Brewers' grain and cassava foliage (Manihot esculenta Cranz) as protein sources for local “Yellow” cattle fed cassava pulp-urea as basal diet

Phanthavong Vongsamphanh, T R Preston¹, Viengsakoun Napasirth² and Pattaya Napasirth³

Department of Livestock and Fisheries, Ministry of Agriculture and Forestry PO Box 6644 Vientiane, Lao PDR
vongsamphanh2015@gmail.com
¹ Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV),
Carrera 25 No 6-62 Cali, Colombia
² Faculty of Agriculture, National University of Laos, Nabong Campus, PO Box 7322, Vientiane, Lao PDR
³ Faculty of Technology, Udon Thani Rajabhat University, Udon Thani, Thailand

Abstract

The experiment was carried out in Soukanya Farm, Xaythany District, situated some 19 km from Vientiane Capital. It was arranged as a random block design with three treatments and two replications (one replicate of intact males and one of females, each replicate with 6 animals of the local “Yellow” breed, intial weight 80-120 kg)). The treatments were sources of protein/fiber to provide approximately 30% of the diet DM: BG-NG: Brewers’ grains and Napier grass (Pennistum purpureum); CF: foliage of bitter cassava variety; CF-BG: 50:50 cassava foliage: brewers’ grains. Rice straw was fed on all treatments at 1 kg/d.

Responses in live weight gain (517 and 495g/d; SEM ±25) and DM feed conversion (7.55 and 8.05; SEM ±0.84) were similar for the diets in which all the protein came from brewers’ grains (BG-NG) or when the source of protein was divided equally between brewers’ grains and bitter cassava foliage (CF-BG). DM feed intake was reduced by 30% and growth rate very poor (160 g/d) when bitter cassava foliage was the only source of protein. The estimates of the margin of the value of the live weight gain (USD 3.00/kg) over feed costs (USD 0.095 – 0.118/ kg DM) were of the order of USD 1.00/day for the diets of CF-BG and BG–NG.

Keywords: bitter cassava, economics, feed conversion, live weight gain, Napier grass

Introduction

Promoting beef production from the local “Yellow” cattle is one of the development activities ear-marked by the Ministry of Agriculture and Forestry (MAF 2015) in Lao PDR. Emphasis is on technological upgrading and innovation to develop intensive fattening systems using the locally available feed resources, especially the by-products from agro-industry.

It is estimated that the five cassava starch factories in Lao PDR have a yearly production of 200,000 tonnes of pulp (MAF 2015). The four breweries produce between 200 and 300 tonnes of brewers’ grains daily (about 150,000 tonnes per year).The availability of rice straw is of the order of 3 million tonnes per year. These resources would be sufficient to fatten some 200,000 cattle per year with an added value of USD 36 million.

In an introductory experiment, an investigation was made of the potential nutritive value of the cassava pulp produced in the Lao-Indochina cassava starch factory in Nashaw village, Pakngum District in Vientiane Capital, where it had accumulated in an open pit over a period of 5 years (Phanthavong et al 2014). It was found that the pulp had ensiled naturally (pH 3.5) and uniformly (Photos 1, 2 and 3) throughout the entire depth of the pit (7m). Microbiological studies on cassava residues also revealed abundant lactobacilli in the fresh pulp (Napasirth et al 2015). The initial evaluation of the ensiled pulp showed that it had a potential nutritive value only slightly inferior to that of fresh cassava roots (Phanthavong et al 2014).

Photo 1. The open pit (100m3) holding the cassava pulp	Photo 2. Takingh samples of the pulp	Photo 3. Core samples taken from top to bottom of the pit

The potential of the ensiled pulp as the basis of an intensive fattening system was demonstrated in an experiment in which the pulp, supplemented with urea, fresh brewers’ grains and rice straw, supported growth rates of over 600 g/day in local "Yellow" catte (Phanthavong et al 2016).

The availability of fresh brewers’ grains is limited, as a major proportion is exported and the cost of transport restricts the economic use of this product to a radius of some 50-100 km around the factories.

An attractive alternative to brewers’ grains is the fresh foliage of cassava which has been shown to be an effective source both of protein and fiber in intensive cattle fattening diets based on molasses-urea in the Dominican Republic (Ffoulkes and Preston 1978). The cassava foliage used by these researchers was of the “sweet” variety as the cassava in the Dominican Republic is grown mainly for human consumption. However, the cassava used for starch production in Lao PDR is produced from “bitter” varieties as these are higher-yielding. The difference between the sweet and bitter varieties is in the level of cyanogenic glucosides which are in higher concentration in the bitter varieties (Phuong et al 2016).

The hypothesis tested in this experiment was that foliage from a bitter variety of cassava could be used as the source of bypass protein and fiber for fattening local “Yellow” cattle on a basal diet of cassava pulp-urea.

Materials and methods

Location and duration

The experiment was carried out in Soukanya Farm, Xaythany District, situated some 19 km from Vientiane Capital, from 1 June to 29 September 2015.

Experimental design

The experiment was arranged as a random block design with three treatments and two replications (one replicate of 6 intact males and one of 6 females). The treatments were sources of protein/fiber to provide approximately 30% of the diet DM, as follows:

BG: Brewers’ grains and Napier grass

CF-RS: Foliage of bitter cassava variety and rice straw

CF-BG-RS: 50:50 bitter cassava foliage: brewers’ grains and rice straw

Animals and housing

Thirty Six “Yellow” cattle, average age 2 years and initial weight of 80-120 kg were housed in six pens each with 6 animals. They were treated for internal and external parasites with Ivomex-F intramuscularly, and vaccinated against Foot and Mouth Disease (FMD).

Feeding system

During a 14 day adaptation period, the diet was changed gradually from Napier grass to the experimental treatments (Tables 1 and 2).The fresh cassava foliage was harvested daily from farmers’ plots near the research farm. It comprised tender stems, leaves and petioles from the top 30-40 cm of the plant. It was chopped by machine into lengths of 2-3cm. The fresh cassava pulp and fresh brewers’ grains were transported to the farm every 1-2 weeks from the factory/brewery in the Vientiane area.

Measurements

The cattle were weighed before morning feeding at the beginning of the trial and every 14 days. Feeds offered and refused were recorded daily.

Chemical analysis

Feed ingredients were analysed using the methods of AOAC (1990).

Statistical analysis

The data were analysed by the general linear model option of the ANOVA program in the Minitab (2000) software (version 16.0). In the model the sources of variation were: treatments and error. Live weight gain was determined by the linear regression of live weight (Y) on days in the experiment (X).

Results

Experimental design

The decision to consider males and females as replicates of the experimental treatments was made on the basis of the cattle available for the experiment. This was justified on the basis of the similar performance of males and females on the experimental treatments (Figure 5).

Feed intake, live weight gain and feed conversion

There was a tendency (p=0.076) for DM intake to be lower on the diet with cassava foliage and rice straw (Tables 3 and 4; Figure 1). Responses in live weight gain and feed conversion were similar for the diets in which all the protein came from brewers’ grains (BG-NG) or when the source of protein was divided equally between brewers’ grains and bitter cassava foliage (CF-BG-RS) (Figures 2 - 3). Animal performance was very poor when bitter cassava foliage was the only source of protein. Effects of treatments were similar for intact male and female cattle (considered as replicates in the statistical analysis).

Figures 1-3. DM intake, live weight gain and DM feed conversion of cattle fed cassava pulp-urea and either brewers' grains-Napier grass (BG-NG), bitter cassava foliage - brewers' grains, rice straw CF-BG-RS,or bitter cassava foliage - rice straw (CF-RS)				Figure 4. Live weight gain of groups of male and female cattle fed the experimental diets

Figure 5. Trends in live weight with time on experiment for Yellow cattle fed a basal diet of cassava pulp supplemented with urea and either brewers’ grains, (BG-NG) or bitter cassava foliage (CF-RS) or a combination of brewers’ grains and bitter cassava foliage (CF-BF-RS)

Economic analysis

At the present time the cassava pulp has no commercial value. The price paid for fresh cassava root for delivery to the starch factory was USD 0.0375/kg. On the basis that the feeding value of the pulp DM is some 80% of the value of the fresh root DM (Phanthavong et al 2014) this would indicate a price for the fresh pulp of the order of US$0.0188/kg (allowing for the differences in DM content: 35% for the root and 23% for the pulp). The data in Table 5 are estimates of the costs of the feed ingredients relative to the value of the live weight gain of the finished animals. The estimates of the margin of the value of the live weight gain (USD 3.00/kg) over feed costs are of the order of USD1.00/day for the diets of BG –NG and CF-BG-RS.

Discussion

The original premise in developing a system for utilizing the cassava pulp was to use fresh cassava foliage as the source of bypass protein and fiber, following the successful results with a similar approach used in developing a fattening system based on molasses-urea in the Dominican Republic (Ffoulkes and Preston 1978).The lack of fresh cassava foliage at the time of initiating the first experiment led to the decision to use brewers’ grains as the source of bypass protein and rice straw as the source of fiber (Phanthavong et al 2016). The present experiment was the first attempt to introduce the use of cassava foliage as the protein-fiber source in a diet based on cassava pulp-urea. The cassava foliage was from a "bitter" variety which has higher root yield than "sweet" varieties and  is exclusively planted by farmers when the roots are destined for starch manufacture. Bitter varieties (hence the use of the description "bitter") have much higher concentrations of HCN precursors (Phuong et  al 2016)

The first observations, when bitter cassava foliage was the only source of protein-fiber to balance the cassava pulp-urea, indicated low feed intakes due to reluctance of the cattle to consume the bitter cassava foliage.  However, it was observed that when some brewers’ grains were also offered then the intake of the bitter cassava foliage was increased. Based on these observations the present experiment was designed.

The results of the experiment show clearly that combining small amounts (15% of the diet DM) of brewers’ grains with the bitter cassava foliage supported the same growth as on diets in which the brewers’grains provided all the bypass protein (29% of the diet) with rice straw (Phanthavong et al 2016) or with fresh Napier grass (this experiment) as the fiber source.  Based on these findings, experiments were subsequently  carried out in which the brewers’ grains were reduced to even lower levels (4% of the diet DM) as the supplement to fattening diets for cattle based on cassava pulp-urea and sweet cassava foliage (Inthapanya et al 2016) or cassava pulp-urea and bitter cassava foliage (Le Binh Phuong personal communication).

The economic analysis of the results of the present experiment illustrate the potential for developing intensive fattening in Lao PDR of local "Yellow" cattle based on the byproduct pulp from cassava-starch factories.This potential is reflected in the recent formation of the “Vientiane Beef  Group”  in which eleven farms (Map 1) are collaborating to use this technology for producing quality beef for the local market and for export.

Map 1. Location of cassava starch factory and eleven farms that are members of the "Vientiane Beef Group" and using the cassava pulp technology

Conclusions

• Responses in live weight gain (517 and 495g/d; SEM ±25) and DM feed conversion (7.55 and 8.05; SEM ±0.84) were similar for the diets in which most of  the protein came from brewers’ grains (BG-NG) or when the source of protein was divided equally between brewers’ grains and bitter cassava foliage (CF-BG-RS).
  
  
• DM feed intake was reduced by 30% and growth rate very poor (160 g/d) when bitter cassava foliage was the only source of protein.
  
  
• The margin of the value of the live weight gain (USD 3.00/kg) over feed costs (USD 0.095 – 0.118/ kg DM) was of the order of USD 1.00/day for the diets of CF-BG-RS and BG–NG.

References

AOAC 1990 Official methods of analysis. Association of official Analysis (15th edition). Washington, D.C, USA.

Ffoulkes D and Preston T R 1978 Cassava or sweet potato forage as combined sources of protein and roughage in molasses based diets: effect of supplementation with soybean meal. Tropical Animal Production, Volume 3, Number 3 pp186-192 http://www.utafoundation.org/UTAINFO1/TAP/TAP33/3_3_1.pdf

Inthapanya S, Preston T R and Leng R A 2016 Ensiled brewers’ grains increased feed intake, digestibility and N retention in cattle fed ensiled cassava root, urea and rice straw with fresh cassava foliage or water spinach as main source of protein. Livestock Research for Rural Development. Volume 28, Article #20 http://www.lrrd.org/lrrd28/2/sang 28020.htm

MAF 2015 Ministry of Agriculture and Forestry 2015 Yearly report, Lao PDR

Minitab 2000 Minitab Software Release 13.2,Minitab Inc., State College Pennsylvania, USA.

Napasirth V, Napasirth P, Sulinthone T, Phommachanh K and Cai Y 2015 Microbial population, chemical composition and silage fermentation of cassava residues. Animal Science Journal. 86(9): 842-849. doi: 10.1111/asj.12362.

Phanthavong V, Viengsakoun N, Sangkhom I and Preston T R 2014 Cassava pulp as livestock feed; effects of storage in an open pit. Livestock Research for Rural Development. Volume 26, Article #169. http://www.lrrd.org/lrrd26/9/phan26169.htm

Phanthavong V, Khamla S and Preston T R 2016 Fattening cattle in Lao PDR with cassava pulp. Livestock Research for Rural Development. Volume 28, Article #10. http://www.lrrd.org/lrrd28/1/phan 28010.html

Phuong L T B, Preston T R and Leng R A 2016 Effect of foliage from “sweet” and “bitter” cassava varieties on methane production in an in vitro incubation with molasses supplemented with potassium nitrate or urea. Livestock Research for Rural Development. Volume 24, Article #189. Retrieved April 2, 2014, from http://www.lrrd.org/lrrd24/10/phuo24189.htm

Received 27 September 2016; Accepted 2 October 2016; Published 1 November 2016

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