The effect of some essential oils on in vitro true digestibility of energy, protein, cellulose source of feeds and milk yield and milk composition in high yeilding dairy cows

The present study was carried out to determine the potential of some essential oils as an alternative to antibiotics in feed additive for ruminants. The study was carried out in three stages and the effects of essential oils on in vitro true digestibility were tested in the first and selected essential oils in the first stage were tested in vitro with their capsulated or uncapsulated form in the second stage. Barley, soybean meal and wheat straw were used as substrat in in vitro studies and thyme (Tymus vulgare), black seed (Nigella sativa), mint (Mentha longifolia), laurel (Laurus nobilis), coriander (Coriandrum sativum), fennel (Foenicum vulgare), rosemary (Rosmarinus officinalis), cummin (Cumminum cyminum), orange (Citrus cinensis) peel, grape (Vitis vinifera) seed, garlic (Allium sativum), anise (Pimpinella anisum), cinnamon (Cinnamomum verum), oleaster (Eleagnus angustifolia) essential oils were used to determine an alternative for antibiotics. After the first in vitro studies, 100 ppm orange peel and 50 ppm garlic essential oils for wheat straw, 100 ppm orange peel and 150 ppm laurel essential oils for barley and 50 ppm oleaster and 150 ppm laurel essential oils for soybean meal were chosen to test in the second in vitro study to evaluate the effect of encapsulation of essential oils on in vitro tru digestibility of nutrients. After the first two in vitro studies, 6 essential oils (garlic-50 ppm, cinnamon-100 ppm, laurel-150 ppm and thyme-180ppm, oleaster-180ppm, orange peel-180 ppm) were selected to test in in vivo studies with dairy cows.After the first two stages, selected essential oils and their doses for in vivo studies were tested to determine the effects of essential oils on milk yield and milk composition in dairy cows with two studies using 28 dairy cows in each. 50-ppm garlic, 100 ppm cinnamon and 150 ppm laurel in concentrate were tested againest to control in completely randomised design in the first study. Thyme, oleaster and orange peel essential oils with 180 ppm dose in concentrate were tested in the second in vivo study. Similar to the first in vivo study, feed intake, milk yield and milk composition were not affected (P>0.05) by essential oils. Essential oils had a minor effect on milk fatty acid composition in both studies. C18:1n3 and total n3 in the first study were decreased by garlic, cinnamon and laurel essential oils. C18:1 n9 and total n9 were decreased by thyme, oleaster and orange peel essential oils.In conclusion, the results revealed that the results of in vitro and in vivo studies with essential oils are not in accordance with each other and tested essential oils had no effect on feed intake, milk yield and milk composition of dairy cows.