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ALPACA RAISING IN THE HIGH ANDES

by Saúl Fernández-Baca

The raising of alpaca is an industry of great value to the economies of some Latin American countries, notably Peru and Bolivia. Because of their great adaptability alpaca are able to utilize the grasslands of the Andean altiplano at altitudes over 4 000 m above sea level, where it is unprofitable to raise either sheep or cattle.

Alpaca can also be raised at lower levels. There is evidence that during the Inca empire they were more widely distributed than at present. With the introduction of sheep and cattle by the conquistadors, alpaca were subsequently confined to marginal areas unsuitable for these new species.

The main products obtained from alpaca are the wool (usually called alpaca fibre to differentiate it from sheep's wool), the flesh, used as meat, and the skins. The fibre is highly prized by the textile industry and its price on the international market is usually two to three times that of sheep's wool. The meat tastes like mutton and is the only source of protein of animal origin for the people of the Andean plateau. The skins, taken from lambs less than three months old, are used for a wide range of handicrafts: in the making of floor carpets (alfombras), quilts (colchas), slippers (zapatillas) and dress coats (casacas).

Peru, with some 2.9 million head, is the leading producer of alpaca. Next comes Bolivia with 300 000 head, while Chile and Argentina have a few that are of no economic significance. It is estimated that 80 percent of the alpaca in Peru belong to small owners and campesino communities and the rest to middle-class owners and associations that have emerged as a result of land reform. At least 200 000 campesino families depend in one way or another on the raising of alpaca.

In view of the economic importance of this species particular emphasis is currently placed on increasing its fibre and meat production through appropriate breeding programmes. Research during the last 15 years has provided considerable knowledge of different aspects of the anatomy, physiology, reproductive biology, health and nutrition of alpaca, thus laying the necessary foundation for technical advancement of their husbandry.

Sául Fernández-Baca is Director of the Instituto Veterinario de Investigaciones Tropicales y de Altura (Veterinary Institute for Tropical and High Altitude Research), Universidad Nacional Mayor de San Marcos, Aptdo. 4270, Lima, Peru.

Origin of alpaca and allied species

The alpaca, Lama pacos (Linnaeus), the llama, Lama glama (Linnaeus), the guanaco, Lama guanicoe (Müller) and the vicuña, Vicugna vicugna (Molina), form the group known as South American or New World camel-like or cameloid species. The alpaca and llama are domesticated and economically the most important. The llama is the larger of the two, adults reaching weights of around 120 kg and yielding a coarse fibre ranging in colour from white to black with all the intermediate hues or combinations of one or more colours. The meat is relished by the campesinos. The llama is also used as a beast of burden in Argentina, Bolivia, northern Chile and Peru.

The alpaca is smaller than the llama, adults weighing about 70 kg; its fibre or wool is finer than that of the llama but has a similar range of colour. The guanaco and vicuña are wild species, the guanaco resembling the llama except for the colour of the fibre, which is a uniform reddish brown. The vicuña is the smallest of all in size, the adults weighing 35–40 kg.

The two types of alpaca: Suri (above) and Huacaya (right)

P ORLANDINI

There is frequent crossing among South American cameloids. The most frequent hybridization is between llama and alpaca, the cross being called huarizo, while that between alpaca and vicuña is called paco-vicuña. Both of these are fertile, probably because of the similarity of the parental karyotypes. Table 1 provides a summary of the distribution and number of South American cameloid species.

Breeds of alpaca

There are two types of alpaca, the Suri and Huacaya. The fundamental difference between them lies in the length and fineness of the fibre. The Suri have very long fibres, usually attaining lengths of over 15 cm in one year's growth, which form ringlets and fall to the side of the body, giving the animal a similarity in appearance to a Lincoln sheep. The Huacaya have a more compact fleece, with shorter fibres, and are similar in appearance to Corriedale sheep. From the standpoint of textile quality, the Huacaya fibre is best. There is no notable difference in body weight between the two types. When Huacaya are bred inter-se, about 2 percent Suri type animals are obtained, while the breeding of Suri animals gives about 17 percent Huacaya types. As a rule on commercial ranches there is a predominance of Huacaya alpaca, although no selection in favour of this type is practised.

Behavioural characteristics

Both the alpaca and llama exhibit certain behavioural characteristics which differentiate them from other domestic animals. They defecate and urinate in circumscribed areas, even if allowed freedom of movement to other places. This habit is very important in the control of internal parasites. Nevertheless to avoid deterioration of the pasture, distribution of the faeces is a necessary task. Another habit of the alpaca is to make use of communal areas as dust baths; under continuous use, these areas soon become barren and serve as places for the spread of ectoparasites, mainly itch mites of the Sarcoptidae family. The habits of spitting and trampling are probably defence mechanisms of the animals against outside aggression, real or potential. Their mating behaviour, described below, also differentiates them from other domestic animals.

Paco-vicuña, the hybrid obtained from the artificial insemination of alpaca with vicuña semen

Recent research on the biology of reproduction (Novoa, 1970; England et al., 1969; and Fernández-Baca, 1970, 1971) of these cameloid species indicates that they differ from most known range animals. The most striking features relate to puberty, seasonality of breeding, oestrus and ovulation, sexual behaviour, fertilization, embryo mortality, gestation and parturition.

Reproductive characteristics

Puberty

Ovarian activity in alpaca may begin as early as 10 months of age. As with other species, the level of nutrition has a marked influence on the inception of puberty. Females 12 to 14 months old exhibit sexual behaviour, ovulation, fertilization and embryonic survival similar to that in multiparous females (FernándezBaca et al., 1972a). They can therefore be bred at one year of age under good conditions, at a body weight of about 40 kg (Novoa et al., 1972).

Males one year old can be used for service; however in most of them at that age the penis sticks to the prepuce. In practice males are used as sires from the age of two to three years.

Breeding season

Alpaca, like other animals of their kind, are considered to have seasonal sexual activity. Thus on commercial ranches, even if males and females live together all year round, births occur only during the rainy season from December to March, when feed is abundant. But when males are kept separate from the females and are brought together solely for mating, it is possible to obtain young all the year round (Fernández-Baca et al., 1972a). This means that continuous association of the sexes produces an inhibiting effect on the sexual activity of the male (Fernández-Baca et al., 1972b). These observations are of particular importance in the handling of animals at breeding time.

Oestrus and ovulation

Alpaca show no well-defined cyclical sexual activity. In contrast to ewes and cows, alpaca are always in the follicular phase so that until they are served they are in a constant state of oestrus. Ovulation is induced by copulation, occurring approximately 26 hours after the coital stimulus (San Martín et al., 1968). Ovulation can be also be induced by the injection of chorionic gonadotropin (HCG), in which case it occurs approximately 24 hours afterwards.

Table 2 shows the effect of various types of stimuli on the induction of ovulation in alpaca (Fernández-Baca et al., 1970a). It can be seen from this table that the introduction of the penis provides the necessary stimulus for the freeing of gonadotropin and subsequent ovulation.

However, not every service induces ovulation, since about 20 percent of females with active ovaries do not ovulate in response to single or multiple services by uncastrated or vasectomized males. In contrast, all females respond by ovulation to the administration of chorionic gonadotropin; thus the failure to ovulate as a consequence of natural mating is due to the deficiency in level of the luteinizing hormones. There are indications that nutritional factors may affect the secretion of this hormone and consequently the incidence of ovulation. The failure to ovulate may be one reason for low fertility. However, females that do not ovulate after first service can be served again and again as they continue to be in oestrus.

Although multiple ovulation occurs in approximately 10 percent of the cases, no multiple births have ever been recorded for alpaca. Only during the first month of gestation has the presence of two live embryos been observed.

Following ovulation, the corpus luteum is formed; it reaches maximum size and secretory activity at around 8 days after ovulation. Should no gestation take place, the corpus luteum becomes involuted, giving way to the formation of new follicles and consequent manifestation of oestrus. The involution of the corpus luteum is completed within 18 days of a sterile copulation (Fernández-Baca et al., 1970c). If gestation starts, the corpus luteum continues its secretory activity; thereafter the female is not sexually receptive.

Sexual behaviour

Alpaca in oestrus exhibit very strange behaviour. When approached by the male the female quickly assumes the copulatory position (ventral decubitus). Since follicular activity continues even in the absence of the male, all females in a herd are sexually receptive at the same time. Consequently when mating begins there is very intense sexual activity. Copulation of alpaca occurs with the female in the ventral decubitus position and lasts from 20 to 50 minutes. Apparently, there is no relation between the duration of copulation and the rate of ovulation or fertilization. A male during the first day of mating may serve up to 12 females; on subsequent days, its activity diminishes considerably.

Fertilization and mortality of the embryo

It has been found that at least 85 percent of the females that ovulate in response to the coital stimulus have at least one ovum fertilized within three days of service (Fernández-Baca, 1970). But there is a very high mortality of embryos during the first month of gestation. Only about 50 percent of the embryos survive beyond 30 days of gestation. The reasons for this high mortality are still unknown but it is obvious that it seriously affects the annual birth rate.

Diagnosis of pregnancy

Changes in sexual receptiveness of females in relation to the secretory activity of the corpus luteum have been taken as the basis for the diagnosis of pregnancy. Once a female has been served, it ovulates, but if it does not become pregnant it invariably goes into oestrus again, starting 13 days after having been served and remaining sexually receptive until such time as it receives another stimulus that induces ovulation. Any female not in oestrus within 18 to 20 days after having been served can be considered pregnant.

The diagnosis of pregnancy based on sexual behaviour can easily, be checked by rectal palpation.

Gestation and parturition

Gestation in alpaca averages 342 and 345 days in Huacaya and Suri respectively (San Martín et al., 1968). The placenta is of the simple-diffuse type, microscopically corresponding to the chorial epithelium type.

Even though both ovaries are equally active in the production of follicles, it has been found that over 95 percent of pregnancies are located in the left horn of the uterus (Table 3). Transuterine migration, from the right horn of the uterus to the left, occurs frequently. This is evident from the location of the corpus luteum in the right ovary and the foetus in the left horn of the uterus. Alpaca drop their young very easily; cases of dystocia are exceptional.

The female returns to a state of oestrus within 48 hours after dropping her young, though with very little follicle growth. Follicle growth capable of responding by ovulation to coitus is observed from the fifth day; nevertheless the highest rate of fertility is obtained from 10 days after parturition (Sumar et al., 1972).

Nutritional factors

The structure of the stomachs of the alpaca and other members of the Camelidae differs from that of other ruminants such as sheep and cattle. The fundamental distinction lies in the third stomach, which is not sharply differentiated. This fact accounts for the view that the Tylopoda group, to which the Camelidae belong, is completely separate and different from the ruminants.

However, it is generally accepted that the Camelidae have four stomachs (Vallenas, 1965) even though these have very special features. One such feature is the existence of oblique furrows with glandular bags in the dorsal sac of the rumen, but the role of these structures in the digestive process is unknown. Digestibility trials suggest that alpaca and llama are able to use the energy contained in forage, especially poor-grade forage, more efficiently than sheep. Recent studies on the concentration of volatile fatty acids along the gastro-intestinal tract of alpaca and llama (Vallenas et al., 1973) also suggest more efficient absorption than in sheep and cattle. These observations may explain the ability of Camelidae to utilize the poor quality lignified grasses found at high elevations.

Management

The organization of stock raising as well as the technological level achieved vary considerably with the communities owning alpaca and with the system of land tenure. In the campesino communities management is generally poor: the animals are all herded together, with no separation by either sex or age, and frequently alpaca and llama are raised together, so that crosses between the two species occur.

Herds

In the associative or cooperative enterprises and among small and middle-class owners, alpaca herds are usually better managed. The animals are classified according to type (Suri or Huacaya), colour of fibre, age and sex, and are kept in herds of 200 to 1 000 head. The percentage of females of breeding age in each herd varies from 30 to 40, while about 30 percent of the herd consists of castrated males kept for fibre production.

Table 1. Estimated population and distribution of South American Camelidae

	Peru	Bolivia	Chile	Argentina
Alpaca	2 887 400	300 000	20 000	Few
Llama	915 000	2 500 000	70 000	500 000 (?)
Vicuña	30 000	2 000	-	-
Guanaco	Very few	Very few	?	100 000

Table 2. Effect of various stimuli on ovulation rate in alpaca

Type of stimulus	Number of females	Number that ovulated	Number with eggs dividing	Number with multiple eggs
Sighting of male1	20	1 (5%)	0	0
A single mounting2	13	2 (15%)	0	0
Mounting + AI	9	3 (33%)	2	0
Interrupted service3	10	6 (60%)	4	1
Sterile service	22	17 (77%)	0	2
Sterile service + AI	21	18 (86%)	43	1
Single service	44	36 (82%)	30	3
Multiple service5	10	7 (70%)	66	0
750 IU HCG	10	10 (100%)	0	1
750 IU HCG + AI	18	18 (100%)	4	4

Source: Fernández-Baca et al. (1970a).
¹ Without servicing.
² Single mounting without introduction of penis.
³ Service interrupted five minutes after start.
⁴ The ova of three animals were not recovered.
⁵ Three services in 24 hours.
⁶ The egg of one animal was not recovered.

Table 3. Relation between the location of the corpus luteum and the embryo in alpaca

Location of the corpus luteum	Number of animals observed	Animals with embryo in one horn of uterus
		Right	Left
Right ovary	472	12	460
Left ovary	440	3	437
Both ovaries1	16	0	16
Total	928	15 (1.6%)	913 (98.4%)

Source: Fernández-Baca et al. (1973).
¹ In all cases a single foetus was found in the left horn of the uterus.

Alpaca are often managed in much the same way as sheep: however, recent studies indicate the need for more appropriate management practices to suit their special characteristics.

On organized farms mating takes place during the rainy season from December to March when pasture is at its best and each male services 20 to 25 females. Recent research shows that by using two groups of males alternately, a much higher birth rate is obtained than with the traditional system of continuous mating.

Alternate mating

In alternate mating, each group of males remains with a herd of females for about 7 days, at the end of which the second group takes over, and so on. Each male therefore gets a 7-day rest between mating periods. This system, which has been applied to commercial herds, has raised the birth rate by about 50 percent (that is, up to about 80 percent). The practice is based on the observation that mating is very intense during the first 2 to 5 days when the males are placed together with the females and then declines rapidly despite the number of receptive females still in the herd. The young are born at an advanced stage of development and weaning occurs at 6–7 months of age. The female can be served again 15 days after dropping her young.

Shearing

Shearing of the fleece is done between October and November; it is recommended that the shearing be done annually in order to obtain high-grade wool and to make the control of external pests, especially the itch mite, easier.

Alpaca depend entirely on natural grassland for feeding; the usual carrying capacity is 1.5 to 3 animals per hectare.

The alpaca's life span extends to 15 years. Starting at the age of 10, however, alpaca usually exhibit marked dental deterioration and should be culled.

Artificial insemination and egg transfer

Artificial insemination of alpaca is technically feasible (Fernández-Baca and Novoa, 1968).

The semen can be collected by means of electrical stimulation; at present semen collection using the artificial vagina in a dummy is being tried. Ovulation is induced either by the use of a vasectomized male or by the injection of chorionic gonadotropin. Practically speaking, the artificial insemination of alpaca females with vicuña semen to obtain paco-vicuñas affords economically good prospects. In trials to date, a fertility rate of around 25 percent has been achieved with AI using undiluted semen. Alpaca have certain advantages in AI over other species because of the continuous follicular activity and the consequent state of sexual receptivity.

Trials conducted show the technical feasibility of transfer of fertilized eggs by laparotomy. However, for large-scale work further research is necessary.

Productivity

The fibre is the principal source of income from the raising of alpaca. However, alpaca also contribute substantially to meat production, which can be considerably increased. Another source of income, which is constantly growing, is from the skins of animals less than three months of age. The skins are used in the production of handicrafts.

The annual fibre clip per animal ranges between 1 and 4 kg, averaging 1.8 kg. There is a highly significant correlation between the weight of the fleece and body weight. At present there is a marked preference for white fibre; however, the expansion of the fur industry is creating a wider market for skins of other colours as well. Little is known about the inheritance of fleece weight or body weight in alpaca and there is no information concerning the hereditary mechanisms influencing fibre colour.

Alpaca meat resembles mutton in flavour, although the meat of adult animals has a very strong, characteristic odour. The flesh of young animals less than one year of age is delicious. At birth, the young weigh about 8 kg; this weight is doubled during the first two months of life, and then increases at a slower rate. A three-year-old male can reach a liveweight of about 75 kg and a female about 65 kg, with corresponding carcass yields of 60 and 55 percent (Calderón and Fernández-Baca, 1972).

Semen collection, using the dummy of a female alpaca

On commercial ranches serious problems arise from the low birth rate and high mortality among the herds. Little culling is practised, the only reason for any at all being old age. Such culling as is adopted on wellorganized ranches does not exceed 8 percent.

The fur industry is now confined to the use of skins of animals that die before the age of three years. The advisability of early slaughter of males that are not to be used as sires is currently under consideration to facilitate the better use of hides and meat.

The udder of the alpaca consists of four glands, each with its own teat. Although it is possible to milk alpaca, this is not normal practice.

The alpaca is not used as a beast of burden; the only species used for this purpose is the llama.

A question frequently asked is whether sheep or alpaca are more efficient from the standpoint of productivity. Without doubt alpaca surpass sheep in their capacity to use rangeland at over 4 000 m above sea level. On lowlands there is no experimental evidence demonstrating the productive superiority of one or the other species.

The main factors influencing production in the Andes are nutrition, low birth rate and disease.

Nutrition

Alpaca are raised entirely on the ranges of the Andean highlands (altiplano). Their productivity therefore depends on the quantity and quality of the nutrients which are provided by these grasslands and which fluctuate with the season. On the Andean highlands where alpaca are raised there are two marked seasons: the rainy season, from December to March, and the dry season, from April to November. Annual precipitation ranges from 900 to 1 200 mm; over 90 percent of this rainfall occurs during the rainy season. Ample forage is available during the rainy season, the opposite being true during the dry season. From all indications, failure to ovulate and mortality of embryos are associated with scarcity of forage. Recent work indicates that it is possible to increase considerably the carrying capacity of the Andean rangeland by the introduction of improved forage and fodder species. By an association of ryegrass (Lolium perenne) and white clover (Trifolium repens), irrigation, and the application of nitrogen fertilizers, up to 30 adult alpaca can be carried per hectare per year as compared with the usual rate of 1 to 1.5 alpaca per hectare on natural grasslands. Despite the altitude and low night temperature it has been found possible to ensure sustained yields of such plant associations all year at elevations up to 4 200 m above sea level.

In campesino communities where each person owns his own animals and no one owns the land, the shortage of feed is aggravated by the improper management (overgrazing) of natural grasslands.

Low birth rate

It is estimated that at present no more than half of the female alpaca of reproductive age produce young every year. Apart from the economic losses resulting from this low reproductive rate, there is also a serious handicap in that it reduces the intensity of selection that can be practised for traits of economic importance. As pointed out earlier, the problem does not lie in fertilization failure but rather in survival of the embryos, about 50 percent of which die during the first month of gestation. The reasons for this high embryo mortality are still unknown but the fact that over 95 percent of gestations that are brought to term are located in the left uterine horn (Table 3), even though ovulation of both ovaries is equivalent, suggests the existence of some endogenous factor that determines the differential survival of the embryos. Apparently only those embryos survive that originate in the left ovary, unless those of the right ovary migrate to the left horn of the uterus. The role of other factors such as nutrition, diseases or genetics on embryonic mortality in alpaca is as yet unknown.

Failure of ovulation may also be an important factor in low birth rates in the alpaca. Proper management of these animals during mating, which offers opportunities for new service (e.g., by alternate mating) to females that have not ovulated or have prematurely lost their embryos, has made possible an increase in the annual birth rate on some ranches to 80 percent (Novoa et al., 1973).

Diseases

Health problems have serious repercussions on the raising of alpaca due to the decrease in productivity and high mortality. Moro and Guerrero (1971) have described the main infectious diseases and pests and have pointed out that alpaca are susceptible to most of the infectious diseases of other ruminants. But they are particularly sensitive to some of them and relatively resistant to others. Thus, the young are very susceptible to the enterotoxaemia caused by Clostridium perfringens (welchii), types A and C. In some years mortality due to this causal agent can amount to 50 percent, depending on local conditions. Among adult animals, the so-called fiebre de los alpacas (alpaca fever) caused by Streptococcus pyogenes leads to high mortality on some ranches. Stomatitis caused by Sphaerophorus necrophorus and osteomyelitis of the mandible caused by Actinomyces spp. are two diseases which, even though they do not cause high mortality, notably affect productivity. Other diseases in alpaca that have been diagnosed are brucellosis (caused by Brucella melitensis), listeriosis, keratitis, otitis, rabies and mastitis.

Alpaca are relatively resistant to foot-and-mouth disease. Despite many outbreaks of this disease among other species in areas adjacent to those where alpaca are raised, only a single outbreak was reported in alpaca (Moro and Guerrero, 1971).

Both endo- and ectoparasites cause considerable losses among alpaca. Among the endoparasites the group of nematodes that cause verminous gastro-enteritis is the worst. The highest incidence of Graphinema aucheniae, Nematodirus lamae and Lamanema chavezi occurs in alpaca. The first produces small nodules and congestion of the mucous membrane of the abomasum, while the others are haematophagous parasites. Lamanema also exhibits the peculiarity of hepatic migration, causing damage to the liver. Other parasitic infestations affecting alpaca are hepatic distomatosis, taeniosis, hydatidosis, cysticercosis and verminous bronchitis. Coccidiosis, produced by species of the Eimeria genus, E. lamae, E. macusanensis, E. alpacae and E. puncensis, the first two being the most pathogenic, is also common among alpaca. When it becomes localized in the mucous membrane of the small intestine, and under certain predisposing circumstances, it may cause serious damage.

Spraying to control and treat ectoparasites

Sarcocystis aucheniae occurs in the muscles of alpaca, some of the cysts measuring up to 1.5 cm. Recent research (Guerrero, 1974, personal communication) indicates that the transmission of the disease is through the faeces of dogs and, probably, man. Although Sarcocystis does not produce clear signs of infection, the commercial value of the meat of infected animals decreases considerably. In some herds, more than 50 percent of alpaca over two years of age have been found to be affected with Sarcocystis.

External parasites cause considerable losses due to the damage to the fibre. The most common one is the scab mite, Sarcoptes scabiei, var. aucheniae. The mites may be found in the skin which is not covered by hairs, and may in serious cases spread all over the body and produce many lesions. The itch, caused by the common itch mite Psoroptes communis var. aucheniae, is localized around the ears and neck.

Conclusions

The importance of South American Camelidae in general, and of alpaca in particular, to the economy of the inhabitants of the Andean altiplano is beyond question. Improvements in alpaca raising and greater economic returns can be achieved through indepth research on the biology and pathology of this species and through application of the knowledge thus gained by dissemination of the findings among alpaca raisers.

Alpaca have certain characteristics that are markedly different from those of other ruminants: it is therefore not possible to adapt animal husbandry techniques developed for other species without running the risk of seriously compromising the alpaca's productivity. Some of the features discussed in this article underline this observation. It is therefore necessary to develop, through research, techniques for alpaca raising compatible with the characteristics of this species and the geographical areas in which it can be raised. The dissemination of new techniques and their application by alpaca raisers present major problems when one considers the social structure and educational level of the mass of campesinos who own the bulk of the alpaca population in both Peru and Bolivia. The incorporation of campesino communities in new associations or cooperatives through land reform in Peru is regarded as one possible way of introducing changes in their stock-raising technology.

Government attention to such vital aspects as the marketing of alpaca fibre and meat and the granting of credit to alpaca raisers will play a decisive role in the improvement of their production.

REFERENCES

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THE FAO TECHNICAL PAPERS:

FAO PLANT PRODUCTION AND PROTECTION PAPERS

1. Horticulture: a select bibliography, 1976 (E*)
2. Cotton specialists and research institutions in selected countries, 1976 (E*)
3. Food legumes: distribution, adaptability and biology of yield, 1977 (E*)
4. Soybean production in the tropics, 1977 (E*)
5. Les systèmes pastoraux sahéliens, 1977 (F*)
6. Pest resistance to pesticides and crop loss assessment - 1, 1977 (E* F*)

FAO ANIMAL PRODUCTION AND HEALTH PAPERS

1. Animal breeding: selected articles from World Animal Review, 1977 (E* F* S*)
2. Eradication of hog cholera and African swine fever, 1977 (E* F* S*)
3. Insecticides and application equipment for tsetse control, 1977 (E* F*)
4. New feed resources, 1977 (E*** F*** S***)
5. Bibliography of the criollo cattle of the Americas, 1977 (biling. E/S*)

FAO CONSERVATION GUIDES

1. Guidelines for watershead management, 1977 (E* F*** S***)
2. Hydrological techniques for upstream conservation, 1977 (E* F*** S***)
3. Conservation in arid and semi-arid zones, 1977 (E* F***)
4. Special readings in conservation techniques (E***)

FAO AGRICULTURAL SERVICES BULLETINS

29 titles published

FAO IRRIGATION AND DRAINAGE PAPERS

28 titles published

FAO SOILS BULLETINS

32 titles published

Availability: May 1977

E — English
F — French
S — Spanish
* Available
** Out of print
*** In preparation

The FAO Techical Papers are available through the authorized FAO Sales Agents or directly from Distribution and Sales Section, FAO, Via delle Terme di Caracalla, 00100 Rome, Italy.