Utilization of concentrate supplements containing varying levels of coconut meal by Thai native Anglo-Nubian goats

Pramote Paengkoum

School of Animal Production Technology, Institute of Agricultural Technology, Suranaree University of Technology,
Muang, Nakhon Ratchasima, 30000, Thailand
pramote@sut.ac.th

Abstract

The objective of this study was to evaluate the effect of varying levels of coconut meal (CCM), replacing soybean meal, on feed intake, digestibility and rumen fermentation of goats fed corn silage. Eight growing Thai native Anglo-Nubian goats between 8 to 10 months of age and pre-trial average body weight of 17.7 + 1.9 kg were allotted into two groups on the basis of body weight in a randomized double 4*4 Latin square design.  The four treatments were levels (%) of replacement of soybean meal by CCM of 0 (control),  25 (CCM25), 50 (CCM50) and 75 (CCM75) in a  concentrate give as a supplement to corn silage.

There were no consistent effects of CCM level on feed intake and  DM, OM and CP digestibility but NDF digestibility was negatively related with CCM level (R² =0.94). At the 75% substitution level of soybean by CCM, performance was reduced as measured by estimated rate of rumen microbial synthesis and live weight change.

Key words: Corn silage, microbial protein synthesis, N balance

Introduction

Most concentrates for goat are grain-based to increase their energy concentration, which typically improves feed efficiency. The use of soybean meal (SBM) as a source of protein in animal feed has been well established for many years. However, high prices and fluctuation in production have raised the interest in alternative protein sources for feeding ruminants. There is a lot of information on chemical composition, digestibility and livestock production potential of coconut meal (CCM). Depending on the method of oil extraction the CCM or copra can contain between 18 and 30% crude protein, and 1–7% oil. Results from feeding trials demonstrated that the inclusion of copra cake improved efficiency of microbial protein synthesis in sheep (Galgal et al 1994), live-weight gain in steers and increased milk production in dairy cows (McIntyre 1973). Recently, CCM is becoming available in Thailand for ruminant nutrition as a local by-product of coconut milk extraction. Thus, CCM could be potentially used as a substitute for SBM. We hypothesize that, as a protein supplement, CCM could replace SBM in rations of small ruminants with similar gain and feed efficiency (Aregheore 2005). The economic important of goat production has recently been given high recognition. Goats are considered to be important domestic animals for tropical regions. However, productivity of goats in this region is generally low, because of poor management, disease and poor quality feed.  

Therefore, the objectives of this research were to study the effect of CCM on feed intake, digestibility of nutrients, microbial protein synthesis, nitrogen balance and on the performance of  Thai native_Anglo-Nubian growing goats.
 

Materials and Methods

Animals and management

Eight growing crossbred Thai native Anglo-Nubian goats between 8 and 10 months of age and pre-trial average body weight of 17.7 + 1.9 kg were allotted into two groups on the basis of body weight in a randomized double 4*4 Latin square design to investigate the utilization of concentrate mixtures of varying levels of coconut meal (CCM). The four concentrate mixtures had CCM included at 0% (control), 7.3 % (CCM505), 14.5% (CCM50) and 22.0% (CCM75) in concentrate as replacing dietary CP supplied by soybean meal (SBM) with CCM at 25, 50 and 75%, respectively.  The goats were housed in individual pens and allowed 3 weeks to adapt to the experimental conditions. The goats were fed a basal diet containing corn silage supplemented with minerals and vitamins. The experimental diets were iso-nitrogenous (CP = 15%) and iso-energetic and based on corn silage supplemented with a concentrate containing soybean meal, coconut meal, cassava pulp, rice bran, urea, minerals and vitamins (Tables 1 and 2). Rations were formulated in accordance with NRC (1981) to achieve a medium activity and average growth rate. Drinking water was freely available to the animals.  

Experimental Procedure

The experiment consisted of three weeks of adaptation, following by four experimental periods. The duration of each period was 32 days, i.e. three weeks of adjustment followed by 11 days of measurements. The later consisted of 2 days of adaptation to the metabolic crates, 7 days of digestibility and N balance studies, 2 days of rumen fluid and blood sampling. Samples of feed refusals, feces and urine were collected before feeding in the morning to determine feed intake, digestibility and N balance.

Sampling Methods

Daily feces of each goat was weighed and a 10% sub-sample collected and stored at –20°C. The sub-samples at the end of each period were bulked, dried (60°C) and ground through a 1 mm sieve and stored until analysis. Daily urine output was collected into a plastic container (containing 25 ml of 10% H₂SO₄). Approximately 10% of the volume was sampled and stored at –20°C pending energy and N analysis. A separate urine sample was collected for determination of purine derivatives (PD). The urine sample was diluted 4 times (to prevent crystallization of uric acid during storage), filtered through Whatman cellulose membranes (25 mm, 0.2 microns) attached to a syringe, thereafter, frozen at –20°C for later analysis of PD content using high performance liquid chromatography (HPLC) according to Balcells et al (1992).

Rumen fluid samples from all goats were collected using a stomach tube at 3 h post-feeding during the digestibility trial. It was strained through 4 layers of cheese cloth and pH measured immediately using a pH meter (Mettler Toledo MP 125) fitted with a combined electrode. The rumen fluid was then acidified with H₂SO₄ (50%, v/v) and stored at –20 °C for analyses of ammonia and VFA.

Blood samples were taken from the jugular vein at 3 h post-feeding and after sampling of rumen fluid. The blood samples were centrifuged (3,000 g for 15 min) and the plasma stored at –20°C for urea analysis.

Chemical Analysis and Calculations

Feed samples were collected twice a week. Representative samples of feed and feces collected during the digestibility trial were analyzed according to AOAC (1984) for DM, ash and CP and for fiber components according to Van Soest et al (1991). Apparent digestibilities were calculated using equations of Schneider and Flatt (1975).

Total VFA and molar proportions of acetic, propionic, and butyric acids in rumen fluid were determined by Shimatzu GC-14 gas chromatography (Shimatzu, Japan) fitted with a Flame Ionization Detector (FID) and a packed column 5% Thermon -3000, Shincarbon A 60/80. Nitrogen was used as the carrier gas at 40 ml/min and the oven temperature was maintained at 220°C; injection and FID temperatures were fixed at 260°C. Plasma urea was determined by using a urea test kit (Sigma Diagnostics INFINITY^TM BUN Reagent).

The purine derivatives (allantoin, uric acid, hypoxanthine and xanthine) were analyzed by reverse-phase High Performance Liquid Chromatography (HPLC), which consisted of a multi-solvent delivery system Model 600 E (Water, USA), an injector Model 712, a multi-wavelength detector Model 490E, set to 205 nm, and a double 4.6_250 mm, C-18 reverse-phase column, according to the technique of Balcells et al (1992). Production of microbial N was calculated using the equation of Chen et al (1992).  

Statistical Analysis

Data were analyzed as a 4*4 Latin square design using the general linear model (GLM) procedure of the Statistical Analysis System Institute (SAS 1988). Duncan’s New Multiple Range Test and Orthogonal Contrast Analysis (Steel and Torrie 1980) were used to compare treatment means. Unless otherwise noted, significance was declared at P< 0.05.
 

Results and Discussion

NDF and ADF in the diets increased as soybean meal was replaced by coconut meal (Table 2).

Dry matter intake based on g/kg BW^0.75 increased with up to 50% replacement of soybean meal by CCM. Thereafter DMI decreased in goats fed CCM75 (Table 3). There were no consistent effects of CCM level on DM, OM and CP digestibility but NDF digestibility was negatively related with CCM level (R² =0.94; Figure 1). Body weight change was less on the CCM75 compared with the other diets.

Table 3. Effect of varying levels of coconut meal (CCM) replacing soybean meal on feed intake, apparent digestibility and body weight change of goats
	Control	CCM25	CCM50	CCM75	SEM
Corn silage DM intake per day
g	371b	373ab	396a	380ab	4.13
% BW	2.33	2.30	2.43	2.28	0.313
g /kg W 0.75	46.6b	46.3b	49.0a	46.0b	0.71
Total DM intake per day
g	578b	582ab	599a	581ab	4.53
%BW	3.55	3.52	3.63	3.49	0.531
g /kg W 0.75 /day	71.4b	70.8b	73.7a	70.6b	0.75
Apparent digestibility, %
Dry matter	56.6bc	58.4a	57.7ab	55.1c	0.27
Organic matter	59.2c	60.7b	62.4a	57.6d	0.39
Crude protein	55.0ab	55.7a	56.1a	54.1b	0.26
Neutral detergent fiber	53.7a	51.2b	50.7b	47.7c	0.38
Body weight change, g/day	60.0a	60.5a	62.5a	54.5b	1.22
a,b,c Means within rows without common superscripts differ at p<0.05

Figure 1. Replacing soybean meal with coconut meal (CCM) in diets of goats led to a linear negative decline in apparent NDF digestibility

Ruminal NH₃-N and PUN concentrations tended to increase with the addition of CCM up to 50% replacement of soybean meal,  thereafter  they decreased in goats fed CCM75 (Table 4). These small and inconsistent differences in both rumen ammonia and PUN indicate that the solubility of the protein in CCM is similar to that in soybean meal. The fact that there were no increases in TVFA supports such a conclusion, since Koster et al (1996) showed that TVFA increased dramatically in response to supplemental rumen degradable protein fed to beef cows. Ruminal pH and molar proportions of  propionic and butyric acids were not affected by level of CCM. The slightly lower value for molar acetate on the CCM75 diet has no nutritional significance.

Table 4. Effect of varying levels of coconut meal (CCM) replacing soybean meal on ruminal pH, ruminal NH3-N, total volatile fatty acid (TVFA), individual VFAs and plasma urea nitrogen (PUN) of goats
	Control	CCM25	CCM50	CCM75	SEM
pH	6.8	6.9	6.9	6.9	0.27
NH3-N, mg%	14.5b	15.6ab	16.5a	14.2b	0.30
TVFA, mmol/liter	67.7a	66.3a	65.9a	62.3b	0.65
VFA proportion, %TVFA
Acetic	69.7a	69.6a	69.2a	67.7b	0.21
Propionic	20.6	20.3	20.6	20.4	0.28
Butyric	9.7	10.2	10.3	11.9	0.36
PUN, mg%	15.1ab	16.5a	17.4a	14.6b	0.38
a,b,c Means within rows without common superscripts differ at p<0.05

Excretion of allantoin, uric acid, hypoxanthine, xanthine and total PD were lower in goats fed CCM75 compared with the other diets (Table 5).   Microbial N synthesis (g N/day) and efficiency of microbial N supply (g N/ kg OM apparently digested in the rumen) showed a similar trend, for which there is no obvious explanation.

There were no effects of dietary treatment on N intake and N in feces. N retention (g/day, % of N intake) was higher for diet CCM50 than for the control and the CCM75 diets; iincreased with the addition of CCM up to 50% substitution of soybean meal, thereafter  decreased in goats fed 75% CCM. Urine N of goats fed CCM50 was lower than in goats fed the CCM75 diet (Table 6) but did not differ from values on the control and CCM25 diets. The data for N retention as percentage of N digested, which is indicative of the biological value of the dietary protein, showed that these were low on all diets, with the CCM75 diet having the lowest value.

Overall there were almost no differences in measured parameters of goats fed the control, CCM25 and CCM50 diets. These results are in agreement with those of   Aregheore (2005) indicating that CCM could replace SBM as a protein source  for ruminant feeding.  The similar growth rates on the control, CCM25 and CCM50 diets are in agreement with reports by Creswell and Brooks (1971), Hennessy et al (1989) and Aregheore (2005). The inferior results on the CCM75 diets may have been the consequence of less available fermentable carbohydrate in CCM compared with soybean meal as reported by Schingoethe et al (1977), Economides (1998) and Irshaid et al (2003). 
 

Conclusions

• There were no differences in the performance of goats fed CCM at levels from 0 to 50% replacement of soybean meal in a concentrate given as a supplement to corn silage.

• At the 75% substitution level of soybean by CCM, performance was reduced as measured by estimated rate of rumen microbial synthesis and live weight change.

Acknowlegements

The author acknowledges the Suranaree University of Technology (SUT) and The National Research Council of Thailand (NRCT) for financial and facilities support of this research. 

References

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Received 1 September 2010; Accepted 28 December 2010; Published 1 February 2011

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