Throughout the world, food requirements favour the use of cattle that can produce both milk and beef for human consumption. Africa has a great need to increase milk and meat production from cattle, and perhaps a great potential if specific constraints can be alleviated. Climate and associated factors in most parts of Africa, including nutrition, disease and parasite environment, favour the use of germ-plasm with varying percentages of Bos indicus cattle because of their higher level of adaptability to environmental stresses.
However, the response capability for milk and meat production characters is generally low in most breeds of Bos indicus cattle as straightbreds. Different breeds of Bos taurus cattle have greater genetic potential for milk and meat production characters, but in many African situations it is not economically feasible to provide the environment necessary for them to realize this potential. Thus, the most logical approach to increasing production appears to be some modification of the environment, as technically and economically practical, combined with the use of organized crossbreeding programmes or the formation of composite breeds based on Bos indicus and Bos taurus parental stock.
Though the possibilities for environmental modification are limited, it should be feasible to improve both the quantity and quality of forage production, to provide shade and to achieve a higher level of control over specific diseases and parasites. A breeding programme must then be in harmony with the environment as modified and with the prevailing economics of production in each situation.
Kenya is the only country in Africa with major resources of Bos indicus Sahiwal cattle and serves as an important source of stock and semen for the continent. Within Kenya, the main utility of the breed is seen in crossbreeding for dual-purpose production in middle- to lower-potential areas. The contribution of the Sahiwal breed to adaptability is well documented in several ecological zones of Africa where Sahiwals have been crossed with exotic Bos taurus breeds that have a high response capability for milk and beef production but lack adaptability to local conditions. The Sahiwal breed also is considered unequalled in transmitted effects for milk production among Bos indicus breeds.
Meyn (1974) notes that the introduction of Sahiwals from India and Pakistan during the colonial era ended attempts to select an improved indigenous dairy breed of Bos indicus cattle for smallholders in the highlands of Kenya. It soon became evident that Sahiwals, when crossed with exotic Bos taurus breeds, produced more milk than the indigenous Bos indicus cattle (Mahadevan et al, 1962). Later evidence showed that in the fertile highlands Bos taurus cattle of European origin or their crosses with Sahiwals produced still higher milk yields than purebred Sahiwals (Mason, 1965). Meyn and Wilkins (1973) and Kimenyi and Russell (1975) further suggested that crosses of European Bos taurus breeds with Sahiwals outyielded their purebred herdmates of either breed in both the semi-arid highlands and the hotter and more humid coastal belt. It was hypothesized that the drier zones could not meet the requirements of crosses with the high-performing Bos taurus breeds, and that improved Bos indicus breeds, with lower nutritive requirements and greater adaptability to drought conditions, would be more suited to the more arid environments, even though their production response capability was relatively low. For these arid areas, the Sahiwal breed was considered a suitable dual-purpose dairy/beef breed to replace the indigenous Small East African Zebu.
In both semi-arid and coastal areas, a two-breed rotational crossbreeding system, combining Sahiwals with a European dairy breed, was considered feasible. If the breeding female had a hump, she was mated to a humpless bull, whereas a humpless female was mated to a Sahiwal bull. According to Kamau (1977), government policy in Kenya during the colonial era encouraged the use of Sahiwals by small African farmers under relatively poor management conditions; this policy tended to prevent them from acquiring Bos taurus cattle of European origin. This effect, he argues, led to the nearly total rejection of the Sahiwal breed by African farmers when this restrictive policy was lifted. There are now indications, however, that small producers in lower-potential areas are recognizing that Sahiwal crosses with Bos taurus breeds have considerable potential for increasing both milk and beef production within the resources available.
The establishment of the National Sahiwal Stud at Naivasha in 1962 marked the beginning of a programme to produce a dual-purpose Bos indicus breed to be kept under extensive pasture conditions with minimal supplemental feeding. The aim was genetic improvement for milk and beef production, and stock were supplied for artificial insemination and sale for both pure breeding and crossbreeding in coastal and drier inland areas (Meyn and Wilkins, 1974).
A number of private breeders have also established nucleus Sahiwal herds, generally maintained alongside crossbred commercial herds. The Sahiwal Breeders Society recognizes three categories of Sahiwal: foundation animals have at least seven-eighths Sahiwal ancestry and have passed inspection, purebred Sahiwals are minimally the progeny of registered animals above foundation stock and have passed inspection and weight-for-age evaluations and pedigree Sahiwals are minimally the progeny of registered animals above foundation stock and have passed inspection, weight-for-age, and dam's minimal lactation evaluations. This evaluation policy of the Sahiwal Breeders Society, requiring weight-for-age and milk-production information, has actively encouraged the recording of these characters in a number of private herds.
Trail (1980) has reviewed published performance criteria for indigenous, exotic and crossbred cattle in Africa south of the Sahara over a 30-year period.
Although considerable success has been reported with individual breeds and crosses, important questions remain concerning which breeds of both Bos indicus and Bos taurus cattle to use, and how to use them - whether as purebreds, or in different crossbreeding systems, or in the formation of composite breeds - given the different feed environments and production situations found throughout Africa. Moreover, the available performance data are generally not suitable for integration into any overall indices of productivity. Only about 20% of 500 bibliographic references contain information on three or more characters sufficient to allow characterization of breed types through a productivity index, or provide comparative information on two or more breed types. Only 5% of the items provide sufficient data to allow breed comparisons on the basis of a productivity index.
The objectives of the present study were to evaluate and compare the productivity under commercial management levels of Sahiwals, Sahiwal/Ayrshire crosses, indigenous Small East African Zebus and Boran, taking the range of management levels and production systems represented by the five Sahiwal-based herds for which data were available. These data, and the results reported here, are from sites in the lower-potential highlands and, in one case, on the coastal heft of Kenya. All of these sites fall within the semi-arid to subhumid zone, as classified by Trail (1980) based on cattle adaptability considerations in Africa south of the Sahara.
1. Location of research sites in Kenya