The effect of increasing levels of dried leaves of sweet potato (Ipomoea batatas) on dry matter intake and body weight gain performance of broiler finisher chickens

Wude Tsega and Berhan Tamir*

Andassa Livestock Research Center, P.O. Box, 27, Bahir Dar, Ethiopia
wude2007@yahoo.com
Addis Ababa University Faculty of Veterinary Medicine, Ethiopia
berhantamir@yahoo.com

Abstract

This study was conducted with the objective of determining the effects of increasing levels of air dried leaves of sweet potato on dry matter intake and body weight gain of Ross broiler finisher chickens. Three hundred chicks with similar body weight of 540 ± 5.28 g and aging 29 days were randomly distributed using completely randomized design in to 15 pens each with 20 chicks and five treatment rations were allocated each with three replications. The five dietary treatments consisted of 0 %, 5%, 10%, 15% and 20% air dried leaves of sweet potato.  The experimental feed ingredients as well as the formulated rations were analyzed for dry matter and nutrient contents. The experiment lasted for 28 days during which dry matter intake and body weight change was measured.

The laboratory chemical analysis results showed that dried leaves of sweet potato contained 25% crude protein  and 2672.44 kcal ME /kg dry matter, indicating its potential to be used as sources of both protein and energy. The dry matter intake and body weight gain of birds fed on diets containing dried leaves of sweet potato up to 10% inclusion was similar with the control group. But, beyond 10% air dried leaves of sweet potato inclusion, the dry matter intake and body weight gain were reduced from the control group.

The results of this study suggested that inclusion of air dried leaves of sweet potato up to the level of 10% of the diet dry matter in the finisher ration might be considered as the optimum level of inclusion when birds are sold on live weight basis.

Key words: byproducts, poultry

Introduction

Most experiments on poultry simply deal with the substitution of one ingredient by another, but within the context of an already well balanced diet, which provide no answer to the question how chickens should be fed where cereals, high quality oil seed cakes, vitamin and mineral premixes are scarce. This situation warrants the evaluation of agricultural by-products (non- conventional feeds) and incorporation of suitable ones into poultry feeds (Moghazy and Elwatak 1982).

In developing countries where labor is cheap and climatic conditions do not demand more than simple and inexpensive housing for poultry, feed cost is the most important expense accounting for 55 to 75 % of total production cost of poultry (Ensminger et al 1990). Replacing cereals and expensive and less available agro-industrial by-products with agricultural by-products, which are less exploited by man is one of the solutions to increase the supply of animal protein. Broiler production should be supported with efficient techniques of incorporating locally available agricultural by-product feeds. The use of agricultural by-products in poultry nutrition represents valuable means of the indirect production of food from waste (El Boushy and Vanderpoel 2000).

Leaves and forages, such as sweet potato leaves, have been traditionally used for other purposes or even wasted, but recently they have been used to replace upto 20% maize in broiler diets (Teguia et al 1993). However, the leaves of sweet potato have some adverse effects on weight gain and feed consumption due to the fact that sweet potato leaf meal is deficient in an essential amino acid lysine, necessitating the inclusion of feed ingredients with adequate lysine contents in poultry diets (Fuller and Chambellain 1982 and Teguia and Beynen 2005). The diets containing leaf meal generally have higher protein content, and the protein content of sweet potato leaves ranges from 24- 29% CP (Nguyen Thi Thuy and Ogle 2004). 

Even though sweet potato is grown in many parts of Ethiopia for tuber production, its by-products are commonly fed to ruminant stock or left on the field during defoliation as well as tuber harvesting. However, information on feeding value of the leaves of sweet potato in the diets of broiler chicks in Ethiopia is generally inadequate. Thus, the objective of this   study was to determine the effect of including different levels of dried sweet potato leaves on dry matter intake and growth rate of finisher Ross Broiler Chickens.

Materials and methods 

The feed ingredients for the formulation of the experimental rations of this study were maize, dried leaves of sweet potato, wheat middling, full fat soybean, peanut cake, dicalcium phosphate, limestone, salt and vitamin and mineral premix. All listed ingredients were used to formulate the finisher chicks ration (Table 1). Sweet potato (Ipomoea batata), Kubato variety was planted using vine cut. The planted vine length was 30 to 60 cm with 100 cm between ridges and 30 cm between plants. It was grown for 110 days undertaking all necessary agronomic management practices. When the tuber matured for human consumption the leaves of sweet potato were cut and sun dried for two to three days on plastic sheet laid on concrete floor. The leaf of sweet potato was separated from the stem before drying. The dried leaves were ground to pass through 7 mm mesh screen for mixing with other ingredients. All samples of feed ingredients, feed offered and refused were analyzed for dry matter, crude protein, ether extract, crude fiber and ash using the Weende or proximate analysis method of the AOAC (1990). The treatment diets were formulated based on 0% dried leaves of sweet potato (SPL), 5% SPL, 10% SPL, 15 % SPL, and 20 % SPL.

The experiment was conducted in a completely randomized design, with five dietary treatments each with three replications. A total of 300 chicks were randomly assigned into five dietary treatments containing of different levels of dried leaves of sweet potato as shown below:

At the age of 29 days, a total of three hundred chicks with similar body weight of 540.19 ± 5.28 g were selected and distributed randomly in to five dietary treatments replicated thrice each with 20 chicks. The birds were kept in 1.5 x 1.65 m wire-mesh partitioned on deep litter housing, which was covered with sawdust litter material of 10 cm depth. The wet litter was changed with dry and clean sawdust whenever necessary. The chicks were fed ad libitum offering twice a day at 0800 and 1700 hours throughout the experimental period. Water was available at all times and the finisher feeding experiment lasted for 28 days. Feed was offered in horizontal feeders, water was provided in plastic fountains. The chicks were vaccinated against new castle disease at day seven and day twenty-five through the ocular route. Other health precautions and disease control measures were taken throughout the study period.

The daily as well as total feed consumption of chicks was calculated as the difference between the amount of feed offered and the amount feed refused. The feed leftover was weighed after removal of the external contaminants. The dry matter intake was computed by multiplying the feed intake by the dry matter content of feed offered.

Birds were weighed individually on weekly basis with sensitive balance, and average body weights of the chicks were computed for each replication. The mean dry matter conversion ratio was determined by dividing the mean daily dry matter intake with a mean daily body weight gain.

To test the relationship and association of dry matter conversion ratio and daily weight gain with the levels of dried leaves of sweet potato, regression analysis were done. To determine the functional relationship between the response of main parameters (mean daily dry matter intake, daily body weight gain, and dry matter conversion ratio) and the treatment levels, trend comparison was undertaken.

Results and discussion 

The laboratory chemical analysis result of feed ingredients used in formulation of the ration is shown in Table 2. The crude protein and energy contents of dried leaves of sweet potato were 25% and 2672 .44 ME kcal/ kg respectively. This can be considered as good sources of protein. Le Van An (2004) also conclude that dried leaves of sweet potato can be considered as valuable protein source in the form of fresh, dried or silage and can replace groundnut cake. Teguia et al (1997) reported similar results regarding the crude protein content of dried leaves of sweet potato. The metabolizabel energy   of dried leaves of sweet potato in this trial was equivalent to that reported by Hoang et al (2003), who reported 2223 kcal ME /kg DM in fresh leaves of sweet potato.  Dried leaves of sweet potato were comparable with maize in terms of EE, indicating its potential used for energy source.

The high ash content of dried leaves of sweet potato reflected the high calcium concentration. Ruiz et al (1980) stated that leaves of sweet potato are a good source of Ca. Since, high Ca to P ratio (1-2:1) needed for poultry as compared to other livestock (Phillips 1990), dried leaves of sweet potato could be a good feed ingredient of mineral source in poultry ration. But, dried leaves of sweet potato seemed to be low in P, content indicating the need for P supplementation of diets containing dried leaves of sweet potato in order to maintain the recommended proportion between Ca and P for the different classes and production stages.

The relationship between sweet potato leaf meal inclusion level and daily live weight gain is significant (Figure1).

Similarly, Teguia et al (1993) reported lower body weight of broiler chicks on 20 % dried leaves of sweet potato inclusion. Generally, the low body weight gain beyond 10% dried leaves of sweet potato might be associated with less feed intake at higher levels of dried leaves of sweet potato inclusion and possibly due to deficiencies of certain amino acids. This idea was supported by the work of Le Van An (2004), who stated that leaves of sweet potato are high in protein content compared to other protein rich forages but lysine is the first limiting amino acid. The same author conducted a feeding trial on pigs and found that pigs fed on sweet potato leaves with additional synthetic lysine had comparable daily live-weight gains with that of pigs that received fishmeal. The birds assigned to 5, 10 and 15% dried leaves of sweet potato in the present study gained approximately similar body weight as reported by Amha (1990) on noug seed cake supplemented birds, indicating its potential to be used substituting noug seed cake. The other feed ingredients in his study were maize, wheat screening, cottonseed meal, meat and bone meal, limestone and salt.

As depicted in Figure 2 there was direct positive linear relationship and strong correlation between the amounts of feed required per unit body weight gain and the levels of dried leaves of sweet potato inclusion.

The variation of 82% in dry matte conversion ratio was accounted for by the linear function of the inclusion levels of dried leaves of sweet potato. The linear response of dry matte conversion ratio to change in the inclusion levels of dried leaves of sweet potato within the range of 0 to 20% was significant at 5% and 1% levels of significance (Table 3). Dry matte conversion ratio increased with the levels of dried leaves of sweet potato, which indicated that the feed is less efficiently used at higher levels of dried leaves of sweet potato inclusion.

The poor feed conversion efficiency could be because of poor nutrient utilization of birds at increasing levels of dried leaves of sweet potato in the ration, which, resulted in lower live weight gain of the chicks. Farrell el al (2000) reported the non-significant difference in dry matter conversion efficiency by broilers fed on 0, 4, 8, 12 and 16% dried sweet potato vine meals

The results of this study clearly indicated the potential of dried leaves of sweet potato to provide adequate energy and protein for optimum growth and feed efficiency when incorporated into the finisher chicks ration up to the level of 10-15% of the diet DM. Similar findings were reported by (Teguia et al 1993), where inclusion of dried leaves of sweet potato up to the level of 20% of the diet DM resulted in no detrimental negative effects on body weight and feed conversion efficiency.

The trend analysis result showed that there were linear, quadratic and cubic responses of chicks to the inclusion levels of dried leaves of sweet potato (Table 4). The linear response of the dry matter intake, body weight gain and dry matter  conversion ratio to the levels of dried leaves of sweet potato were highly significant (P<0.01), where as the quadratic and cubic responses to the inclusion levels of dried leaves of sweet potato, were not statistically significant (P>0.05).

Conclusions

• The results of laboratory chemical analysis showed that the CP content and ME values of dried leaves of sweet potato were 25% CP and 2672.44 kcal/kg DM, respectively.

  
  

• Inclusion of dried leaves of sweet potato beyond 10% in the diet of finisher broilers resulted in reduced dry matter intake than the control diet. 

  
  

• Inclusion of dried leaves of sweet potato at the levels of 15 and 20% of the diet resulted in significant lower weight gain than the control group.

  
  

• The results of this study revealed that dried leaves of sweet potato inclusion levels up to 10% in the finisher ration resulted in similar nutrient intake and live weight gain of finisher chicks and this level can be considered as the good level of inclusion with less negative effect on the dry matter intake and body gain performance of the chickens.

References 

AOAC 1990 Official Methods of Analysis (13^th ed.). Association of Official Analytical Chemists.15^th edition. AOAC Arlington, Virginia, USA. pp 12-98.

Amha Kassahun 1990 Evaluation of the nutritive and supplementary values of noug seed meal (Guizotia abyssinica) in commercial broiler chicks ration.  M.Sc. Thesis Submitted to School of Graduate Studies of Alemaya University. 143p.

EI Boushy R Y and Vanderpoel F B 2000 Handbook of poultry feed from waste processing and use. (2^nd edition). Netherlands. pp 301- 310.

Ensminger E M, Oldfield J E and Heinemann W W 1990 Feeding Poultry. pp. 413 – 430 In: Feed and Nutrition (2^nd edition).  Ensminger publishing company. Clovis California.

Farrell R D, Jibril  J, Maldonada H.  and Mannion P 2000 A note on a comparison of the feeding value of sweet potato vines and Lucerne meal for broiler chicks. Journal of Animal Feed Science and Technology 85: 145-150

Fuller M F and Chambelain A G 1982 Protein requirements of pigs. In: W Haresign (edition). Recent Advances in Animal Nutrition. Butterworth, London. 176p.

Hoang Nghia Duyet, Nguyen Dinh Son, Nguyen Van An and Truong Thi Thuan 2003  Effect of high dietary levels of sweet potato leaves on the reproductive performance of pure and crossbred Mong Cai Sows. Livestock Research for Rural Development 15 (6) http://www.lrrd.org/lrrd15/6/duye156.htm

Le Van An 2004 Sweet potato leaves for growing pigs, biomass yield, digestion and nutritive value. Department of Animal Nutrition and Managment, Uppsala. http://diss-epsilon.slu.se/archive/00000639/01/Agraria470.pdf

Moghazy M E and Elwatak S A 1982 Some neglected feedstuffs from vegetable and fruit wastes. Journal of World Poultry Science 38: 18-25

Nguyen Thi Thuy and Ogle B 2004 The effect of supplementing different green feed (water spinach, sweet potato leaves and duck weed) to broken rice based diets on performance, meat and egg yolk color of Luong Phuong chickens. Department of Animal Nutrition and Management, Sweden. http://www.mekarn.org/Research/thuyctu.htm

Phillips J 1990 Types and roles of feedstuffs. pp. 250-264. In: M E Ensminger (edition). Feeds and Nutrition. Clovis California, 2^nd edition.

Ruiz A E, Pezo D and Martinez L 1980 The use of sweet potato (Ipomoea butatas). Journal of Tropical Animal Production 5: 144-151

Teguia A and Beyenen A C 2005 Alternative feedstuffs for broiler in Cameron.  http://www.lrrd.org/lrrd17/3/tegu17034.htm

Teguia A Tchoumboue J, Mayaka B T  and Tankou C M 1993 The growth of broiler chicks as affected by the replacement of graded levels of maize by sweet potato leaves (Ipomea batatas). Animal Feed Science and Technology  40: 233-237

Teguia A, Niwe R M and Nguekouo Foyette C 1997 Effect of replacement of maize with dried leaves of sweet potato (Ipomea batatas) and perennial peanuts (Arachis glabratas) on the performance of finishing broilers. Animal Feed Science and Technology 66: 283- 287

Received 26 September 2008; Accepted 6 August 2009; Published 3 December 2009

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