Last update: November 19, 2010 11:38:37 AM E-mail Print

 

Ewe productivity and supplementation

 

JH Hoon


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

e-mail: Jan Hoon

 


INTRODUCTION

 

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. The price premium that is paid for mohair from Angora kids, makes it essential to produce and wean as many kids as possible. Increasing the conception rate and number of multiple births can enhance weaning percentage, but the best option is probably to decrease the kid mortality rate. Most kid 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 kidding and the first weeks after kidding. The amount of colostrum available at kidding and the milk production of the ewe after kidding are important factors influencing kid survival and the growth rate of kids. 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 Angora goat producing areas of South Africa.

 

The objectives of the project were:

 

MATERIAL AND METHODS

 

The project was carried out over a four year period (2000-2004) at three localities in the Jansenville, Willowmore and Graaff-Reinet districts. At the start of the project at each locality, a flock of the farmer’s own ewes was mated as one group for a six week period, scanned at 42-49 days after mating and randomly divided into three equal groups four weeks prior to kidding. A minimum of 70 ewes per group were used. The groups were then placed in different camps, comparable in size and veld quality, for the 12-week supplementation period. The animals remained in their respective groups for the duration of the study. The three groups at each farm consisted of a control group (no supplementation) and two treatment groups receiving supplementation with a high and low rumen undegradable (bypass) protein content respectively. The two supplementary diets were supplied at 300g/ewe/day. Supplement intakes of both groups were kept at the same level for the duration of the supplementation period. All the procedures were repeated for four consecutive years with the same nucleus of animals at each locality to minimise year effects.

 

A commercial pelleted diet was used as high bypass protein supplementation, while a urea-based pelleted diet was used as low bypass protein supplementation. Both diets had a protein content of 25% and energy content of 55% TDN (total digestible nutrients), with a UDP (rumen undegradable / bypass protein) content of 5.5% and 2.8-3.3% for the high and low bypass diets respectively.

 

The following data were recorded at all the localities: body weight of kids at 42-day age and at weaning, body weight of ewes at 42-day kid age, weaning percentage and hair production. Monthly rainfall was also recorded at the three localities for the duration of the project. Fleece samples, collected in 2002 from Angora ewes at Willowmore and Graaff-Reinet, was analysed by means of the OFDA2000. An economic analysis was 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.

 

RESULTS AND DISCUSSION

 

The average 42-day body weight and weaning weight of kids, body weight of ewes at 42-day kid age, conception percentages and weaning percentages of the different groups at the respective localities over the four year period, are presented in Table1.

 

Table 1. Growth and reproduction data of the different groups (±SE)

 

Control 

Low Bypass

High Bypass

42-day body weight – Kids (kg)

 

 

 

Graaff-Reinet

10.2 ± 0.19a

11.9 ± 0.20b

12.0 ± 0.20b

Jansenville

11.4 ± 0.17a

10.7 ± 0.15b

10.6 ± 0.15b

Willowmore

12.8 ± 0.17a

13.3 ± 0.16b

14.6 ± 0.16c

Average

11.5 ± 0.10a

12.0 ± 0.10b

12.4 ± 0.10c

Weaning weight – Kids (kg)

 

 

 

Graaff-Reinet

16.7 ± 0.25a

17.5 ± 0.26b

17.9 ± 0.25b

Jansenville

14.7 ± 0.21a

15.8 ± 0.20b

14.8 ± 0.21a

Willowmore

16.0 ± 0.21a

16.5 ± 0.21a

17.9 ± 0.20b

Average

15.8 ± 0.14a

16.7 ± 0.14b

16.9 ± 0.14b

Ewe body weight – 42-day kid age (kg)

 

 

 

Graaff-Reinet

34.1 ± 0.29a

35.3 ± 0.29b

34.9 ± 0.29b

Jansenville

33.2 ± 0.26

33.6 ± 0.24

33.3 ± 0.25

Willowmore

37.6 ± 0.21a

38.9 ± 0.23b

40.7 ± 0.22c

Average

34.9 ± 0.15a

35.9 ± 0.15b

36.3 ± 0.15b

Conception percentages (%)

 

 

 

Graaff-Reinet

87.4

89.1

85.8

Jansenville

90.2

88.4

90.1

Willowmore

84.1

87.9

86.3

Average

87.6

88.5

87.5

Weaning percentages (%)

 

 

 

Graaff-Reinet

70.1

66.5

74.3

Jansenville

76.6

77.8

76.4

Willowmore

61.8

75.1

80.0

Average

69.5

73.1

76.9

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

 

At Graaff-Reinet, the 42-day body weight of the kids of the two supplementation groups (High and Low Bypass) was higher (P<0.05) over the four year period than the Control group. At Jansenville, the Control group performed better (P<0.05) than the two treatment groups, while at Willowmore all three groups differed significantly, with the highest body weight for the High Bypass group. Overall, the 42-day body weight of kids differed significantly from one another, with the highest weight for the High Bypass group and the lowest for the Control group.

 

The weaning weights of the kids followed more or less the same pattern as the corresponding 42-day body weights. At Graaff-Reinet, the weaning weight of the kids of the two supplementation groups (High and Low Bypass) was higher (P<0.05) over the four year period than the control group. At Jansenville, the weaning weight of the Low Bypass group was higher (P<0.05) than the other two groups, while at Willowmore the High Bypass group had the highest weaning weight (P<0.05). Overall, it appears that supplementation (High and Low Bypass) had a positive effect (P<0.05) on the growth of kids.

 

At Graaff-Reinet, the body weight of the ewes at 42-day kid age was higher (P<0.05) for the two supplementation groups (High and Low Bypass) over the four year period than the control group. At Jansenville, no differences between the three groups were observed, while at Willowmore all three groups differed (P<0.05) from one another with the highest body weight for the High Bypass group. Overall, it is evident that the ewes of the supplementation groups had higher (P<0.05) body weights at 42-day kid age than the control group. Ewes receiving supplementation were more able to maintain their body weight during the lactation period than ewes not receiving any supplements.

 

Differences in the conception percentage of ewes of the different groups were very small. As the project was repeated each year with the same nucleus of animals in each group, no carry-over effect with regard to increased reproduction rate, owing to the effect of supplementation during the previous kidding season, could be observed.

 

At Graaff-Reinet, the ewes receiving the High Bypass supplement had higher weaning percentages, while at Willowmore the weaning percentages were also in favour of the two supplementation groups. At Jansenville no differences could be observed among the groups. Overall, it would appear that supplementation during late pregnancy and lactation in general had a positive effect on the weaning percentages of the ewes. External factors not related to the nutrition of the ewe, such as kid losses due to problem animals, also influenced the weaning percentages at some of the localities.

 

Fleece characteristics of the ewes of the different groups, as determined in 2002, are presented in Table 2.

 

Table 2. Fleece characteristics of the ewes of the different groups (±SE)

 

Control

Low Bypass

High Bypass

Graaff-Reinet

 

 

 

Fibre diameter (μm)

34.46 ± 0.56

35.15 ± 0.56

35.11 ± 0.53

Standard deviation (μm)

9.21 ± 0.19

9.27 ± 0.19

9.36 ± 0.18

Coefficient of variation (%)

26.97 ± 0.61

26.66 ± 0.61

26.81 ± 0.57

SD along length of fibre (μm)

2.04 ± 0.10a

1.60 ± 0.10b

1.58 ± 0.09b

Willowmore

 

 

 

Fibre diameter (μm)

38.18 ± 0.44

37.93 ± 0.42

37.29 ± 0.42

Standard deviation (μm)

9.41 ± 0.15

9.09 ± 0.15

9.21 ± 0.15

Coefficient of variation (%)

24.76 ± 0.42

24.16 ± 0.40

24.81 ± 0.40

SD along length of fibre (μm)

1.63 ± 0.07a

1.33 ± 0.07b

1.41 ± 0.07b

ab Values with different superscripts, differ significantly (P<0.05).

 

With the exception of standard deviation (SD) along the length of the fibre, no differences (P>0.05) were observed for any of the fleece characteristics among the different groups. Standard deviation along the length of the fibre was higher (P<0.05) for the control group compared to the two supplementation groups at both localities. It would, therefore, appear that supplementation (Low and High Bypass) of ewes during late pregnancy and lactation had a positive effect on evenness of fibre diameter along the length of the fibre.

 

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 with the SM2004 computer simulation model. The average meat and wool prices over the trial period were also 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.

 

 

Table 3. Gross margin per ewe (R/ewe) for the different treatments at the different localities over the four year period

 

Control

Low Bypass

High Bypass

Graaff-Reinet

R411.25

R372.22

R402.32

Jansenville

R466.61

R443.77

R433.79

Willowmore

R356.40

R404.87

R412.16

 

Over the four year period, the economic analysis indicate that it was financially viable to supply supplementary feeding at Willowmore, but not at Graaff-Reinet and Jansenville. It is, however, important to keep in mind that the rainfall (Table 4) and subsequent grazing conditions played a major role in the results obtained over the four year period. There were, therefore, individual years where supplementary feeding provided a higher gross margin per ewe than the control group at the latter two localities too. As weaning percentage is one of the important factors determining the profitability of Angora goat farming, it is clear that the gross margin are influenced mainly by differences in weaning percentages between the groups.

 

The monthly rainfall figures for the four years at the different localities are presented in Table 4.

 

Table 4. Monthly rainfall (mm) at the different localities

 

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Total

Graaff-Reinet

 

 

 

 

 

 

 

 

 

 

 

 

 

2000

100

14

136

36

0

5

0

0

46

15

98

0

450

2001

87

90

37

133

4

6

10

3

76

20

65

39

570

2002

29

7

39

10

16

26

20

90

47

13

16

57

370

2003

7

58

32

40

31

0

2

12

6

27

79

12

306

Jansenville

 

 

 

 

 

 

 

 

 

 

 

 

 

2000

39

17

75

24

0

9

0

0

16

0

108

15

303

2001

79

11

40

85

11

0

0

0

22

15

85

8

356

2002

17

0

45

32

0

0

44

54

22

0

10

18

242

2003

8

41

65

2

27

0

0

18

0

29

0

10

199

Willowmore

 

 

 

 

 

 

 

 

 

 

 

 

 

2000

37

30

140

61

0

0

0

0

0

0

55

0

323

2001

22

40

24

51

0

21

13

0

28

10

60

0

269

2002

5

0

5

18

9

16

11

45

0

0

0

54

163

2003

0

0

43

0

20

0

0

0

0

18

8

6

95

 

The supplementation of ewes during late pregnancy and lactation occurred between August and November each year and the rainfall prior to and during these periods had the largest influence on the results. High rainfall that occurred prior to and during the supplementation period at some of the localities, with the subsequent good grazing conditions, were probably the main reason for the small differences in production and reproduction observed between the groups at these localities. At the localities where the supplementation period was relatively dry, differences between the control and treatment groups were in general larger.

 

CONCLUSION AND RECOMMENDATIONS

 

The production and reproduction data collected over the past four kidding seasons at the three Angora goat localities in general indicated a positive response with supplementation of ewes during late pregnancy and lactation on body weight of ewes, growth rate of kids and weaning percentages. It would, however, appear that this response was only substantial when grazing conditions were less favourable. The small differences that were observed between the different treatments at some localities, can largely be attributed to high rainfall and subsequent good grazing conditions. With average and below average rainfall prior to and/or during the supplementation period, differences between control and treatment groups, and even between the two treatment groups, were larger. The economic analysis indicated that the average gross margin/ewe over the four year period was in favour of the supplementation groups, compared to the control group, only at one locality (Willowmore). At the other two localities (Graaff-Reinet and Jansenville) there were, however, individual years, when lower rainfall with subsequent poorer grazing conditions occurred, where the gross margin per ewe also favoured the supplementation groups. Supplementation of Angora ewes during late pregnancy and lactation also had a positive effect on the evenness of fibre diameter along the length of the fibre.

 

It is evident that the advantages of supplementation of Angora ewes during late pregnancy and lactation are mainly determined by the prevailing grazing conditions. 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 essential to focus more attention on the high producers in the flock (ewes with twins) when planning a supplementation program.

 

In summary, the following important factors must be kept in mind when planning a supplementation program for Angora goats 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 be always 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. a 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 declined after six weeks into the lactation period and kids 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

Mohair SA

CMW

Eastern Cape Department of Agriculture

Cape Wools

RMRDT

NWGA