Effect of Some Essential Oils and Natural Botanical Extracts on Food Consumption and Some Physiological Aspects of Mulberry Silkworm, Bombyx mori L.

The effects of different concentrations of marjoram oil, thyme oil, (1%, 0.5%, and 0.25%) and their botanical extracts (2%, 1%, and 0.5%) as a nutritional additives offered to silkworm larvae during the 4^th and 5^th larval instars on food consumption, Approximate weight of digested food (A.D), Approximate digestibility (A.D%), efficiency of conversion of food ingested to body substance (E.C.I%), and efficiency of conversion of food digested to body substance (E.C.D%) were studied. Also, to determine their effects on total carbohydrates and total protein in larval haemolymph. Results showed significant variation in most of the studied parameters of oils and botanical extracts different concentrations compared to control; E.C.D% was found maximum with 0.5% marjoram oil (74.995%) and thyme oil (71.465%), in the botanical extracts 2% of both thyme, and marjoram exhibited the highest ratio (63.170% and 60.975%), respectively compared with control which recorded the minimum (38.830%). The efficiency with which the ingested food is converted into body substances (E.C.I%) 0.5% of marjoram and thyme oils showed the highest efficiency of conversion (21.000% and 20.555%), respectively compared to (13.445%) for the control. 2% of both thyme (19.960%) and marjoram extract (18.845%) showed also the highest ECI% while the control recorded the least result. The highest AD% was shown by control group (43.185%) and AD of the control group exhibited the highest among them (3.400 gm). Results revealed a significant variation between the both larval instars in most parameters. The quantity of food consumed in both oils and extracts varied significantly between the both instars with no significant values among different concentrations of them. Total protein exhibited the highest value when feeding larvae on mulberry leaves supplemented with 0.5% of both marjoram and thyme oils (41.067 and 39.867 mg/ml haemolymph), respectively, and 2% of both thyme and marjoram extracts (36.9 and 36.567 mg/ml haemolymph), respectively while the control group showed the minimum value (22.633 mg/ml haemolymph). The same trend was observed for total carbohydrates. It can be concluded that mulberry leaves fortified with different concentrations of marjoram and thyme oils and extracts were proved to be more efficient in rearing mulberry silkworm as it improved food acquisition, high ingestion, high (E.C.I & E.C.D) and low (A.D),also it increased protein and carbohydrates metabolism.