Foaling and mortality of equines in The Gambia: a national survey

By

J. Sowe¹, B. Gai², J. Sumberg² and E. Gilbert³

Ministry of Agriculture, The Gambia

¹Department of Animal Health and Production, Abuko, The Gambia.

²Planning Programming and Monitoring Unit, Banjul, The Gambia.

³Department of Agriculture, Cape St. Mary, The Gambia.

Abstract

A national survey of 642 Dabadas in The Gambia was conducted in December 190°7 to determine foaling and mortality rates for horses and donkeys. Foaling rates were estimated at 24% for horses and 29% for donkeys, while the overall mortality was 27% for both equine species. These figures, in conjunction with data on reported sales and purchases, indicate that the equine populations in The Gambia are not presently self-sustaining. The economic implications of low foaling and high mortality rates are explored. Three scenarios to make the equine populations self-sustaining by increasing foaling and/or decreasing mortality are presented.

Introduction

Equines have been present in The Gambia for some time; for example the 1909 livestock census reported national populations of over 1,500 horses and 4,000 donkeys (Colonial Secretary, 1909). However, apart from an occasional census, sample survey, or informal observation, there has been little quantitative information on their numbers, use, management, mortality or reproductive performance.

There are, nonetheless, a number of widespread beliefs about equines in The Gambia. This "common knowledge" might be summarized as follows: in the past the use of equines was limited by the disease trypanosomiasis; horses and donkeys were relatively inexpensive and were not expected to survive over long periods, much less reproduce. While the tsetse challenge has declined in recent years as a result of lower rainfall, it is believed that large numbers of equines are still imported from neighbouring countries, and that the sex (predominately male), age and condition of these imported animals may help explain the presumably poor reproductive performance of the country's horses and donkeys.

Equines, and particularly donkeys, are thought to have rapidly increased in popularity Starkey (1986) concluded that "during the period 1965 to 1985, donkeys changed from being of minor importance to their present status as the dominant draft animal in The Gambia." The extent and rapidity of this change is illustrated by the fact that in their wide ranging and highly detailed study of Gambian agriculture between 1972 and 1975, Dunsmore et al., (1976) who put significant emphasis on ox cultivation, make only passing reference to equines. The 1987/88 national draft animal populations were estimated at 13,000 horses, 28,000 donkeys and 20,000 oxen (PPMU/NASS, unpublished data).

The mortality and foaling of equines were identified as possible problem areas during a rapid reconnaissance survey carried out in 1986 by the Animal Traction Research Task-force of the Ministry of Agriculture (Cham et al., 1987). This present survey was carried out as an activity of this Animal Traction Task-force. The objective of the survey was to develop quantitative information concerning the population dynamics of horses and donkeys throughout The Gambia, including sex ratios, mortality and foaling rates.

Materials and methods

A questionnaire was developed to estimate populations of horses and donkeys, by age and sex, that were present in December 1987 and a year earlier in December 1986. In addition, information on the number of births, deaths, purchases, sales and other exchanges during the 12 month period between December 1986 and December 1987 was collected.

The survey utilised the national sample frame developed by the Planning, Programming and Monitoring Unit (PPMU) of the Ministry of Agriculture for its National Agricultural Sample Survey (NASS). This frame, which uses the Dabada (a Mandika word describing a subdivision of a compound) as the basic sampling unit, divides The Gambia into six divisions comprising 36 districts. Villages in each district are stratified by size (small, medium and large), with two villages being randomly selected from each strata. Three randomly selected Dabadas are sampled in each village, giving a total of 18 Dabadas per district or 648 Dabadas over the entire country. The PPMU/NASS sample frame was designed to enumerate approximately 2% of all Dabadas in The Gambia.

Immediately before the survey, PPMU field supervisors and enumerators were introduced to the objectives of the survey and the questionnaire form. The survey was conducted during the first three weeks of December, 1987.

The questionnaire sought to determine the number, sex and age of horses and donkeys present in each Dabada in December 1986 and December 1987. This is the time immediately following the harvest of groundnuts, a major event in the agricultural calendar, which was used to provide a convenient reference point for the respondents. All questionnaires were completed based on the recall of the Dabada head: no animals were actually counted by the field staff. Similarly, the classification of animals as adults or foals was based solely on the judgement of the respondents. In addition, information on all births, deaths, purchases, sales and other exchanges involving equines during the 12 month period was gathered.

Foaling and mortality rates were calculated on a district, division and national level as:

where:
F.R.	= Foaling rate
Foals born	= No. born, 12/86 to 12/87
AF86	= adult females, 12/86
AF87	= adult females, 12/87

where:
M.R.	= Mortality rate
Total died	= No. died, 12/86 to 12/87
Pop86	= Total population, 12/86
Purchases	= No. purchased, 12/86 to 12/87
Births	= No. born, 12/86 to 12/87
Sales	= No. sold, 12/86 to 12/87

where:
F. M.	= Foal mortality rate
Foals died	= No. died, 12/86 to 12/87
Foals 86	= Foal population, 12/86
Births	= Foals horn, 12/86 to 12/87
Purchases	= Foals purchased, 12/86 to 12187
Sales	= Foals sold, 12/86 to 12/87

Results

The reported population of equines in all sample Dabadas in December 1987 was 241 horses and 541 donkeys (Table 1). Overall, 23% of Dabadas reported having horses while 52% reported donkeys. The average number of horses per Dabada with horses ranged from 1.0 in Lower River to 1.8 in Upper River, while the number of donkeys per Dabada with donkeys ranged from 1.4 in Western to 2.2 in McCarthy Island (S).

Table 1: 1987 national equine survey in The Gambia

Division	Districts (no)	Dabadas sampled (no)	Horses (no)	Donkeys (no)	Percentage of Dabadas with
					Horses (%)	Donkeys (%)
Western	8	144	31	65	13	32
North Bank	7	125	73	99	38	54
Lower River	6	108	4	114	4	62
McCarthy Isl. (N)	5	89	44	73	33	56
McCarthy Isl. (S)	5	89	25	105	16	53
Upper River	5	87	64	85	41	64
The Gambia	36	642	241	541	23	52

Reported populations for December 1987

Table 2: Ratio of adult females to adult males

Division	Horses	Donkeys
Western	0.8	1.0
North Bank	0.9	0.8
Lower River	05	1.1
McCarthy Isl. (N)	0.9	1.3
McCarthy Isl. (S)	0.8	1.5
Upper River	1.5	1.2
The Gambia	1.0	1.1

Table 3: Foaling rates of horses and donkeys (% per anum)

Division	Horses	Donkeys
Western	60	42
North Bank	30	27
Lower River	0	31
McCarthy Isl. (N)	17	26
McCarthy Isl. (S)	21	30
Upper River	14	22
The Gambia	24	29

Fig. 1: Frequency distribution (percentage of all districts) of adult sex ratios for horses and donkeys.

The number of adult female horses per adult male ranged from 0.8 in Western, McCarthy Island (S) and McCarthy Island (N) to 1.5 in Upper River, and averaged 1.0 for The Gambia as a whole (Table 2). Adult female donkeys per adult male ranged from 0.8 in North Bank to 1.5 in McCarthy Island (S), and averaged 1.1 over the entire country. The frequency distributions of the number of adult females per adult male computed by district are shown in Figure 1. The approximately equal proportion of adult females and adult males in the December 1987 population is also reflected in the ratio of adult females and adult males purchased, which, on a national basis, was 1:1 for both horses and donkeys.

Foaling rates for horses ranged from 0% in Lower River to 60% in Western, and averaged 24% over the entire country (Table 3). Foaling rates for donkeys were generally higher than those of horses, ranging from 22% in Upper River to 42% in Western, and averaging 29% overall.

Overall mortality rates for horses ranged from 14% in McCarthy Island (S) to 67% in Lower River, and averaged 27% in The Gambia as a whole (Table 4). Similarly, mortality rates for donkeys ranged from 16% in Western to 33% in Lower River, and averaged 27% nationally. The mortality rates for foals were slightly higher than those of the population as a whole, averaging 35% for horse foals and 31% for donkey foals.

Table 4. Mortality rates of horses and donkeys (% per anum)

Division	Horses	Donkeys
Western	24	16
North Bank	25	23
Lower River	67	33
McCarthy Isl. (N)	19	30
McCarthy lsl. (S)	14	26
Upper River	33	26
The Gambia	27	27

Discussion

Variation in mortality and foaling rates must be interpreted with caution, particularly at the district level, because the samples often had small numbers of animals. This is especially true with horses, as illustrated by the 0% foaling rate in Lower River, which was based on an adult female population of only three. With such small numbers of animals the distributions of district level mortality and foaling rates are skewed toward very high and very low values, as can be seen in Fig. 2 for mortality rates. Nevertheless, the divisional and national estimates of mortality and foaling rates, which are generally based on larger numbers, are assumed to be accurate estimates of equine performance over the survey period.

Fig. 2: Frequency distribution (percentage of those districts with horses and donkeys) of mortality rates for horses and donkeys.

Table 5: Reported changes in equine populations between December 1986 and December 1987

	% of population in Dec. 1986
	Horses	Donkeys
Total population Dec. 86	100	100
	(259)	(624)
Births	+ 10	+ 12
Purchases	+ 21	+ 17
Sub-total	+ 31	+ 29
Deaths	- 34	- 32
Sales	- 4	- 8
Sub-total	- 38	- 40
Total population Dec. 87	93%	87%

Results from the survey indicate that during the year between December 1986 and December 1987 the populations of horses and donkeys in the sample Dabadas decreased by 7% and 13%, respectively (Table 5). In the face of what appear to be high mortality and low foaling rates, a significant number of equines were purchased. Without these purchases the populations of horses and donkeys would have decreased by approximately 24% and 20%, respectively. (This was calculated on the basis of "net purchase", which is defined as total purchases minus total sales, and is assumed to represent the number of animals "imported" into The Gambia.)

Since the survey covered only a single year it is impossible to judge if mortality and foaling rates such as these are typical. However, even if the survey tended to overestimate mortality and underestimate foaling, it is still apparent that the equine populations within The Gambia are capable of supporting little if any internal growth.

In a study of 365 donkeys in Mali, Wilson and Wagenaar (1982) estimated the foaling rate at 4045%. In his 1978 study on 449 donkeys in Darfur, Sudan, Wilson (1978) reported a sex ratio of 1:1. He classified 35% of the population as "breeding females" (over two years old judged on their teeth) and estimated the foaling rate at 65% - 70%. Lhoste (1983) reported that in the Sine Saloum region of Senegal, the percentage of adult female horses increased from 27% to 51% between 1973 and 1981. In the light of the common observation that there were until recently few female equines in The Gambia, it would appear that in the last few years the Gambian equine populations have gone through a structural transformation similar to that reported in Senegal.

Table 6: Estimated replacement costs for equines in The Gambia

	Horses	Donkeys	Total
Estimated population	13 000	28 000	41 000
Number of net purchasesa	2 210	2 520	4 730
Cost per animal (D)b	1200	300
Total cost (D x 1000)	2 652	756	3 408
Total cost ($ x 1000)	408	116	524

a) Net purchases = total purchases minus total sales
b) D = Dalasis = US$ 0.15

The survey provided few direct insights into factors that might affect mortality and foaling. Historically, trypanosomiasis has been considered a major health problem of equines in The Gambia. Relatively recent changes in rainfall, and continued destruction of tsetse habitat due to expanded agricultural activities are assumed to have allowed the spread and expanded use of equines. However, there may still be a sufficient tsetse challenge to cause mortality, or to adversely affect reproductive performance through chronic conditions. Other possible causes of mortality might include African horse sickness and lymphangitis.

Since horses and donkeys are often fed during the dry season with groundnut hay (a feed of reasonable quality) which is sometimes supplemented with millet or sorghum grain, it seems unlikely that poor nutrition would be a major factor related to either mortality of foaling.

Possible factors affecting foaling can be classified as either biological or management related. While the number of adult females per male, as shown in Table 2, suggests that there should be more than sufficient numbers of males for breeding purposes, the fact that equines are often owned and housed singly may prevent successful breeding. It is also possible that under some circumstances breeding is actively discouraged, since pregnancy is thought to necessitate some modification of work patterns.

There are important economic implications of high equine mortality and low foaling rates, and the resulting high level of purchases (Table 6). If national populations of 13,000 horses and 28,000 donkeys are assumed, the cost of "net purchases" during the survey period would have been 3.4 million Dalasis (US$524,300), or approximately 297 Dalasis per Dabada with horses and 38 Dalasis per Dabada with donkeys. It is important to note that this calculation does not allow for any growth in the population. If the foaling and mortality rates estimated from this survey are typical, it is clear that the dramatic increase in the use of equines over the last 15 years must have necessitated a very substantial cash outlay. It is noteworthy that during this period there have been no formal credit programmes geared to the purchase of equine draft animals. Thus, Gambian farmers appear to be using large amounts of cash, or perhaps going into debt, in order just to maintain their present number of equines. It is clear that reductions in mortality and increased foaling could have profound effects on cash flow and wealth among farmers using draft equines. It could also reduce the current high level of risk associated with equine ownership, and thereby make animal draft power more accessible to poorer Dabadas.

Table 7: Three possible scenarios to eliminate net purchases by increasing foaling rates and/or decreasing mortality rates

Scenario	Horses		Donkeys
	Change1 (%)	New rate2 (%)	Change1 (%)	New rate2 (%)
1. Decreasing mortality	- 35	18 (27)	- 30	19 (27)
2. Increasing foaling	+ 170	65 (24)	+ 75	50 (29)
3. Decreasing mortality	- 18	22	- 15	23
and increasing foaling	+ 85	44	+ 38	40

¹Change relative to current rate.
²Current mortality and foaling rates in parenthesis

Three possible scenarios for making the equine populations self-sustaining, and thus eliminating the need for importations, are presented in Table 7. Scenarios 1 and 2 rely on changing either mortality or foaling rate, while scenario 3 assumes changes in both foaling and mortality. In Scenario 3 it is assumed that changes in foaling and mortality will contribute equally to overcoming the deficit. It is evident that the need for the current level of "net purchases" could be eliminated with relatively smaller changes in mortality than foaling rate.

Conclusion

Further research is needed to determine the key factors affecting equine mortality and reproductive performance, and to identify and evaluate cost-effective interventions. Specifically, sample populations of horses and donkeys in districts and divisions with high mortality rates should initially be screened for the presence of trypanosomes, and then for signs of other diseases. In relation to foaling, perhaps the most important immediate task is to determine the role of current management practices by case studies of equine owners who have or have not successfully bred their animals. If management does not appear to be a major factor affecting reproductive performance, other factors such as disease, environmental or nutritional stress should be explored.

One immediate research and development goal might be to decrease mortality and/or increase foaling so that the Gambia's equine populations become self-sustaining. Table 6 provides quantitative estimates of the changes in mortality and foaling needed to achieve this goal, while Table 7 provides information against which the cost of various interventions could be evaluated.

Résumé

En décembre 1987, une enquête nationale portant sur 642 Dabadas a été menée en Gambie pour déterminer les taux de mortalité et de poulinage des chevaux et des ânes. Les taux de poulinage ont été estimé à 24% pour les chevaux et 29% pour les ânes. Le taux de mortalité de 27% est commun aux deux espèces. Ces chiffres, en corrélation avec les données enregistrées pour les achats et les ventes, indiquent qu'actuellement en Gambie le cheptel équin ne suffit pas à sa reproduction. Les conséquences économiques de cette situation sont actuellement étudiées. Trois stratégies sont envisagées pour accroître le taux de poulinage et/ou réduire le taux de mortalité.

Acknowledgments

In addition to the field and supervisory staff of the Planning Programming and Monitoring Unit, the contributions of the following individuals are gratefully acknowledged: M. Timajchy, P. O'Neil, A. Johnson and J. Rowe.

References

Cham P. and collaborators 1987. Report of the rapid reconnaissance survey/literature review conducted in January/February 1987 to identify research priorities. Animal Traction (ANTRAC) Working Group. Ministry of Agriculture, The Gambia. (E).

Colonial secretary 1909. Correspondence of the Colonial Secretary, Reference Nos. 2/140 2/143. Gambian National Archives, Banjul, The Gambia. (E).

Dunsmore J.R, Blair R.A., Lowe G.D.N., Moffat D.J., Anderson I.P., Williams J.B. 1976. The agricultural development of The Gambia: an agricultural, environmental and socioeconomic analysis. Land Resources Study 22, Land Resources Division, Overseas Development Administration, London, UK. (E).

Lhoste P. 1983. Développement de la traction animale et évolution des systèmes pastoraux au Sine Saloum, Sénégal. Rev. Elev. Med. Vet. Pays Trop. 36: 291-300. (F)

Starkey P. 1986. Strengthening animal traction research and development in The Gambia through networking. Consultancy Report 12, Gambian Agricultural Research and Diversification Project, Ministry of Agriculture, Banjul, The Gambia. (E).

Wilson R.T. 1978. Studies on the livestock of southern Darfur, Sudan. VI. Notes on equines. Tropical Animal Health and Production 10, 183-189. (E).

Wilson R.T. and Wagenaar K 1982. An introductory survey of livestock population demography and reproductive performance in the area on the Niger Range and Livestock Project. Arid Zone Programme Document. International Livestock Centre for Africa, Bamako, Mali. (E).