A note on ensiling the foliage of New Cocoyam (Xanthosoma sagittifolium)

Lylian Rodríguez and T R Preston

TOSOLY, AA48 Socorro, Santander, Colombia
lylianr@utafoundation.org

Abstract

Complete leaves and petioles of New Cocoyam (Xanthosoma sagittifolium) were harvested from 40 plants grown in the TOSOLY farm in Santander province, Colombia. Ten plants were separated into leaves and stems, which were weighed and then each chopped finely with a knife to give representative samples of leaves and petioles, which were taken for analysis for DM, N and ash. The other 30 plants were macerated in an ensiling machine and the  macerated product thoroughly mixed and enclosed in 28 air-tight plastic containers of 200ml capacity. Four samples were allocated for analysis on each of days 0 (before ensiling), 1, 2, 3, 4, 5 and 7 days later. The containers were kept at ambient temperature in an enclosed room.

DM and crude protein contents of fresh petiole (7.3 and 5.2) were much lower than in the fresh leaf (17 and 18% in DM, but sugars were higher (38 and 20% in DM). On a fresh basis, there was twice as much biomass in the petiole than in the leaf, but these proportions were reversed in terms of DM. The pH fell from 5.81 in the fresh mixture of leaf+petiole to 4.37 within 24h, and to 3.98 in 48h. Lactic acid was 2.07% in DM.

Key words: Crude protein, lactic acid, pH, pigs

Introduction

Early research on determining the nutritive value for pigs of the foliage of New Cocoyam (Xanthosoma sagittifolium) was based on feeding the fresh leaves (Rodriguez et al 2007, 2009a,b), This is not very convenient under practical farm conditions as regular daily supplies are not always available and often the foliage is not harvested at the most appropriate physiological6he next step was to ensile the leaves so that the harvest stage could be optimized and also to ensure a regular supply of the leaves for feeding to the pigs. To facilitate the fermentation, 10% fresh sugar cane juice (20% sugars) was added to the leaves.  This was effective, but time-consuming to ensure thorough mixing of the juice with the leaves (Rodríguez Lylian 2007, unpublished observations). There was also the question of what do with the petioles, as harvesting only the leaves is not appropriate for the plant growth cycle; also transporting the leaves alone was not practicable by the traditional system of loading them on the horse; by contrast it was easy to load the leaf and petiole together (Photo1).

Photo 1. New Cocoyam leaves + petioles transported by  “Mariscal” in TOSOLY farm

Ensiling the chopped petioles was then tested, with the idea that they could be part of the diet of pregnant sows. Despite the high moisture content (over 90%) the process of ensiling proved to be easy, with the pH falling to below 4.5 within 24 h (Rodríguez Lylian 2007, unpublished observations). Expressing the juice from the fresh petiole and measuring the brix by refractometer indicated a sugar content in the juice of 3, equivalent to approximately 38% of sugar  in the DM.

On the basis of these observations and the practical daily work in TOSOLY farm it was hypothesized that the petiole could serve as a useful additive for facilitating the ensiling of the leaves of New Cocoyam and other forages.

Materials and Methods

Location

The study was carried out in the "Finca Ecológica", TOSOLY, Morario, Guapota, Department of South Santander, Colombia (6° 18" N, 73° 32" W, 1500 masl) between 1 and 14 August 2009. At that time the air temperature ranged between 19 and 28°C in the day, falling to around 12°C during the night.

Experimental design

Complete leaves and petioles of New Cocoyam were harvested from 40 plants. Ten plants were separated into leaves and stems, which were weighed and then each chopped finely with a knife to give representative samples for analysis of leaves and petioles for analysis of DM, N and ash. The other 30 plants were macerated in an ensiling machine (Tormetal, Funza, driven by 3KW electric motor at 3500 rpm). The macerated product was thoroughly mixed and enclosed in 28 air-tight plastic containers of 200ml capacity. Four containers were assigned for analysis on each of days 0 (before ensiling), 1, 2, 3, 4, 5 and 7 days later. The containers were kept at ambient temperature in an enclosed room.

Measurements

pH was measured with a digital electrode (Pocket sized pH meter - HANNA) immediately after opening the containers. The contents were then dried by micro-wave radiation (Undersander et al 1993). Samples of the dried material were analyzed for DM, crude protein, ash and lactic acid by AOAC (1990) procedures. The descriptive statistics option in the Minitab (2000) software was used to derive mean values and standard deviations of  the pH values of the New Coocoyam silage. 

Photo 2. Mixed New Cocoyam leaves + petioles ensiled in 200 ml containers

Results and discussion

Composition of New Cocoyam leaves and petioles

DM and crude protein contents of petiole were much  lower than in the leaf but sugars were higher (Table 1). On a fresh basis, there was twice as much biomass in the petiole than in the leaf, but these proportions were reversed in terms of DM.

Effect of ensiling

The pH fell from 5.81 in the fresh mixture of leaf+petiole to 4.37 within 24h, and to 3.98 in 48h, subsequently remaining below 4.0 though the rest of the ensiling period (Figure 1). The rapid fall in pH is indicative of conditions, under which the breakdown of the protein can be expected to be minimized (McDonald 1981). The levels of DM and of lactic acid were lower (Table 2) than what are considered to be preferred levels (>25% and >6.0%, respectively, for well preserved silage) (McDonald 1981).  However, other attributes such as smell and colour were normal. with excellent acceptability by pigs, ducks and hens. There was no mould development.  The process has been applied successfully in the TOSOLY farm with over 40 tonnes of New Cocoyam silage being made over the past 30 months.

Figure 1. Mean values (with SD) of pH of mixed leaf+petiole of New Cocoyam, before and at 1, 2, 3, 4, 5 and 7 days after ensiling

Acceptability of the technique by people is also important and has been very positive as the ensiling of the intact leaves  + petioles is much easier than the process of ensiling only leaves. To ensile leaves + petioles requires passing the intact foliage through the ensiling machine such that the final product  goes directly  into the plastic container. By contrast, to ensile only the leaves it was necessary to spread them on the floor to be mixed with the sugar cane juice, the mixture then being packed into the plastic container. (Photos 3, 4, 5, 6, 7 and 8).

Photo 3. Ensiling New Cocoyam leaves (mixing with Sugar cane juice at 10 % in fresh bases)	Photo 4. Ensiled New Cocoyam leaves
Photo 5. New Cocoyam separated into petiole and leaves prior to each being macerated in the ensiling machine.	Photo 6. Petiole ensiled directly in a plastic container.
Photo 7. New Cocoyam leaves and petiole being introduced into the ensiling machine and directly from the machine into the plastic container	Photo 8. Macerated leaves + petioles delivered directly from the machine into the plastic container

Conclusions

• Mixed leaves and petioles of New Cocoyam, in the proportions that occur naturally in the plant, can be ensiled successfully without the need for additives.
  
  
• The process has been applied successfully with over 40 tonnes of New Cocoyam silage made in the TOSOLY farm over the past 30 months. Acceptability by pigs, ducks and hens has been excellent.
  
  
• The ensiling process is a fundamental feature of the appropriate management of the New Cocoyam crop, as well as ensuring a permanent supply of silage for the pigs.

Acknowledgments

We are grateful to Dr Nguyen Thi Hong Nhan of Cantho University, Vietnam, for arranging the analysis of the samples for lactic acid and crude protein

References

AOAC 1990 Official methods of analysis of the Association of Official Analytical Chemists (15^th Edition.), Washington, DC. 1, 69-90.

McDonald P 1981 Biochemistry of Silage. John Wiley & Sons Ltd (July 15, 1981)

MINITAB 2000 Minitab Reference Manual, PC Version, Release 13.2. Minitab Inc., State College, PA.

Rodríguez Lylian, Lopez D J, Preston T R and Peters K 2006 New Cocoyam (Xanthosoma sagittifolium) leaves as partial replacement for soya bean meal in sugar cane juice diets for growing pigs. Livestock Research for Rural Development. Volume 18, Article No. 91. http://www.lrrd.org/lrrd18/7/rodr18091.htm

Rodríguez Lylian, Peniche Irina, Preston T R and Peters K 2009a  Nutritive value for pigs of New Cocoyam (Xanthosoma sagittifolium); digestibility and nitrogen balance with different proportions of fresh leaves and soybean meal in a basal diet of sugar cane juice.  Livestock Research for Rural Development. Volume 21, Article #16.  http://www.lrrd.org/lrrd21/1/rodr21016.htm

Rodríguez Lylian, Preston T R and Peters K 2009b Studies on the nutritive value for pigs of New Cocoyam (Xanthosoma sagittifolium); digestibility and nitrogen balance with different levels of ensiled leaves in a basal diet of sugar cane juice.  Livestock Research for Rural Development. Volume 21, Article #27.  http://www.lrrd.org/lrrd21/2/rodr21027.htm

Undersander D, Mertens D R and Theix N 1993  Forage analysis procedures. National Forage Testing Association. Omaha pp 154

Received 11 September 2009; Accepted 27 September 2009; Published 1 November 2009

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