Probiotic and organic acids improve growth performance of pigs fed diets containing Catfish (Pangasius hypophthalmus) protein hydrolysate

Nguyen Thi Thuy

Department of Animal Sciences, College of Agriculture and Applied Biology, CanTho University, 3/2 Street, Ninh Kieu District, Can Tho City.
nthithuycn@ctu.edu.vn

Abstract

A feeding trial was carried out to evaluate the effects of a probiotic and organic acids on growth performance and carcass quality of pigs fed diets containing Tra catfish (Pangasiushypophthalmus) scrap meat protein hydrolysate (HMB) as the major protein source. Thirty-two crossbred castrated (Yorkshire x Landrace) male pigs with an initial average body weight of 25.2kg were housed in individual pens in a randomized complete block design of 4 treatments and 8 replications. The diet was based on maize and soybean meal with the scrap meat hydrolysate (HMD) as the major (60%) source of protein. The treatments were: CTL (no additive), PR (a probiotic of beneficial microorganisms), OA (a mixture of organic acids) and the two additives combined (PROA).

The overall growth rates of 641 to 677 g/day, and feed conversion values of 3.26 to 3.40, indicate that Tra catfish scrap meat hydrolysate was efficiently utilized as a protein source for pigs. Growth rate was improved 5 % by each of probiotic and organic acid additives with no advantage from combining them. Feed intake was not affected with the result that feed conversion tended to be improved slightly by the additives. There appeared to be beneficial effects on meat color from feeding the additives.

Key words: additives, longissimus dorsi, meat color, protein

Introduction

Pig production is dominant in the Mekong Delta of Viet Nam. At householder scale, there are many farmers who try to reduce feed cost by using locally available feed resources. Tra catfish culture is the major system of freshwater fish production in Vietnam. Processing the fish for export yields many byproducts: the head, bone, skin and scrap meat that remain after separating the fillets. A recent development is to produce a protein hydrolysis from these byproducts, using the enzyme Bromelain (Hien et al 2015). The protein in the catfish residue was effectively hydrolyzed into low molecular weight peptides and amino acids. Despite the high fat content, initial trials using the hydrolysate as a protein source in the diets of weaned piglets (Thuy et al 2015) and chickens (Thuy and Ha 2017) were encouraging.

The present study aimed: (i) to evaluate the use of the protein hydrolysate as a replacement for fish meal in the diets of growing-finishing pigs; and (ii) to determine the potential benefits from adding sources of probiotics and organic acids, previously shown to improved growth and feed conversion in diets of weaning pigs (Le Thi Men et al 2015).

Materials and methods

Animals and experimental design

Thirty-two crossbred castrated, male pigs (Yorkshire x Landrace) with an initial average body weight of 25.2 ± 1.6 kg were housed in individual pens according to a randomized block design with 4 treatments and 8 replications. The diet was based on maize, broken rice and rice bran, with Tra catfish scrap meat hydrolysate (HMD) providing 60% of the diet protein (Table 2). The treatments were: CTL (no additive), PR (a probiotic of beneficial microorganisms), OA (a mixture of organic acids) and PROA a 50:50 combination of PR and OA. The HMB was prepared as described by Hien et al (2015) and was made before starting the experiment.

Experimental diets

The probiotic (PR) contained Bacillus subtilis, Lactobacillus spp., Saccharomyces cerevisiae and vitamins B1 and K3. The OA additive contained fumaric acid (15%), lactic acid (5%), calcium formate (10%) and phosphoric acid (30%).The additives were included at a level of 2g/kg of diet for PR, OA and PROA. The diets were fed ad libitum with fresh feed offered at 08:00, 11:00, 14:00 and 17:00h. The refusals were collected the following morning before the first meal. Samples of feeds and refusals were stored at -18^oC for analysis.

Measurements

The pigs were weighed at the beginning and end of the experiment. Feeds offered and refused were weighed daily. At the end of the experiment, 3 pigs/treatment were slaughtered for carcass evaluation; samples of Longissimus dorsi muscle at the 10^th rib were taken for chemical and physical analysis.

Chemical analysis

The proximate composition of diet ingredients, feed offered and refusals was determined according to AOAC (1990). The pH of the Longissimus dorsi muscle was measured 24 h after slaughter using a digital pH meter. Meat color was recorded using a colorimeter (Chromameter Minolta, CR- 200 Japan), which indicated degrees of lightness of a meat sample (L), red-ness (a) and yellow-ness (b).

Statistical analysis

The data were analysed using the General Linear Model (GLM) of Minitab Statistical Software Version 16.0. The statistical model used was:

Y_ij = µ + α_i+ β_j + e _ij

where: Y_ij is growth performance; µ is overall mean averaged over all treatments and all possible blocks; α_iis effect of treatment i; β_j is effect of block j; e _ij is random error associated with assigned treatment i in block j.

Results and discussion

Dry matter intake, growth rate and feed conversion

Growth rate was improved 4.7% by the probiotic and organic acid additives with no advantage from combining them (Table 3). Feed intake was not affected with the result that feed conversion tended (p=0.22) to be improved slightly by the additives.

The benefits manifested equally by the probiotic and the mixed organic acids, although of a relatively low order (4.5% for growth and 3.2% for feed conversion), are in line with results reported by Le Thi Men (2015) using the same additives in diets of weaning pigs. Probiotics are thought to benefit pig performance by competing with harmful gut flora, and by stimulating the immune system (Lan et al 2017; Hentges 1992). Increased diet digestibility from feeding probiotics has been reported by Choi et al (2011) and (Meng et al 2010) with better growth rates (Balasubramanian et al 2016). Lan et al 2017) considered that probiotics helped to maintain beneficial intestine microbiota by producing organic acids, thus inducing competitive exclusion of pathogenic bacteria.

The probable mode of action of organic acids includes reducing pH in the gastrointestinal tract, regulating the balance of microbial populations in the gut and stimulating the secretion of digestive enzyme (Thaela et al 1998). Galfi and Bokori (1990) showed that organic acids promoted the growth and recovery of the intestinal morphology.

The range of growth rates (641 to 677 g/day), and feed conversion values (3.26 to 3.40), indicate that the Tra catfish scrap meat hydrolysate was efficiently utilized as a protein source, as it completely replaced marine fish meal, supplying overall some 60% of the dietary protein.

Carcass traits

Carcass and meat quality measurements did not differ among treatments (Table 4).

The color of the meat is an important indicator affecting consumer choice. In this respect, the meat from pigs fed the diets with additives had higher red and yellow meat indexes, considered to be positive quality attributes. These results are similar to those reported by Cho et al (2005), who indicated increased values of redness in the meat of growing-finishing pigs fed diets supplemented with Bacillus spp probiotic.

Conclusions

• The overall rates of growth rates of 641 to 677 g/day, and feed conversion values of 3.26 to 3.40, indicate that Tra catfish scrap meat hydrolysate (HMB) was efficiently utilized as a protein source for pigs.
  
  
• Growth rate was improved 4.7% by probiotic and organic acid additives with no advantage from combining them. Feed intake was not affected with the result that feed conversion tended to be improved slightly by the additives.

Acknowledgements

This research was funded by the MEKARN II project, supported by Sida. The author expresses her sincere thanks to the owners and staff of the pig farm in An Giang province for facilitating the conduct of the experiment.

References

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Thuy N T and Ha N C 2017 Effects of inclusion of protein hydrolysis from Tracat fish by-product waste water in the diets on apparent ileal digestibility and total tract retention coefficients of local chickens. Livestock Research for Rural Development, 29 (3), Article 55 http://www.lrrd.org/lrrd29/3/nthi29055.html

Received 4 April 2018; Accepted 4 May 2018; Published 1 August 2018

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