A simple in vitro test for evaluation of the usefulness of industrial enzymes as additives to broiler diet based on rye

The effect of 7 commerically produced enzyme preparations on reducing the viscosity of rye grain substances in water extract (in vitro) and in the digestive tract of chicken (in vivo) was studied. The enzyme preparations tested were: FC-1 and FC-2 (amylase, protease, /j-glucanase), DP-2885 and DP-2985 (amylase, protease, /?-glucanase, cellulase), WF-078 (/J-glucanase), Zymine xbp (xylanase, /?-glucanase, pentosanase, cellulase, pectinase) and Avizyme (/i-glucanase, cellulase, protease). Rye var. Dańkowskie Złote, containing 12.9% dietary fiber and 3.1% soluble fiber was used. The most efficient in reducing the viscosity of a water extract of rye flour (in vitro) and digesta (in vivo) was Zymine xbp (by 44 and 77% respectively), followed by DP-2885 (by 31 and 55% respectively), the effects of the remaining enzyme preparations were statistically insignificant. A M E N of unsupplemented rye was 10.97 + 0.73 and supplemented with 0.1% Zymine xbp, 11.87 < 0.76 MJ per kg of dry matter. It seems that the usefulness of commercial enzyme preparations as additives to broiler diets based on rye may be preliminary checked by means of a simple in vitro test.

Feeding trials with young chicks indicate that substances which depress growth and cause sticky faeces are present in rye.Antoniou and Marąuardt (1981) and Antoniou et al. (1981) found that the principal antinutritional factors in rye grains are highly viscous water-soluble and water-insoluble pentosans and pectins.According to Raczyńska-Bojanowska et al. (1983) rye grain contains 17.5% non-starchy polysaccharides in which: 6.8% are pentosans; 8.4% pectins and 4.3% betaglucan.Due to their high water binding properties, all of these substances form highly viscous solution in the digestive tract of chicken and increase the weight and bulk of the digesta.
The above effects support proliferation of intestinal microflora which is detrimental to the chick and interferes with digestion and absorption of such nutrients as fat, protein, Na ions, vitamin D 3 and others.Several authors reported that the growth-depressing properties of rye were overcome by addition of enzymes capable of hydrolysing pentosanes.The current studies were conducted to compare the effect of different industrial enzymes on reducing the viscosity of rye grain substances in water solutions (in vitro) and in the digestive tract of chickens (in vivo).

Experiment 1
Rye grain was ground until it passed a 0.49 mm sieve.Rye flour was mixed with distilled water in a proportion of 1:9 by weight and slowly agitated for one hour.The mixture was centrifuged at 1000 x g for 10 min.This extraction time allows for optimal extraction of the water-soluble fraction of rye pentosans (Fernandez et al., 1973, Raczyńska-Bojanowska et al., 1983).Twenty five ml of supernatant were taken into an Erlenmayer fiask and 0.5 ml of distilled water (control sample) or 0.5 ml freshly prepared enzyme solution (10 mg/ml) was added.The flasks were closed and kept for 1 h in a slowly shaking water bath at 40°C.Next they were cooled to 30°C and the relative viscosity was immediately measured using Baker's "Jelmeter" viscosity pipette.

Experiment 2
Twenty four Cornish-White Rock broiler małe chicks aged 5 weeks were divided into 6 groups of 4 birds each.After 6 h of fasting the birds were offered the experimental diet containing 70% rye and 100 mg per kg of one of the 5 enzyme preparations used in Experiment 1 (experimental groups) or starch (control group).Feed and water were supplied ad libitum.After 16-18 h the chickens were killed by decapitation, the content of the smali intestine extracted into weighed beakers, mixed with the same amount of distilled water, agitated for 3 min.and centrifuged at 1000 x g for 10 min.The relative viscosity of the supernatant was measured immediately as in Experiment 1.

Experiment 3
Two groups of 9 małe Cornish x White Rock broiler chickens aged 4 weeks were fed ground rye with or without the addition of 100 mg/kg of Zymine xbp.After 2 days the birds were kept fasting for 24 h, fed the same diets for the next 48 h.Excreta were collected during this 48 h period and the following 24 h fast.Dry matter, total N and gross energy content were determined in the samples of rye and excreta and AME N values for rye with or without enzyme added were calculated.

RESULTS AND DISCUSSION
The rye used in the experiments contained 12.88% dietary fiber in which 3.1 % was soluble fiber that gives a solution 3-4 times more viscous than soluble wheat fiber (Karlsson, 1985).Incubation of the water extract of rye grain for 1 h at 40°C reduced its relative viscosity by 34%, probably due to the action of endogenous grain pentosanases, which according to Karlsson (1985) are 3 types: endoxylanase, beta-xylosidase and arabinosidase.They did not, however, decompose all of the viscous substances because incubation with enzyme preparations added in amounts correspoding to 200 mg/kg of flour caused further reduction of relative viscosity (see Table 2).The most efficient was Zymine xbp containing the broadest spectrum of enzymes, followed by DP 2885, DP 2985, FC-2 and Avizyme.
The results of the test in vivo were highly correlated with those obtained in vitro.Zymine xbp and DP-2885 were the most effective in reducing digesta viscosity.This reduction had a positive effect on digestion and utilization of rye grain.AME N of unsupplemented rye (Experiment 3) was 10.97 ± 0.73 M J and rye with 0.1% of Zymine xbp added 11.87 + 0.76 MJ per kg of dry matter.
The enzyme preparations tested in these experiments were also used by Nierodzik (1987) in broiler fattening trials.They were added in amounts of 0.05 or 0.012% to diets composed of locally produced components and containing 10 or 20% rye.Only 2 preparations, Zymine xbp and DP 2885, significantly improved the weigth gain of chicken and feed efficiency.Jackisch and Jeroch (1990) obtained marked improvement in weight gain and Relative viscosity of initial supernatant liąuid prior to incubation was 4.74.
a, b, c -means in the same column not having a common superscript are significantly different (P=g0.05)feed efficiency after supplementation of a 50% rye diet with Zymine xbp preparate.Scholtyssek and Knorr (1987) supplementing a 30% rye diet with an enzyme mixture containing cellulase, beta-glucanase, xylanase and pectinase obtained better performance of chicken.A balance trial showed that enzyme supplementation had a positive effect on the digestibility of organie matter, particulary its non-starchy carbohydrate fraction.
Ali the results show clearly that addition of enzymes, which accelerate decomposition of viscous rye pentosans and pectines, improves utilization of feed mixtures containing a high proportion of rye grain.