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AN ANALYSIS OF PRE-WEANING KID MORTALITY IN SOUTH AFRICAN ANGORA GOATS

 

M.A. Snyman


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

E-mail: Gretha Snyman

 


INTRODUCTION

Reproduction and kid survival rate are the most important traits influencing income in Angora goats. High reproductive and kid survival rates will ensure a large proportion of the more expensive kid and young goat mohair in the clip, and will also contribute to higher selection intensity. The poor reproductive performance and high kid mortality rate of Angora goats are well documented. Factors influencing the survival rate of kids include birth weight of the kid, genetics, mothering ability and milk production of the dam, adverse environmental or feeding conditions, diseases and predators.

 

Very little work on mortality rate in goats, especially Angora goats, has been published to date (Van der Westhuizen, 1980; Terblanche, 1988; Husain et al., 1995; Geyer, 1998; Perez-Razo et al., 1998; Awemu et al., 1999). These authors cited losses from 10 to 30 %. Similar losses occur in sheep flocks and much work has been done investigating possible causes for lamb mortality (Alexander, 1984; Rook et al., 1990; Haughey, 1991). The difference between sheep and Angora goats is that very little losses occur in sheep lambs after weaning, while kid mortality could be as high as 15 % from weaning till 18 months of age (recorded for the Jansenville experimental flocks over a 10-year period).

 

A study was done on 12 Angora goat studs with the objectives of firstly, to quantify the extent of kid mortalities, secondly to identify the major causes of mortality, thirdly to determine if management practices influence kid mortality rate and fourthly to quantify the effect of certain known variables on mortality rate.

 

MATERIAL AND METHODS

The data used for this study were collected during a project that involved an investigation into reproductive performance and kid mortality aspects in South African Angora goats. This study was conducted from 2000 to 2004 in 12 Angora goat studs, kept under different management systems.

 

Data collected during the kidding seasons included the following information for each kid: Kid ID, Dam ID, Sire ID (if known), birth date, birth weight, sex, birth and rearing status, rearing group and weaning weight. Ewes that failed to kid, aborted or delivered stillborn kids, needed help with kidding, had udder defects, or kids that needed help suckling, were also recorded. Furthermore, probable cause of death was recorded where possible. Data collected on 17534 kids born alive in the different studs were included in the analyses.

 

Heritability of mortality rate was estimated, using 16 644 data records collected from 2000 to 2004 in the 12 studs. The following sire model, with sires nested within stud-year, was used (Harvey, 1990):

 

Yijklm = µ + ri + bj  + sk + rl + b1BW + eijklm

Where

Yijklm = trait of the m'th animal of the l'th birth status of the k'th sex of the j’th stud-year of the i’th sire,

µ = overall mean,

ri = random effect of the i'th sire,

bj = fixed effect of the j'th stud-year,

sk = fixed effect of the k'th sex,

rl = fixed effect of the l'th birth status,

b1 = linear regression coefficient of the appropriate deviation from the mean of birth weight,

eijklm = random error with zero mean and variance Is2e

 

RESULTS AND DISCUSSION

Mortality rate from birth to weaning is summarized in Table 1 for data collected from 2000 to 2004. Average pre-weaning mortality rate was 11.5 %, and ranged from 8.6 % to 16.5 % among years (of the 17534 kids born alive, 2018 kids died between birth and weaning at four months of age). Mortality rate in ram kids was higher than that recorded for ewe kids (11.9 % vs. 11.1 %). This is supported by the findings of Perez-Razo et al. (1998). Pre-weaning mortality rates for kids in the different studs are presented in Table 2. There was a large variation in kid mortality rate among the different studs, ranging from 3.0 % to 17.1 %.

 

Table 1. Pre-weaning mortality rate of ram and ewe kids over the survey period

Year

All kids

Ram kids

Ewe kids

Kids born

Kids died

Mortality rate (%)

Kids born

Kids died

Mortality rate (%)

Kids born

Kids died

Mortality rate (%)

2000

3087

327

10.6

1565

181

11.6

1522

146

9.6

2001

3229

364

11.3

1679

179

10.7

1550

185

11.9

2002

4352

376

8.6

2200

182

8.3

2152

194

9.0

2003

4000

478

12.0

2007

255

12.7

1993

223

11.2

2004

2866

473

16.5

1428

257

18.0

1438

216

15.0

Total / Average

17534

2018

11.5

8879

1054

11.9

8655

964

11.1

 

Table 2. Pre-weaning mortality rate of ram and ewe kids in the different studs

Stud

Number of kids born

Number of kids died

Mortality rate (%)

All kids

Ram kids

Ewe kids

1

833

25

3.0

3.2

2.8

2

2055

273

13.3

12.9

13.7

3

1542

177

11.5

12.1

10.9

4

1168

108

9.2

8.2

10.4

5

2506

378

15.1

16.1

14.0

6

1140

95

8.3

9.3

7.2

7

666

114

17.1

17.0

17.3

8

1017

164

16.1

16.0

16.3

9

3752

367

9.8

10.0

9.5

10

172

18

10.5

9.2

11.8

11

1515

166

11.0

11.0

10.9

12

1168

133

11.4

14.2

8.6

 

When comparing the management systems followed from mating up until weaning in the different studs (Table 3) with the corresponding pre-weaning mortality rate, it is obvious that there was no discernible trend. For example, Stud 1 with the lowest mortality rate and Studs 7 and 8 with the highest rates had the same general management practices, all providing none or the minimum additional feeding.

 

During the last six weeks of pregnancy, foetal growth increases rapidly, with the consequence that the nutritional requirements at that stage are almost double that of a dry ewe. Nutritional requirements of a ewe suckling twins, is three times higher than that of a dry ewe. In a study by Jordan & Le Feuvre (1989), there were more lamb deaths, more deaths from starvation, mismothering and desertion in each of two groups fed a below maintenance ration than in an above maintenance group. More lambs died and more lambs’ deaths were due to starvation in a group with unsound udders than in a sound udder group. Van der Westhuizen (1980) reported kid mortalities in four groups of Angora ewes receiving either high/low protein/energy diets during the last six weeks of pregnancy. Mortality rates of 8 %, 83 %, 42 % and 100 % were recorded for ewes that received high/high, high/low, low/high and low/low protein/energy diets respectively.

 

The ewes in most studs did not receive any supplementary feeding during pregnancy. The exceptions are the ewes in Studs 5, 9, 11 that were supplemented with energy licks during the last part of pregnancy and those ewes in Stud 12 that were run on pastures for the duration of pregnancy. However, kid mortality rates were not lower in the latter studs, compared to those studs where the ewes did not receive any supplementation.  

 

Table 3. Management systems and average mortality rate per system followed in the various studs

Stud

Mortality rate

Management practices

Before mating

During pregnancy

During kidding

During lactation

1

3.0

Ewes on veld, no supplementation

Ewes on veld, no supplementation

Ewes kid in veld, no supplementation

Ewes on veld, some years supplemented with chocolate grain

7, 8

16.5

Ewes on veld, no supplementation

Ewes on veld, no supplementation

Ewes kid in veld, no supplementation

Ewes on veld, some years supplemented with chocolate grain

5

15.1

Ewes on veld, no supplementation

Ewes supplemented with energy blocks last part of pregnancy

Ewes kid on pastures and in veld

Ewes on veld, some years supplemented with feed pellets / blocks

6

8.3

Ewes on veld, no supplementation

Ewes on veld, no supplementation

Ewes kid in veld and on pastures

Ewes on veld, some years supplemented with chocolate grain

2, 3, 4

11.7

Ewes on veld, no supplementation

Ewes on veld, no supplementation

Ewes kid on pastures

Ewes on veld, some years supplemented with chocolate grain

10

10.5

Ewes on veld, no supplementation

Ewes on veld, no supplementation

Ewes kid on pastures and in veld

Ewes on veld, some years supplemented with chocolate grain

9, 11

10.1

Flushing of ewes

Ewes supplemented with energy blocks last part of pregnancy

Ewes kid on pastures

Ewes on veld, some years supplemented with feed pellets

12

11.4

Ewes on pastures

Ewes on pastures

Ewes kid on pastures

Ewes on pastures

 

Causes of kid mortalities from birth till weaning are summarized in Table 4 for the data collected from 2000 to 2004. Of the 2018 deaths recorded, the probable cause for only 601 (29.8 %) deaths is known. When estimating the relative importance of the various causes, only data from these 601 kids were used, and the contribution of each cause was expressed relative to the number of deaths and not relative to the number of kids born. From these, mortality rates due to the various causes were calculated on a flock basis, expressed as number of kids that died per 100 kids born alive (Table 4).

 

The most important problems were predators (39.1 %), small, unthrifty kids who needed help suckling (18.6 %), ewes having little or no milk (6.8 %) and ewes discarding their kids (6.8 %). When combining the latter three causes with udder problems (3.5 %), 35.7 % of pre-weaning mortalities were due to these causes.

 

 

Table 4. Relative importance of various causes of kid mortalities from birth to weaning and calculated mortality rate due to each cause

Code
Cause

Number of deaths (n=2018)

% Contribution of each cause a

Calculated mortality rate due to each cause b

C1

Predators

235

39.1

4.5

C2

Kalbas teats / thick teats / udder problems (blue udder)

21

3.5

0.4

C3

Kid born prematurely / small, weak kid / kid needed help suckling

112

18.6

2.1

C4

Ewe had no / little milk

41

6.8

0.8

C5

Ewe discarded kid

41

6.8

0.8

C6

Illness

36

6.0

0.7

C7

Ewe died

15

2.5

0.3

C8

Accidents (Drowned or stuck in feeding or water troughs, etc.)

35

5.8

0.7

C9

Rain and cold

32

5.3

0.6

C10

Deformed kids

27

4.5

0.5

C11

Stuck in vegetation

6

1.0

0.1

C20

Cause of death unknown

1417

 

 

TOTAL

 

100

11.5

a Each cause expressed as number of deaths due to the specific cause relative to the number of deaths with known causes (e.g. for Predators = 235/601)

b Calculated mortality rate due to each cause (expressed as number of kids that died per 100 kids born alive)

 

The causes of kid mortalities indicated in Table 4 can also be classified into the following categories, namely causes with a genetic basis (C3, C4, C10), causes which could be addressed through the application of relevant management practices (C1, C2, C4, C6, C8, C9, C11), reasons to which the dam contributed (C2, C3, C4, C5, C7, C10) and reasons to which the sire contributed (C3, C10). Of these four categories, the most important were the one that can be addressed through management, which was responsible for 67.5 % of the known deaths, followed by reasons to which the dam contributed, which accounted for 42.7 % of deaths.

 

In sheep, extensive research proved that the largest proportion of lamb mortalities occurred at birth or during the first three days following birth (Alexander, 1984; Haughey, 1989; Rowland et al., 1992). There was general agreement among authors that many of these lamb mortalities could be avoidable by improvements in the management and feeding of the lambing flock.  It is rare for the death of the lamb to occur prior to the start of parturition; the generally accepted incidence of antenatal death is about 2 % (Haughey, 1991).  Survival of the live-born lamb depends mainly on its ability to withstand environmental stress, cold and starvation. The results of two studies, the first investigating causes of lamb mortality in the United Kingdom (Wiener et al., 1983) and the second kid mortality, as perceived by Angora goat farmers in South Africa (Terblanche, 1988), indicated that the major causes of mortality can be categorized under the starvation / mismothering / exposure (SME) syndrome. SME is discussed fully by Haughey (1991). Mortalities due to “weakly lambs” and “drought, cold exposure and weak kids” were categorised as SME-deaths in these studies.

 

Mortalities related to delayed births and dystocia are largely due to injury to the central nervous system (Haughey, 1991). Other workers (discussed by Alexander, 1984) also reported a high incidence of central nervous system lesions in lambs at autopsy. An important implication of these findings lies in the incidence of central nervous system haemorrhage in dead lambs in the SME category. These authors believe that birth injury caused most of these lambs to fail to thermo-regulate normally.

 

Over the five-year period from 2000 to 2004, a total of 1995 kids born from 1662 ewes, died between birth and weaning age (23 kids out of the 2018 kids that died had unknown dams). Of these ewes, 1381 only lost one kid, while 236 ewes lost two kids, 38 lost three and 7 ewes lost 4 kids. More than 45 % of kid mortalities of ewes that lost three kids, were due to small, unthrifty kids who needed help suckling, ewes having thick teats and udder problems, ewes having little or no milk or ewes discarding their kids. This indicates that these problems will occur repeatedly in the same ewes. Ewes experiencing these kinds of problems should preferably be eliminated, especially ewes with teat or udder problems. 

 

South African workers identified mismothering as a major cause of deaths from three days to weaning (Haughey, 1991; Cloete, 1992). Neuro-hormonal factors control the induction of maternal behaviour and the formation of the selective ewe-lamb bond (Keverne et al., 1992).  It is clear that maternal behaviour in the ewe is induced by signals from the vagina and cervix during labour. Maternal and neonatal behaviour in goats is similar to that of sheep (Blauvelt, 1954; Klopfer, 1971).  However, according to Alexander et al.  (1974), goats appear less likely than sheep to reject one of twins. According to the behaviour studies of Sambraus & Wittmann (1993), the interval between the birth of the first and second kids in triplet-bearing does, averaged 15 min and that between the birth of the second and third kid 6 min.  They also recorded that 98 % of kids did not attempt to suck any doe other than their own mother and that the average time from parturition to first sucking was 35 min for first-born kids and 51 min for subsequent kids.

 

If the goat has been observed straining for more than one hour without apparent progress in the birth process, it is time to provide assistance; the most common and easily corrected dystocia results from two or more kids in the birth canal simultaneously. Once the kids are delivered, it is important to ensure that the dam has the opportunity to lick them dry.  As well as providing essential stimulation for the kids, it helps in establishing the mother-kid bond; licking for 5 - 10 min is usually adequate for acceptance.  According to Smith (1986), there is a critical period of about two hours after birth during which the doe must be exposed to her kid if she is to accept it.  It is also important that the kids feed within an hour or two of birth.  As with sheep, newborn goats that are too weak to suck from their mothers should be fed by stomach-tube until they have gained enough strength to suck on their own. 

 

The relative importance of the various factors responsible for pre-weaning mortality in kids varies between the different studs, as presented in Table 5. Differences in recording contributed largely to this, as is evident from the difference in percentage of unknown deaths among the studs.

 

Rather large variation in mortality rate of kids born to different sires within a specific flock was also observed. Overall, mortality rate ranged from zero to 50 % among different sires that had at least 10 progeny within a specific year. Causes of kid mortality of progeny born to different sires within the same stud, also varied considerably, as is evident from Table 6. When considering the two causes of death to which the sire could contribute, small, weak kids varied from 0 % to 40 % among sires in Stud 5, while deformed lambs ranged from 0 % to 14.3 %. For instance, Sire 7 lost 27.3 % kids due to them being small and weak, 18.2 % due to illness and 9.1 % kids were deformed. All these causes have a genetic background and should be taken into consideration during selection of breeding sires.

 

Table 5. Causes of kid mortality in the different studs, expressed as a percentage of all mortalities, including those due to unknown causes

Stud

Kids born

Kids died

Mortality rate (%)

Percentage of deaths resulting from:

Predators

Udder problems

Weak kids

Little milk

Discarded kids

Illness

Ewe died

Accident

Rain cold

Deformed kids

Stuck

Unknown cause

1

833

25

3.0

28.0

0.0

0.0

0.0

0.0

12.0

0.0

4.0

16.0

4.0

4.0

32.0

2

2055

273

13.3

3.3

0.7

6.2

1.8

2.2

1.1

0.0

2.6

5.1

0.7

0.0

76.2

3

1542

177

11.5

4.5

0.0

5.6

2.3

1.1

0.6

0.0

0.6

0.0

1.1

0.0

84.2

4

1168

108

9.2

4.6

0.0

0.0

0.0

0.0

6.5

0.0

0.9

0.0

0.9

0.9

86.1

5

2506

378

15.1

20.9

2.6

12.4

6.9

4.2

2.4

1.9

0.5

1.6

2.4

0.3

43.9

6

1140

95

8.3

2.1

1.1

9.5

1.1

9.5

3.2

0.0

0.0

0.0

1.1

2.1

70.5

7

666

114

17.1

27.2

0.9

1.8

1.8

0.0

0.0

0.0

0.9

0.0

0.0

0.0

67.5

8

1017

164

16.1

25.6

1.8

6.7

1.8

2.4

0.0

1.2

0.6

0.6

0.0

0.6

58.5

9

3752

367

9.8

0.0

1.1

0.5

0.0

0.0

1.1

1.1

2.7

0.8

1.6

0.0

91.0

10

172

18

10.5

5.6

0.0

0.0

0.0

0.0

0.0

0.0

11.1

0.0

0.0

0.0

83.3

11

1515

166

11.0

28.9

0.0

7.8

0.0

1.2

1.8

0.0

2.4

0.0

1.2

0.0

56.6

12

1168

133

11.4

2.3

0.0

0.8

0.0

1.5

2.3

1.5

3.8

3.0

2.3

0.0

82.7

 

 
Table 6. Causes of kid mortality of progeny born to different sires in Stud 5 (Only sires with more than 10 % mortality included)

Sire

Kids born

Kids died

Mortality rate (%)

Percentage of deaths resulting from:

Predators

Udder problems

Weak kids

Little milk

Discard kids

Illness

Ewe died

Rain cold

Deformed kids

Unknown cause

1

18

5

27.8

0.0

0.0

40.0

0.0

20.0

0.0

0.0

20.0

0.0

20.0

2

13

4

30.8

50.0

25.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

25.0

3

16

8

50.0

0.0

0.0

25.0

25.0

0.0

0.0

0.0

12.5

0.0

37.5

4

66

9

13.6

11.1

0.0

11.1

0.0

22.2

0.0

0.0

11.1

11.1

33.3

5

37

7

18.9

14.3

0.0

28.6

0.0

28.6

0.0

0.0

0.0

0.0

28.6

6

30

8

26.7

0.0

0.0

12.5

25.0

0.0

0.0

0.0

25.0

0.0

37.5

7

37

11

29.7

27.3

0.0

27.3

0.0

0.0

18.2

0.0

0.0

9.1

18.2

8

24

7

29.2

28.6

0.0

28.6

14.3

0.0

0.0

0.0

0.0

14.3

14.3

9

23

6

26.1

16.7

0.0

33.3

0.0

33.3

0.0

0.0

0.0

0.0

16.7

10

31

7

22.6

42.9

0.0

0.0

14.3

14.3

0.0

14.3

0.0

0.0

14.3

 

 

Birth weight and sex of the kid had a significant influence on pre-weaning mortality rate. In this study, single born kids had the lowest mortality rate (10 %), followed by twin born (13 %) and triplet born (22 %) kids. The relationship between survival rate and birth weight are depicted in Figure 1 for all kids born, while the corresponding curves for single and twin-born kids are depicted in Figures 2 and 3 respectively. These findings are supported by those of Husain et al. (1995), who reported an increased survivability of kids with an increase in birth weight of kids and milk yield of their dams. Single kids also had a higher survival rate than twin kids.

 

A review article by Alexander (1984) notes that mortality in sheep is typically related to birth weight by a “U”-shaped curve. Mortality is likely to be lowest at a weight between 3 and 5 kg, depending on breed and age of ewe. According to Gordon (1996), lambs at both low and high birth weights may be at a disadvantage. In the one case, it would be because the lamb’s energy resources may not be adequate and in the other case because of difficulties during the birth process.  Management practices should obviously be aimed at ensuring that all lambs are as close as possible to the optimum birth weight for the breed in question.  Multiple births usually have the disadvantage of lower than optimum birth weights and it is obviously beneficial for ewes to be separated during the final trimester of pregnancy and fed according to the number of lambs they carry. The relationship between birth weight and mortality rate in Angora goats are more curvi-linear than “U” shaped (Van der Westhuizen, 1980). In this study, kids at the lower as well as higher ends of the range tend to have lower survival rates, except for twin born kids (Figure 2).

 

Despite large differences in mortality rate recorded between sires within flocks, a heritability of 0.04±0.01 was estimated for pre-weaning mortality rate. This could be explained by the fact that causes of mortality differed considerably among kids and many of these causes have no genetic background. Similar heritabilities of between 0.03 and 0.05 were estimated for sheep breeds for pre-weaning mortality rate (Morris et al., 2000).

 

Figure 1. Relationship between survival rate and birth weight in Angora kids

 

Figure 2. Relationship between survival rate and birth weight in single born Angora kids

 

Figure 3. Relationship between survival rate and birth weight in twin born Angora kids

 

CONCLUSIONS

The following conclusions can be drawn:

From the results of this survey, the following recommendations could be made to decrease pre-weaning kid mortalities:

 

ACKNOWLEDGEMENTS

The author wishes to convey her sincere appreciation to all the breeders who participated in the project, to everybody who assisted with data collection on the farms and to Mohair South Africa for funding of the project.

 

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Grootfontein Agric 8 (1)