| Two experiments were conducted to evaluate the stability and bioefficacy of liquid enzymes for broilers.Experiment 1: In this experiment, four liquid enzymes were selected and the xylanase was used as an indicator to determine the stability of the liquid enzyme products. The xylanase activity and its optimum pH and stability in gastric liquor (pH 4.0) of finishing pigs were analsyed. All liquid enzymes were stored under 3 temperatures (20 oC, 35 oC and 50 oC) and xylanase activity was assayed at different time intervals. The the last part of this trial, DDGS and wheat bran were used as substrate for xyalnase to determine the degradability of dietary fibre using an in vitro method. The result showed that the activity of xylanases in four liquid enzyme products (L1, L2, L3, L4) were 4 349U/mL, 5 042U/mL, 18 749U/mL, 9 314U/mL, respectively. The optimum pH of xylanase was 3.5 for L2 and 5.5 for L1, L3 and L4. After 8 h incubation at 40°C in gastric liquor, the retained activity of xylanases was 27.95%,46.39%,71.26%,61.26% for L1, L2, L3 and L4, respectively. After stored at 20℃for 10 weeks,the retained activity of xylanases was 47.32%, 63.84%, 83.12%, 73.79% for L1, L2, L3 and L4 respectively. However, when the storage temperature increased to 35℃,the retained activity of xylanases were 6.95%, 43.34%, 29.87%, 20.06%;At the extreme storage temperature (50℃) for 8 weeks,the xylanases in four liquid enzymes were inactivated. Four liquid enzymes degraded NDF in wheat bran significantly, but L2 and L4 showed a better degradation of NDF and hemicellulose in DDGS.Experiment 2:This experiment was designed to assess the bioefficacy of four liquid enzyme products tested in the in vitro experiment. 576 day-old Arbor Acres broilers were randomly divided into 6 treatment groups. Each group has 8 replications(4 female and 4 male)of 12 broilers. The growth performance was measured over 3 weeks of age and the digestibility of nutrients was estimated during the last week of the experiment. The dietary treatments include positive control (I), negative control (II), Neg+ L1 (III), Neg+L2 (IV), Neg+L3 (V) and Neg+L4 (VI). The results showed that the feed intake of treatment I is higher than other treatments (P<0.05). The weight gain was higher for treatments I than for treatment II, III, VI and V, but birds in treatment VI was heavier than those in treatment III (P<0.05). FCR in treatment VI is better than in treatment IV (P<0.1). The ileal protein digestibility was higher for treatment IV and VI than for treatment II (P<0.05) and numerically higher than the positive control (treatment I). The ileal energy digestibility for treatment II was lower than for treatment I and VI (P<0.05). There was no difference in faecal apparent metabolic energy content and nitrogen retention between all treatments. There is no interaction between sex and dietary treatment in all parameters measured (P>0.05).
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