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  • 學位論文

亞洲黑熊之表面消化率及校正係數

Apparent Digestibility and Correction Factors of Asiatic Black Bears (Ursus thibetanus)

指導教授 : 黃美秀 林美峰

摘要


亞洲黑熊(Ursus thibetanus)為大型的食肉目動物,但其食性卻屬以植物為主的雜食性。本研究旨在探討此物種對於不同種類食物之消化及利用情形,並計算校正係數(correction factor)以作為利用排遺回推野外黑熊之進食量之參考依據。 試驗動物為特有生物中心低海拔試驗站所圈養之4隻亞洲黑熊(2雄2雌),試驗食物共8類,每次實驗期為12天,並由第10天開始連續採樣3天,每日記錄試驗個體之進食量、排糞時間,並收集排遺和測量其乾、濕重,以計算校正係數。食物中添加三氧化二鉻(Cr2O3),追蹤食物通過消化道及其停留時間。同時分析食物及排遺之營養含量,以測定各項營養成分之表面消化率(apparent digestibility)。 黑熊進食不同種類食物平均每日排糞坨數為5-6坨,排遺量變異很大,排遺總濕重為904-2,984 g,總乾重為217-391 g。各項食物通過消化道之時間(passage time)平均為6.4±3.7 hr,停留時間則為34.4±9.5 hr,總平均停留時間(total mean retention time)為22.0±3.1 hr。食物通過時間與粗纖維含量顯著負相關,食物於消化道之表現似乎亦受到顆粒大小、攝食行為等影響。 黑熊對於動物性和植物性食物的表面消化率,不論在乾基(83.2±10.6>62.6±24.6)、粗蛋白(94.2±2.5>62.2±11.2)、粗脂肪(94.1±5.8>61.8±30.4)及總能(93.8±3.0>64.4±24.1),皆顯示黑熊對於動物性食物具備較高表面消化率(P<0.001)。粗蛋白、無氮抽出物之表面消化率,分別與食物的粗蛋白、無氮抽出物含量呈顯著正相關(r2=0.70、0.55,P<0.001),然各項營養成分之表面消化率皆與粗纖維含量呈負相關。   黑熊排遺經篩網沖洗後之校正係數(prey mass presented)為未經沖洗(prey mass consumed)之2-5倍,前者為7.1-32.7,後者為1.9-22.4,兩種校正係數呈正相關(r2=0.643,P<0.001)。食物粗纖維含量與消化校正係數呈負相關(r2=0.212,P=0.027);黑熊之乾基、總能表面消化率亦分別與消化校正係數呈顯著正相關(r2=0.393,r2=0.287,P≦0.002)。顯示食物纖維含量低或具高消化率,將導致排遺殘渣含量減少,校正係數遂提高。利用本研究所得之消化校正係數推估野外台灣黑熊之食性組成,發現無脊椎動物的百分比例經校正後顯著提高5倍,相對重要性提高。

關鍵字

台灣黑熊 食性 消化 營養 通過時間 校正係數

並列摘要


Asiatic black bears (Ursus Thibetanus) are one of the largest carnivores、but they are omnivorous、especially drawan to vegetation food. The objective of this study was to determine the digestion and utilization of different types of foods by Asiatic black bears. Four captive bears (2 males and 2 females) at the Low Altitude Experiment Station of the Endemic Species Research Institute of Taiwan were the study subjects and fed eight foods. With a specific food、each feeding trial lasted 12 days、but food intake and defecation was monitored by collecting and weighing all feeding and fecal residues for only the last 3 days. Cr2O3 was added into the food to track the passage and retention time of ingested food. The apparent digestibility of various nutrition components was determined by nutrition analysis of test food、including dry matter、crude fat、crude protein、crude fiber、ash、nitrogen-free extractives and gross energy. The daily defecation rate of bears averaged 5-6 scats、and the weight of fecal residues varied by foods、i.e.、904-2,984 g and 217-391 g for wet and dry scats、respectively. The average passage、retention、and total mean retention time were 6.4±3.7 hr、34.4±9.5 hr、and 22.0±3.1 hr. The passage time was negatively correlated to crude fiber content、but it was likely influenced by other factors、such as particle size and feeding behavior. For the vegetation and animal foods tested、the apparent digestibility of 4 nutrient components were significantly different (P<0.001). Bears had a higher apparent digestibility for animal foods than for vegetation foods: 62.6% and 83.2% for dry matter、62.2% and 94.2% for crude protein、61.8% and 94.1% for crude fat、64.4% and 93.8% for gross energy. The apparent digestibility of crude protein and nitrogen-free extractives were correlated to their nutrition content correspondingly (r2=0.70、0.55,P<0.001). However、the apparent digestibility of all nutrition components was negatively correlated to the content of crude fiber. The correction factor of prey mass presented (PMP)、i.e.、with fecal samples washed over 2 mm screens、was greatest for invertebrates (32.7) and lowest for Machilus zuihonsis (7.1). The PMP was 2-5 times that of the correction of the prey mass consumed、i.e.、1.9-22.4. These 2 correction factors correlated positively (r2=0.643、P<0.001). The correction factor of prey mass consumed was negatively correlated to the dietary fiber content (r2=0.212,P=0.027)、but positively correlated to the digestibility of both the dry matter and the gross energy (r2=0.393,r2=0.287,P≦0.002). The results indicated that the correction factor increased with lower fiber content or higher digestibility.

參考文獻


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