Trop. Anita. Hlth Prod. (1992) 24, 135-142
R E P R O D U C T I O N OF P I G S I N T H E H I L L S O F E A S T E R N NEPAL RUTH M. GATENBY' and PURNAB. CHEMJONG Pakhribas AgriculturalCentre, PO Box 106, Kathmandu, Nepal SUMMARY A survey oflOlfarmers with sows was conducted in the Koshi Hills of Nepal. Estimates of those reproductive traits which did not differ significantly between local and Pakhribas crossbred sows, are farrowing interval 7.4 months, litter size at birth 8"3, age of piglets at weaning 2.2 months and total number offarrowings 13.2. Local pigs reach sexual maturity sooner than Pakhribas crossbreds; age at first farrowing for the two genotypes is 10.7 and 12.0 months (P < 0.05), and age at first mating of boars is 6.5 and 7.4 months (P < 0.05). Sows farrow throughout the year and there is no clearly defined best season for farrowing. Pre-weaning mortality rates are estimated to be 22% for local piglets and 15% for Pakhribas crossbreds. Almost all farmers practise controlled mating in which either the sow is taken to the boar or the boar is brought to the sow. The proportion of farmers (with sows) who own a boar is only about 5 per cent.
INTRODUCTION Pigs are important domestic animals in the hills of Nepal yet have received little scientific attention. O1 (1986) and Gurung (1989) have studied growth and meat production of pigs but there have been no reports of reproductive aspects. There are an estimated 85,000 pigs in the Koshi Hills (Gurung et al., 1989). Forty-five per cent of farmers have pigs, though about half these only buy in pigs for fattening. Most of the farmers who have breeding herds have only one or 2 sows. The local pigs in the Koshi Hills are small and black. Fayuen, Tamworth, Saddleback, Hampshire and Yorkshire pigs have been interbred at Pakhribas Agricultural Centre to produce what is known as the Pakhribas breed. Pakhribas pigs are black, larger than the local pigs and distinguishable by their superior conformation. In 1988 the proportion of purebred and crossbred Pakhribas pigs in the Koshi Hills had reached 17% (Gurung et al., 1989). The aims of this study were to estimate the reproductive traits of local and Pakhribas crossbred pigs, to identify the most serious constraints and to suggest ways in which production could be improved. The results are likely to be of relevance in other countries with similar systems of smallholder pig husbandry. METHOD A survey of the reproduction of pigs was conducted between June and August 1988 in 22 panchayats in Bhojpur, Dhankuta, Terathurn and Sankhuwasabha Districts in eastern Nepal. Eleven field staff asked farmers a series of questions about the reproductive performance, mortality and system of mating of their pigs (Table I). The survey was conducted in Nepali and the farmers' reponses written on the questionnaire; the responses were translated into English and analysed on a microcomputer using Lotus 1-2-3. 1Presentaddress:Animal ResearchInstitute, PO Box 1, Galang, DeliSerdang, North Sumatra, Indonesia. 135
136
GATENBYAND CHEMJONG Txe~ I The questionnaire
PAC Survey 1988: REPRODUCTION OF PIGS Farmer's name: Panchayat and ward: Breed: Local/Pakhribas cross/Pakhribas I. In which months are there most farrowings? 2. Which are the best months for farrowing? 3. What is the interval between farrowings? 4. What is the average litter size? 5. What is the age at weaning? 6. What is the preweaning mortality? 7. What are the main causes of preweaning mortality? 8. What is the age at which boars are first used for mating? 9. What is the age at which sows first give birth? 10. What is [he total number of farrowings in the life of a sow? 11. For what reason are sows culled? 12. What is the system of mating: uncontrolled sow taken to boar when oestrus observed boar brought to sow when oestrus observed artificial insemination 13. Do you have your own boar? If noL do you pay for a service by a boar? Name of interviewer: Date:
RESULTS A total o f 10l farmers were interviewed, 53 with local sows, 41 with Pakhribas crossbred sows and 7 with purebred Pakhribas sows, F o r simplicity o f analysis the information gathered for the purebred Pakhribas pigs was grouped together with that f r o m the larger n u m b e r o f crossbred pigs, and in this paper the composite g r o u p is designated "Pakhribas crossbreds". Farrowing interval The farmers' estimates o f farrowing interVal are summarised in Table II. F o r both local and Pakhribas crossbred sows the mean farrowing interval is 7.4 months. The gestation period o f pigs is 114 days or 3.8 months. This means that the sows conceive an average o f 3.6 m o n t h s after farrowing. Litter size The farmers' estimates o f litter size at birth ranged f r o m 4 to fourteen. The mean is 7-9 for local and 8.8 for Pakhribas crossbred sows (Table II). These means are not significantly different and the overall m e a n litter size is 8.3. Litter sizes o f local, imported ( E u r o p e a n type) and crossbred sows o n experimental stations in Thailand range f r o m 5.0 to 8.7, and those in Taiwan f r o m 7.4 to 9-7 (Koh, 1981). In the S o l o m o n Islands the mean litter size is only 5.1 (Fredrick, 1977). These figures suggest that the size o f litters in the K o s h i Hills is reasonably
high.
PIGS IN NEPAL
137
TABLEII Reproductive traits of local and Pakhribas crossbred pigs Pakhribas crossbred
Local
Farrowing interval (months) Litter size Age at first farrowing (months) Age at first mating of boar (months) Age at weaning (months) Total number of farrowings
n
Mean + s.d. (months)
n
Mean 5: s.d. (months)
Difference between means
51
7.4 + 2.14
44
7.4 _+ 2.21
NS
53 51
7.9 + 1.86 10-7 + 1.64
48 48
8.8 _+ 2.15 12"0 + 2-63
NS P < 0.05
52
6.5 + 1.76
48
7-4 _ 2.48
P < 0.05
53
2.3 _+ 0.62
47
2-1 + 0.70
NS
52
13.0 _ 4.58
42
13.5 _+ 4.58
NS
Age at sexual m a t u r i t y T h e age a t first f a r r o w i n g averages 10.7 m o n t h s for local sows a n d 12-0 m o n t h s for P a k h r i b a s c r o s s b r e d s (Table II). T h e m e a n age at which b o a r s are first used for m a t i n g is 6.5 m o n t h s for local pigs a n d 7-4 m o n t h s for crossbreds. T h e differences between these m e a n s are significantly different ( P < 0.05), i n d i c a t i n g t h a t local pigs reach sexual m a t u r i t y m o r e r a p i d l y t h a n c r o s s b r e d pigs.
Season of farrowing T o e v a l u a t e the f a r m e r s ' statements a b o u t the season o f farrowing, each f a r m e r was given a score o f one which was d i s t r i b u t e d evenly between the m o n t h s he specified. T h e seasonal p a t t e r n o f f a r r o w i n g is s h o w n in Fig. 1. Sows f a r r o w in all m o n t h s o f the y e a r b u t there are m o r e farrowings in the d r y season b e t w e e n D e c e m b e r a n d M a y t h a n in the rest o f the year.
r-
I.I-
0
, J FNAN
J J ASON
D
Month FIe. 1. Seasonal pattern of farrowing. Because Nepali months begin halfway through each English month, the abbreviations on the X-axis refer to the period beginning in the middle of the specified English month. Thus J is January-February, F is February-March, etc.
138
GATENBY AND CHEMJONG
I
g 101-
"
0
It-7Mr--7
11I!i
J FHAM J J A SOND Month FiG. 2. Optimal season for farrowing.
The farmers':statements about the best season for farrowing are summarised in Fig. 2. The best months are August and September followed by January and February. These months are in the monsoon and in the dry winter season respectively. Few farmers thought that sows should farrow between March and June at the end of the dry season when food supplies are very limited. It appears that provided there is adequate food for the sow and her litter, farrowing can take place in any season without serious problems. This is not the case for cattle and buffaloes in the Koshi hills in which calving between October and April is detrimental (Gatenby et al., 1989).
Weaning The mean age at weaning is 2.2 months (Table II). This is not significantly affected by breed of sow. At Pakhribas Agricultural Centre piglets are routinely weaned at 1.5 months. This practice could be adopted in villages provided that adequate food is available for the young piglets. The data on pre-weaning mortality rates are summarised in Table III. Some farmers estimated the percentage mortality rates of their piglets (a and b in Table III), some stated the usual number of piglets dying in each litter (c to f), some stated that piglets died but did not state how many (h) and some said there was no mortality of piglets (i). The overall mean mortality rate was calculated to be 18 per cent. Mortality is higher for local piglets (22%) than for Pakhribas crossbreds (15%). This may be because farmers look after their crossbred piglets more carefully. The major causes of mortality in piglets are (i) lack of milk, (ii) overlying by the sow and (iii) disease. These factors are interrelated; a piglet which is getting little milk is likely to become ill and be overlaid by the sow.
Mating Approximately half the farmers took their sow to the boar for mating and half brought the boar to the sow. Only one farmer reported uncontrolled mating. Only 4. of the farmers with local sows and 2 of the farmers with crossbred sows owned a boar. In one case the ownership of a boar was shared between 2 farmers. Thus the proportion of farmers owning a boar is about 5 per cent.
PIGS IN NEPAL
139
TABLEIII Pre-weaning mortality rates of piglets
(a) (b) (e) (d) (e) (f) (g) (h) (i) (j) (k)
Number of farmers specifying mortality rate as a percentage Mean mortality rate specified(%) Number of farmers specifying number of piglets dead per litter Mean number of piglets dead per litter Mean litter size (Table II) Mean mortality rate calculated (%)= IOO x die Weightedmean of mortality rates b and f (%) Number of farmers stating mortality is observed, but not estimating rate Number of farmers who stated mortality was zero in their herds Total number of replies = a + e + h +i Overallmean mortality rate (%) = g(a + e + h)/j
Local
Paldaribas crossbred
7
4
11.4
3.3 20
26
All
2.5
2.2
7.9 31.6
8-8 25.0
27.4
21.4
4
4
10
13
47
41
88
21.5
14-6
18-3
Farmers are reluctant to keep a boar because of the cost, particularly o f food. Whether they are sold or kept by the breeder, mate pigs are castrated soon after puberty and fattened for meat production. The consequences o f this are (i) there may not be an uncastrated male in the vicinity when a sow is in oestrus so that farrowing intervals are longer than necessary; (ii) young boars which have not yet been castrated serve sows which are close relatives so that inbreeding results, with consequences of lower productivity and reduced vigour and (iii) improved boars distributed by breed improvement programmes tend to be castrated and fattened instead of being used for breeding. O f the 95 farmers who did not own a b o a r 16 (i.e. 17%) obtain the services of a neighbour's boar free of cost, while the remaining 79 farmers (83%) pay for service. In some villages service was generally free while in others payment was the norm. In some cases payment is made in the form of one piglet from the resulting litter. The fact that most farmers pay for service by a b o a r means that there is scope for breed improvement by schemes in which a farmer with a superior b o a r charges for services at a rate which enables him to recoup the cost of its maintenance. Lifetime p r o d u c t i v i t y The farmers' estimates of total number of farrowings o f each sow are summarised in Table II. F o r both local a n d crossbred sows the mean number of farrowings is about thirteen. The age at culling can be calculated from the total number of farrowings, farrowing interval and age at first farrowing according to: AC = (TF x FI/12) + AFF[12 where: AC is age at culling (years); T F is total number o f farrowings; F I is farrowing interval (months); and A F F is age at first farrowing (months). The ages at culling calculated using this equation are 8.9 years for local sows and 9.3 years for crossbred sows.
140
GATENBY AND CHEMJONG
Most farmers cull sows when they become old and their productivity is lowered although problems of management such as housing and food supply are also important. A significant proportion said they sold a sow when they needed money. Few mentioned disease as a reason for culling.
Ethnic group of pig farmers The ethnic group of each farmer was determined from his or her name. The most numerous ethnic groups in the survey were Rai (37 farmers) and Limbu (32 farmers). There were a total of 15 farmers from other hill ethnic groups and 13 from occupational and other castes. There were no Brahmin, Chhetri or Newar farmers in the survey even though these groups account for about 37% of the population in the Koshi Hills. People of these ethnic groups observe religious restrictions on keeping pigs and eating pig meat. DISCUSSION
Pigs have great potential for rapid reproduction compared with ruminants but to do this successfuly a good supply of high quality food is needed. One or 2 sows fit well into the farming' system. They consume brewing residues, household waste and limited quantities of other foods. There is little scope for the development of large herds of pigs on the small farms in the hills of Nepal partly because of inadequate food supplies and partly because of the limited market. Ethnic traditions limit pig-keeping in Nepal although a few Chhetri, Brahmin and Newar families are starting to keep pigs because they appreciate the economic possibilities.
Potential for improving reproductive rate After farrowing sows come into oestrus for the first time about one week after their piglets are weaned. As weaning takes place at an average age of 2.2 months, this means that most sows could be mated and conceive within 2.4 months of farrowing. In contrast the present weaning-to-conception interval is 3-6 months. This indicates that the majority of sows are not mated at the first oestrus and a large proportion are not mated at the second oestrus, 3 weeks later. If earlier mating could be achieved farrowing interval could, in theory, be reduced to 6.2 months without changing the age at weaning. If weaning age was reduced to 1.5 months, farrowing intervals could be only 5.6 months. Thus each sow would produce 2 litters per year. The reasons why sows are not rapidly remated after their piglets are weaned are probably managemental rather than nutritional or physiological. Oestrus may not be observed, or if it is, the boar is not introduced to the sow. Extension effort needs to be given to make sure that farmers expect their sows to come into oestrus shortly after weaning, and heat detection techniques should be demonstrated. Disease appears to be of relatively little importance in reducing productivity, either through piglet mortality or as a reason for culling sows. Previous work in other countries has shown that most deaths occur in the first week of life and thereafter mortality rate declines. Nutrition of the sow has a large effect on piglet mortality (Holness and Smith, 1974). Nutritional levels for sows need to be boosted otherwise the benefits of reduced farrowing interval may be offset by high levels of piglet mortality as well as a reduction in litter size. Also high quality food must be provided to piglets if they are to be weaned at a younger age.
PIGS IN NEPAL
141
Comparison of local and crossbred sows Pakhribas pigs reach puberty at a later age than the locals, but have slightly lower pre-weaning mortality rates. The 2 genotypes do not differ significantly in farrowing interval, litter size, age at weaning or total number of iarrowings. The annual production of piglets can be calculated from farrowing interval, litter size and piglet mortality rate. Local sows produce an estimated 10-1 piglets per year whereas Pakhribas crossbreds produce about 12.2. The advantage of crossbreds is substantial as crossbred piglets are bigger than local piglets and have greater growth potential. However, it must be remembered that crossbreds are considerably larger than local pigs (Gatenby et al., 1988) so they need more food. ACKNOWLEDGEMENTS
We thank the field staff, namely T. P. Bimoli, Miss L. D. Gautam, K. K. Karki, R, B. Magar, H. Poudel, T. B. Rai, T. D. Rai, T. S. Rai, M. B. Shrestha, M. P. Shrestha and B. K. Singh, for conducting the survey. We also thank S. K. Chimariya for translating the farmers' responses into English. Accepted for publication June 1991 REFERENCES FREDRICK, D. F. DE (1977). Tropical Animal Health and Production, 9, 113-123. GAT~,~BY, R. M., NEoPAN'E,S. P. & SHRESTHA,N. P. (1988). Description of farm animals in the Koshi Hills. Technical paper 98. Pakhribas Agricultural Centre, Dhankuta, Nepal. GAT~'NBY,R. M., ~ O N G , P. B. & PAKH~N, B. (1989). Reproduction of buffaloes and cattle in the Koshi Hills. Technical paper 118. Pakhribas Agricultural Centre, Dhankuta, Nepal. GtmUNG, H. B. (1989). A study on the growth rate of local, crossbred and exotic breeds of pigs and carcass evaluation of local pigs. Technical paper 116. Pakhribas Agricultural Centre, Dhankuta, Nepal. GtmUNG, H. B., GATe,Y, R. M., NEOPANE, $. P., SH~THA, N. P. & CH~OONG, P. B. (1989). Numbers of animals on farms in the Koshi Hills. Technical paper 109. Pakhribas Agricultural Centre, Dhankuta, Nepal. HOLN~S, D. H. & SMITH, A. J. (1974). Rhodesian Journal of Agricultural Research, 12, 27-42. KOH, F. K. (1981). Evaluation of animal genetic resources in Asia and Oceania. (Eds J. S. F. Barker, T. K. Mukherjee, H. N. Turner and S. Sivarajasingam). Proceedings of the second SABRAO workshop on Animal Genetic Resources. Kuala Lumpur, May 1981. pp 121-127. OLI, K. P. (1986). Comparative study of carcass yields of different breeds of pigs in the eastern hills of Nepal. Technical paper 90. Pakhribas Agricultural Centre, Dhankuta, Nepal. REPRODUCTION DES PORCS DANS LES COLLINES DE L'EST DU NEPAL R~sum~---Une enqu~te portant sur 101 fermiers poss~dant des trnies a ~t~ conduite dans les collines de Koshi au N~pal. Les caract~ristiques estim~es de ces reproductions, qui ne different pas significativement entre les truies de race locale et les croisements Pakhribas, sont pour l'intervalle de raise bas de 7,4 mois, 8,3 porcelets par pottle, 2,2 mois pour l'fige au sewage et un nombre total de mise bas de 13,2. Les pores de race locale atteignent la maturit~ sexuelle plus t6t que les croisements Pakhribas. L'fige ~i la premiere raise bas pour los deux #notypes est de 10,7 et 12,0 mois (P < 0,05), l'fige au premier accouplement pour les verrats est de 6,5 et 7,4 mois pour P < 0,05, respectivement. Les trnies mettent bas toute l ' a n n ~ et il n'existe pas, ~ cet ~gard, de saison optimale clairement individualis~. Les taux de mortalit~ avant sevrage sont estim~s 422 p. I00 pour la race locale et ~ 15 p. I00 pour les croisements Pakhribas. Presque tousles fermiers pratiquent le contr61e des saillies pendant lequel la trnie est conduite au verrat ou inversement. La proportion des fermiers ayant des truies et poss&iant aussi des verrats n'est que de 5 p. I00. REPRODUCCION DE CERDOS EN LA ALTURAS DE NEPAL ORIENTAL Resumen---Se llev6 a cabo un estudio de 101 porquerizas en las alturas Koshi de Nepal. Los indices zoot~nicos reproductivos, que no difirieron significativamente entre hembras locales y cruzadas Pakhribas fueron, intervalo entre partos 7.4 meses, tamafio de la camada al nacimiento 8-3, edad de los cerdos al destete 2-2 meses y nfmero total de partos 13-2. Los cerdos locales alcanzaron la madurez sexual mils rfipido que los cruzados. La edad al primer parto de los dos genotipos rue de 10.7 y 12"0 meses (P < 0.05),
142
GATENBY AND CHEMJONG
y la edad a la primera monta de los machos fue de 6-5 y 7.4 meses (P < 0-05).
No hubo tma estaeirn del afio definidapara la parieibn. La mortalidad antes del destete se estim6 eta 22% para los ecrdos locales yen 15% para los cruces. Casi todos los eerdos praetiean monta eontrolada, eta donde la hembra r llevada al macho, o el macho a la hembra. La proporeirn de fmquerosque tienen reproduetor r de apcnas einco pot eiento.
BOOK REVIEW Review Scientifique et Technique de I'OIE. Vol. 10, No. 3, September 1991. Animals, pathogens and the environment. Office International des Epizooties. 1991. 352 pp. Soft back, FF175, US$32. ISBN 92-9044-297-2. This issue, in the continuing series o f extremely informative review papers, considers the topical subject of the impact which animal populations, or their health status, may have on the environment. Part 1, comprising 7 papers, considers the relationship between animals and their environment. There are two papers that have particular relevance to the tropics where the role of livestock in the process o f desertification (English summary only) and the impact of large scale aquaculture are considered. Part 2 comprises 9 papers which consider various aspects of the relationship between animal pathogens and the environment. The information provides a valuable guide to the role o f environmental factors in the development, circulation and survival o f pathogens and transmission routes to susceptible animal and human hosts. One paper, which describes methods for environmental protection during animal disease eradication programmes, will be of particular interest to managers o f large scale disease control projects. Although by no means a comprehensive treatise of all aspects o f the topic addressed this review is recommended reading. The issue provides a unique collection of papers on the changing relationship in the classic disease triad of host, agent and environmental factors and highlights the role o f contemporary animal husbandry practices as a prime mover in this change. C. J . D a b o r n
R E P R O D U C T I O N OF P I G S I N T H E H I L L S O F E A S T E R N NEPAL RUTH M. GATENBY' and PURNAB. CHEMJONG Pakhribas AgriculturalCentre, PO Box 106, Kathmandu, Nepal SUMMARY A survey oflOlfarmers with sows was conducted in the Koshi Hills of Nepal. Estimates of those reproductive traits which did not differ significantly between local and Pakhribas crossbred sows, are farrowing interval 7.4 months, litter size at birth 8"3, age of piglets at weaning 2.2 months and total number offarrowings 13.2. Local pigs reach sexual maturity sooner than Pakhribas crossbreds; age at first farrowing for the two genotypes is 10.7 and 12.0 months (P < 0.05), and age at first mating of boars is 6.5 and 7.4 months (P < 0.05). Sows farrow throughout the year and there is no clearly defined best season for farrowing. Pre-weaning mortality rates are estimated to be 22% for local piglets and 15% for Pakhribas crossbreds. Almost all farmers practise controlled mating in which either the sow is taken to the boar or the boar is brought to the sow. The proportion of farmers (with sows) who own a boar is only about 5 per cent.
INTRODUCTION Pigs are important domestic animals in the hills of Nepal yet have received little scientific attention. O1 (1986) and Gurung (1989) have studied growth and meat production of pigs but there have been no reports of reproductive aspects. There are an estimated 85,000 pigs in the Koshi Hills (Gurung et al., 1989). Forty-five per cent of farmers have pigs, though about half these only buy in pigs for fattening. Most of the farmers who have breeding herds have only one or 2 sows. The local pigs in the Koshi Hills are small and black. Fayuen, Tamworth, Saddleback, Hampshire and Yorkshire pigs have been interbred at Pakhribas Agricultural Centre to produce what is known as the Pakhribas breed. Pakhribas pigs are black, larger than the local pigs and distinguishable by their superior conformation. In 1988 the proportion of purebred and crossbred Pakhribas pigs in the Koshi Hills had reached 17% (Gurung et al., 1989). The aims of this study were to estimate the reproductive traits of local and Pakhribas crossbred pigs, to identify the most serious constraints and to suggest ways in which production could be improved. The results are likely to be of relevance in other countries with similar systems of smallholder pig husbandry. METHOD A survey of the reproduction of pigs was conducted between June and August 1988 in 22 panchayats in Bhojpur, Dhankuta, Terathurn and Sankhuwasabha Districts in eastern Nepal. Eleven field staff asked farmers a series of questions about the reproductive performance, mortality and system of mating of their pigs (Table I). The survey was conducted in Nepali and the farmers' reponses written on the questionnaire; the responses were translated into English and analysed on a microcomputer using Lotus 1-2-3. 1Presentaddress:Animal ResearchInstitute, PO Box 1, Galang, DeliSerdang, North Sumatra, Indonesia. 135
136
GATENBYAND CHEMJONG Txe~ I The questionnaire
PAC Survey 1988: REPRODUCTION OF PIGS Farmer's name: Panchayat and ward: Breed: Local/Pakhribas cross/Pakhribas I. In which months are there most farrowings? 2. Which are the best months for farrowing? 3. What is the interval between farrowings? 4. What is the average litter size? 5. What is the age at weaning? 6. What is the preweaning mortality? 7. What are the main causes of preweaning mortality? 8. What is the age at which boars are first used for mating? 9. What is the age at which sows first give birth? 10. What is [he total number of farrowings in the life of a sow? 11. For what reason are sows culled? 12. What is the system of mating: uncontrolled sow taken to boar when oestrus observed boar brought to sow when oestrus observed artificial insemination 13. Do you have your own boar? If noL do you pay for a service by a boar? Name of interviewer: Date:
RESULTS A total o f 10l farmers were interviewed, 53 with local sows, 41 with Pakhribas crossbred sows and 7 with purebred Pakhribas sows, F o r simplicity o f analysis the information gathered for the purebred Pakhribas pigs was grouped together with that f r o m the larger n u m b e r o f crossbred pigs, and in this paper the composite g r o u p is designated "Pakhribas crossbreds". Farrowing interval The farmers' estimates o f farrowing interVal are summarised in Table II. F o r both local and Pakhribas crossbred sows the mean farrowing interval is 7.4 months. The gestation period o f pigs is 114 days or 3.8 months. This means that the sows conceive an average o f 3.6 m o n t h s after farrowing. Litter size The farmers' estimates o f litter size at birth ranged f r o m 4 to fourteen. The mean is 7-9 for local and 8.8 for Pakhribas crossbred sows (Table II). These means are not significantly different and the overall m e a n litter size is 8.3. Litter sizes o f local, imported ( E u r o p e a n type) and crossbred sows o n experimental stations in Thailand range f r o m 5.0 to 8.7, and those in Taiwan f r o m 7.4 to 9-7 (Koh, 1981). In the S o l o m o n Islands the mean litter size is only 5.1 (Fredrick, 1977). These figures suggest that the size o f litters in the K o s h i Hills is reasonably
high.
PIGS IN NEPAL
137
TABLEII Reproductive traits of local and Pakhribas crossbred pigs Pakhribas crossbred
Local
Farrowing interval (months) Litter size Age at first farrowing (months) Age at first mating of boar (months) Age at weaning (months) Total number of farrowings
n
Mean + s.d. (months)
n
Mean 5: s.d. (months)
Difference between means
51
7.4 + 2.14
44
7.4 _+ 2.21
NS
53 51
7.9 + 1.86 10-7 + 1.64
48 48
8.8 _+ 2.15 12"0 + 2-63
NS P < 0.05
52
6.5 + 1.76
48
7-4 _ 2.48
P < 0.05
53
2.3 _+ 0.62
47
2-1 + 0.70
NS
52
13.0 _ 4.58
42
13.5 _+ 4.58
NS
Age at sexual m a t u r i t y T h e age a t first f a r r o w i n g averages 10.7 m o n t h s for local sows a n d 12-0 m o n t h s for P a k h r i b a s c r o s s b r e d s (Table II). T h e m e a n age at which b o a r s are first used for m a t i n g is 6.5 m o n t h s for local pigs a n d 7-4 m o n t h s for crossbreds. T h e differences between these m e a n s are significantly different ( P < 0.05), i n d i c a t i n g t h a t local pigs reach sexual m a t u r i t y m o r e r a p i d l y t h a n c r o s s b r e d pigs.
Season of farrowing T o e v a l u a t e the f a r m e r s ' statements a b o u t the season o f farrowing, each f a r m e r was given a score o f one which was d i s t r i b u t e d evenly between the m o n t h s he specified. T h e seasonal p a t t e r n o f f a r r o w i n g is s h o w n in Fig. 1. Sows f a r r o w in all m o n t h s o f the y e a r b u t there are m o r e farrowings in the d r y season b e t w e e n D e c e m b e r a n d M a y t h a n in the rest o f the year.
r-
I.I-
0
, J FNAN
J J ASON
D
Month FIe. 1. Seasonal pattern of farrowing. Because Nepali months begin halfway through each English month, the abbreviations on the X-axis refer to the period beginning in the middle of the specified English month. Thus J is January-February, F is February-March, etc.
138
GATENBY AND CHEMJONG
I
g 101-
"
0
It-7Mr--7
11I!i
J FHAM J J A SOND Month FiG. 2. Optimal season for farrowing.
The farmers':statements about the best season for farrowing are summarised in Fig. 2. The best months are August and September followed by January and February. These months are in the monsoon and in the dry winter season respectively. Few farmers thought that sows should farrow between March and June at the end of the dry season when food supplies are very limited. It appears that provided there is adequate food for the sow and her litter, farrowing can take place in any season without serious problems. This is not the case for cattle and buffaloes in the Koshi hills in which calving between October and April is detrimental (Gatenby et al., 1989).
Weaning The mean age at weaning is 2.2 months (Table II). This is not significantly affected by breed of sow. At Pakhribas Agricultural Centre piglets are routinely weaned at 1.5 months. This practice could be adopted in villages provided that adequate food is available for the young piglets. The data on pre-weaning mortality rates are summarised in Table III. Some farmers estimated the percentage mortality rates of their piglets (a and b in Table III), some stated the usual number of piglets dying in each litter (c to f), some stated that piglets died but did not state how many (h) and some said there was no mortality of piglets (i). The overall mean mortality rate was calculated to be 18 per cent. Mortality is higher for local piglets (22%) than for Pakhribas crossbreds (15%). This may be because farmers look after their crossbred piglets more carefully. The major causes of mortality in piglets are (i) lack of milk, (ii) overlying by the sow and (iii) disease. These factors are interrelated; a piglet which is getting little milk is likely to become ill and be overlaid by the sow.
Mating Approximately half the farmers took their sow to the boar for mating and half brought the boar to the sow. Only one farmer reported uncontrolled mating. Only 4. of the farmers with local sows and 2 of the farmers with crossbred sows owned a boar. In one case the ownership of a boar was shared between 2 farmers. Thus the proportion of farmers owning a boar is about 5 per cent.
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TABLEIII Pre-weaning mortality rates of piglets
(a) (b) (e) (d) (e) (f) (g) (h) (i) (j) (k)
Number of farmers specifying mortality rate as a percentage Mean mortality rate specified(%) Number of farmers specifying number of piglets dead per litter Mean number of piglets dead per litter Mean litter size (Table II) Mean mortality rate calculated (%)= IOO x die Weightedmean of mortality rates b and f (%) Number of farmers stating mortality is observed, but not estimating rate Number of farmers who stated mortality was zero in their herds Total number of replies = a + e + h +i Overallmean mortality rate (%) = g(a + e + h)/j
Local
Paldaribas crossbred
7
4
11.4
3.3 20
26
All
2.5
2.2
7.9 31.6
8-8 25.0
27.4
21.4
4
4
10
13
47
41
88
21.5
14-6
18-3
Farmers are reluctant to keep a boar because of the cost, particularly o f food. Whether they are sold or kept by the breeder, mate pigs are castrated soon after puberty and fattened for meat production. The consequences o f this are (i) there may not be an uncastrated male in the vicinity when a sow is in oestrus so that farrowing intervals are longer than necessary; (ii) young boars which have not yet been castrated serve sows which are close relatives so that inbreeding results, with consequences of lower productivity and reduced vigour and (iii) improved boars distributed by breed improvement programmes tend to be castrated and fattened instead of being used for breeding. O f the 95 farmers who did not own a b o a r 16 (i.e. 17%) obtain the services of a neighbour's boar free of cost, while the remaining 79 farmers (83%) pay for service. In some villages service was generally free while in others payment was the norm. In some cases payment is made in the form of one piglet from the resulting litter. The fact that most farmers pay for service by a b o a r means that there is scope for breed improvement by schemes in which a farmer with a superior b o a r charges for services at a rate which enables him to recoup the cost of its maintenance. Lifetime p r o d u c t i v i t y The farmers' estimates of total number of farrowings o f each sow are summarised in Table II. F o r both local a n d crossbred sows the mean number of farrowings is about thirteen. The age at culling can be calculated from the total number of farrowings, farrowing interval and age at first farrowing according to: AC = (TF x FI/12) + AFF[12 where: AC is age at culling (years); T F is total number o f farrowings; F I is farrowing interval (months); and A F F is age at first farrowing (months). The ages at culling calculated using this equation are 8.9 years for local sows and 9.3 years for crossbred sows.
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Most farmers cull sows when they become old and their productivity is lowered although problems of management such as housing and food supply are also important. A significant proportion said they sold a sow when they needed money. Few mentioned disease as a reason for culling.
Ethnic group of pig farmers The ethnic group of each farmer was determined from his or her name. The most numerous ethnic groups in the survey were Rai (37 farmers) and Limbu (32 farmers). There were a total of 15 farmers from other hill ethnic groups and 13 from occupational and other castes. There were no Brahmin, Chhetri or Newar farmers in the survey even though these groups account for about 37% of the population in the Koshi Hills. People of these ethnic groups observe religious restrictions on keeping pigs and eating pig meat. DISCUSSION
Pigs have great potential for rapid reproduction compared with ruminants but to do this successfuly a good supply of high quality food is needed. One or 2 sows fit well into the farming' system. They consume brewing residues, household waste and limited quantities of other foods. There is little scope for the development of large herds of pigs on the small farms in the hills of Nepal partly because of inadequate food supplies and partly because of the limited market. Ethnic traditions limit pig-keeping in Nepal although a few Chhetri, Brahmin and Newar families are starting to keep pigs because they appreciate the economic possibilities.
Potential for improving reproductive rate After farrowing sows come into oestrus for the first time about one week after their piglets are weaned. As weaning takes place at an average age of 2.2 months, this means that most sows could be mated and conceive within 2.4 months of farrowing. In contrast the present weaning-to-conception interval is 3-6 months. This indicates that the majority of sows are not mated at the first oestrus and a large proportion are not mated at the second oestrus, 3 weeks later. If earlier mating could be achieved farrowing interval could, in theory, be reduced to 6.2 months without changing the age at weaning. If weaning age was reduced to 1.5 months, farrowing intervals could be only 5.6 months. Thus each sow would produce 2 litters per year. The reasons why sows are not rapidly remated after their piglets are weaned are probably managemental rather than nutritional or physiological. Oestrus may not be observed, or if it is, the boar is not introduced to the sow. Extension effort needs to be given to make sure that farmers expect their sows to come into oestrus shortly after weaning, and heat detection techniques should be demonstrated. Disease appears to be of relatively little importance in reducing productivity, either through piglet mortality or as a reason for culling sows. Previous work in other countries has shown that most deaths occur in the first week of life and thereafter mortality rate declines. Nutrition of the sow has a large effect on piglet mortality (Holness and Smith, 1974). Nutritional levels for sows need to be boosted otherwise the benefits of reduced farrowing interval may be offset by high levels of piglet mortality as well as a reduction in litter size. Also high quality food must be provided to piglets if they are to be weaned at a younger age.
PIGS IN NEPAL
141
Comparison of local and crossbred sows Pakhribas pigs reach puberty at a later age than the locals, but have slightly lower pre-weaning mortality rates. The 2 genotypes do not differ significantly in farrowing interval, litter size, age at weaning or total number of iarrowings. The annual production of piglets can be calculated from farrowing interval, litter size and piglet mortality rate. Local sows produce an estimated 10-1 piglets per year whereas Pakhribas crossbreds produce about 12.2. The advantage of crossbreds is substantial as crossbred piglets are bigger than local piglets and have greater growth potential. However, it must be remembered that crossbreds are considerably larger than local pigs (Gatenby et al., 1988) so they need more food. ACKNOWLEDGEMENTS
We thank the field staff, namely T. P. Bimoli, Miss L. D. Gautam, K. K. Karki, R, B. Magar, H. Poudel, T. B. Rai, T. D. Rai, T. S. Rai, M. B. Shrestha, M. P. Shrestha and B. K. Singh, for conducting the survey. We also thank S. K. Chimariya for translating the farmers' responses into English. Accepted for publication June 1991 REFERENCES FREDRICK, D. F. DE (1977). Tropical Animal Health and Production, 9, 113-123. GAT~,~BY, R. M., NEoPAN'E,S. P. & SHRESTHA,N. P. (1988). Description of farm animals in the Koshi Hills. Technical paper 98. Pakhribas Agricultural Centre, Dhankuta, Nepal. GAT~'NBY,R. M., ~ O N G , P. B. & PAKH~N, B. (1989). Reproduction of buffaloes and cattle in the Koshi Hills. Technical paper 118. Pakhribas Agricultural Centre, Dhankuta, Nepal. GtmUNG, H. B. (1989). A study on the growth rate of local, crossbred and exotic breeds of pigs and carcass evaluation of local pigs. Technical paper 116. Pakhribas Agricultural Centre, Dhankuta, Nepal. GtmUNG, H. B., GATe,Y, R. M., NEOPANE, $. P., SH~THA, N. P. & CH~OONG, P. B. (1989). Numbers of animals on farms in the Koshi Hills. Technical paper 109. Pakhribas Agricultural Centre, Dhankuta, Nepal. HOLN~S, D. H. & SMITH, A. J. (1974). Rhodesian Journal of Agricultural Research, 12, 27-42. KOH, F. K. (1981). Evaluation of animal genetic resources in Asia and Oceania. (Eds J. S. F. Barker, T. K. Mukherjee, H. N. Turner and S. Sivarajasingam). Proceedings of the second SABRAO workshop on Animal Genetic Resources. Kuala Lumpur, May 1981. pp 121-127. OLI, K. P. (1986). Comparative study of carcass yields of different breeds of pigs in the eastern hills of Nepal. Technical paper 90. Pakhribas Agricultural Centre, Dhankuta, Nepal. REPRODUCTION DES PORCS DANS LES COLLINES DE L'EST DU NEPAL R~sum~---Une enqu~te portant sur 101 fermiers poss~dant des trnies a ~t~ conduite dans les collines de Koshi au N~pal. Les caract~ristiques estim~es de ces reproductions, qui ne different pas significativement entre les truies de race locale et les croisements Pakhribas, sont pour l'intervalle de raise bas de 7,4 mois, 8,3 porcelets par pottle, 2,2 mois pour l'fige au sewage et un nombre total de mise bas de 13,2. Les pores de race locale atteignent la maturit~ sexuelle plus t6t que les croisements Pakhribas. L'fige ~i la premiere raise bas pour los deux #notypes est de 10,7 et 12,0 mois (P < 0,05), l'fige au premier accouplement pour les verrats est de 6,5 et 7,4 mois pour P < 0,05, respectivement. Les trnies mettent bas toute l ' a n n ~ et il n'existe pas, ~ cet ~gard, de saison optimale clairement individualis~. Les taux de mortalit~ avant sevrage sont estim~s 422 p. I00 pour la race locale et ~ 15 p. I00 pour les croisements Pakhribas. Presque tousles fermiers pratiquent le contr61e des saillies pendant lequel la trnie est conduite au verrat ou inversement. La proportion des fermiers ayant des truies et poss&iant aussi des verrats n'est que de 5 p. I00. REPRODUCCION DE CERDOS EN LA ALTURAS DE NEPAL ORIENTAL Resumen---Se llev6 a cabo un estudio de 101 porquerizas en las alturas Koshi de Nepal. Los indices zoot~nicos reproductivos, que no difirieron significativamente entre hembras locales y cruzadas Pakhribas fueron, intervalo entre partos 7.4 meses, tamafio de la camada al nacimiento 8-3, edad de los cerdos al destete 2-2 meses y nfmero total de partos 13-2. Los cerdos locales alcanzaron la madurez sexual mils rfipido que los cruzados. La edad al primer parto de los dos genotipos rue de 10.7 y 12"0 meses (P < 0.05),
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GATENBY AND CHEMJONG
y la edad a la primera monta de los machos fue de 6-5 y 7.4 meses (P < 0-05).
No hubo tma estaeirn del afio definidapara la parieibn. La mortalidad antes del destete se estim6 eta 22% para los ecrdos locales yen 15% para los cruces. Casi todos los eerdos praetiean monta eontrolada, eta donde la hembra r llevada al macho, o el macho a la hembra. La proporeirn de fmquerosque tienen reproduetor r de apcnas einco pot eiento.
BOOK REVIEW Review Scientifique et Technique de I'OIE. Vol. 10, No. 3, September 1991. Animals, pathogens and the environment. Office International des Epizooties. 1991. 352 pp. Soft back, FF175, US$32. ISBN 92-9044-297-2. This issue, in the continuing series o f extremely informative review papers, considers the topical subject of the impact which animal populations, or their health status, may have on the environment. Part 1, comprising 7 papers, considers the relationship between animals and their environment. There are two papers that have particular relevance to the tropics where the role of livestock in the process o f desertification (English summary only) and the impact of large scale aquaculture are considered. Part 2 comprises 9 papers which consider various aspects of the relationship between animal pathogens and the environment. The information provides a valuable guide to the role o f environmental factors in the development, circulation and survival o f pathogens and transmission routes to susceptible animal and human hosts. One paper, which describes methods for environmental protection during animal disease eradication programmes, will be of particular interest to managers o f large scale disease control projects. Although by no means a comprehensive treatise of all aspects o f the topic addressed this review is recommended reading. The issue provides a unique collection of papers on the changing relationship in the classic disease triad of host, agent and environmental factors and highlights the role o f contemporary animal husbandry practices as a prime mover in this change. C. J . D a b o r n
