Studies on the nutritive value of composite cassava pellets for poultry: chemical composition and metabolizable energy

S N Ukachukwu

Michael Okpara University of Agriculture, Umudike, PMB 7267 Umuahia, Abia State, Nigeria
snukachukwu@yahoo.com

Abstract

An experiment was conducted to determine the proximate composition and true metabolizable energy (TME) value of composite cassava pellets (CCP). The CCP were analysed for proximate composition in two different laboratories, and two feeding trials were carried out for the TME determination. In the first trial, there were five feed input levels of 15g, 20g, 25g, 30g and 35g and in the second trial, levels were 20g, 25g and 30g, based on the results of the first trial. Thirty and eighteen adult (12 weeks-old) broilers (with weight range of 2.52 - 2.55 Kg), respectively, were used for the two trials, and were individually weighed, paired on weight basis and birds in each pair were randomly assigned to fed or fasted groups. Excreta were collected after 24 hours, dried, weighed and preserved for analysis.

Analysed values for dry matter (89.7%) and ash (6.75% and 6.70%) from the two laboratories were similar, and ether extract values were also similar but low (1.21% and 1.50%). Crude protein (10.75% and 10.05%) and crude fiber (23% and 23.70%) contents were also similar for the two laboratories. In the first experiment for the TME determination, feed input levels of 20g, 25g and 30g resulted in similar TME values of 2.18kcal/g, 2.19kcal/g and 2.08kcal/g, respectively. These were lower  than that of the input level of 15g, and higher  than that of the input level of 35g. In trial 2, input levels 25g and 30g produced similar TME values (2.20 kcal and 2.19 kcal respectively), which were also similar to the values obtained in experiment 1, with the yield of the 25g input level being more consistent. This suggests that an input of 25g is the most suitable input in the determination of TME of feeds using adult broilers.

Keyword: alternative energy feedstuff, broilers, composite cassava pellet, proximate composition, true metabolisable energy

Introduction

Among the factors contributing to improvement in poultry production in the tropics, feed is undoubtedly the most important, and represents 60-80% of the total cost of production for intensively reared poultry (Tewe 1997; Fajimi et al 1993). In most tropical areas, the seasonality and cost of conventional feedstuffs are such that some degree of supplementary feeding and/or alternative energy sources is required.

The chief source of energy in diets for monogastric animals in Nigeria is maize (Zea mays), but maize is also required by humans and processing industries. An increasing demand for maize has resulted in an escalating price in Nigeria, and a reduction in the amount used in diets for livestock. To increase the productivity, as well as to exploit fully the genetic potential of animals, efforts should be directed towards finding alternative sources of energy and protein. The use of such feedstuffs in ration formulation will bring about reduction in the cost of production of compound feeds, as well as the overall cost of animal production. Composite cassava pellets can be exploited in this respect.

Composite cassava pellet is a product of the whole cassava plant, made up of cassava leaves, stems and tubers. The composite cassava pellets used in this experiment were produced by the International Institute of Tropical Africa (IITA), Ibadan, Nigeria. Presently in Nigeria, cassava peels, leaves, and discard stems (very old and tender parts) are thrown away and constitute environmental hazard/pollution. Only very few are utilized as feed materials for ruminant animals. Transformation of such by-products into a friendly material will mean adding value to otherwise waste. Definitely, such transformation will involve some costs. However, the cost of production of CCP can be compensated by the environmental improvements. Even so, the cost of production would not equal the worth of the product (CCP) since the waste products are cost-free.

Cassava-based products, in form of flours and chips, have been in use for some time. However, the use of these products in livestock (especially poultry) feeding is limited by their poor texture, microbial contamination, low protein level and dustiness (Okeke 1978). The poor texture and dustiness associated with the products cause crop impaction and irritation of the respiratory tract of chickens unless the feed is pelleted or some oil is added (Okeke 1978). Composite cassava pellets thus were developed to get round these problems. Incorporation of cassava leaves, whose protein content ranges from 24 to 40% on dry matter basis, and with relatively good profile of essential amino acids (Okeke 1978; Tewe et al 1976; Muller et al 1974), will improve the protein content of the CCP. The process of pelleting will reduce the level of cyanoganic glucosides (HCN), which is the major drawback in the use of cassava (Tewe et al 2002) as well as improve the texture and reduce the dustiness.

Cassava is high energy yielding and continuously available (Okeke 1980). Its use as an alternative to conventional energy feedstuffs like maize could help reduce cost of feed and alleviate the problem of direct competition between livestock and humans for maize (Akinfala 2000; Tewe 1997).

It was therefore considered important to obtain some preliminary information about the nutrient profile of composite cassava pellet (CCP) and this study aimed at assaying CCP for its proximate components and true metabolizable energy (TME) content, as well as assessing the effect of CCP input level on TME.

Materials and methods

Two force feeding trials were carried out in sequence according to the procedure of Sibbald (1976), as modified by Sibbald (1978) for period of starvation, and according to Wehner and Horald (1982) for feeding technique. The study was carried out in the Teaching and Research Poultry Farm of the Michael Okpara University of Agriculture, Umudike, Nigeria. In trial 1, thirty 12-week old Anak strain broilers were force fed five input levels of 15g, 20g, 25g, 30g and 35g of composite cassava pellet (CCP) made into slurry by adding water at five times the volume of each sample input. There were 6 birds per input level (treatment) divided into three pairs on a live weight basis. The birds (of weight range of 2.52 - 2.55 kg), were weighed individually and housed in individual cages with free access to water, and were starved for 24 hours. Thereafter, one of each pair was randomly selected and force fed its respective sample input level and returned to the cage over clean excreta collection tray, the time recorded and allowed to stay for further 24 hours. The other member of each pair continued on starvation for the same period and is referred to as fasted member, while the former is termed the fed member. Both the fed and fasted birds still had access to water. Exactly 24 hours after placement, the trays were removed. The excreta that accumulated on tray during each 24 hour period was collected quantitatively, oven dried at 60⁰C according to the recommendation of Sibbald (1978), allowed to come to equilibrium with atmospheric moisture and weighed.

The procedure was repeated in trial 2, but with 18 birds and 3 feed input levels of 20g, 25g and 30g selected based on the results of trial 1.

Samples of the CCP and excreta were ground and stored in air-tight sample bottles for relevant assays. The CCP was analyzed for both its proximate components in two different laboratories according to AOAC (1990) methods, and its energy content by the Parr Adiabatic Oxygen Bomb Calorimetric Technique, while the excreta samples were analyzed for their energy content only.

The equation used for calculating the true metabolisable energy (TME) was as given by Sibbald (1976).

Where:

G.E_f = Gross energy of the feedstuff (kcal/g)
Y_ef = Energy voided as excreta by fed birds
Y_ec = Energy voided as excreta by unfed birds
X = Weight of feedstuff fed (g)

Data obtained were subjected to analysis of variance (ANOVA) in a completely randomized design and least significant difference (LSD) was employed to separate means, where applicable (Steel and Torrie 1980).

Results and discussion

Comparison of results of two laboratories on chemical composition and gross energy

Table 1 shows the result of the assays for proximate composition and gross energy of the composite cassava pellet carried out in two different laboratories. The gross energy and dry matter yields from the two analyses were the same (3.64Kcal/g and 89.8%). Also, values for ash were similar (6.75% and 6.70%). Ether extract values were similar but low. There were also similar values for crude protein (10.8% and 10.1%) and crude fibre (23.0% and 23.7%). The crude protein (CP) values are slightly higher than the figure (9.00% CP) reported by Akinfala (2000) and CF values were much higher (4.94% CF) than that reported by the same author. However, it should be noted that Akinfala (2000) used whole cassava and did not indicate that the material received any special treatment.

The composite cassava pellets were prepared by IITA, Ibadan, Nigeria. Unpeeled cassava root tubers were used and the tender part of the foliage (comprising the young stems and leaves with petioles) were incorporated into the pellets. The incorporated leaves account for the high crude protein, while the leaf petioles, young stems and peels account for the high crude fibre.

Comparison of true metabolisable energy of composite cassava pellets at different input levels using adult broilers

Table 2 shows the gross energy and true metabolisable energy yields of the pellets when force-fed at varying levels. The TME (Kcal/g) values in the first experiment were 2.74, 2.18, 2.19, 2.08 and 1.80 which corresponded to 15g, 20g, 25g, 30g, and 35g feed input levels respectively. In the second experiment, the TME (Kcal/g) values were 2.56, 2.20 and 2.19 corresponding to 20g, 25g, and 30g feed input levels, respectively.

Experiment 1 was more or less a preliminary survey of the energy yield of the composite cassava pellets. The TME yields at input levels 20g, 25g and 30g were statistically the same but lower than that of the 15g input and higher than that of the 35g level in the first trial. Therefore, the 20g, 25g, and 30g input levels were selected for the repeat of the study in experiment 2. The results obtained for the 25g and 30g input levels in experiment 2 were similar and consistent with the results from experiment 1, but lower than that of 20g input level. Sibbald (1976) had suggested an input level of 20g or 25g. Comparisons of the two levels under the two experiments show more consistency with the 25g input level. It could therefore be argued that 25g is the most suitable input level for the determination of TME using adult broilers.

The energy yield of the CCP was generally low, irrespective of input level. This was probably due to the incorporation of peels, tender stems and leaves (with petioles), which all have high crude fibre content, which would have reduced the metabolisable energy (ME) of cassava tuber. The lowered ME of the CCP was, however, compensated by the increase in the crude protein value and lowered cost of the product.

The CCP is a novel product from cassava and being investigated for its suitability as livestock/poultry feedstuff. The cassava used in the production of the CCP is the ordinary cassava available in the Nigerian economy. The only additional step in the process technology of CCP is the pelletization of the mixture of the whole root floor (unpeeled root tuber) and the ground dried stems and leaves.

Conclusions

• The analysis of composite cassava pellet (CCP) showed moderate true metabolisable energy, increased crude protein content and, by reason of the inclusion of some cost-free by-products of cassava, such as the peels, tender stems and leaves, the CCP would have reduced feed cost.

•  These results suggest that CCP could be a useful alternative feedstuff in the diets of livestock, especially poultry and pigs.

Reference

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