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Effects of urea treatment on chemical composition, feed intake, linear body measurements, feed cost/kg gain, blood urea and ammonia of maize stover and the growth performance of calves were investigated using 8 N’dama calves of 5 to 8 months of age and an average initial live weight of 92.5 kg. The animals were divided into two groups each of which were individually fed experimental diets of either untreated maize stover and Centrosema
pubescens (Diet A) or 5 % urea treated maize stover and Centrosema pubescens (Diet B) for 90 days. The calves were allowed free access to mineral/vitamin blocks and drinking water ad libitum. Urea treatment increased the CP content of maize stover in Diet B by 22.12% over the untreated stover in Diet A. Compared with the untreated stover, urea treatment brought an improvement of 28% in daily feed intake. These improvements in terms of chemical composition, daily feed intake led to a highly significant (p<0.01) live weight gain of animals fed urea treated stover diet compared with those fed untreated stover diet. There was no significant (p>0.05) difference in blood urea levels, feed cost/kg gain and linear body measurements between the animals fed Diet A and those fed Diet B. Therefore, urea ammoniation of maize stovers significantly (p<0.01) improved the chemical
composition of Diet B, daily feed intake and live weight gain of N’dama calves fed Diet B.


The problems of ruminant feeding have received considerable attention in the tropics and sub-tropics (Tesfayohannes, 2003). Most of the research has focused on treating roughage in the late dry season when the quality and quantity of food supply from natural pastures become limiting. Moreover, ruminant animals have evolved the ability to utilize and digest fibrous materials. In contrast to the situation in the tropics and sub-tropics, in many
developed countries, foods that are suitable for human consumption are very often used for feeding both monogastrics and ruminant animals.

It has been suggested that ruminants should be fed, as much as possible, roughage based diets and other feeds that are not directly used by humans (Orskov, 1998). Thus, maize stover is becoming an important and staple feed for ruminants in most parts of the developing world. This is because of an increase in animal population density and failure to modify traditional grazing practices, especially in the arid tropics and subtropics, which have caused serious deterioration of natural vegetation cover. In many parts of the world today crop residues makes up 60 to 90 per cent of the bovine diet (Verma and Jackson, 1984).

Though maize stovers is the most abundant of all agricultural residues and has a great potential as a feed-stuff for ruminants, it appears that 1ivestock production based on these stovers are rather low (Tesfayohannes, 2003). Verma and Jackson (1984) reported that nearly half of the world’s bovine population is reared and maintained on diets composed of 50% or more stovers. Thus, these animals are the worlds least productive in terms of annual output per animal. The reasons for this low level of production are the low digestibility and intake of the maize stover based diets. Coxworth et al. (1977) reported that the voluntary intake and digestibility of maize stovers are limited by its high lignin content, the manner in which this indigestible material is bound to the digestible cellulose and hemicelluloses and its low nitrogen concentration. Kamstra et al. (1958) and Van Soest (1967) reported that poor digestibility is related to the extent of lignifications of the cell wall components of the low quality roughages.

The degree of fill in the reticulo-rumen has also been suggested as the dominant factor limiting voluntary intake of poor quality roughage diets because they have relatively long rumen retention times (Grovum and Williams, 1979). However, decreasing the retention time by increasing the rate of passage tends to decrease the extent of fiber digestion in the rumen (Van Soest, 1982).
Chemical up-grading of maize stovers by means of ammoniation with gaseous or liquid ammonia has received considerable attention in many countries (Sundstol and Coxworth, 1984). An alternative method of ammoniation, using urea as the source of ammonia has been reported by several research workers (Saadullah et al., 1981; Hadjipanayiotou, 1982; Cloete and Kritzinger, 1984; Dias-Da-Silva and Sandstol, 1986). According to Davis et al. (1983), of
all the alkalis tested, ammonia is the most preferred because it provides both the alkaline effect and a source of nitrogen. However, alkali treatments are generally expensive and the chemicals are not readily available in many parts of developing countries (Tesfayohannes, 2003).

Consequently, urea has been studied as a source of ammonia for treating roughages (Hadjipanayiotou, 1982; Cloete et al., 1983; Khanal et al., 1999). Many of the factors influencing the effectiveness of crop residue treatment with urea (Cloete and Kritzinger, 1984, 1985), like type and level of chemical reaction, period, ambient temperature and amount of water (moisture level), are closely related to the economics of maize stover treatment (Hadjipanayiotou, 1989). With the increase in human and animal populations, and a consequent reduction in the cropping and grazing land, it is possible that this strategy will be attractive to many farmers in the future. However, unless adequate feed resources are made available, grazing animals will continue to be undernourished with consequent low productivity (Tesfayohannes, 2003).
Urea-ammoniation of maize strovers generally results in increased digestibility and intake (Cloete and Kritzinger, 1984; Djajanegara and Doyle, 1989; Flachowsky, et al., 1996). There is a view that urea-ammoniated diets such as barley, maize stovers, oat, wheat straw and oat hay may not be adequate for production functions like growth, pregnancy and lactation (Brand et al., 1991). Therefore, addition of legumes to urea-ammoniated diets could give
better results in the production function of animals. This is due to the fact that legumes based diets are more digestible (Orskov and Ryle, 1990) and therefore more volatile fatty acid, (VFA) are produced per unit weight than from forage. Evidence from the literature suggests that the inclusion of protein at low levels may improve fiber digestibility (Williams, 1984). For instance, it has been shown that tropical legumes are higher in protein and lower in fibre
than their grass counterparts, and thus could serve as valuable supplements to straw or stoverbased rations (Van Soest, 1994).




Among the breeds of cattle domesticated in the tropics, the N’dama is the most common in the South Eastern part of Nigeria. N’dama is hardy, trypano-tolerant and is best suitable for the environmental condition of the South Eastern part of Nigeria. The N’dama is gradually going into extinction and to preserve its genetic stock, one factor critical to its survival is nutrition. During rainy season there is abundant pasture for them to feed on but as dry season sets in feeding N’dama becomes problematic. The problem of dry season livestock feeding, has directed research efforts towards harnessing
and enhancing the utilization of abundant arable by-products and crop residues.

Maize is the most common grain cultivated in the South Eastern part of Nigeria. During harvest, farmers are only interested in the maize cob and large quantities of maize stovers produced on private and government farms in Nigeria are wasted year after year. Some are left to rot in the field, which may improve soil fertility anyway, but most are burned (Onyeonagu and Njoku, 2010). Since, N’dama cattle are ruminants, they can feed on these maize stovers converting it to meat for the teeming population of the South Eastern Nigeria. Maize stovers are generally low in nutrients (Owen, 1994).

In other to make maize stovers useful to N’dama cattle, they need to be processed. Cereal crop residues are low in nutritive value because of their relatively low digestibility, low crude protein content and low content of available minerals and vitamins (Owen, 1994). Ani (2012) cited various strategies that have been adopted in improving crop residue nutrients and utilisation and they include; physical method (brisquetting, pelleting, extrusion, chopping, grinding), chemical method (treating with Sodium hydroxide, wood ash, ammonia) and biological method (using fungi to degrade lignin in crop residue and using solid state fermentation system).

Efforts to improve the nutritive value of the cereals residues through treatment with urea and other chemicals have not been very popular because technologies are often at the ‘high tech’, for application by small holder subsistence farmers (Owen and Jayasuriya, 1989). The abundant supply of crop residues and agro-industrial by-products at reasonable prices could enhance production and reduce cost of compounded feeds while not adversely affecting the performance of the animals. Because of increases in human population and consequent high cost and demand for conventional feedstuffs such as groundnut cake and soya bean meal, it has become increasingly necessary that alternative feed ingredients be found to reduce the competition between man and livestock (Iyeghe-Erakpotobor et al., 2002).There is evidence that livestock fed with crop residues and agro-industrial by-products could achieve substantial weight gains (O’Donovah, 1979).
The trend has changed from the situation in which maize stovers were considered as waste and are now being converted to animal protein for human consumption (Singh et al., 2004 and Singh et al., 2011). There has been growing policy recognition of the role of nonconventional feed resources in livestock production (FAO, 1999). Ruminants depend on two major feed resources: these are crop residues and agro-industrial by-products and they play a significant role in the nutrition of ruminant animals (Agarwal and Verma, 1983). There is very little information on the actual availability and usage of crop residues and agroindustrial by-products in the South Eastern Nigeria compared to the northern part (Onyeonagu and Njoku, 2010). Inspite of the increasing importance of crop residues, there is paucity of information available on crop residue in the South Eastern Nigeria.


The objectives of this study were as follows:
1. To determine the improvement in chemical composition due to urea treatment of maize stover as compared with the untreated stover and Centrosema pubescens.
2. To determine the potential of urea treated maize stover for growth and fattening performances of N’dama calves during dry season in humid tropics.
3. To evaluate the economics of feeding urea treated maize stover as compared with feeding untreated maize stover and Centrosema pubescens to N’dama calves.
4. To determine blood urea and ammonia levels of N’dama calves fed urea treated maize stover as compared with feeding untreated maize stover and Centrosema pubescens.



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