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

Sangkhom Inthapanya, T R Preston¹ and R A Leng²

Faculty of Agriculture and Forest Resources, Souphanouvong University, Luang Prabang, Lao PDR
inthapanyasangkhom@gmail.com
¹ Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV), Carrera 25 No 6-62 Cali, Colombia
² University of New England, Armidale NSW, Australia

Abstract

The experiment was carried out to study effects of supplementary dietary protein of differing solubilities, and of brewers' grains on feed intake, digestibility and N balance in local “Yellow” cattle fed ensiled cassava root, urea and rice straw as basal diet. Four local (“Yellow”) male cattle were assigned to 4 treatments in a 4*4 Latin square arrangement: BG-CSF: brewers’ grains with cassava foliage, BG-WS: brewers’ grains with water spinach, NBG-CSF: no brewers’ grains with cassava foliage, NBG-WS: no brewers’ grains with water spinach. Experimental periods were of 15 days: 9 days for adaptation, 5 days for collection of feces and urine and the last day to take rumen fluid by stomach tube.

Adding 5% of brewers’ grains to the diet increased the DM intake, the apparent DM digestibility and N retention. Similar but smaller benefits were found when water spinach replaced cassava foliage as the main source of (true) protein.

Key words: bypass protein, byproduct, soluble protein, rumen ammonia

Introduction

Livestock production in tropical areas plays a crucial role, which extends beyond its traditional supply of meat and milk. Livestock are used for multiple purposes as draft power, means of transportation, capital, credit, meat, milk, social value, hides, and provide a source of organic fertilizer for seasonal cropping (Wanapat and Kang 2013a; Jetana and Bintbihok 2013). Cattle and buffaloes also are important on smallholder farms in most developing countries to provide meat, milk, traction power and manure in integrated crop and livestock farming systems (Preston and Leng 2009).

Cassava (Manihot esculenta Crantz) is an annual crop grown widely in the tropical and subtropical regions. It is currently the third most important crop in Laos, after rice and maize. It is widely grown throughout the country by upland farmers but in small areas using local varieties and with very few inputs (CIAT 2001). Roots of cassava have high levels of energy (75 to 85% of soluble carbohydrate) and minimal levels of crude protein (2 to 3% CP); they have been used as a source of readily-fermentable energy (Kang et al, 2015; Polyorach et al, 2013). Cassava foliage is an agricultural by-product, considered to be a good source of bypass protein for ruminants (Ffoulkes and Preston 1978; Wanapat et al 2001; Promkot and Wanapat 2003; Sath et al 2008). It has been fed succcessfully to improve performance of sheep (Hue et al 2008), goats (Ho Quang Do et al 2001; Phengvichith and Ledin 2007) and cattle (Wanapat et al 2000; Thang et al 2010) in fresh, wilted or dried form. Cassava leaves are known to contain variable levels of condensed tannins; about 3% in DM according to Netpana et al (2001) and Bui Phan Thu Hang and Ledin (2005).

Water spinach (Ipomoea aquatica) plays an important role for farmers in rural areas. It is easy to cultivate and has a very high yield of biomass with a short growth period; it can be harvested in dry or flood period (Sophea and Preston 2001). The crude protein content in the leaves and stems can be as high as 32 and 18 % in dry basis, respectively (Ly Thi Luyen 2003). Water spinach is widely used for human food, but at the same time this vegetable can be given to animals such as rabbits, pigs, poultry and small ruminants. Kongmanila et al (2011) reported positive responses in feed intake and N retention when foliage from the Mango tree, which is rich in tannins and of low digestibility (Kongmanila et al 2007), was supplemented with water spinach (Ipomoea aquatica), the protein in which is considered to be highly degradable by rumen microbes (Kongmanila et al (2007).

Brewers’ spent grains (BG) are the major by-product of the brewing industry, representing around 85% of the total by-products generated (Mussato et al 2006. It is a lignocellulosic material available in large quantities throughout the year. It is considered to be a good source of bypass protein (Promkot and Wanapat 2003).

Materials and methods

Location and duration

The experiment was conducted in the farm of the Department of Animal Science, Faculty of Agriculture and Forest Resource, Souphanouvong University, LuangPrabang province, Lao PDR, from September to November, 2015.

Treatments and experimental design 

Four local “Yellow” cattle were fed ensiled cassava root ad-libitum supplemented with urea (2% of diet DM) and rice straw (1% of LW). The following treatments were applied in a 2*2 factorial arrangement within a 4*4 Latin square:

• BG-CSF: brewers’ grains with cassava foliage

• BG-WS:  brewers’ grains with water spinach

• NBG-CSF: no brewers’ grains with cassava foliage

• NBG-WS:  no brewers’ grains with water spinach

Experimental periods (Table 1) were of 15 days: 9 for adaptation, 5 for collection of feces and urine and the last day to take rumen fluid by stomach tube.

Animals and housing

The cattle (initial live weight about 90 kg) were confined in metabolism cages (made from wood and bamboo with the floor area of 100*130 cm) with an arrangement to separate feces and urine. Before the commencement of the experiment, the cattle were vaccinated against epidemic diseases and drenched to control internal parasites.

Feeding and management

The cassava roots and rice straw were bought from farmers in Luang Prabang province area. The cassava root was sliced by hand then ground (Photo 1), and stored in plastic bags for ensiling over 7 days. Rice straw was chopped into small pieces (3-5cm). Brewers’ grains were bought from Beer Lao factory in Vientiane province. Water spinach (Photo 2) and cassava (Photo 3) were grown on the farm of Souphanouvong University.  Animals were adapted gradually over a 2 week period to the cages (Photo 4) and the experimental diets. 

The ensiled cassava root was fed ad-libitum. Rice straw was offered at 1% of live weight and urea was added to the ensiled cassava root at the rate of 3% (fresh basis). Brewers’ grains (BG treatments) were fed at 5% of diet DM. Water spinach (WS) or cassava foliage (CSF) were offered at 30% of estimated DM intake. The feeds were offered two times a day (7.00 am and 4.30 pm). Water was always available.

Data collection and measurements

The cattle were weighed in the morning before feeding at the beginning of the trial and after finishing each experiment period of 15 days. Feeds offered and refused were weighed and samples collected daily to determine feed intake. Feces and urine were collected daily during days 10 through 14 of each period. 100 ml of a solution of 10% H₂SO₄ were added daily to the urine collector to maintain the pH below 4.0. At the end of each period (day 15), samples of rumen fluid were taken 3 hours after feeding in the morning using a stomach tube. The pH was measured on the fresh sample; 10 ml were preserved with H₂SO₄ for determination of ammonia.

Chemical analysis

N in urine, pH and ammonia in rumen fluid, DM, ash, N, NDF and ADF in feed offered and refused and in feces were determined by standard methods (AOAC 1990).  Water soluble N was determined in feed samples by extraction with Molar NaCl (Whitelaw and Preston 1963).

Statistical analysis

The data were analyzed by the general linear model (GLM) option of the ANOVA program in the Minitab software (Minitab 2000).  Sources of variation were animals, periods, main effects and interaction, and error.

Results and discussion

Chemical composition of feeds

NDF and ADF were lower, but ash and crude protein were similar, in water spinach compared with cassava foliage (Table 2). Brewers' grains had highest level of crude protein and NDF and ADF values similar to those in cassava roots.  N solubility in water spinach was twice that in cassava foliage with intermediate values for brewers' grains.

Feed intake

Total daily intake of DM and intake per unit live weight (g/kg LW) were higher when brewers’ grains were fed and when water spinach replaced cassava foliage (Table 3; Figure 1a;b). The level of 11-12% crude protein in DM would appear to be adequate to maximize the feed intake on a basal diet of ensiled cassava root/urea.

Figure 1a. Effect of brewers’ grains on DM intake of cattle fed ensiled cassava root, urea, rice straw and either fresh cassava foliage or water spinach	Figure 1b. Effect of water spinach compared with cassava foliage on DM intake of cattle fed ensiled cassava root, urea and rice straw with and without brewers’ grains

Apparent digestibility, N balance and rumen ammonia

Apparent digestibility of DM, OM and CP were higher when brewers’ grains were fed and when the main protein source was water spinach rather than cassava foliage (Table 4; Figure 2a;b). N retention was higher when brewers’ grains were fed and when water spinach rather than fresh cassava foliage was the main protein source (Table 4; Figure 3a;b).

Figure 2a. Effect of brewers’ grains on DM digestibility in cattle fed ensiled cassava root, urea, rice straw and either fresh cassava foliage or water spinach	Figure 2b. Effect of water spinach compared with cassava foliage on DM digestibility of cattle fed ensiled cassava root, urea and rice straw with and without brewers’ grains

Figure 3a. Effect of brewers’ grains on N retention in cattle fed ensiled cassava root, urea, rice straw and either fresh cassava foliage or water spinach	Figure 3b. Effect of water spinach compared with cassava foliage on N retention of cattle fed ensiled cassava root, urea and rice straw with and without brewers’ grains

Discussion

The stimulation of growth in ruminants with small inputs of brewers' grains into a low true protein diet has been demonstrated in many publications (Preston and Leng 1987) and has usually been attributed to the "escape" properties of the protein where ammonia levels in the rumen are adequate for optimal microbial growth. In the case reported here the large response in N retention to a very small input of protein as brewers grains may be explained by a high level of protection (escape characteristics) or a high level of essential amino acids in the escape component. Brewers' grains are also rich in phenolic compounds, particularly ferulic acid and p-coumaric acid. These soluble secondary plant compounds could precipitate protein in cassava and water spinach foliage, thus enhancing their "escape protein" properties. In other words, the brewers' grains enhances the protein to energy ratio in the metabolisable protein arising in the intestines and which are digested and absorbed. This is a similar effect to that of fish meal added to a diet of molasses-urea fed to ruminants (Preston 1971).

However, the dramatic increase in the nutritive value of the experimental diet (42% increase in N retention) as a result of supplementation with small quantities of brewers' grains (5% of diet DM) implies that the effect of this supplement was more than its contribution in enhancing the supply of escape protein. As a result of the process of fermentation by yeast in the production of beer, it can be expected that the residual "spent" grains would contain a range of "B" vitamins and other fermentation products such as Lactobacilli bacteria as well as the yeast per se.  Beneficial effects on milk production and composition in dairy cattle have been reported from replacement of soybean meal by brewers' grains (Belibasakis and Tsirgogianni 1996).  Finally there are the known health benefits from soluble phenolic compounds, including ferulic acid and p-coumaric acid, manifested in anti-oxidant, anti-cancer, anti-atherogenic and anti-inflammatory effects (McCArthy et al ---). Thus potential pre- and pro-biotic benefits may also be expected from supplemention of cattle diets with small amounts of brewers' grains.

Conclusions

• Adding 5% of brewers’ grains to a diet of ensiled cassava root-urea, with either water spinach or cassava foliage as the main protein source, increased the DM intake, the apparent DM digestibility and N retention in local Yellow cattle. Similar but smaller benefits were found when water spinach replaced cassava foliage as the main source of (true) protein.

Acknowledgement

This research is part of the requirement for the PhD of the senior author. The authors acknowledge support for this research from the MEKARN II project financed by Sida and the help from Mr. Linsay, Mr. Xang Visay and Mr Phonephilom Harkpadit in the farm of Department of Animal Science. The Faculty of Agriculture and Forest Resource, Souphanouvong University is acknowledged for providing the facilities to carry out this research.

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Received 25 November 2015; Accepted 30 December 2015; Published 1 February 2016

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