Nutritive value of fresh cassava tubers , cassava root meal and cassava chips for growing-finishing pigs

Three experiments were carried out to evaluate the nutritive value of fresh unpeeled cassava tubers, peeled, soaked cassava tubers, cassava root meal and cassava chips as energy sources for growingfinishing pigs. The varieties used were sweet and bitter types. The initial weight of the pigs ranged from 12 to 38 kg and were slaughtered when they made 90 kg. Their feed intake, growth rate and carcass characteristics were determined. The digestibility trial involved 4 castrated males in a 4x4 Latin square design. Performance of pigs was comparable to pigs fed other energy sources (or commercial cereal based diet). Pig growth rate ranged from 478 to 660 g/pig /day. Digestibility and feed efficiency of cassava-based diets were high, although young pigs (below 20 kg) tended to develop gastro-intestinal disturbances and parakeratosis when fed fresh cassava. The carcass quality was slightly affected. Carcasses from pigs fed on cassava diets were leaner and heavier than those on other rations. The studies concluded that varieties of sweet cassava could be fed fresh to pigs either peeled or unpeeled or in form of cassava chips. Further, fresh cassava can be soaked in water for one day whereas cassava chips can be dried for 8 to 10 hours prior to feeding to reduce HCN levels. Cassava can constitute the only energy source in diets of pigs provided that such diets are well balanced for protein, minerals and vitamins. The use of cassava in livestock feeds will promote cassava production and provide a sustainable outlet for this underutilised but highly adaptable crop. Introduction The currently fast expanding global human population suggests that large proportion of meat will come from pigs and poultry for they are very prolific, have a high, growth rate, feed efficiency and short generation interval compared to ruminants. Moreover, the pig serves as a source of cooking fat (lard), biogas, manure and bristles/leather. Consequently, pig production is fast rising in many countries including Tanzania. However, there are constraints to pig production in Tanzania. Among these is the nutritional deficiency particularly energy and protein. These contribute to the low productivity of pigs. This is usually a result of competition for feed stuff with humans and other livestock. The supply of essential nutrients from commercial sources is becoming expensive. Milling by-products, which are the main feed sources for pigs, are relatively expensive and not accessible in many parts of the country. Feed costs account for about 70-80% of costs of raising pigs (Henry and Correa, 2003). So the majority of smallholder farmers feed their pigs on grass, brewery wastes and human food leftovers. Efficiency and economy of production can greatly be improved by use of fairly-balanced rations based on cheap and abundant energy source. Recently, cassava has been found to be a cheap source of energy capable of replacing up to 50% of expensive cereals like maize, sorghum and wheat. Moreover, its starch is highly digestible (Balagopalam, et al., 1997). Cassava is resistant to drought, diseases, and Proceedings of the 13th ISTRC Symposium, Arusha, Tanzania, 2007 522 pests and has no critical time of planting, thus is very suitable for low-income smallholder farmers. Nevertheless, it is deficient in proteins and vitamins, thus it must be supplemented with other source of feeds rich in these ingredients (Liliana, 1995; FAO and IFAD, 2000). The cyanogenic glucosides present in cassava have to be reduced to sage levels before feeding to animals. Cassava root meal presents a problem in animal feed, as it is very dusty, a condition, which may lead to reduced palatability and intake, and ulcerogenic conditions. Some of the measures suggested for improving cassava root meal include addition of oil, molasses and pelleting. This present study was carried out to evaluate different processing methods and feed formulations to address the above problems as a means of promoting the use of cassava in livestock feeds. Materials and Methods This study was conducted at the Department of Animal Science and Production of Sokoine University of Agriculture (SUA), Morogoro, Tanzania. Three experiments were carried out using Large white and Landrace crosses of pigs. Economics of using cassava chips in pig rations was also evaluated. Carcass characteristics were also determined in all growth experiments. Experimental procedures. In all trials, animals were dewormed two weeks prior to the start of the experiments and observed further for a period of 7 days. Feeding was done at 8 and 15 hours every day. Animals were allocated to dietary treatments by ensuring a balance of initial weight and sex. They were fed according to a standard scale. Water was supplied ad libitum during the day throughout the experimental period. Body weight changes were recorded weekly. Feed intake was recorded and feed conversion ratio (FCR) computed. The animals were slaughtered when they made 90 kg and their carcass characteristics determined. The economics of pork production was also determined. In experiment 1, twenty-four pigs weighing on average 33 kg each were allocated to four dietary treatments in a completely randomised design. Diet 1 was a control diet based on maize and sorghum as energy sources. Diet 2 was a complete diet based on cassava root meal (CRM); diet 3 was made of raw (peeled and soaked) cassava root fed separately with protein concentrate (cafeteria system), whereas diet 4 was based on rice polishing. Fresh cassava tubers were purchased from nearby farms and the varieties involved were all sweet viz. Kigoma, Mzungu, Msenene and Ndunga. In treatment 3, the tubers (CRT) were washed, peeled and soaked in static water for 24 hrs. Before being fed, the tubers were chopped. The pigs were first offered 1.01.5 kg of the protein concentrate. After clearing, they were offered the peeled cassava semi-ad libitum by closely monitoring the daily intake so that no refusals were collected. Each day’s feed offered was determined by feed consumption the previous day. The cassava root meal (CRM) was prepared by peeling the cassava, chopping, dying and milling. The hydrocyanic acid (HCN) content in the cassava root meal was determined. Metabolic studies were also done to determine the digestibility and metabolisable energy content of the diets, and nitrogen retention of the pigs. A 4x4 Latin square design was used. A preliminary period of 5 days was followed by a collection period of 7 days during which faeces and urine were collected. In experiment 2, twelve pigs weighing on average 19 kg were allotted to three dietary treatments by sex, weight and litter. In treatment 1, the animals were fed fresh unpeeled cassava and protein concentrate (in the same way as diet 3 above). Cassava was fed semiad libitum. The protein mixture was fed at a rate of 1.0 – 1.5 kg/pig/day. Diets 2 and 3 each consisted of 55% peeled cassava root meal with different proportions of cotton seed/sunflower cake.