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Reproductive performance of Tswana ewes and Boer does in south-eastern Botswana

D. Seabo, A.A. Aganga and M. Mosienyane

Department of Animal Science and Production, Botswana College of Agriculture
Private Bag 0027, Gaborone, Botswana

Materials and methods


The reproductive performance over a five-year period (198993) of Tswana ewes and Boer does kept under semi-intensive management at Estate Management Unit farm of the College at Sebele-Gaborone, Botswana, was analysed. A total of 70 lambings and 152 kiddings involving 202 lambs and 288 kids were subjected to statistical analysis. The parameters studied were age at first parturition (AFP), parturition intervals (PI), annual parturition rate (APR), birth weight (BOO) and correlation between dam weight (DW) and young birth weight. The results showed that for Tswana ewes, AFP, PI, APR and BW were 18.00±1.39 months, 365±28.50 days, 1.00 and 3.30±0.89 kg, respectively, while for Boer goats they were 18.00±0.69 months, 350±2.4 days, 1.00 and 3.23±0.76 kg, respectively. Tswana ewes are seasonal breeders, they lamb in late spring and early summer (October-December). Male to female sex ratio was 49.0% for the 202 lambs and 52.78% for the 288 kids recorded. The rate of single and twin lambings were 80.59% and 19.41%, respectively, while the rate of single, twin, triplet and quadruplet kiddings were 28.29%, 53.28%, 16.45% and 1.32%, respectively. Mortality and stillbirths were 3.43% and 0.5%, respectively, for sheep while mortality, stillbirths and abortions for goats were 10.42%, 2.78% and 0.66%, respectively. The analyses show that Tswana ewes and Boer does are early maturing breeders. There was a poor correlation (r2 = 0.02 for sheep r2 = 0.04 for goats) between the dam's body weight and the young's birth weight.


Tswana sheep are indigenous to Botswana while Boer goats are imported from South Africa. The Tswana sheep is fat-tailed with some coarse negligible wool on the coat. The coat colour is predominantly black and white and is mainly kept for mutton. The Boer goat is white with a reddish brown head and neck. The goat has broad droopy ears, horns and is used for meat, milk and skin.

In 1990, there were 2,096,000 goats and 317,000 sheep (MoA 1990); 267,000 sheep were under traditional management and about 50,000 were on commercial farms while about two million goats were under traditional management and 62,000 were on commercial farms. The average flock sizes were 17.5 sheep and 30.2 goats per farm. Mannathoko (1993) reported that the total number of sheep slaughtered at the Botswana Meat Commission (BMC) abattoirs were 5963 and 3573 head for 1992 and 1993, respectively, while the goats slaughtered were 6685 and 3456 for the same years, respectively. The offtake of both sheep and goats was 11.0% (MoA 1990). Small stock play an important role in the socio-economic life of the Botswana. Small ruminant ratio to cattle is about 44%.

This study examines the reproductive performance of Tswana ewes and Boer does which are the predominant breeds of small stock in Botswana.

Materials and methods

The data for this study were collected from a flock of Tswana ewes and Boer does kept under a semi-intensive system of management at the Estate Management Unit (EMU) Sebele-Gaborone, in south-eastern Botswana. The flock grazed daily for eight hours on natural pasture and was housed at night in kraals with corrugated roofing. Sheep and goats were fed lucerne or groundnut hay as supplementary feeds in winter and drought periods. They were also provided with bonemeal and salt or dicalcium phosphate and salt mixture mixed in a 2:1 ratio as mineral lick. The flock was treated against ectoparasites, e.g. ticks once a week in summer and every other week in winter and endoparasites three times a year, i.e. every four months routinely. Flushing of the ewes and does was practised just before mating for two weeks. Mating occurred on pasture using two Tswana rams and two Boer bucks in May-June every year. Veterinary care was provided whenever necessary.

The parturition period was October-December every year; parturition records included sex, birth weight and type of birth. The analyses covered a five-year period (1989-93) and involved 170 lambings of 202 lambs and 152 kiddings of 288 kids. The parameters evaluated were age at first parturition (AFP), parturition interval (PI), birth weight (BOO) and type of birth (TB). Data were analysed using descriptive analysis for means and t-test used to test significant differences between means at P<0.05 (Steel and Torrie 1980).


BW, frequency of TB, stillbirth and preweaning mortality values are shown in Table 1. Sex was not a significant source of variation in lamb survival. There was a high incidence of multiple births in both species. Abortions and stillbirth incidences were very low in both species. The average birth weights of singles were higher (P<0.05) than those of twins. In most years the males were heavier (P<0.05) at birth than the females. There was poor correlation (r2 = 0.02 sheep and r2 = 0.04 goats) between dam's body weight and the young's birth weight in the flock.

Table 1. Mean and standard deviations of some reproductive parameters of Tswana ewes and Boer does.


Tswana sheep

Boer goats

Number of mature breeding females



Gestation period (days)



Age at first parturition (months)



Parturition interval (days)



Live weight of dam (kg)



Birth weight (kg)









3. 10±0.71













Frequency (%)



















Pre-weaning mortality (%) (1-3 months)



Prolificacy rate (%)



Productivity to weaning/ewe doe (%)




Tswana sheep can be improved genetically by careful selection, improved nutrition and management with a lambing interval of 365±28.50 days (Table 1). This study showed a gestation period of 150±0.23 days for sheep. Capote and Vazquez (1986) reported that the gestation length and lambing interval in Suffolk x Criollo ewes averaged 148.7 days and 318.2 days, respectively. They stated that 54% of the lambs born were females and 58% of the lambings occurred during the dry season. They concluded that neither sex of lamb, nor season of lambing had a significant effect on gestation length, but there was a significant interaction of type of lambing (single or twin) and sex of lamb. Adu et al (1985) studied the reproductive performance of Balami and Desert Sudanese sheep in a dry hot environment. They observed that lambing interval was significantly shorter in Desert Sudanese ewes than in Balami ewes (254 vs 279 days) but the number of lambs born per ewe per annum in both breeds was similar (1.6). This study showed age at first lambing of 18.00±1.39 months. Kabuga and Akovuah (1991) reported that age at first lambing averaged 506.2 days in Djallonké x Sahelian crossbred ewes. They found that the interval between parturitions averaged 279 days, and litter size and number of lambs produced per year averaged 1.1 and 1.5, respectively.

Age at first kidding of 18.00±0.67 months shows a short generation interval for the Boer goats. This is in line with 11.33±18.47 months reported by Husain et al (1990) for Bengal goats in Bangladesh. The kidding interval observed in this study averaged 350.00±2.4 days which is lower than the 451±16.6 days reported by Lawar et al (1991) for Angora goats in India and higher than the 274.2 and 293.6 days reported by Dickson et al (1990) for Anglo-Nubian and French Alpine goats, respectively.

Mean birth weight of 3.31±0.87 kg for Tswana lambs is higher than the 2.44 kg reported for Djallonké x Sahelian crossbred lambs by Kabuga and Akowuah (1991). The Boer kids recorded 3.23±0.76 kg for birth weight which is higher than the 1.47 kg reported for Bengal kids by Verma et al (1991). Boer goats are classified as medium sized breed by Devendra and McLeroy (1987). There was low abortion rate and preweaning mortality in both lambs and kids which could be due to the adequate management practices and the good veterinary care received on the farm.

Verma et al (1991) reported that litter size was not affected by parity in Black Bengal goats. They also found that the percentages of single, twin and triplet births were 74.7,24.0 and 1.3, respectively, in a herd of 20 female Bengal goats. Mellado et al (1991) reported the reproductive performance of 40 Anglo-Nubian female goats. They observed that the interval between kiddings averaged 301 days and prolificacy averaged 1.77. Multiple birth was very frequent in the herd over a five-year period. Maternal size in Tswana sheep and Boer goats did not influence young birth weight significantly. Milne (1987) reported that maternal size appears to become a less important determinant of energetic efficiency during gestation as litter size increases. Prolificacy rate of Boer goats in this study was 193.42%. This is higher than the 1.77 (177%) reported for Nubian goats in northern Mexico (Mellado et al 1991) where fecundity rate was found to be correlated with rainfall in the month preceeding mating.

Values obtained in this study are indications that Tswana sheep and Boer goats are highly productive under good management and productivity can be improved upon by planned breeding programmes. This will obviously increase the level of goat and sheep meat production for local consumption and export in Botswana.


The authors would like to express their gratitude to the management of Estate Management Unit (E.M.U.) at Sebele-Gaborone for permission to publish the data.


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