Studies on the utilization of brewers dry grains and wheat offals by calves

F.I. Ogundola
Institute of Agricultural Research and Training
P.M.B. 5029, Moor Plantation, Ibadan, Nigeria

Abstract
Introduction
Materials and methods
Results
Discussion
Conclusion
References

Abstract

Digestibility, metabolism and rumen studies were conducted to study the growth performance of 24 calves fed concentrates consisting of 20, 40 and 60% levels of both brewers' dry grains (BOG) and wheat offals (WO) to replace maize in a 16-week trial period.

There were no trends established between dry matter, total digestible nutrient and energy intakes and levels of BDG and WO except the digestible crude protein intake which increased 8.69.5 g/W kg^0.75 with increasing levels of BDG & WO in the ration.

The growth rates of 0.26, 0.27, 0.24 and 0.31 kg/day of calves on diets A, B. C and D respectively were positively but not significantly (P>0.05) correlated (r = 0.99).

The N intake (av. 49.7 g/day) and N retention (av. 52.5%) were high and increased as the level of BDG and WO increased in the ration.

The rumen pH ranged between 6.4 and 6.8 and was not different among the diets. The NH₃ -N levels were high in all the diets (av. 14.0 mg/100 ml) showing that N was not limiting and enough to support the growth of the calves. The total VFA showed no particular trend but moderate accumulation and averaged 9.8 m-equiv/litre. However, the acetic acid level (av. 73%) was high enough to furnish energy for the N utilisation. For the individual acids, no definite pattern was established in relation to the supplemental levels of BDG and WO.

The growth made by the calves indicated that both N and energy were not limiting even at 60% substitution level.

Introduction

In view of the rapidly growing population and declining grain production in Nigeria there is an increased need to utilise agro-industrial by-products and crop wastes to feed livestock. Furthermore, it is becoming increasingly difficult to supply cereal grains to the livestock industry.

Recently a large number of breweries and flour mills have been established in almost all the states of Nigeria from which large quantities of brewers' dried grains (BDG) and wheat offals (WO) become available as sources of energy and protein for livestock feeding. Adebowale (1985) reported that about 100,000 and 320,000 tons of wet brewers' grains and wheat offals were available from the brewery and flour milling industries. Some of the breweries have facilities for drying the grains while others have none. The dried grains are made available free to livestock farmers to avoid environmental pollution while the cost of a tonne of wheat offals is about 25% of the cost of a tonne of maize.

Adebowale and Ademosun (1981) and Ogundola (1987) analysed some samples of the BOG and WO and found that generally they contain about 20% and 15% crude protein as well as 21 KJ/g and 17 KJ/g gross energy respectively. These values are higher than those of maize and guinea corn which are commonly used as energy sources in rations for livestock.

This paper reports on the metabolism and rumen studies using different levels of BDG and WO as maize replacement in rations for young growing calves.

Materials and methods

Twenty-four white Fulani (Zebu) calves aged between 14 and 16 months were selected from the flock of the Institute's Research Farm for the experiment. The average weight of each animal was 81 kg.

Before the digestibility experiment, the animals were kept on concrete floor pens and zero-fed 3 kg of grass (Cynodon nlemfuensis) and a daily allowance of 1.5 kg of the test diets (concentrates) A, B, C and D in groups of six, for 16 weeks to evaluate their feed intakes and growth rates. After the trial, 12 calves were selected for the metabolism and rumen studies. All the calves were housed in specially constructed metabolic cages to facilitate separate collection of faeces and urine. The animals were fed at the same rate with three on each test diet. A preliminary period of 14 days was allowed before faeces and urine collection which lasted 7 days was started. Fresh clean water was available ad lib in plastic buckets placed at the corner of each metabolic cage.

Faecal collection

Faecal collection was done by means of collection bags fitted with harness and the total weight of faeces voided weighed and recorded. A sample of the faeces voided daily was taken, dried in the oven at 80°C for 24 hours. The daily dried faeces for each animal over the 7- day collection period were bulked. The samples were then milled and stored in airtight bottles until required for analysis. Urine was collected over 5 ml of 10% mercuric chloride solution in a plastic container. The daily volume was measured every morning and 10% aliquot taken for nitrogen and energy determinations. Samples not ready for immediate analysis were kept in a deep freezer at -5°C. The methods for the collection of feed refusals and faeces were as described by Oyenuga (1961).

Fresh faeces, herbage fed and residues meant for proximate analysis were dried at 80°C in a forced-draught electric oven for 3 days and later milled in a Christy-Norris hammer mill fitted with 2 mm sieve. The milled samples were later analysed for their proximate analysis.

Sampling of the rumen liquor

Rumen samples were collected during the last 3 days of the collection period by putting the collection tube through the mouth into the rumen using the method of Alexander (1964) as modified by Mba and Olatunji (1971). The sampling lasted 5 minutes during which about 200 ml of rumen liquor was obtained. The samples were taken one hour before and one hour after feeding. They were then stored in a deep freezer at -5°C until required for analysis.

Analytical procedure

The AOAC (1970) procedures were used for the proximate constituents in feed and faeces, nitrogen in urine and volatile fatty acids (VFAS). Individual fatty acid was determined on the Beckman's Gas-liquid Chromatography model 65. The pH was measured on pH Meter E520 using glass reference electrodes. The gross energy of faeces and feed was determined in a Gallenkamp ballistic bomb calorimeter while gross energy in urine was determined by drying a known volume soaked in a pre-weighed ashless filter paper over P₂O₅ in a desiccator reweighed after drying followed by bombing.

All data were subjected to analysis of variance (Steel and Torrie, 1960). Regression analysis was thereafter used to measure the trend of association (r-value) between BDG and wheat offals level in diet (X) and nutrient (Y).

Results

The brewers' dried grain and wheat offals used in the metabolism and rumen studies had crude protein of 18.3% and 12.1%, 17.4 and 14.8% crude fibre; 4.5 and 42% ether extract; 6.4 and 7.1% ash; and 19.4 and 17.9 KJ/g respectively (Table 1).

Generally values for voluntary dry matter (DM), digestible crude protein (DCP), total digestible nutrient (TDN) and energy intakes are high in all the four diets (Table 2). However, there are not significant negative correlation between DM intake (r -0.65), and energy intake (r = -0.088) but significant negative correlation existed between (TDN) (r = 0.94) and level of supplementation of BDG and WO in the diets. But there is a positive correlation between pop intake and level of supplementation (r = 0.99). There was no established trend in the intake of nutrients between the four diets. The weight gained by the calves were moderately high (0.24-0.31 kg/day) on all the diets while a non-significant correlation (r = 0.03) was obtained between these gains and level of supplementation of BDG and WO.

Table 1. Composition of experimental diets.

Ingredients (%)*	A	B	C	D
Maize	77.5	57.5	37.5	17.5
Groundnut cake	15.0	15.0	15.0	15.0
Palm kernel meal	5.0	5.0	5.0	5.0
Dry brewers' grain	0.0	10.0	20.0	30.0
Wheat offals	0.0	10.0	20.0	30.0
Chemical composition (%) on DM basis
Crude protein	13.96	15.03	16.13	17.21
Crude fibre	3.20	5.71	8.21	10.71
Ash	2.40	3.23	4.06	4.89
Nitrogen-free extractives	71.45	64.80	58.20	51.6
Gross energy (MJ/Kg)	15.49	15.97	16.53	17.09

* All diets contain 1% bone meal, 0.5% salt, 1.0% mineral/vitamin mixture. Cynodon nlemfuensis had a chemical composition of 6.4% crude protein, 27% crude fibre, and 17.9 MJ/Kg gross energy. Composition of min/vit mixture as quoted by Ogundola (1984) .

Table 2. Intake and growth rate of calves.

DM intake	DCP	TDN	Energy	Growth	Cost/kg
Diet	0. 75	0. 75	0. 75	intake	rate	ration
	g/w kg	g/w kg	g/w kg	ME/Kg DM	kg/day	(N)
A	92.8	8.6	81.3	67.8	0.26	1.31
B	90.2	8.9	74.0	60.1	0.27	1.22
C	93.4	9.3	72.8	67.8	0.24	1.14
D	86.5	9.5	69.5	64.4	0.31	1.05
Mean ± SE	91.7 ± 2.7	9.1 ± 0.4	74.4 ± 4.3	65.0 ± 3.2	0.27 ± 0.03	1.18 ± 0.1
r-value	0.84ns	0.99**	-0.95*	0.08ns	0.53ns	0.99***

ns = not significant
* = significant at 5%.
*** = significant at 0.1%.
N = unit of local currency.

There was no definite trend in the digestibilities of the various components as the level of BDG and WO increased in the diet (Table 3). However, non-significant negative correlations were obtained between dry-matter, crude protein and crude fibre digestibilities and level of supplementation. Energy digestibility however correlated positively (r = 0.30) but not significantly with levels of BDG and WO in the diet.

Table 3. Mean coefficient of apparent digestibilities.

(%) of diets
Diets	DM	CP	CF	Energy
A	68.8	73.4	70.2	76.8
B	66.3	70.7	68.4	73.2
C	69.7	72.0	65.7	74.6
D	61.9	70.9	69.6	78.0
Mean ± SE	66.7 ± 3.0	71.8 ± 1.1	68.5 ± 1.7	75.7 ± 1.9
r-value	-0.64ns	-0.29ns	-0.29ns	-0.30ns

ns = not significant.

At the end of the trial, all the animals were in positive nitrogen balance (Table 4). Intake of N increased with the level of supplementation (43.6-54.7g/day). Also faecal-N and urinary-N excretion increased with the levels of BDG and WO levels in the diet as shown by the ® values. However, though N retention positively correlated (r =0.85) with level of BDG and WO in the diet, it was not significant (P>0.05).

Table 4. Nitrogen utilisation by calves.

Diets	A	B	C	D	Mean ± SE	r value
Nitrogen intake(g/day)	43.6	47.9	52.4	54.7	49.7 ± 4.3	0.99*
Faecal-N(g/day)	9.8	10.4	10.9	11.2	10.6 ± 0.53	0.99*
Urinary-N (g/day)	11.4	13.0	13.3	14.1	13.0 ± 0.98	0.96*
N-retention (g/day)	22.4	24.5	28.2	29.4	26.1 ± 2.8	0.98*
N-retention(% of intake)	51.4	51.1	53.8	53.7	52.5 ± 1.3	0.86ns

ns = not significant.
* = significant at 5%.

There were non-significant (P>0.05) positive correlations between the various contents and levels of BDG and WO in the diet as shown by their r values (Table 5). Rumen pH varied between 6.4 and 6.8, ruminal-NH₃-N 11.7-15.4 mg/100 ml. Total VFA 9.6-10.1 m-equiv/litre, acetic acid 69-76%, propionic Acid 14.8-20% and butyric acid 5.2-12.1% in all the diets. However, only ruminal NH₃-N content exhibited a gradual increase with the level of supplement in the diet.

Table 5. Mean rumen pH, NH₃-N, total and individual VFAs of the calves.

Diets	Rumen pH	Ruminal NH3-N	Total VFA	Acetic acid (%)	Propionic acid (%)	Butyric acid (%)
A	6.8	11.7	9.9	69.4	19.2	11.4
B	6.5	14.8	9.7	74.8	20.0	5.2
C	6.4	14.2	10.1	76.0	17.2	6.8
D	6.5	15.4	9.6	73.1	14.8	12.1
Mean ± SE	6.6 ± 0.15	14.0 ± 1.4	9.8 ± 0.19	73.0 ± 2.5	17.8 ± 2.0	8.9 ± 2.9
r value	-0.75ns	0.83ns	0.29ns	0.55ns	-0.89ns	0.14ns

ns = not significant.

Discussion

Consumption of feed by the calves was generally high in the four experimental diets A, B, C and D and even compared with NRC(1966) recommendation for calves of similar weight. This showed that the feeds were well accepted by the calves. However, DM consumption of calves on diet D with 30% each of BDG and WO recorded the lowest value. This appeared to agree with Adebowale's (1985) report that supplementation of BDG above 25% tended to depress DM consumption, and that the BDG should be in wet form because calves generally consumed the wet BDG than the dry one at this level of supplementation.

The high digestibility coefficient obtained for the DM, CP, CF and energy reflected the high CP in the diet which ranged between 14 and 17% and is known to affect particularly the digestibilities of DM and CF. The daily weight gains of the calves (0.24-0.31 kg) on the different diets were high compared to earlier report by this author. The observations of Fehr et al (1976) and Naude and Hofmeyer (1981) that high feed intake and high growth rate positively affect feed utilisation efficiency is adequately supported by the present findings. The growth made by calves on rations B. C and D indicated that both CP and energy were adequate in the diets and the highest rate of (0.31 kg/day) was recorded on ration D.

In all the diets, there was a positive correlation between N intake and N retention. The latter seemed to increase with the level of BDG and WO substitution. All the animals were therefore in positive N balance, indicating that the N contents of BDG and WO were well utilised by the calves.

The results of the rumen studies showed a generally high ruminal NH₃-N (11.7-15.4 mg/100ml) fairly low acetic acid levels of 69-76%. These high NH₃-N levels would support high microbial growth which in turn will lead to efficient utilisation of N in the diet. These findings agree with the explanation of Mba and Olatunji (1972) that acetic acid depression enhance N retention and reduces absorption of NH₃-N. The relatively low acetic acid level and the high growth rate recorded in this trial agreed with Mba et al (1971) observation.

Conclusion

The experiment has shown that both BDG and WO which are abundant in Nigeria could be incorporated in the diet of growing calves up to 60% of the ration without adverse effect on nutrient digestibility and utilisation. However, inclusion of BDG above 30% may have to be in wet form. The greatest hope for the utilisation of these by-products lies in the fact that they need no further processing before they could be used as feed. However, most of the flour mills and breweries are located in the coastline of the country, and government should now force new flour mills and breweries to be established in the hinterland to reduce transportation costs to large livestock population areas. In addition, breweries with no drying facilities should be compelled to install drying plants to make more BDG available for livestock. From experience, the more frequently one calls at the source of any agro-industrial by-product centre, the more likely one is asked to pay some money for whatever quantity one collects even though the owners may have no particular use for such products. Government should enforce price control to keep the price of BDG and WO very low to encourage their use as a livestock feed.

References

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Steel, R.G.D. and Torrie, J.H. 1960. Principles and procedures of statistics. McGraw-Hill Book Co., New York.