Brewers’ grains (5% of diet DM) increases the digestibility, nitrogen retention and growth performance of goats fed a basal diet of Bauhinia accuminata and foliage from cassava (Manihot esculenta Crantz) or water spinach (Ipomoea aquatica)

Phonevilay Silivong^1,3, T R Preston², Nguyen Huu Van³ and Duong Thanh Hai³

¹ Animal Science Department, Faculty of Agriculture and Forest Resource. Souphanouvong University Lao PDR
silivongpvl@yahoo.com
² Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV), Carrera 25 No 6-62 Cali, Colombia
³ Faculty of Animal Sciences, Hue University of Agriculture and Forestry, Hue University, Vietnam

Abstract

Digestibility, N balance and growth studies were carried out with local goats to determine the effect of supplementing foliage of the legume tree Bauhinia accuminata) with cassava foliage or water spinach (30-40% of diet DM) with and without low levels of brewers’ grains (5% of diet DM).

The supplement of brewers’ grains improved the growth rate of the goats by 44% and the DM feed conversion by 25% when the protein supplement was cassava foliage. Comparable data when water spinach was the protein supplement were 11 and 5%. It is suggested that brewers’ grains, a fermented byproduct from brewing “beer”, act as a prebiotic when added to a diet containing potentially toxic elements such as the cyanogenic glucosides present in cassava foliage.

Key words: biochar, prebiotics, protein solubility, synergism

Introduction

Research by Silivong and Preston (2015) showed that the growth rate of goats fed foliage of the legume tree Bauhinia accuminata was increased by supplementation with fresh water spinach and biochar. The protein in water spinach is very soluble (Silivong and Preston 2015) and it is thought that its role in improving the utilization of foliages of low digestibility, such as Bauhinia accuminata, is because the water spinach acts as a source of readily available nitrogenous compounds for rumen micro-organisms (Silivong and Preston 2015, 2016).

The positive role of biochar as a supplement in ruminant diets is thought to reflect another feature of ruminant nutrition, namely as a support mechanism for biofilms that host consortia of micro-organisms facilitating the utilization of nutrients with major benefits for the process of rumen fermentation (Leng 2014). In this role, it appears that biochar is acting as a “prebiotic”, by promoting synergism between nutrients and micro-organisms in the animal’s digestive system.

A similar synergism appears to be the explanation for the beneficial effects on growth rates of cattle (Binh et al 2017) and goats (Sina et al 2017) of small proportions in the diet of brewers’ grains, a byproduct derived from the industrial brewing of beer. The research with goats (Sina et al 2017) highlighted a major interaction between the effect of the supplementary brewers’ grains and the nature of the basal diet. The improvement in growth rate due to addition of brewers’ grains was 130% when the basal diet was fresh cassava foliage but only 30% when the basal diet was water spinach (Sina et al 2017).

The hypothesis that was tested in the present experiment was that goats fed foliage of the legume tree Bauhinia accuminata wwould respond positively in growth rate and feed conversion to a supplement of brewers’ grains, and that the degree of response would be greater when cassava foliage, rather than water spinach, was the complementary source of protein.

Materials and Methods

Location and duration

The experiments were conducted in the Department of Animal Science Farm, Souphanouvong University, Luang Prang Province, Lao PDR, from August 2017 to January 2018.

Experimental treatments and design

The basal diet was fresh foliage from the legume tree Bauhinia accuminata fed ad libitum, ssupplemented with biochar (1% of diet DM) and cassava root chips (4% of diet DM).

The treatments in a 2*2 factorial arrangement were:

Source of protein-rich foliage:

• Water spinach (WS)
• Cassava (CF)

Supplementary brewers’ grains

• 4% of DM feed intake (BG)
• No supplement (NoBG)

In the digestibility study  (Table 1) the design was a 4*4 Latin Square with 4 female goats and 4 periods each of 12 days: 7 days for adaptation and 5 days for collection of feed refusals, feces and urine.

The goats (local breed) weighed 15.5±0.65 kg and were 5-6 months of age. They were purchased from farmers around Luang Prabang city. They were housed individually in metabolism cages made from bamboo (dimensions of width 0.8 m, length 0.9 m and height 1 m), designed to collect separately feces and urine.

In the growth study the design was a random block with 4 replications of the two factors in a 2*2 factorial design, with sixteen goats (balanced males and females) with initial body weight of 14.4 ± 1.45 kg and 5-6 months of age. They were housed in individual pens made from wood and bamboo.

In both studies, the goats were vaccinated against Pasteurellosis and Foot and Mouth disease and were de-wormed before the start of the experiment.

Feeding and management

Foliages of Bauhinia accuminata and water spinach (Ipomoea aquatica) were collected daily from natural stands in and around the University campus. Cassava (Manihot esculenta Crantz) foliage was collected daily from a demonstration plot in the Department of Animal Science Farm. Cassava root was harvested from the demonstration plot in the department of Animal Science Farm. It was chopped into small pieces and exposed to sunlight for 48h to reduce the moisture to about 15%. Brewers’ grains were purchased from a brewery in Vientiane city.

The biochar was produced by burning rice husks in a top lit updraft (TLUD) gasifier stove (Olivier 2010). It was ground to a particle size that passes through a 1 mm sieve. The biochar was mixed with the cassava root chips and fed from a plastic bucket. Bauhinia foliage, water spinach and cassava foliage were hung in bunches above the feed trough (Photos 1-3). Fresh feeds were offered twice daily at 07:30 and 16:00h. Water was freely available.

Photo 1. Cassava foliage hanging above the feed trough	Photo 2. Water spinach hanging above the feed trough	Photo 3. Bauhinia accuminata hanging above the feed trough

Measurements

Metabolism study

Live weight was recorded in the morning before feeding at the beginning and at the end of each period. Feeds offered, and refusals were collected daily during the 5 days of the collection period. Urine was collected in buckets with 20 ml of a solution of sulphuric acid to ensure a pH of less than 4 (10% sulphuric acid concentrate + 90% distilled water). Feces and urine were collected daily and stored in the refrigerator (4-8ºC) until the end of each period, when sub-samples were mixed together.

Growth study

Live weight was recorded in the morning before feeding at the beginning and at 10-day intervals until the end of the 90-day experiment. Live weight gain was calculated from the linear regression of live weight (Y) on days from the start of the experiment (X).

FeFeed consumption was recorded daily. Refusals were collected from individual animals every morning before offering new feed. Samples of Bauhinia, water spinach and cassava foliage (offered and residues) were separated into stems and leaves (containing attached petioles). Representative samples of each component were stored at -18°C until they were analysed. Samples of rumen fluid were taken on the last day of the experiment, using a stomach tube.

Chemical analyses

The samples of feeds offered and refused were analysed for DM, NDF, ADF, N and ash according to AOAC (1990) methods. The pH of rumen fluid was measured with a digital pH meter, prior to addition of sulphuric acid for subsequent analysis of ammonia by steam distillation (AOAC 1990) and VFA by high pressure liquid chromatography (Water model 484 UV detector; column novapak C18; column size 3.9 mm x 300 mm; mobile phase 10 mM H₂ PO₄ [ [pH 2.5]) (Samuel et al 1997). Solubility of the protein in the diet components was determined by extraction with M NaCl (Whitelaw et al 1961).

Statistical analyses

Metabolism study

The data were analyzed by the general linear model (GLM) in the ANOVA program of the Minitab software (Minitab 2000).

The statistical model used in the digestibility study was:

Y_ijk = μ + T_i + P_j +A_k + e _ijk

Where, Y_ijk = Dependent variables

μ = Overall mean

T_i = treatment effect (i=1-4)

P_j = column effect (j=1-4)

A_k = row effect (k=1-4)

e_ijk = random error

Growth study

The statistical model was:

Y_ijk = μ + B_k + P_i + A_j + P _i*A_j+ e_ijk

μ = Overall mean

B_k= Block effect

P_i = replacing water spinach by cassava foliage

A_j = with or without Brewers’ grains

P_i*A_j = Interaction between source of protein (water spinach or cassava foliage) and with or without brewers’grains

e_ijk = random error

Results and discussion

Chemical composition of diet components

The low values for solubility of the protein in the leaves of Bauhinia and cassava, and the high values for the leaves of water spinach (Table 2), are in agreement with previous observations (Silivong and Preston 2016) and are assumed to reflect different levels of tannin-rich compounds in the leaves of all three species.

Metabolism study

The two factors had contrasting effects on digestibility of DM and on daily N retention (Table 3). Supplementation with brewers’ grains increased the digestibility of DM but the effect was more pronounced when cassava foliage was the source of additional protein as compared with water spinach. Daily N retention was similar for both foliages in the absence of brewers’ grains but, when brewers’ grains were added, N retention was greater with cassava than with water spinach (Figure 1).

Figure 1. Effect of brewer’s grain on N retention in goats fed water spinach or cassava foliage as supplementary protein source

Figure 2. Effect of brewer’s grain on N retention as % of digested N in goats fed Bauhinia accuminata and water spinach or cassava foliage as supplementary protein source

Growth study

The Bauhinia foliage accounted for two thirds of the total DM consumed (Table 4; Figure 3). Other components were in similar proportions in each of the diets, except for the brewers’ grains which was slightly higher (5% of diet DM) compared with the planned level of 4% of diet DM. Addition of the brewers’ grains resulted in a small increase in diet crude protein content from 13.6 to 14.2% and from 13.8 to 14.5%, for the cassava foliage and water spinach treatments, respectively.

Figure 3. Proportions of dietary components in each treatment

There was an interaction between the effects of the two dietary factors on DM intake, growth rate and DM feed conversion (Table 5). When the protein-rich foliage was from cassava, the supplement of brewers’ grains increased the DM intake and the growth rate and improved the feed conversion but did not affect these criteria when the supplementary protein source was water spinach (Figures 3 and 4). This result is in line with the findings of Sina et al (2017) who supplemented brewers’ grains (5% of diet DM) to goats fed fresh cassava foliage or water spinach, as the sole diet. In that study there was a 129% increase in live weight gain when brewers’ grains were added to cassava foliage, compared with only 25% improvement on the water spinach diet.

Figure 4. Effect of a supplement of brewers’ grains on live weight gain of goats fed Bauhinia accuminata in combination with cassava foliage (CF) or water spinach (WS).	Figure 5. Effect of a supplement of brewers’ grains on DM feed conversion of goats fed Bauhinia accuminata in combination with cassava foliage or water spinach.

The higher values for rumen ammonia on the diets with water spinach (Table 6) were to be expected in view of the greater solubility of the protein in water spinach compared with cassava foliage (Table 1). However, on all diets, ammonia levels were sufficiently high to support normal rumen function. On each foliage source, rumen ammonia values were higher when brewers’ grains were included in the diet.

There were minor differences in molar proportions of the VFA, and the Ac:Pr ratio, apparently related to the treatments; however, the small order of magnitude of the differences means they are unlikely to be of importance in relation to animal performance.

Discussion

We propose that the interaction in the degree of improved animal performance, according to whether the brewers’ grains were added to the diet with cassava foliage, compared with the diet containing water spinach, was because the brewers’ grains act as a prebiotic when included in diets containing potentially toxic elements such as the cyanogenic glucosides present in cassava foliage. A similar explanation can be applied to the effects of “Kilao” (the byproduct from the fermentation/distillation of “rice wine”) in increasing growth and feed conversion of cattle fed ensiled cassava root and cassava foliage (Sengsouly and Preston 2016).

The improved performance appears to be manifested by increased diet digestibility and improved biological value of the digested protein. The greater response to brewers’ grains when cassava foliage was fed, compared with water spinach, could be because of enhanced capacity to detoxify the cyanogenic glucosides present in cassava foliage as reported by Binh et al (2017).

Conclusions

• Supplementing growing goats with brewers’ grains (5% of diet DM) increased diet digestibility and the biological value of the absorbed protein, resulting in improvement of live weight gain of 44% and in DM feed conversion of 25% when the basal diet was a legume tree foliage (Bauhinia accuminata) and the protein supplement was cassava foliage. Comparable data when water spinach was the protein supplement were relative improvements of 11 and 5%.
  
  
• It is proposed that brewers’ grains, a fermented byproduct from brewing “beer”, act as a prebiotic when added to a diet containing potentially toxic elements such as the cyanogenic glucosides present in cassava foliage.

References

AOAC 1990 Official Methods of Analysis. Association of Official Analytical Chemists. 15th Edition (K Helrick editor). Arlington pp 1230.

Binh P L T, Preston T R, Duong K N and Leng R A 2017 A low concentration (4% in diet dry matter) of brewers’ grains improves the growth rate and reduces thiocyanate excretion of cattle fed cassava pulp-urea and “bitter” cassava foliage. Livestock Research for Rural Development. Volume 29, Article #104. http://www.lrrd.org/lrrd29/5/phuo29104.html

Leng R A 2014 Interactions between microbial consortia in biofilms: a paradigm shift in rumen microbial ecology and enteric methane mitigation. Animal Production Science.54(5) 519-543 http://dx.doi.org/10.1071/AN13381Animal Biosciences

Minitab 2000 Minitab Software Release 16

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Samuel M, Sagathewan S, Thomus J and Mathen G 1997 An HPLC method for estimation of volatile fatty acids of rumen fluid. Indian Journal of Animal Science 67:805–807.

Silivong P and Preston T R 2015 Growth performance of goats was improved when a basal diet of foliage of Bauhinia accuminata was supplemented with water spinach and biochar. Livestock Research for Rural Development. Volume 27, Article #58. Retrieved March 20, 2015, from http://www.lrrd.org/lrrd27/3/sili27058.html

Silivong P and Preston T R 2016 Supplements of water spinach (Ipomoea aquatica) and biochar improved feed intake, digestibility, N retention and growth performance of goats fed foliage of Bauhinia accuminata as the basal diet. Livestock Research for Rural Development. Volume 28, Article #98. Retrieved June 9, 2016, from http://www.lrrd.org/lrrd28/5/sili28098.html

Sengsouly P and Preston T R 2016 Effect of rice-wine distillers’ byproduct and biochar on growth performance and methane emissions in local “Yellow” cattle fed ensiled cassava root, urea, cassava foliage and rice straw. Livestock Research for Rural Development. Volume 28, Article #178. Retrieved June 1, 2017, from http://www.lrrd.org/lrrd28/10/seng28178.html

Sina V, Preston T R and Tham T H 2017 Brewers’ grains have a synergistic effect on growth rate of goats fed fresh cassava foliage (Manihot esculenta Crantz) as basal diet. Livestock Research for Rural Development. Volume 29, Article #137. Retrieved July 3, 2017, from http://www.lrrd.org/lrrd29/7/sina29137.html

Whitelaw F G, Preston T R and Dawson G S 1961 The nutrition of the early weaned calf, 2: A comparison of commercial groundnut meal, heat-treated groundnut meal and fish meal as the major protein source in the diet, Animal Production 3:127.

Received 9 February 2018; Accepted 22 February 2018; Published 1 March 2018

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