups at the different localities are presented in Table 9.

Table 9. Mean blood Se values (± s.e.) for the control and treatment groups

 

CONTROL (ng/g)

SUPPLEMENTATION (ng/g)

ANGORA GOATS

 

 

Jansenville

222.6 ± 9.2

202.5 ± 8.3

Willowmore

209.2 ± 15.9a

277.0 ± 8.7b

Aberdeen

219.4 ± 8.7a

248.0 ± 9.2b

Beaufort West

290.7 ± 8.7

311.8 ± 8.7

Middelburg

213.0 ± 8.7

223.8 ± 8.7

Steytlerville

184.5 ± 8.7

191.6 ± 9.2

Murraysburg

219.2 ± 8.7

226.5 ± 8.7

Cradock

151.2 ± 6.0

169.2 ± 7.1

SHEEP

 

 

Utrecht

114.9 ± 9.0

138.6 ± 9.0

Cradock

132.0 ± 13.6

139.0 ± 7.8

ab Values with different superscripts in rows differ significantly (P<0.05)

With the exception of Jansenville, blood Se values for the ewes of the supplementation groups were higher than the control groups. The differences between the supplementation and control groups were, however, only significant at Willowmore and Aberdeen. In general, a marginal deficiency in the Se status of sheep and goats can be classified as a value less than 40 ng/g and a deficiency as a value less than 20 ng/g, while an excess can be classified as a value of more than 800 ng/g (Puls, 1994). There is, however, evidence suggesting that levels of approximately 200 ng/g are essential for optimum production and reproduction in livestock (Kincaid, 1995). From the mean blood Se values, it appears that the animals had access to sufficient Se for optimum production and reproduction at most of the localities, even without supplementation. These results concur with the results reported by Van Ryssen (2001).

  

Economic analysis

The average production and reproduction data and gross margin/ewe of the control and supplementation groups of Angora goats and sheep are presented in Table 10.

Table 10. Production and reproduction data (± s.e.) and gross margin per ewe of Angora goats and sheep

 

CONTROL

SUPPLEMENTATION

ANGORA GOATS

 

 

42-day weight – kids (kg)

12.5 ± 0.2

12.8 ± 0.2

Weaning weight – kids (kg)

17.0 ± 0.3

17.2 ± 0.3

Weaning percentage (%)

75.0

78.7

Gross margin (R/ewe)

454.26

471.79

SHEEP

 

 

42-day weight – lambs (kg)

16.8 ± 0.3a

17.7 ± 0.3b

Weaning weight – lambs (kg)

27.8 ± 0.4a

28.8 ± 0.4b

Weaning percentage (%)

83.3

87.9

Gross margin (R/ewe)

373.59

389.17

ab Values with different superscripts in rows differ significantly (P<0.05)

Gross margins of R454.26 and R471.79 per ewe for Angora goats and R373.59 and R389.17 per ewe for sheep were calculated for the control and supplementation groups respectively.  Although the differences in gross margin per ewe were not significant, the economic analysis indicated that the supplementation of Angora goats and sheep with a commercial trace mineral supplement during the experimental period was economically viable.

The economic analysis also indicated that an increase of 0.4-0.5% in the weaning percentages of Angora goats and 0.7-0.8% in the weaning percentages of sheep, were sufficient to cover the cost of the supplementation. An increase in the weaning percentages of more than the above-mentioned values, which can specifically be attributed to the effect of the trace mineral supplement, will therefore make the practice of trace mineral supplementation a financially viable option.

 

 

CONCLUSION

From the results it appeared that supplementation of Zn, Mn and Se by means of commercial product (Multimin® - Virbac) in general had a positive effect on the measured reproduction traits of sheep and Angora ewes and the production of lambs/kids, although differences were relatively small at most localities. In areas known for possible mineral deficiencies such as Kareedouw, a large increase in the reproductive rate of the ewes, as well as the growth rate of the lambs, were observed. At some localities, however, no differences in production and reproduction traits could be observed and some of the results were even in favour of the control groups. Good grazing conditions were probably one of the reasons for the small differences observed between the control and treatment groups at most of the localities.

 

The average gross margin per ewe, as calculated with the SM2000 model, indicated an economic advantage in the use of trace mineral supplementation for sheep and Angora goats. As the cost of trace mineral supplementation is relatively low, an increase of less than 1% in the weaning percentages of the ewes as a result of the supplement was sufficient to make this practice economically viable.

 

REFERENCES

Herselman, M.J., 2002. The role of simulation models in agricultural extension. Proc. 39th SASAS Cong., Christiana, 13-17 May 2002, 189.

Kincaid, R.L., 1995. Assessment of trace mineral status of ruminants: A review. Proc. Am. Soc. Anim. Sci., 1-10.

Littell, R.C., Freud, R.J., & Spector, P.C., 1991. SAS System for Linear Models. Third Edition. SAS Institute Inc. Cary, NC.

Puls, R., 1994. Mineral Levels in Animal Health: Diagnostic data. 2nd Ed. Sherpa International, Clearbrook, B.C., Canada.

Van Ryssen, J.B.J., 2001. Geographical distribution of the selenium status of herbivores in South Africa. S.Afr. J. Anim. Sci. 31, 1-7.

Underwood, E.J. & Suttle, N.F., 1999. The Mineral Nutrition of Livestock. 3rd Ed. CABI Publ., Oxon, UK.

 

 

ACKNOWLEDGEMENTS

The following organisations and people funded and participated in the execution of the project:

 

 

Participating farmers

Provincial Departments of Agriculture (Eastern Cape, Northern Cape)

University of Pretoria – Department of Animal and Wildlife Sciences

Mohair SA

Virbac

Cape Mohair and Wool (CMW)

 

Published

Grootfontein Agric 7 (1), 7-13