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Animal Feed Science and Technology 177 (2012) 124– 129

Contents lists available at SciVerse ScienceDirect

Animal Feed Science and Technology

journal homepage: www.elsevier.com/locate/anifeedsci

almon protein hydrolysate as a protein source in feed for young pigs

.V. Nørgaard ∗, K. Blaabjerg, H.D. Poulsenepartment of Animal Science, Aarhus University Foulum, P.O. Box 50, DK-8830 Tjele, Denmark

r t i c l e i n f o

rticle history:eceived 12 October 2011eceived in revised form 1 August 2012ccepted 8 August 2012

eywords:ish mealish protein concentrateigsalmon protein hydrolysateoy protein concentrate

a b s t r a c t

Salmon protein hydrolysate (SPH) is made from fresh by-products from farmed salmonthat are minced and acidified to hydrolyse proteins into peptides and free amino acids. Theobjective of this study was to evaluate SPH in young pigs compared to soy protein concen-trate (SPC), fish meal (FM) and combinations hereof. Five diets were composed, all fulfillingthe nutrient recommendations for young pigs. All diets contained 172 g soy bean meal/kg.One diet was supplemented with 123 g SPH/kg, and equivalent protein was supplied as SPCor FM in two other diets. Two diets were composed by combining half the amount of SPHand SPC or half the amount of SPH and FM. One week after weaning, one hundred indi-vidually housed pigs were allocated to one of five diets (n = 20) and fed ad libitum for fourweeks. Pigs fed the SPH and SPH + FM diets ate 12–14% more (P<0.05) than pigs fed theSPC diet, but the results on gain and feed utilization was not significantly different amongtreatments. No differences were observed in faeces characteristics when scored by visualjudgment during two 5-d periods. In conclusion, pigs responded equally to diets containingSPH and FM, and SPH resulted in greater feed intake than SPC.

© 2012 Elsevier B.V. All rights reserved.

. Introduction

The use of highly digestible and palatable feedstuffs is important in diets for young pigs. Especially the challenge ofandling diarrhoea problems after weaning have focused on minimizing the level of dietary crude protein (CP) and themount of undigested crude protein (e.g. Bikker et al., 2006; Nyachoti et al., 2006; Heo et al., 2008). Processing of soy beaneal (SBM) into soy protein concentrate (SPC) or soy protein isolate results in protein sources well tolerated by young pigs

Li et al., 1991a). Soy bean protein sources often have an amino acid composition somewhat different from the ideal aminocid profile (Boisen et al., 2000), but the amino acid composition of fish products is often complementary to that of vegetablerotein sources, and the use of fish meal (FM) in weaner diets is therefore common.

The salmon protein hydrolysate (SPH) (H-pro, Hordafor DK, Aabybro, Denmark) used in this study was in the form ofoncentrated salmon silage produced by acid hydrolysis of salmon protein. In the process, fresh by-products from farmedalmon are minced and mixed with formic acid until the pH value has stabilized between 3.5 and 4.0. At this pH range,

roteases in the salmon tissue such as pepsin are able to hydrolyse the proteins into peptides and free amino acids.

The suitability of fish protein hydrolysates is well described for fish (Espe et al., 1999; Refstie et al., 2004; Hevrøy et al.,005), where it is known to be a good and easily digestible protein supplement. The explanation for the positive effects ofhe fish protein hydrolysate on animal performance may be the high content of short peptides and free amino acids which

Abbreviations: ADG, average daily gain; Ca, calcium; CP, crude protein; DM, dry matter; FCR, feed conversion ratio; FM, fish meal; HPLC, high performanceiquid chromatography; P, phosphorus; SBM, soy bean meal; SEM, standard error of mean; SID, standardized ileal digestible; SPC, soy protein concentrate;PH, salmon protein hydrolysate.∗ Corresponding author. Tel.: +45 87157816; fax: +45 87154249.

E-mail address: jan.noergaard@agrsci.dk (J.V. Nørgaard).

377-8401/$ – see front matter © 2012 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.anifeedsci.2012.08.003

J.V. Nørgaard et al. / Animal Feed Science and Technology 177 (2012) 124– 129 125

Table 1Analysed chemical composition (g/kg as-fed) of wheat, barley, toasted dehulled soy bean meal (SBM), salmon protein hydrolysate (SPH), soy proteinconcentrate (SPC), and fish meal (FM).

Item Wheat Barley SBM SPH SPC FM

Dry matter 859 871 882 478 912 924Gross energy, MJ 15.8 16.3 17.5 10.3 18.1 19.9Crude protein (CP) 101 111 478 346 532 697CP digestibilitya 904 914 954 978 951 959Crude fat 22 26 28 65 21 113Lysine 3.1 4.2 29.4 22.7 32.6 50.4Methionine 1.6 1.8 6.7 8.8 6.5 19.3Cysteine 2.4 2.5 7.1 3.3 7.2 5.4Threonine 3.0 3.8 19.3 14.1 20.9 28.8Valine 4.7 5.8 24.0 15.8 26.1 35.3Isoleucine 3.3 3.8 22.3 13.0 24.4 29.8Leucine 6.8 7.8 36.0 22.5 39.3 49.1Phenylalanine 4.6 6.0 23.5 12.8 27.2 26.8

Histidine 2.6 2.7 13.2 7.8 14.4 14.7

a In vitro ileal digestible protein (g/kg crude protein) (Boisen and Fernández, 1995).

are palatable and more readily absorbed than intact protein without preceding digestion by pancreatic proteases (Gilbertet al., 2008). Furthermore, SPH may exhibit some biological activity as peptides from fish protein hydrolysates are thought toact immune-stimulating when used in aquaculture (Gildberg et al., 1996; Kotzamanis et al., 2007; Taheri et al., 2010). Theseaspects of SPH have not been studied in pigs, and the documentation on growth performance is sparse. It is hypothesizedthat pigs respond equally well to SPH as to FM, which is often used as a positive reference in experimental diets for piglet.

The objective of the present study was to evaluate effects on feed intake, feed utilization and growth of young pigsreceiving SBM containing diets supplemented with SPH, FM, SPC or equal amounts of SPH + FM or SPH + SPC.

2. Materials and methods

2.1. Animals, diets and protocol

A total of 100 crossbred (Landrace-Yorkshire × Duroc) female and castrated male pigs at the same proportion were weanedat 27.6 ± 1.6 d of age and individually housed in pens with visual and physical contact to neighbouring littermates. The penscomprised one-third concrete flooring and two-thirds plastic flooring which permitted drainage. Five similar rooms of 10pens were used twice, i.e. the experiment was divided into two periods. During the first wk after weaning, the pigs were feda standard diet containing 1.0 g zinc/kg without growth promoters.

Seven days after weaning, the pigs weighed 9.0 kg (SEM, 0.3 kg) and were allocated to one of the five treatments. Thetreatments were balanced according to sex and weight. The experiment started one wk after weaning to assure that all pigsconsumed sufficient feed and were adapted to the individual pens. Pigs were provided feed ad libitum for 28 d. The feed wassupplied twice daily, with feed dispensers adjusted on a regular basis to minimize feed spillage. The pigs had permanentaccess to fresh water from nipple drinkers. The experiment complied with the Danish Ministry of Justice Law no. 382 (June10, 1987), Act no. 726 (September 9, 1993), concerning experiments with animals and care of experimental animals.

The chemical composition and the in vitro CP digestibility (Boisen and Fernández, 1995) of the main ingredients weredetermined before diets were optimized (Table 1). Five diets with different main protein sources were composed (Table 2). Allfive diets contained 172 g dehulled SBM/kg and were supplemented up to 170 g SID CP/kg with either SPH (H-pro, Hordafor,Aabybro, Denmark), SPC (HP 200, Hamlet Protein, Horsens, Denmark), FM (FF Classic, FF Skagen, Skagen, Denmark) or acombination of these protein sources giving raise to SPH + SPC and SPH + FM diets, where SPH, FM and SPC contributedwith equal amounts of SID protein. The contribution from the sum of SPH, SPC and FM to the total content of dietary CPwas from 17 to 22 percent. The five diets were optimized to contain identical levels of net energy (9.45 MJ/kg as-fed) andmain nutrients according to the Danish requirements (Jørgensen and Tybirk, 2008). Therefore, the diets contained similarconcentrations of essential nutrients per kg diet as-fed.

2.2. Registrations and faeces scoring

Pigs were weighed at d 0, 14 and 28 of the experimental period, and the accumulated feed intake was registered for theperiods d 0 to 14 and 14 to 28. Faeces characteristics were evaluated twice during five consecutive days from d 6 to 10 and d13 to 17 of the experiment. By visual judgment, the faeces were given one of four scores: 0, normal/firm consistency; 1, soft

consistency; 2, thin/sloppy consistency, or 3, watery consistency. The scores 2 and 3 were evaluated as diarrhoea, and score3 pigs were treated for diarrhoea with injections of Clamoxyl Vet (150 mg/ml amoxicillintrihydrate, Orion Pharma AnimalHealth, Nivå, Denmark) for three days as prescribed by the veterinarian. The general health status was recorded daily.

126 J.V. Nørgaard et al. / Animal Feed Science and Technology 177 (2012) 124– 129

Table 2Composition and calculated chemical composition (g/kg, as-fed basis) of experimental diets containing salmon protein hydrolysate (SPH), soy proteinconcentrate (SPC), and fish meal (FM).

SPH SPC FM SPH + SPC SPH + FM

IngredientWheat 494 562 598 528 546Soy bean meal, dehulled 172 172 172 172 172Barley 150 150 150 150 150SPH 123 – – 62 62SPC – 65 – 32 –FM – – 48 – 24Animal fat 26 11 1.0 18 13Calcium carbonate 15.5 16.1 13.6 15.8 14.5Mono-calcium phosphate 7.5 9.5 5.6 8.5 6.6Vitamin-mineral premixa 4.0 4.0 4.0 4.0 4.0Salt 2.5 3.6 2.5 3.0 2.5l-Lysine HCl (780 g/kg) 3.4 4.0 3.6 3.7 3.5dl-Methionine (990 g/kg) 0.6 1.2 0.7 0.9 0.6l-Threonine (980 g/kg) 0.8 1.1 1.0 1.0 0.9l-Tryptophan (980 g/kg) 0.6 0.4 0.5 0.5 0.6Phytase (Natuphos 5000) 0.2 0.2 0.2 0.2 0.2

Calculated chemical compositionDry matter 826 875 872 850 849Crude ash 54.5 56.6 52.1 55.5 53.3Crude fat 53.2 33.8 28.3 43.4 40.8Crude protein 196 196 198 196 197SID crude proteinb 170 171 171 171 171SID lysine 11.4 11.4 11.4 11.4 11.4

a Trouw Nutrition Denmark A/S. Provided per kg diet: 10,000 IU vitamin A, 2000 IU vitamin D3, 94 IU vitamin E, 2.4 mg vitamin K3, 2.4 mg vitamin B1,4.8 mg vitamin B2, 2.4 mg vitamin B6, 0.02 mg vitamin B12, 12 mg d-panthotenic acid, 26 mg niacin, 0.2 mg biotin, 85 mg �-tocopherol, 200 mg Fe (Fe(II)sulphate), 165 mg Cu (Cu(II) sulphate), 200 mg Zn (Zn(II) oxide), 56 mg Mn (Mn(II) oxide), 0.3 mg KI, 0.3 mg Se (Se-selenite).

b SID, standardized ileal digestible.

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.3. Analysis

Dry matter (DM) content was determined for diets and faeces by oven drying at 103 ◦C for 20 h. Gross energy waseasured using bomb calorimetry (Calorimeter 6300, Parr Instrument Company, Moline, USA). Crude protein content (total

itrogen × 6.25) in urine was analysed by the Dumas method (Hansen, 1989) and in diets and faeces by a modified Kjeldahlethod (AOAC 984.13). Crude fat was extracted with petroleum ether after hydrochloric acid hydrolysis (Procedure B,

egulation EC 152/2009). Amino acids were hydrolysed for 23 h at 110 ◦C with or without performic acid oxidation (Directive8/64/EC). In vitro ileal digestibility of protein was estimated as described by Boisen and Fernández (1995). Molecular weightistribution of the solubilised protein in SPH was determined by using high performance liquid chromatography (HPLC).amples were mixed and centrifuged for 10 min at 3000 × g in a buffer containing 0.1 M sodium chloride, 0.3% sodium dodecylulphate (SDS) and 0.001 M sodium azide before injection into the HPLC fitted with a TSK-G 2000 SW gel permeation column7.5 mm × 300 mm) equilibrated with the same buffer at pH 6.8. The flow rate was set at 0.5 ml/min at 2413 kPa, and peptidesere detected with a Perkin Elmer Series 200 UV/VIS detector at 220 nm.

.4. Calculations and statistical analysis

Animal performance data were statistically analysed by the MIXED procedure of SAS (Littell et al., 2002) according to aodel including diet (diet 1 to 5), sex (castrate, female), the interaction term diet × sex and the initial weight used as a covari-

te. Room (room 1 to 5), period (1, 2; rooms were used twice), the interaction terms room × period, room × period × diet,oom × period × sex, and room × period × diet × sex were handled as random variables.

Faeces score data are presented as the distribution of scores during the two evaluation periods from d 6 to 10 and from 13o 17. The distribution of days on the four faeces scores were analysed using the GLIMMIX procedure of SAS (SAS Institute,999) with a multinomial distribution (a generalization of the binomial distribution) and a cumulative logit link functioni.e. the response was restricted to one of a finite number of ordinal values). The model included diet (diet 1 to 5), scoreay (d 6 to 10, or d 13 to 17), the interaction term diet × score day, and the initial weight as a covariate. Room (room 1 to), the interaction term room × period (1, 2; rooms were used twice) and pig were handled as random effects (Littell et al.,

002). Statistical significance was accepted at P<0.05 and tendencies at P<0.15. Presented data are least squares means andtandard error of mean (SEM).

J.V. Nørgaard et al. / Animal Feed Science and Technology 177 (2012) 124– 129 127

Table 3Average daily feed intake (ADFI), average daily gain (ADG) and feed conversion ratio (FCR) of pigs.a,b

Item SPH SPC FM SPH + SPC SPH + FM SEM P value

ADFI, g, d 1–14 542 494 519 524 536 25 0.45ADG, g d 1–14 417 384 429 408 429 23 0.38FCR, g/g, d 1–14 1.31 1.30 1.23 1.30 1.25 0.05 0.29ADFI, g, d 14–28 968 858 920 867 927 44 0.28ADG, g, d 14–28 749 663 722 699 727 35 0.31FCR, g/g, d 14–28 1.33 1.32 1.28 1.29 1.28 0.06 0.83ADFI, g, d 1–28 759y 668x 721xy 691xy 745y 29 0.08ADG, g, d 1–28 583 527 577 561 586 22 0.19FCR, g/g, d 1–28 1.32 1.29 1.25 1.28 1.27 0.03 0.38

x,y Means within rows without a common superscript differ (P≤0.05).a Diets differing primarily in protein sources: salmon protein hydrolysate (SPH), soy protein concentrate (SPC) and fish meal (FM).b Values are least squares means and standard errors of the means. n = 20.

3. Results

The proportion of water soluble proteins was analysed in SPH to 293 g/kg as-fed, i.e. 85% of the total amount of CP. Themolecular weight distribution of the water solubilised protein fraction in SPH showed a fraction of 81% below 1000 Da, afraction of 14% between 1000 and 10,000 Da, and a fraction of 5% above 10,000 Da. This indicates that the majority of theprotein fraction was in the form of di-, tri- and oligo peptides as well as free amino acids.

In general, pigs maintained good health during the experiment. No significant differences were found between pigs fedSPH and FM (Table 3). From d 1 to 28, pigs fed the SPH and SPH + FM diets ate 12–14% more (P<0.05) than pigs fed SPC diet,but ADG and FCR did not differ significantly among treatments.

Faeces characteristics were evaluated from d 6 to 10 and from d 13 to 17. Neither the first (P=0.51) nor the second (P=0.42)evaluation period showed a difference between diets during the distribution of days where pigs were given the differentscores (Table 4).

4. Discussion

Only very little is published on the response to SPH in pigs. The feeding of salmon head protein hydrolysate to pigletsshould be limited to 100 g/kg or less for early weaned pigs (Husby, 1991). The use of fish silage from mackerel added formicacid for 20–55 kg pigs was not limiting the animal performance at the highest inclusion level of 150 g/kg (Green et al., 1988).The inclusion level of 123 g SPH/kg used in the present experiment was apparently well tolerated by young pigs.

In aquaculture, fish hydrolysate is well studied and has shown synergistic effects with FM (Espe et al., 1999; Refstie et al.,2004; Hevrøy et al., 2005; Taheri et al., 2010). Due to the large proportion of low molecular weight peptides, SPH may bemore readily digestible and available for absorption than protein sources containing larger peptides and complex protein

structures (Gilbert et al., 2008). However, the effect of feeding small peptides compared to intact protein has apparently notbeen studied in pigs. Marine-derived peptides are furthermore known to possess bioactive properties in humans (Kim andWijesekara, 2010), although these effects have not been studied in pigs.

Table 4Distribution of days with faeces scores.a,b

SPH SPC FM SPH + SPC SPH + FM P valuec

Day 6–10 0.51Score 0 69 73 66 64 73Score 1 28 17 30 30 22Score 2 3 5 2 2 2Score 3 0 5 2 4 3

Day 13–17 0.42Score 0 81 71 76 75 71Score 1 19 28 24 25 29Score 2 0 1 0 0 0Score 3 0 0 0 0 0

a Faeces scores: 0, normal/firm consistency; 1, soft consistency; 2, thin/sloppy consistency, or 3, watery consistency.b Diets differing primarily in protein sources: salmon protein hydrolysate (SPH), soy protein concentrate (SPC) and fish meal (FM).c The P value is based on an F-test for differences in the distribution of days with score 0–3 among the diets.

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28 J.V. Nørgaard et al. / Animal Feed Science and Technology 177 (2012) 124– 129

The diet based on SPC resulted in the lowest feed intake. This is in agreement with Solá-Oriol et al. (2011), who havehown that pigs have a great preference for FM compared to other protein sources, but in contrast to Jones et al. (2010)ho, at similar inclusion levels of SPC, found animal performances comparable to pigs fed FM. At high inclusion rates (up

o 286 g SPC/kg) Lenehan et al. (2007) found lower feed intake compared to SBM, but other studies on high levels of SPCnclusion (241–251 g/kg) have shown better responses to SPC than to SBM, and similar responses than for pigs fed driedkim milk (Sohn et al., 1994) or dried whey (Li et al., 1991b). The underlying reasons for the results of pigs fed SPC alone orn combination with SPH are therefore not clear.

The registration of faeces characteristics indicated no diet dependent effect on the incidence of diarrhoea, and the inci-ence of diarrhoea was in general low. One reason for the low incidence of diarrhoea may be the seven days pre-experimentaleriod of feeding a zinc-containing diet (1.0 g/kg) which was included to secure that all pigs ate from the beginning of thexperimental period, and pigs have thus already been adapted to the shift from sow milk to dry feed. Another reason maye that diets had only 171 g SID CP/kg, which is lower than diets reported to cause diarrhoea (Heo et al., 2008; Wellock et al.,008a).

. Conclusions

Salmon protein hydrolysate resulted in animal performances similar to FM. Pigs fed the SPH and SPH + FM containing dietsad greater feed intake than pigs fed the SPC containing diet, but results on gain and feed utilization was not significantlyifferent among treatments. The incidence of diarrhoea was not affected by the protein source which may be due to relatively

ow levels of dietary CP and high health standards of the pigs.

cknowledgements

This work was funded by Hordafor DK and Aarhus University, Department of Animal Science.

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