Performance of growing pigs given diets in which fish meal was replaced by Tra catfish by products

Tran Trung Tuan and Brian Ogle¹

Department of Animal Husbandry and Veterinary Science, Faculty of Agriculture and Natural Resources, Angiang University (AGU), Angiang province, Vietnam
tttuan@agu.edu.vn
¹ Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, PO Box 7024, S-750 07 Uppsala, Sweden

Abstract

The effects of diets with four different protein sources were determined with respect to average daily gain, feed conversion ratio, back fat thickness and economic benefits in growing pigs. The four treatments were based on cassava root meal as energy source: A control treatment (FM) was cassava root meal plus marine fish meal; Treatment BM was cassava root meal plus catfish broken meat by-product meal; Diet OE was cassava root meal plus oil extracted catfish by-product meal and Diet BH was cassava root meal plus bone and head catfish by-product meal. The four diets were fed to twenty four growing pigs in a Randomized Complete Block Design with four treatments and six replications, and the experimental unit was one pig.

There were differences among the diets in the average daily gain (ADG), dry matter intake (DMI), feed conversion ratio (FCR) and back fat thickness, with a descending trend from BM, OE, FM and BH (p<0.05). The DMI, ADG, back fat thickness and iodine number were highest in BM (1955g, 629g, 13.7mm and 52.8, respectively) and lowest in BH (925g, 182g,7.81mm and 40.1, respectively). FCR in BM was the lowest (3.13 kg/kg gain) and highest in BH (5.31 kg/kg gain).  It can be concluded that growth performance on the treatment with catfish broken meat by-product meal (BM) was best, followed by OE, FM and BH.

Key words: byproducts, feed conversion, growth rate, Viet Nam

Introduction

Pig production in the Mekong delta increased strongly by 25.5 % between 2000 and 2006. However, during the same period production in Cantho Province decreased by 45 %, and continued to decline, by 4.3 % annually between 2006 and 2008 (Viet Nam Statistical Yearbook, 2008).

According to Nguyen Thi Thuy et al (2007) catfish residue meals contain high levels of fat and minerals which vary considerably among by-products and factories. For example, ash content ranged from 3.5 to 33.8% depending on catfish by-product, and calcium and phosphorus concentrations ranged from 7 to 13%, and 2 to 3%, respectively, which means that catfish by-products are a good source of macro- minerals for growing pigs and sows.  The nutritive value of any protein is directly related to the amino acid composition of that protein. A protein that does not contain the proper amounts of amino acids will be imbalanced. Tra catfish by-product meal (broken meat and skin) contains an excellent balance of essential amino acids, especially with respect to lysine and methionine (Nguyen Thi Thuy et al 2007). According to Le Thi Men et al (2005), Tra catfish residue meal can completely replace fish meal in fattening pig diets based on broken rice as the main ingredient and without effects on back fat thickness.

The present study was conducted in order to determine average daily gain, feed conversion ratio, back fat thickness and economic benefits among diets based on cassava root meal, with marine fish meal and different by-product meals from processing catfish as protein sources.

Materials and methods

Location and climate of the study area

The experiment was carried out in the experimental station of An Giang University, in Chau Phu district, An Giang Province. The average annual daily temperature is 27 °C, with the highest temperatures of 35 to 36°C from April to May and the lowest of 20 to 21°C from December to January. The mean rainfall is 1400 to 1500 mm. The climate has two seasons, the rainy season from May to November and the dry season from December to April (An Giang Portal 2008).

Animals and management

Twenty four crossbred (Landrace x Yorkshire x Duroc) castrated male pigs with a mean body weight of 22.7 kg ± 0.5 at 70 days of age were bought from a pig farm in An Giang Province. They were vaccinated against hog cholera and foot and mouth disease and were treated against round worms with Levamysole before starting the experiment.

Housing was in individual pens (0.6 m x 1.2 m) made of bamboo with feeding troughs to allow recording of offered feed and to collect refused feed. Feeding was  ad-libitum four times per day at 07:00, 11:00, 14:00 and 17:00h; feed refusals were collected and weighed before the morning and afternoon feeding.

During the trial, one pig in treatment FM died due to lung problems.

Experimental diets

The diets were based on cassava root meal, marine fish meal, broken meat by-product, oil extracted by-product and head and bone by-product, and were formulated to contain from 17 to 18% crude protein (CP) in DM. All ingredients were bought at one time at the beginning of the experiment. The bone and head, broken meat and oil extracted catfish by-product meals were bought in local processing factories, and the cassava root meal and fish meal from an animal feed shop in An Giang province. Before making the diet formulae, ingredients were analyzed for crude protein, and then were mixed every week.

Treatments

These were:

• FM: cassava root meal plus marine fish meal
• BM: cassava root meal plus broken meat catfish by-product meal
• OE: cassava root meal plus oil extracted catfish by-product meal
• BH: cassava root meal plus bone and head catfish by-product meal

Experimental design

The experiment was designed as a Randomized Complete Block with four treatments and six replications The pigs were allocated to blocks based on initial live weight and at random within blocks according to treatment. The experiment was conducted over four months (finishing when the pigs reached slaughter weight, at 90 to 100 kg).

The chemical composition of the ingredients and the ingredient composition of the diets are shown in Tables 2 and 3.

Measurements and data collection

The  pigs were weighed at the beginning and end of the experiment. Feed offered and refused wasrecorded every day.  Back fat thickness at the last rib was measured at the end of the experiment by an ultrasonic technique (RENCO Co., Ltd, Minneapolis, USA).

Chemical analysis

Ingredients were analyzed for dry matter (DM), ether extract (EE) and ash according to the standard methods of AOAC (1990). Crude protein (CP) was determined by the Kjeldahl procedure. DM in feeds was determined by microwave radiation (Undersander et al 1993). One representative pig in each treatment was slaughtered, and back fat samples taken for analysis of iodine number according to the method of AOAC (1984).

Statistical analysis

The data for feed intake, growth rate and feed conversion ratio were analysed using the General Linear Model (GLM) of the Analysis of Variance (ANOVA) procedure of the Minitab statistical software,  release 14 (Minitab 2003). Sources of variation were: animals, treatments, blocks and error. The Tukey Test for pair-wise comparisons was used to separate means when the differences were significant at p<0.05.

Results

There were differences in the average daily gain, feed conversion ratio, back fat thickness and iodine number among diets, with a descending trend from BM through OE, FM and BH (Table 3).  Dry matter intake was highest in BM, followed by FM, OE and BH. There were no differences among treatments in back fat thickness adjusted for live weight.

Average daily gain was highest in BM followed by OE, FM and BH (Table 3). The FCR in BM was lower than in FM, but not different from OE. The FCR was poorer in BH than in FM. Back fat thickness of pigs fed the FM and OE diets did not differ, while BM had the highest value, and BH the lowest. Iodine number of BM was higher than for FM and OE, and was lowest in BH.

Discussion

The metabolisable energy (ME) concentration in diet BH was very low (10.8 MJ/kg) because of the very high ash content and low concentration of EE. In contrast diet BM had a high concentration of EE, low concentration of ash, and therefore a high ME content (13.4 MJ/kg). Crude fibre content in all diets was very low.

The DM intake differed among diets. The low ME content of diet BH would have been expected to have increased DMI, as pigs try to adjust their feed intake to give a constant ME intake. However, that this was not the case could have been due to the lower palatability of diet BH, probably due to the very high ash content, and also due to possible rancidity. This could also explain the positive relationship between DMI and ratio of ME:CP in the diets, as diets FM and OE also had a high ash content, and DMI that were much lower than that of pigs on BM, which had an ash content of only 3%. Furthermore, there were positive relationships between apparent digestibility of DM and CP (Tuan and Brian Ogle 2018) and the DMI. Cole et al (1972) concluded that voluntary feed intake is reduced when digestible energy and nutrient density in the diet were decreased, and Pomar et al (2003) and Speedy (1997) confirmed that voluntary feed intake is limited when the feed is unbalanced in terms of energy and protein ratio.

Average daily gains in descending order were BM, OE, FM and BH (Table 3), and generally reflected daily dry matter intakes. Growth rates were highest on diet BM, which also had the highest DMI. Average daily gain and DMI were very low in diet BH, but although DMI was higher in the fish meal (FM) diet than in the diet containing the oil extracted meal (OE), ADG in these two diets were similar, probably because the ME content in the diets and ratio of ME:CP between the treatments were different. Calculated ME content in diet BH was lower than the requirement of tropical pigs, as the ideal mean ME in diets for pigs in the tropics from 20 to 120 kg is 12.0 (Holness 2005). Several authors confirmed that subsequent growth performance was reduced when pigs had low energy intake in the early growing period (Chadd and Cole 1999; Smith et al 1999; De la Llata et al 2001). In addition, ash content in the diet could also have negatively affected growth rate for a different reason, because animals must excrete minerals through urine and use energy to do this function when intakes are higher than body demand. Consequently, all the above factors probably affected ADG.

The FCR among the diets were different. This can be explained by the fact that the diets contained different ME contents, and thus protein deposition in pigs, and therefore, the efficiency of feed utilization were different. These results are in agreement with Lopez et al (1997) who found that when the ME in the diets was higher, the FCR was lower, and when the ratio of ME : CP was high, the FCR was reduced (Le Bellago et al 2002).

The back fat thickness was different among treatments, and there was a positive relationship between ME content in the diet and back fat deposition. According to Renaudeau et al (2006) the higher the ME intake, the thicker the back fat.

There were differences among the treatments in iodine number of back fat, with the BM diet having the highest value. Generally, when the catfish oil level was increased, the iodine number was higher. This can be explained by the fact that the proportion of EE in diets BM and OE was higher than in FM and BH and the unsaturated fatty acid content in catfish by-product meal is very high. According to Nguyen Thi Thuy et al (2007) the unsaturated fatty acid content in catfish by-product meal is higher than in other fish meals. However, our values for iodine number were lower than those reported by Le Thi Men et al (2003) in a study on the effects of catfish oil in diets for fattening pigs.

Acknowledgements

The authors would like to express most sincere thanks to SIDA-SAREC (Swedish International Development Cooperation Agency - Department for Research Cooperation), through the regional MEKARN program for  financial support of this study.

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Received 10 December 2018; Accepted 22 December 2018; Published 1 January 2019

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