(Ross-Performance of Broiler Chicks Fed Normal and Low Viscosity Rye or Barley with or without Enzyme Supplementation

: This experiment was conducted to measure nutrient digestibility and performance in broiler chicks fed diets based on normal and low viscosity rye or barley fed with and without enzyme (pentosanase and β -glucanase) during a 17 day growth trial. A total of 150 one-day old, male broiler chicks (5 birds per pen and 5 pens per treatment) were randomly assigned to one of six dietary treatments in a 3 × 2 factorial design experiment (3 cereals × 2 enzyme levels). Digestibility coefficients were determined using chromic oxide. Digestibility coefficients for dry matter and crude protein were significantly (p=0.0001) higher for the barley-based diets than for any of the rye-based diets. Digestibility coefficients for gross energy did not differ (p>0.05) due to cereal grain. There were no differences in the digestibility coefficients for dry matter and gross energy between chicks fed normal and low viscosity rye. However, the digestibility coefficient for crude protein was higher (p=0.01) for the low viscosity rye compared with the normal viscosity rye. Addition of enzyme to the diet significantly (p=0.0001) increased digestibility coefficients for dry matter, crude protein and energy. There were no significant differences in weight gain, feed intake or feed conversion between birds fed barley or rye or between birds fed normal or low viscosity rye. Enzyme supplementation significantly improved (p=0.0001) weight gain, intake and feed conversion. The overall results of this experiment indicate that unsupplemented barley and rye do not support adequate growth rates in poultry. Enzyme supplementation dramatically improved broiler performance. In addition, genetic selection to reduce the viscosity of rye had only a modest effect on the nutritive value of rye for broilers. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 2 : 234-238)

INTRODUCTION 308 line; Lilydale Hatchery, Wynyard, Saskatchewan) were randomly assigned to one of six dietary treatments in a 3×2 factorial design experiment (3 cereal grains×2 enzyme levels). The cereal component of the diet (approximately 60%) comprised either barley, low viscosity rye or normal viscosity rye fed with or without enzyme (Table 1). Soybean meal (32%) was used as the source of supplementary protein and all diets were supplemented with sufficient vitamins and minerals to meet or exceed the levels recommended by the NRC (1994). The experimental diets were provided in mash form (3 mm screen) and the experiment was conducted over a 17 day period.
The enzyme supplement (Aspergillus niger, GNC Bioferm Incorporated, Saskatoon, Saskatchewan) supplied 2250 pentosanase units and 700 β-glucanase units per gram (unit is mg total reducing sugars (glucose equivalent) released in 10 min at 30°C and pH 4.0; manufacturer's specifications) as well as lesser quantities of other enzymes (cellulase, amylase, arabinofuranosidase and pectinase). Previous work has shown the enzyme to have activity at a pH below 2.5 and at temperatures in excess of 60°C (GrootWassink et al., 1989).
The chicks were housed in raised-floor battery cages (83.8 cm×45.7 cm×25.4 cm; Jamesway Manufacturing Co., Ft. Atkinson, WI, USA) with five birds per pen and 5 replicate pens per treatment. Feed and water were available ad libitum throughout the experiment. The battery brooder was maintained at a temperature of 35°C for the first week with the temperature gradually reduced to 29°C by the end of second week. Incandescent lighting was provided continuously during the experiment.
Broilers were weighed individually at the start (day 1) and end of the experiment (day 17). Weighed amounts of feed were added as required with a single weigh back at the conclusion of the experiment to allow for the calculation of feed consumption and feed conversion on a pen basis.

Digestibility determination
Chromic oxide (0.5%) was added to all diets as a digestibility marker and was fed throughout the experimental period. During the final three days of the experiment, feces were collected from each pen. The fecal samples were frozen for storage. Prior to analysis, the samples were dried in a forced oven dryer at 55°C for 72 h, followed by fine grinding. The digestibility coefficients for dry matter, crude protein and energy were determined using the equations for the indicator method described by Schneider and Flatt (1975).

Chemical analysis
Samples of the experimental diets and feces were analysed according to the methods of the Association of Official Analytical Chemists (1980; Table 2). Analyses were conducted for moisture (AOAC method 930.15), crude protein (AOAC method 984.13), acid detergent fibre (AOAC method 973.18), ash (AOAC method 942.05) and ether extract (AOAC method 920.39). An adiabatic oxygen bomb calorimeter (Parr, Moline, Illinois) was used to determine gross energy. Diet viscosity was determined following the method of Scoles et al. (1993). A 0.3 g sample of diet was mixed with 900 µL of 0.1 M sodium acetate buffer (pH 5.0) and incubated 30 min at 40°C. The slurries were centrifuged (5.0 min at 12,000×g), the supernatant decanted and viscosity (centipose) read using a Brookfield cone-plate viscometer (Model LVTDCP-11, Brookfield Engineering Laboratories Inc., Stoughton, MA) maintained

Statistical analysis
Broiler performance and digestibility data were analyzed as a 3×2 factorial using the General Linear Models procedure of the Statistical Analysis System (SAS, 1999) with the factors in the model consisting of type of cereal grain and level of enzyme supplementation as well as their interaction. Pen was the experimental unit. Single degree of freedom contrasts were used to compare differences between the barley control and the rye-based diets, differences between the normal and low viscosity rye and finally differences between enzyme supplemented and nonenzyme supplemented diets.

RESULTS
The results of the digestibility study are presented in Table 3. Digestibility coefficients for dry matter and crude protein were significantly (p=0.0001) higher for the barleybased diets than for any of the rye-based diets. Digestibility coefficients for gross energy did not differ (p>0.05) due to cereal grain. There were no differences in the digestibility coefficients for dry matter and gross energy between birds fed normal and low viscosity rye. However, the digestibility coefficient for crude protein was higher (p=0.01) for the low viscosity rye compared with the normal viscosity rye. Addition of enzyme to the diet significantly (p=0.0001) increased digestibility coefficients for dry matter, crude protein and energy.
The effects of enzyme supplementation and choice of cereal grain on broiler performance during the 17 day trial are shown in Table 4. There were no significant differences in weight gain, feed intake or feed conversion between birds fed barley vs rye or between birds fed normal vs low viscosity rye. Enzyme supplementation significantly improved (p=0.0001) weight gain, intake and feed conversion.

DISCUSSION
The breeding program designed to reduce the viscosity of the rye was successful with the two diets formulated with the normal viscosity rye averaging 8.58 cp while the two diets formulated with the low viscosity rye averaging 4.6 cp. However, under the conditions of this experiment, no significant differences were observed for weight gain, feed intake or feed conversion between birds fed normal and low viscosity rye. In addition, no significant differences were observed in nutrient digestibility as a result of feeding ryes of differing viscosity. An earlier study conducted in our laboratory indicated that a high viscosity rye had a viscosity in excess of 18 cp (Thacker et al., 1999), indicating that both of the ryes used in the present experiment were on the low end in terms of diet viscosity. Therefore, it is possible that, had a wider range in rye viscosity been available, larger differences may have been observed in the performance of the broilers.
Regardless of the viscosity of the rye fed, supplementation with pentosanase dramatically improved broiler performance. Weight gains increased 48% for the low viscosity rye and 59% for the normal viscosity rye as a  result of enzyme supplementation. The improvements in growth rate can be largely attributed to an increased feed intake with feed intakes increasing 23% for the low viscosity rye and 28% for the normal viscosity rye as a result of enzyme supplementation. Improvements in dry matter and crude protein digestibility could also account for a portion of the increase in growth rate with dry matter and crude protein digestibility increasing 13 and 20% respectively as a result of enzyme supplementation. Improved broiler performance as a result of enzyme supplementation has been reported previously (Fengler et al., 1988;Bedford and Classen, 1992;Teitge et al., 1991).
The results of the current experiment confirm previous research showing dramatic improvements in the performance of broiler chicks fed barley-based diets when provided with dietary enzyme (Classen et al., 1985;Classen et al., 1988;Campbell et al., 1993). Water-soluble β-glucan, found in the endosperm of the barley grain, is believed to be the predominant factor responsible for the poor performance of broilers fed barley-based diets (White et al., 1981). Soluble β-glucans can cause fairly stable viscous conditions in the small intestine which can lead to impairment in the digestion and absorption of nutrients when birds are fed barley (Burnett, 1966). Supplementation with β-glucanase is generally thought to reduce intestinal viscosity leading to improvements in nutrient digestibility (Edney et al., 1989). However, the mechanism by which enzyme supplementation exerted its effects on broiler performance in the present trial is unclear since there were no differences in dry matter, crude protein or gross energy digestibility between birds fed enzyme supplemented or unsupplemented diet.
In conclusion, the overall results of this experiment indicate that breeding efforts towards reducing the viscosity of rye did not appreciably improve the nutritional value of rye for poultry. Rye would appear to be competitive with barley as an energy source for use in diet formulation for broilers. However, enzyme supplementation can significantly increase growth rates and lead to great improvements in feed efficiency when barley or rye based diets are fed to young broilers by increasing nutrient digestibility.