Effects of inclusion of catfish (Pangasius hypophthalmus) by-product meal and probiotics on performance, carcass quality and ileal and total amino acid digestibility in growing chickens 

Nguyen Thi Thuy

College of Agriculture, CanTho University, CanTho, Vietnam
nthithuycn@ctu.edu.vn

Abstract

Two experiments were conducted to determine the effects of Catfish by-product meal (CB) replacement at  0, 50 and 100% of sea fish meal (FM) with and without Probiotic (P) supplementation in the diets of improved,  chicken. The digestibility was conducted with 24 male Luong Phuong chickens at 6 weeks of age, placed in individual pens to collect excreta and ileal digesta. Six treatments (CB0, CB0P, CB50, CB50P, CB100, CB100P) were introduced to determine the apparent ileal (AID) and total tract (ATD) digestibility of nutrients and amino acids using Chromic oxide (Cr₂O₃) as indigestible marker. After 4 days of colleting excreta, the chickens were killed to collect the ileal digesta.

Replacing fish meal with catfish by-product meal in the diets of Luong Phuong chickens resulted in a decrease in apparent total and ileal digestibility of crude protein and an increase in the apparent total and ileal digestibility of ether extract. Diets with probiotic supplementation had higher ileal and total digestibility of crude protein. Amino acid digestibility was not affected by replacing fish meal with catfish by-product meal, nor by addition of probiotic.

Growth performance of the chickens in an on-farm trial was not affected by replacing fish meal with catfish by-product meal. but the fat content of the breast meat and its content of polyunsaturated fatty acids was increased.

Key words: Fatty acids, Luong Phuong, on-farm trial, slaughter

Introduction

Poultry production  has an important role in agriculture in the Mekong Delta accounting for 28% of total poultry production in the country. Poultry meat accounts for 11.5% of total meat consumption of Vietnamese people (GSO 2010). Chicken production also generates 19% of the income for householders,  in second place after pig production (Desvaux et al 2008). Among many kinds of local breeds, improved chickens known as Luong Phuong that came to Vietnam from China have become popular in the South of Vietnam. They are usually confined and fed commercial feed, which may have additives such as antibiotics and growth promoting substances. These feeds are also expensive. Misuse of feed additives for animals can result in high residues in meat, which can affect human health. This situation has been pressing researchers and state officials in Vietnam to find alternative solutions.

Probiotics containing beneficial bacteria can strengthen the immune system and help chicken to remain healthy and gain weight faster (Patterson and Burkholder 2003). Recently, several commercial probiotic products have been imported into Vietnam such as from  Bayer (Germany) and Biomin Co. Ltd. (Austria).

Catfish by-product meals that have been produced by small scale factories are abundant and potentially valuable protein resources for livestock. Recently, we showed that catfish by-product meal was acceptable and highly utilisable as a protein and nutrient substitute in the diets for pigs (Thuy et al 2010). However, there is a lack of  studies on evaluation of catfish by-product meal in chickens especially in terms of ileal and total tract digestibility. Therefore, the main objectives of this research were: (i) to determine the optimal level of catfish by-product meal in diets with or without probiotic supplementation;  and (ii) to record the effects of the best treatments from (i) on growth performance and meat quality characteristics of chickens in an on-farm situation. .

Materials and methods

Experiment 1. Digestibility trial

Animal and experimental design

The experiment was conducted in Vinh Long Province, with 24 male Luong Phuong chickens  at 6 weeks of age which were placed into individual cages and allocated to 4 replicates of 6 treatments. The cages were 30 cm x 30 cm x 50 cm in width, length and height, respectively. The trial was designed as a 2*3 factorial with 3 levels of catfish by-product meal (CB) replacing fish meal at 0, 50 and 100%; and with or without Probiotic. The birds were weighed at the beginning and the end of the trial and at the beginning and end of excreta collection.

Experimental diets

Experimental diets were formulated from broken rice, rice bran and maize meal as energy sources with 40% of the protein from fish meal (FM) or CB. Chromic oxide was added to all diets at 5g/kg feed as indigestible marker. CB was collected from small catfish by-product meal processing factories in Can Tho City.

Procedure and measurement

Coefficients of total tract apparent digestibility of OM, CP, EE, Ash and amino acids were measured by total excreta collection. The trial was for 12 days. After 4 days of adaptation, excreta was  collected daily for 4 days from plates under the cages and stored frozen (-20^oC) prior to analysis. The excreta collection was followed by a further 3-day adaptation period, 24 h fasting and 4 h free access to feed after which the birds were slaughtered for the collection of ileal digesta (Perttila 2002). Feeding and slaughter were started at the same time for the whole group. This procedure was conducted as quickly as possible in order to minimise changes in digesta composition. Digesta were collected from the terminal ileum by gently flushing with distilled water into plastic containers. The ileum is defined as that portion of the small intestine extending from the vitelline diverticulum to a point 60mm proximal to the ileo-caecal junction (Huang et al 2005). Daily digesta samples of individual birds were pooled and stored at -20^oC before chemical analysis.

Calculations

The total apparent digestibility is expressed in terms of the difference between the intake and the excretion as a proportion of amount consumed (McNab 1994).

Thus:

Total AA digestibility (%)   =  (AA consumed  – AA feces)/ AA consumed .....(1)

 Apparent ileal digestibility coefficients of amino acids were calculated using Cr₂O₃  as an indigestible marker.

Apparent Ileal AA digestibility (%)   = {(AA in feed/Marker in feed)  - (AA in ileum/Marker in ileum)}/(AA in feed /Marker in feed) ,.....(2)

Experiment 2. Feeding trial

Animals, feeds and experimental design

Sixty Luong Phuong chickens (4 weeks old) were allocated in a randomized block design (RBD) to each of 4 households (replicates) to compare 3 treatments , which were selected on the basis of the results from the digestibility trial. There were 20 birds (balanced male and female) in each of three pens in each household.  The chickens were allowed to scavenge in  the farm  garden from 07.00h to 17.00h, with the experimental feeds provided in the scavenging area, and at night time inside the pen. Experimental feeds and water were offered ad libitum.

Measurements

The trial lasted for 10 weeks. The chickens were weighed every week, and weight gain and feed conversion ratio were calculated. At the end of the experiment, 3 chickens per pen (female) were slaughtered. The carcass characteristics were recorded and samples of breast meat collected and  analyzed for chemical composition.

Chemical analysis

The chemical composition of feed, excreta, digesta and breast meat were determined using the methods of AOAC (1990). Dry matter (DM) was measured by drying the fresh samples at 105^oC.. Crude protein was determined by the Kjeldahl method. Total ash was the residue after ashing the samples at 550^oC and organic matter (OM) was calculated by difference. The ether extract (EE) was determined by  Soxhlet extraction. Amino acid concentrations of the feed, excreta and ileal digesta were analyzed using HPLC procedure (Spackman et al 1958). Chromium was measured by atomic absorption spectrophotometer after ashing and digesting the sample in a mixture containing perchloric and nitric acid  (Fenton and Fenton 1979).  Fatty acid composition of breast meat was analyzed by Gas Chromatography  (GC/FID – ISO/CD 5509:94).

Statistical analysis

Data collected were analyzed by ANOVA using the General Liner Model (GLM) of Minitab Statistical Software Version 16. Tukey pair-wise comparisons were used to determine differences between treatment means at P<0.05. Sources of variation in Experiment 1 were: level of catfish residue, probiotic, interaction catfish meal and probiotic, and error. In Experiment 2, the sources of variation were: block, level of catfish residue and error.

Results and discussion

Experiment 1

Analyses of feed

As expected, there were no differences in DM, OM and CP among diets (Table 1). The calculated ME increased with the level of CB in the diets.

Apparent total (ATD) and ileal digestibility (AID) of dietary nutrients

As expected, the AID of OM, CP, EE and ash in all diets were lower than  in the ATD (Table 2), because there is extensive bacterial activity in the caeca of chickens, stimulating effect of the gut micro-flora on protein synthesis. In addition, the fermentation that occurs in the caeca of poultry influences the nutrient content of excreta and thus modifies  results for digestibility (Short et al 1999). Therefore most poultry nutritionists have focused on digestibility trials in poultry at ileal level rather than with total excreta because ileal digestibility can give more accurate digestibility data due to eliminating hind gut micro flora effects (Applegate et al 2004).

Replacing fish meal with catfish byproduct increased the ileal and total tract digestibility of EE but reduced that of CP in total excreta with no effect at the level of the ileum. The CB in the present study was made from head and bone by-product, for which the amino acid composition would be less balanced in than in sea fish meal (Thuy and Loc 2007). Moreover, the Fish meal was dried at a temperature >80^oC, while the CB was boiled at a temperature >100^oC . This increase in temperature may also have contributed to reduce protein digestibility. This is agreement with Parsons (1999) who showed that fish meal produced at processing temperatures below 70-80^oC had higher CP digestibility than when the meal was processed at temperatures above 100^oC. The higher values for EE digestibility in the CB diets, could be explained by the higher concentration of EE in the feeds containing CB.  In addition, the CB fat is rich in unsaturated fatty acids  (Thuy and Loc 2007), and this may be also be responsible for higher energy digestibility values because unsaturated fatty acids are more efficiently digested and absorbed than saturated fatty acids (Lesson and Summers 2001; Baiao 2005). The diets with probiotic supplementation had higher digestibility values for CP, for both AID and ATD, and for ATD for EE. Viet et al (2009) showed that supplementation with probiotic to chicken diets resulted in increased digestibility of all components of the proximate analysis: DM, OM, CP and CF.

Apparent total and ileal digestibility of amino acids

There were no dietary effects on apparent digestibility coefficients for individual amino acids for both ileal and total collection (Table 3), with values for the former tending to be lower than for the latter.  This is in agreement with Onimisi (2008) and Kadim et al.(2002) who showed that there were differences between fecal and ileal digestibility of amino acids for animal meals. This may be due to the fermentation that occurs in the caeca of poultry, which is likely to influence the amino acid contents of excreta and thus modify results for digestibility (Short et al 1999).  

Experiment 2

Analyses of feed

The ingredients and chemical composition of the on-farm experimental diets (Table 4) were similar to those in the digestibility experiment.

Chicken performance

Performance of the chickens, measured by feed intake, weight gain and feed conversion, was not affected by replacing fish meal with catfish by-product meal (Table 5). 

 Slaughter characteristics

The characteristics of the carcasses were not affected by replacement of fish meal with catfish by-product meal (Table 6). The EE content of the breast  meat was higher in chickens fed the catfish by-product meal.

Fatty acid content of breast meat 

The main fatty acids in  breast muscle were oleic acid (C18:1), palmitic acid (C16:0), linolenic acid (C18:2) and alpha linolenic (C18:3), which increased slightly with replacement of fish meal by catfish by-product meal, reflecting the composition of the dietary fat sources. Baiao (2005) who showed that in birds, body fat composition is similar to the composition of the fat from the diet. , due to fatty acid profile is highly dependent on the dietary supply.

Conclusions

• Replacing fish meal with catfish by-product meal in the diets of Luong Phuong chickens resulted in a decrease in apparent total and ileal digestibility of crude protein and an increase in the apparent total and ileal digestibility of ether extract

• Diets with probiotic supplementation had higher ileal and total digestibility of crude protein

• Amino acid digestibility was not affected by replacing fish meal with catfish by-product meal, nor by addition of probiotic.

• Growth performance of the chickens in an on-farm trial was not affected by replacing fish meal with catfish by-product meal

• The fat content of the breast meat and its content of polyunsaturated fatty acids was increased by replacing fish meal with catfish by-product meal..

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 Received ; Accepted 22 September 2012; Published 1 October 2012

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