Last update: November 22, 2010 10:47:23 AM E-mail Print

 

Protein supplementation of late pregnant and lactating sheep

in the different grazing areas of South Africa  

 

JH Hoon


Grootfontein Agricultural Development Institute, Private Bag X529,

Middelburg (Eastern Cape), 5900

e-mail: Jan Hoon

 


BACKGROUND  

 

Ewe productivity is the most important factor that determines the profitability of small stock farming. The important components of ewe productivity are the total weight of offspring produced, body weight at marketing/culling and in the case of fibre producing animals, the amount and quality of the fibres produced. Increasing the conception rate and number of multiple births can enhance weaning percentage, but the best option is probably to decrease the lamb mortality rate. Most lamb mortalities occur in the period just before birth until seven days after birth. Nearly 80% of these mortalities are related to the nutrition of the ewe during the last weeks before lambing and the first weeks after lambing. The amount of colostrum available at lambing and the milk production of the ewe after lambing are important factors influencing lamb survival and the growth rate of lambs. The supply of sufficient protein during late pregnancy and lactation influences the quantity as well as quality of milk produced. It is reported that the supply of a high level of bypass or rumen undegradable protein (UDP) is essential to increase the colostrum and milk production of ewes. The fact that relatively little information on the efficiency and economy of supplementation of reproducing ewes under veld conditions in South Africa are available, necessitated the initiating of a comprehensive study in the small stock producing areas of South Africa.

 

The objectives of the project were:

 

MATERIAL & METHODS  

 

The project was carried out at 13 different localities, representative of the different small stock grazing areas of South Africa, to include as much as possible of South Africa’s diverse vegetation.

 

At the start of the project at each locality, a flock of the farmer’s own ewes was mated as one group and randomly divided into three equal groups four weeks prior to lambing. The groups were then placed in different camps, comparable in size and veld quality and quantity, for the 12-week supplementation period. The animals remained in their respective groups for the duration of the study. Where the grazing conditions allowed it, a control group was kept (no supplementation), while the two treatment groups received supplementation with a high and low rumen undegradable (bypass) protein content, respectively. The total protein and energy contents of the two treatment diets were the same. The supplementary diets were supplied at 300g/animal/day for four weeks prior to lambing and 400g/animal/day for eight weeks after lambing. The supplement intake of both groups was kept at the same level for the duration of the supplementation period. All the procedures were repeated at least three times with the same nucleus of animals at each locality to minimise year effects.

 

The following data were recorded at all the localities: body weight of lambs at 42-day age and at weaning, body weight of ewes at 42-day lamb age and weaning percentage. An economic analysis was also done on the combined data of each locality, using the SM2004 computer simulation model, to determine the economic viability of supplementation of ewes during late pregnancy and lactation. Data from some of the localities, where the type as well as quality and quantity of grazing were comparable, were combined for the economic analysis. The average weaning percentages, body weight of ewes and weaning weight of lambs over the trial period were used to determine the economic viability of the different treatments at each locality. Furthermore, the average meat and wool prices over the trial period were used in the economic analysis. The cost of supplementary feeding for the control, low and high bypass groups were R0.00, R34.84 and R39.82 per ewe per year respectively. Other costs included in the model were marketing, shearing and health costs.

 

RESULTS AND DISCUSSION  

 

The weaning percentage, body weight of ewes at 42-day lamb age, 42-day body weight and weaning weight of lambs for the different treatments at each of the localities, as well as the average gross margin per ewe, are presented in Tables 1 to 4.

 

Table 1. Average production and reproduction data at the localities in the South and Western Cape and the gross margin/ewe for the different treatments

LOCALITY

TREATMENT  

Control

Low Bypass

High Bypass

HEIDELBERG/CALEDON  (Lucerne pastures – good quality)

Weaning percentage (%)

116.3

--

113.9

Body weight – ewes (kg)

63.2

--

62.0

42-day body weight – lambs (kg)

17.3

--

16.4

Weaning weight – lambs (kg)

25.3

--

24.6

Gross Margin (R/ewe)

518.09

--

466.66

HEIDELBERG  (Lucerne pastures – poorer quality)

Weaning percentage (%)

--

117.5

117.0

Body weight – ewes (kg)

--

64.3

66.8

42-day body weight – lambs (kg)

--

22.6

24.8

Weaning weight – lambs (kg)

--

29.8

30.6

Gross Margin (R/ewe)

--

489.38

486.05

PORTERVILLE/MALMESBURY (Wheat stubble)

Weaning percentage (%)

--

105.0

121.5

Body weight – ewes (kg)

--

60.8

61.8

42-day body weight – lambs (kg)

--

13.0

13.9

Weaning weight – lambs (kg)

--

30.0

31.4

Gross Margin (R/ewe)

--

436.80

496.09

CALEDON  (Poor quality pastures – Cynodon sp)

Weaning percentage (%)

82.8

95.0

101.8

Body weight – ewes (kg)

46.7

50.3

51.4

42-day body weight – lambs (kg)

17.2

17.8

18.0

Weaning weight – lambs (kg)

26.2

26.9

27.1

Gross Margin (R/ewe)

367.06

383.80

406.29

 

Table 2. Average production and reproduction data at Fraserburg and Philippolis and the gross margin/ewe for the different treatments

LOCALITY  

TREATMENT  

Control

Low Bypass

High Bypass

FRASERBURG  (Karoo shrub veld)

Weaning percentage (%)

95.3

93.7

96.9

Body weight – ewes (kg)

49.5

50.5

52.6

42-day body weight – lambs (kg)

19.7

20.2

20.7

Weaning weight – lambs (kg)

34.8

35.5

35.4

Gross Margin (R/ewe)

418.65

379.14

389.33

PHILIPPOLIS  (Mixed grass/shrub veld)

Weaning percentage (%)

88.0

88.5

90.0

Body weight – ewes (kg)

44.5

51.1

47.5

42-day body weight – lambs (kg)

20.5

21.9

19.8

Weaning weight – lambs (kg)

29.8

30.7

30.2

Gross Margin (R/ewe)

383.74

360.18

355.80

 

Table 3. Average production and reproduction data at Noupoort, Cedarville and Ermelo and the gross margin/ewe for the different treatments

LOCALITY

TREATMENT

Control

Low Bypass

High Bypass

NOUPOORT  (Sour grass veld)

Weaning percentage (%)

--

82.9

91.4

Body weight – ewes (kg)

--

40.9

42.1

42-day body weight – lambs (kg)

--

18.5

18.4

Weaning weight – lambs (kg)

--

24.3

23.9

Gross Margin (R/ewe)

--

324.37

353.47

CEDARVILLE  (Sour grass veld)

Weaning percentage (%)

--

81.5

88.6

Body weight – ewes (kg)

--

48.8

48.8

42-day body weight – lambs (kg)

--

18.5

18.8

Weaning weight – lambs (kg)

--

25.2

25.1

Gross Margin (R/ewe)

--

R330.25

352.32

ERMELO  (Sour grass veld)

Weaning percentage (%)

--

59.6

67.3

Body weight – ewes (kg)

--

46.8

47.6

42-day body weight – lambs (kg)

--

14.9

14.9

Weaning weight – lambs (kg)

--

25.9

25.5

Gross Margin (R/ewe)

--

244.11

269.48

 

Table 4. Average production and reproduction data at Pofadder and Koopmansfontein and the gross margin/ewe for the different treatments

LOCALITY

TREATMENT  

Control

Low Bypass

High Bypass

POFADDER (Stipagrostis sp. grass veld)

Weaning percentage (%)

69.8

71.0

75.1

Body weight – ewes (kg)

54.6

57.4

57.9

42-day body weight – lambs (kg)

16.0

19.4

20.6

Weaning weight – lambs (kg)

27.5

30.9

30.2

Gross Margin (R/ewe)

233.35

207.80

219.97

KOOPMANSFONTEIN  (Tarchonanthus shrub veld with grass)

Weaning percentage (%)

68.2

74.6

73.7

Body weight – ewes (kg)

54.4

55.2

56.4

42-day body weight – lambs (kg)

20.2

19.8

19.3

Weaning weight – lambs (kg)

27.7

27.2

27.3

Gross Margin (R/ewe)

227.61

219.90

213.74

 

Supplementation of ewes during late pregnancy and lactation had a positive effect on the growth rate of lambs (42-day body weight) at most of the localities. Between the two treatment groups (low and high bypass), the differences were in general small. It would appear that supplementation influenced milk production of the ewes favourably, which is reflected in the higher growth rate of lambs at 42-day age at most of the localities. The body weight of lambs at weaning followed more or less the same pattern as their corresponding 42-day weights, with higher values for the supplementation groups at most of the localities. Between supplementation groups the differences in weaning weight of lambs were in general small.

 

It appeared that the ewes receiving supplementation were more able to maintain their body weight during lactation than ewes not receiving any supplement, depending on the grazing conditions. Between the two treatment groups the body weights of the ewes varied, with some in favour of the High Bypass and other in favour of the Low Bypass groups. It also appeared that supplementation during late pregnancy and lactation in general had a positive effect on the weaning percentages of the ewes, especially when grazing conditions were not favourable. The data with regard to weaning percentages also indicated a positive tendency in favour of the High Bypass groups compared to the Low Bypass groups where grazing condition were less favourable e.g. animals on wheat stubble (Malmesbury/Porterville), poor quality Cynodon sp. pastures (Caledon) and the sour grass veld areas (Noupoort, Cedarville, Ermelo).

 

Supplementation of ewes during late pregnancy and lactation, especially with high bypass diets, had a positive effect on the gross margin per ewe at Caledon (poor quality Cynodon sp. pastures), compared to the control group. No difference in gross margin per ewe was observed between the two supplementation groups at Heidelberg (poorer quality lucerne pastures). At Malmesbury/Porterville (wheat stubble),  Noupoort (sour grass veld), Cedarville (sour grass veld) and Ermelo (sour grass veld), supplementation with high bypass diets was economically more viable than low bypass diets. At Heidelberg/Caledon (good quality lucerne pastures), Fraserburg (Karoo shrub veld), Philippolis (mixed grass/shrub veld), Pofadder (Stipagrostis sp grass veld) and Koopmansfontein (Tarchonanthus shrub veld with grass), supplementation (high and low bypass) did not have any advantages in terms of increased income per ewe. It would, therefore, appear that the quality of grazing is the most important factor influencing the economy of supplementary feeding, as illustrated by positive responses on sour grass veld, stubble lands and other poor quality grazing. It would furthermore appear that supplementation with a high bypass diet is more profitable than a low bypass diet on these poor quality grazing. It is, however, important to keep in mind that the rainfall and subsequent grazing conditions played a major role in the results obtained over the trial period. There were, therefore, individual years with lower rainfall and poorer grazing conditions where supplementary feeding provided a higher gross margin per ewe than the control group at some of the other localities. As weaning percentage is one of the most important factors determining the profitability, it is clear that the differences in gross margin per ewe are mainly influenced by the weaning percentages of the different groups.

 

 

CONCLUSION & RECOMMENDATIONS  

 

The results in general indicated a positive response with supplementation of ewes during late pregnancy and lactation on body weight of ewes, growth rate of lambs and weaning percentages. It would, however, appear that this response is only substantial when grazing conditions are relatively poor, in quality and/or quantity. It would, furthermore, appear that under less favourable grazing conditions, supplementation, especially with a high bypass protein diet, had a positive effect on certain traits, specifically the number of lambs weaned/ewes mated. This is supported by the economic analysis that indicated a positive response in gross margin per ewe on sour grass veld, stubble lands and other poor quality grazing, especially with high bypass diets.

 

The results indicated a specific pattern in the performance of the different groups of animals in direct relation to the type and quality of the veld/pasture. Under good grazing conditions, differences in production and reproduction data were small. However, under less favourable grazing conditions, animals receiving supplementation seem to perform better, especially with high bypass protein supplements. The prevailing grazing conditions (i.e. type, quantity and quality of vegetation) will therefore determine the type, period and amount of supplementation required to ensure that the implementation of a supplementary program during late pregnancy and lactation is an economically viable option. As weaning percentage is a very important factor in determining the economic viability of supplementation, it is important to focus more attention on the high producers in the flock (ewes with twins). It can therefore be concluded that the results indicated that different levels of bypass protein should be supplemented under different veld types and conditions to late pregnant and lactating ewes, thereby creating considerable savings in supplementation costs.

 

In summary, the following important factors must be kept in mind when planning a supplementation program for ewes during late pregnancy and lactation:

 

Type of grazing – The type of grazing available to the animal, both in terms of quality and quantity, is probably the main factor in determining whether supplementation should be supplied, what kind of supplementation should be supplied and how much supplementation should be supplied. From this study, it is evident that the prevailing grazing conditions had a large effect on the response observed with supplementation. In general, more emphasis should always be placed on protein supplementation of animals under grass veld conditions than under shrub veld (“bossieveld”) conditions.

 

Effect of individual years – The results of this study indicated that there were differences in production and reproduction data recorded between individual years. The producer must therefore evaluate the climatic conditions of individual years, e.g. rainfall (amount of rainfall, distribution of rainfall, etc.) and the expected grazing conditions. The rainfall conditions in the month prior to the start of the supplementation period will in most cases determine whether or not supplementation will be necessary, and if necessary, the type and amount of supplementation to be supplied.

 

Feed cost/price – The price and the availability of different feeds are important factors when deciding on a supplementation program. Cheaper feed prices, e.g. the lower maize price, can influence decision-making regarding whether or not to supplement, as well as the amount of supplementation to be supplied.

 

Duration of supplementation period – The rainfall prior to and during the supplementation period and the subsequent grazing conditions, will largely determine the duration of the supplementation period. Under favourable grazing conditions, the supplementation period can therefore be shortened since the milk production of the ewes declines after six weeks into the lactation period and lambs are becoming less dependant on their mothers.

 

Scanning of animals  - As weaning percentage is probably the most important factor in determining the economic viability of supplementation, more attention should be focused on the high producers in the flock when planning a supplementation program. The practice of ultrasound scanning is a valuable management tool in this regard to identify ewes with multiple foetuses and give more attention to these animals in a supplementation program.

 

 

ACKNOWLEDGEMENTS  

 

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

Department of Agriculture – Grootfontein A.D.I., Participating farmers, Provincial Departments of Agriculture (Northern Cape, Mpumalanga, Eastern Cape), Cape Wools, Mohair SA, RMRDT, NWGA and CMW.