Effects of sweet potato meal on the growth rate of broilers

E A Ayuk

Dept of Animal Science, College of Agriculture and Forestry,
Cross River University of Technology, PMB 1123, Calabar, Nigeria.
obubragenesis@yahoo.com

Abstract

The study was conducted to find out the performance of broiler birds fed different levels of sweet potato meal (SPM). The levels of sweet potato meal in the different treatment rations were 0, 10, 20, 30, 40 and 50%, respectively.

There was a curvilinear decline in growth rate (from 27.9 to 23.3 g/day) as the maize was replaced by sweet potato root meal with a pronounced  reduction in performance overall of 17% when all the maize was replaced by sweet potato meal.

It is concluded that sweet potato root meal can replace maize meal in the diet of broilers over the weight range 50 to 1400 g, with only a slight reduction in growth rate (17% with complete substitution of maize), which may be compensated by the lower cost of the sweet potato meal.

Key words: Broilers, growth rate, sweet potato meal

Introduction

The scarcity and prohibitive cost of commercial energy sources like maize and sorghum for poultry rations, has been the main cause of the high cost of poultry products especially in developing countries. To arrest this situation, poultry raisers all over the world and particularly those of the developing countries, are forced to think of those plants that can be easily grown and yield more per unit area as compared to maize for inclusion in poultry rations. This will subsequently lead to a reduction of the cost of production of poultry meat. Sweet potato readily comes to mind as a promising alternmative.

Sweet potato tubers are used for livestock feed in Taiwan and China where this root crop is classified among low ranking priority crops (Huarg 1982).  Over 95% of sweet potato is produced in developing countries (CGIAR 2001).Asia is the world's largest producer of sweet potato with an annual production of 125 million tonnes; China alone produces more than 117 million tonnes, representing 80% of the world's production.

Sweet potato  (fresh basis) contains approximately 20% starch and 5% simple sugars. The protein of sweet potato contains about two-thirds globulin. It contains a reasonably high amount of most amino acids but is limiting in tryptophan and sulphur-containing amino acids. The peel of the sweet potato is higher in proteins, minerals and other non-carbohydrate constituents than the rest of the tuber (Uadia 1984). Sweet potato is generally considered a high-energy food and is the staple crop of many parts of the world.  The cost of production of sweet potato is much lower compared to cereal crops according to Huarg (1982).

This paper provides some preliminary data on the effect of sweet potato meal on the growth rate of broilers

Materials and methods

The study was conducted for a period of  49 days at the Gregario Araneta University, Calocan City, The Phillipines. One hundred and eighty day old broiler chicks were used. Complete Randomized Design (CRD) was used. The one hundred and eighty birds were randomly distributed into six treatment groups in three replicates. Thirty (30) birds were allotted to each ration, ten (10) birds per replicate. The birds were wing-banded for identification and then were weighed individually at the start of the experiment, each week thereafter, and lastly, at the end of the study. This was done at the same time and day of the week

The yellow variety of sweet potato tubers were bought, washed and sliced into small chips and dried under the sun until they were brittle. The chips were then milled using a hammer mill. The six treatment rations (SW0 through SW50) were formulated to contain 0, 10, 20, 30, 40 and 50% sweet potato meal, respectively. Fishmeal, soyabean (full fat), copra meal, rice bran, leucaena leaf meal, vitamin-mineral premix, bone meal and vegetable oil were the other ingredients in the treatment rations (Table 1). Feeding was ad libitum.

The data were analysed using analysis of variance (SAS1998).

Result and discussion

The crude fibre content increased (from 5.09 to 6.19%) and the calculated ME value decreased (2941 to 2809 kcal/kg)  as sweet potato meal replaced maize in the diet (Table 2). .

Analysis of variance indicated no differences among sweet potato levels between 0 and 40% with a significant reduction at the 50% substitution (Table 3). Regression indicated that in fact there was a curvilinear decline in growth rate as the maize was replaced by sweet potato root meal (Figure 1) with a pronounced  reduction in performance overall of 17% when all the maize was replaced by sweet potato meal.

The slight but consistent reduction in growth rate as sweet potato root replaced maize may have been due to the presence of unidentified inhibitors of digestive and / or metabolic processes as suggested by Gerspacio (1978). The diets became increasingly dusty as the level of inclusion of sweet potato meal in the diets increased and this may have been another limiting factor.

Conclusions

• It is concluded that sweet potato root meal can replace maize meal in the diet of broilers over the weight range 50 to 1400 g, with only a slight reduction in growth rate (17% with complete substitution of maize) which, depending on local circumstances, may be compensated by the lower cost of the sweet potato meal.

References

CGIAR 2001 Sweet potatoes: CGIAR research: areas of research. http://www.cgiar.org/research/res_sweetp.html

Gerspacio A L 1978 Sweet Potato and Cassava-based rations for broilers. The Philippines Agriculturist pp. 4-11

Huarg C P 1982 Nutritive value of sweet potato, AVROC.

SAS 1998 SAS Users Guide, Stat Inc.Cary NC.

Uadia I O 1984 Nitrogen digestion in the gut of broilers fed potato-soyabean rations. Unpublished B.Sc Thesis, Department of Animal Science, University of Ibadan, Nigeria