圈養台灣黑熊攝食與繁殖的關係探討

An Exploration on Relationship between Food Intakes and Reproductive Success of Captive Formosan Black Bears (Ursus thibetanus formosanus)

圈養的台灣黑熊（Ursus thibetanus formosanus）雌熊於交配且受孕後，分別在懷孕初期及懷孕中期增加給飼量及其營養濃度，結果在懷孕中期增加給飼時正常生產，但在懷孕初期增加給飼時有發生早產現象，本研究認爲懷孕初期增加給飼量增加了早產的機率，其原因是促使孕酮（progesterone）的分泌濃度提前上升，且其最高峰的水準未達一定的程度，可能因此改變了母體子宮環境暨其子宮腔液的蛋白質組成，使著床後的胚胎發育未與子宮環境同步而引起。野外熊隻於懷孕中期後獲得較多食物，是長期配合食物季節性變化的一種韻律性適應，而熊隻演化出的延遲著床（delayed implantation）是一種內在生理適應。因此，若對圈養雌熊於懷孕初期增加飼糧的給飼量，可能擾亂牠們性類固醇荷爾蒙的自然分泌與延遲著床機制相關的韻律性，此可能是促使異常生殖的主因。

After the captive female Formosan black bear (Ursus thibetanus formosanus) mated and was fertilized, her daily food ration was increased from either early-pregnancy or mid-pregnancy. The results showed that the female bear had normal deliveries when received the food increment from the mid-pregnancy but had preterm deliveries when received the food increment from the early-pregnancy. The food increment from the early-pregnancy might result in higher probability of the preterm delivery which was because the rise of progesterone secretion ahead of time, and it didn't reach to some certain higher level. Hence, it probably led to change the uterine environment and the protein composition of the uterine luminal secretion, of which became unsuitable for the fetus development after embryo implantation. In nature there is a seasonal change in food composition and abundance, and wild female bears consume food with nutritional values at the stage of mid-pregnancy than that at the stage of early pregnancy. It is an adaptive synchronization of the internal physiological rhyme of the bears with the embryo delayed implantation to the seasonal rhyme of food abundance in the natural environments. Accordingly, we hypothesize that increasing the feeding of captive bears at the early pregnancy may disturb their natural sexual steroid hormone secretion rhyme associated with the delayed implantation mechanism, which was probably the main reason to cause abnormal reproduction.