S. Sibanda
Livestock Section, Grasslands Research Station, Private Bag 3701, Marondera,
Zimbabwe
Summary
Introduction
Agro-ecological regions and cattle distribution
Quantities of crop residues produced in communal areas
Use of crop residues and impact on productivity
Suggested ways of improving nutritive value of crop residues
Conclusion
References
The basis of animal production in Zimbabwe is natural grazing from the range. The quantity and quality of grazing fluctuate with the rainy season which is from November to March. For the remainder of the year, grazing is very poor and in communal areas the situation is further aggravated by very high overstocking rates, with a national overstocking rate of 64%. Communal areas are located in regions IV and V where rainfall is low (less than 510 mm) and soils are poor. Crop residues assume great importance in decreasing the level of feed deficit, but the quantities vary and depend mainly on rainfall. The main crop residues used are maize and sorghum stover and legume haulms, mainly groundnut. Most stovers are fed to animals in situ, but some farmers harvest and store these residues to feed to their animals later in the year. Generally, these residues are fed without any attempt to improve their nutritive value, save for a salt lick in some cases. There is potential for improving the feeding of these residues by use of such simple measures as supplementation with poultry litter, legume haulms and physical processing.
The basis of cattle production in Zimbabwe is natural grazing from the veld (range). The seasonal fluctuations in the quality and quantity of natural grazing follow the seasonal rainfall distribution. With the advent of the warm, rainy season in November there is regrowth of highly nutritive grass but its quality declines progressively as the season advances to the dry winter in April. The decline in quality of grazing is due to a drop in the crude protein content of veld herbage from about 15% early in the Zimbabwe summer to about 3% by the end of Nay (Elliott, 1964). The situation in the communal areas is further aggravated by very high overstocking rates. Without the use of crop residues, especially maize stover, during the dry winter months the level of animal production would be far lower than it is.
Zimbabwe is divided into five agro-ecological regions based mainly on the quantity of rainfall and the type of agricultural production they can support. Details of these regions may be found in the publication by Vincent and Thomas (1960). The distribution of rainfall ranges from more than 710 mm in region I to less than 410 mm in region V. Most communal areas are in regions IV and V with annual rainfall figures of 510 mm and below. The total livestock numbers correspond to the land mass distribution, and the recommended livestock carrying capacities decrease from 4 ha per livestock unit (LU) in region I, to 12 ha per LU in region V.
With 25% of overall communal land area under cultivation, there is a national overstocking rate of 64% (Sandford, 1982). This varies with the province, being highest in Masvingo (170%) and lowest in Mashonaland (6% understocked). In some areas, stocking rates may be as high as 15 times the recommended levels (Agritex, 1983).
The quantities of the different crop residues produced depend on the total area cultivated and the quality of the season, as well as other inputs such as fertilizers. It is very difficult to give an accurate estimate of the quantities. The main crop residues are from maize, sorghum, bulrush millet, finger millet and legume crops such as groundnuts and bambara nuts.
The annual economic review issued by the Agricultural Marketing Authority (1983) gave figures for grain production from maize, sorghum, soybean and groundnuts for 1980/81 and/or 1981/82.
Assuming that the grain yields are equivalent to the stover or crop residues, it follows that maize stover ranges from about 665 000 t to just over 2 000 000 t, sorghum 40 000 t, soybean 677 000 t and groundnuts 71 100 t at least. The allocation of cultivated land to the different crops is not constant every year but maize occupies the bulk of it. In one survey carried out in Mashonaland East, maize occupied 68% and groundnuts 12% of the cultivated area, the rest being cultivated with bulrush and finger millet (PTA, 1982).
According to Mombeshora et al (1985), crop residues constitute a major source of feed for livestock in communal areas. Some farmers leave the crop residues in the field while others harvest the stover and store it for feeding in the dry season. The residue used most frequently is maize stover. The proportion of farmers harvesting stover before feeding varies from one area to another. In a survey carried out in two communal areas, Mombeshora et al (1985) found that in Mangwende only 17% of cattle owners harvested or stored crop residues compared with 96% in Chibi. The picture is therefore far from uniform throughout the country.
Differences are also found in the importance of harvested crop residues as a source of livestock feed or as manure or bedding, depending on whether the stover is from grain or legume crops. In Chibi, more farmers prefer grain stover as feed rather than bedding and vice versa in Mangwende. Legume stover, despite its higher nutritive value, is preferred primarily for bedding in both areas.
It is possible that farmers who do not collect their stover, but leave it in the field, lose half its value through trampling by the animals.
Pen fattening of cull cows and old oxen is practiced sporadically by individual farmers using crop residues, homegrown grain and a purchased protein supplement.
There is very little evidence of differential feeding of crop residues to the more productive animals, such as draught oxen and milking cows. This area may be worth investigating. Similarly, no attempt has been made to improve the nutritive value of crop residues.
The impact of feeding crop residues on the productivity of communal area livestock is difficult to quantify. With an estimated average calving rate of 41%, and an offtake of 2%, (Sandford, 1982) productivity is very low. As most areas are severely overgrazed, the crop residues made available to cattle during winter play a major role in keeping animals alive. In some areas, nutritional stress may be more acute in summer since in winter cattle have access to cropping areas. It is possible that crop residues provide the main source of nutrients for half the year from about Nay to October. It is quite likely that without these residues cropping would be jeopardised since the condition of the draught animals at ploughing and planting would be far worse.
The potential value of unimproved crop residues, especially maize stover, may be shown from the results of a trial carried out at Grasslands Research Station. A herd of 60 cows, which was grazed on planted dryland star grass-legume pastures during the summer months (November to Nay), obtained all its feed from unharvested stover for the remainder of the year. Allowing a hectare of stover per cow these animals achieved a mean calving rate of about 85% over 5 calving seasons (Grant et al, 1985). The average calving rate in the absence of crop residues was 41% (Sandford, 1982).
Very little research effort has been directed to improving animal production by feeding crop residues in communal areas. This work has been achieved by extension workers who advise the farmers to harvest and store their stover. A survey was made by the Farming Systems Research Unit in two communal areas mentioned already (Mombeshora et al, 1985). This survey and several others have shown several possible areas of intervention to improve the value and contribution of crop residues to animal production in communal areas.
Harvesting methods
It is known that the nutritive value of stover depends, among other factors, on the stage at which it is harvested. Early harvesting followed by grain drying may be beneficial. This needs investigating.
Supplementation of grain stovers with other residues
Legume stovers such as groundnut and soybean haulms have a higher nutritive value than grain stovers. It is worth determining what levels may be fed to improve animal gains on grain stovers, while the practice of intercropping grain legumes with maize to improve the nutritive value of stover may be worth studying.
The use of urea in drinking water, or sprayed on to stover, has been suggested as a possible means of improving the nutritive value of crop residues.
Strategic feeding of crop residues
This includes selectively feeding productive animals, such as draught oxen and milking cows, on harvested and stored stover. It is necessary to investigate the effect of feeding oxen, either throughout the winter season until the stover runs out, or just before and during the planting period.
The use of crop residues on their own is unlikely to provide sufficient forage for large numbers of animals. Methods aimed at improving nutritive quality will go a long way towards reducing the magnitude of the feed deficit. When the potential contribution of crop residues is taken into account, the level of overstocking in the communal areas is not as high as is normally depicted. However, the position gets worse every year as more and more grazing land is converted into arable land.
Agricultural Marketing Authority, 1983. Economic review of the agricultural industry of Zimbabwe. Harare.
Agritex Management Services, Branch-Monitoring and Evaluation Section (Socio-Economic Research), 1983. Buhera Chiveshe Ward. Report of a socio-economic survey 1982-83. Ministry of Agriculture, Zimbabwe.
Elliott R C, 1964. Some nutritional factors influencing the productivity of beef cattle in Southern Rhodesia with particular reference to the effect of seasonal changes in the composition of veld, provision of nutritional supplements to veld grazing, and observations on maintenance protein requirements of two breeds of African cattle. PhD Thesis, University of London.
Grant J L, Sibanda S. de Souza C R and Mlilo N. 1985. Systems of beef production using veld and legume-based pasture. Annual Report 1983/84. Division of Livestock and Pastures, Department of Research and Specialist Services, Ministry of Lands, Agriculture and Rural Settlement. Harare, Zimbabwe. In press.
Mombeshora B. Agyemang K and Wilson R T. 1985. Livestock ownership and management in the Chibi and Mangwende communal areas of Zimbabwe. Small Ruminant and Camel Group Document No SRC 2, International Livestock Centre for Africa, Addis Ababa.
PTA Consulting Services, 1982. Study for the Agricultural/Rural Development of the Communal Areas of Mashonaland, East Province. Ministry of Lands, Resettlement and Rural Development, Harare.
Sandford S. 1982. Livestock in the communal areas of Zimbabwe. Report prepared for the Ministry of Lands, Resettlement and Rural Development. Harare.
Vincent V and Thomas R G. 1960. An agricultural survey of Southern Rhodesia, part 1. Agro-ecological survey. Government Printer, Salisbury.
