[Music] so how to measure net energy uh just a reminder of the previous section of these videos is that net energy is calculated as energy gain or nature retention plus fasting reproduction so this means that for measuring net energy we need to measure first energy gain and then to measure or to estimate fasting reproduction with regard to energy gain there is a first technique that has been widely used in the past which is the combat the so-called comparative throttle technique this technique consists in measuring the final energy content in the body of an animal minus its initial energy content at the beginning of the experiment or beginning of the trial so we obtained there the energy gain over the trial this technique has been widely used in the past even in first in small size animals but also in larger size animals but this technique has been progressively used probably replaced by the so-called carometry methods consisting in measuring or evaluating or calculating heat production so the these techniques uh are more are very much used now uh and the most popular technique for that is the so-called indirect carometry and in usually in open circuit respiration chambers consisting in measuring the oxygen uptake of an animal and the carbon dioxide production and so the reproduction is calculating according to a formula uh taking into account the oxygen uptake and the carbon dioxide production so this technique is widely used now in most types of animals and even in small size animals like poultry or fish and from that reproduction that is measured in the chamber we can calculate the amount of energy gain or retain energy as the difference between heavy intake and heat production so the second aspect of the net energy measurements is to get estimates of values for fasting reproduction