• 환경생물
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• 제33권1호
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• pp.83-91
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• 2015

본 실험은 왕우렁이를 대상으로 대발생한 식물플랑크톤을 제어할 수 있는 가를 파악하기 위해 섭식율 (grazing rate, GR) 및 유기물 생산 (pseudofaeces production)을 조사하였다. 섭식 효율을 조사하기 위해 시간 (12시간), 개체크기, 개체밀도, 먹이농도 조건 등의 조건을 달리하여 실험하였다. 왕우렁이는 투입 후 2시간 후에 2.5 L. $gAFDW^{-1}h^{-1}$의 최고 GR를 보이다가 12시간까지 일정한 섭식 경향을 나타내었다. 유기물 생산량은 4시간 후에 15.3 mg $AFDW^{-1}$로 가장 많은 양을 나타냈다. 서로 다른 크기조건에서 각고가 1.5 cm 미만의 섭식율 변화가 크고 6시간 후에 비슷하였으며, 중간 크기(2.5 cm)가 3.0 cm 이상인 것보다 섭식율이 높았다. 밀도가 5 indiv. $L^{-1}$ 에서 엽록소 ${\alpha}$ 농도감소율이 가장 높았으며, 그 외의 밀도에서는 비슷한 변화를 나타내었다. 유기물 생산 역시 밀도가 높은 실험군에서 4시간에 최대로 증가하였다. 먹이농도가 $600{\mu}g$ $L^{-1}$일 때 0.54 L. $gAFDW^{-1}h^{-1}$의 가장높은 섭식율과 유기물 생산을 나타내었다. 본 연구에서 왕우렁이뿐만 아니라 논우렁이를 이용하여 식물플랑크톤 대발생을 제어 가능함을 본 연구를 통해 확인하였지만, 이들이 배설한 유기물의 제거 및 배설물의 분해에 다른 2차 문제에 대한 철저한 연구가 필요하다.

• Asian-Australasian Journal of Animal Sciences
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• 제20권4호
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• pp.556-562
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• 2007

A total of 126 crossbred weanling pigs (average body weight of $6.3{\pm}0.3$ kg) were used to investigate the effect of chito-oligosaccharide (COS) on growth performance, nutrient digestibility, pH of gastro-intestinal tract (GI), intestinal and fecal microflora of young piglets. Pigs were allocated to three dietary treatments based on body weight and gender in a single factorial arrangement. Treatments were control (No COS), T1 (0.2% COS during starter (6-13 kg) and 0.1% COS during grower (13-30 kg) phases, and T2 (0.4% COS during starter (6-13 kg) and 0.3% COS during grower (13-30 kg) phases, respectively. Each treatment had 3 replicates and 14 pigs were raised in each pen. COS is a low molecular weight water-soluble chitosan that can be obtained from chitin of the crab shell after deacetylation with concentrated sodium hydroxide at high temperature and then further decomposition by chitosanase enzyme in the presence of ascorbic acid. For the starter and grower periods, there were no significant differences (p>0.05) in average daily gain (ADG) and feed to gain ratio among treatments. However, during the overall period (6-30 kg), T2 showed better (p<0.05) feed to gain ratio than other treatments. A digestibility study was conducted at the end of grower phase which showed improvement (p<0.05) in DM and crude fat digestibility in T2 over the control. At 25 kg body weight, 6 pigs per treatment (2 per replicate) were sacrificed to determine the effect of diets on pH and microbial count at different sections of the GI tract. The pH of the cecal contents in pigs fed 0.1% COS was higher (p<0.05) than in the other treatments. Total anaerobic bacterial number increased from cecum to rectum in all treatments. The weekly total bacterial counts showed higher (p<0.05) in feces of pigs fed COS than that of untreated pigs at the $8^{th}$ week. The number of fecal E. coli in untreated pigs at $4^{th}$ wk was 7.35 log CFU/g compared to 6.71 and 6.54 log CFU/g in 0.1 and 0.3% COS-treated pigs, respectively. Similarly, at $8^{th}$ wk, fecal clostridium spp. were lower in pigs fed 0.3% COS (5.43 log CFU/g) than in untreated pigs (6.26 log CFU/g). In conclusion, these results indicated that chito-oligosaccharide could improve feed efficiency in young pigs and inhibited the growth of harmful bacteria.