Net energy lactation

Net Energy Lactation (NEL) is the energy value in forage or concentrate feedstuff directly available for milk production in dairy cows. 

Metabolisable energy (UK, MAFF 1975) Metabolisable energy (Sweden) Metabolisable energy (UK, ARC 1980) Net energy lactation (Netherlands)... 

Net energy of lactation (NEL, NE, ) is used for assessing energy requirements of dairy cattle (9). The relationships between different energy partitions for fish (11) are shown by a balance sheet in Figure 4. By this scheme, NE for fish is conceptually similar to NE +p for poultry, and recovered energy (RE) is equivalent to NEp. 

When glycolysis occurs under anaerobic conditions, it is followed by fermentation reactions, such as the lactate and alcohol fermentations. These reactions reduce pyruvate—or a molecule produced from pyruvate—and simultaneously oxidize the NADH produced in glycolysis. As a result, the net energy yield from glycolysis under anaerobic conditions is only two ATP. No further ATP energy is harvested from the oxidation of the NADH. It is simply reoxidized in the fermentation reactions. 

In the US system, NE values for lactation (NEj) are calculated fromTDN, DE or NE by an equation similar to that used in the Dutch system. For example, in the US system, foods containing 10 or 12 MJ ME/kg DM would be calculated to provide 6.0 and 7.1 MJ NEi/kg DM, respectively, whereas in the Dutch system, they would be calculated to provide 5.8 and 7.2 MJ NEi/kg DM, respectively. Net energy requirements for body maintenance and milk synthesis are expressed as NE, as they are in the Dutch and related European systems. 

In the UK metabolisable energy system for ruminants, animal requirements are expressed in terms of net energy (NE) and food energy values are expressed as metabolisable energy (ME). Animal ME requirements are calculated using efficiency factors (k) for different productive processes (e.g. maintenance, lactation or growth), which depend on the ME concentration of the diet (M/D). 

Energy requirements for lactation involve an estimate of the gross energy value (EVi) of the milk, which may be used along with the yield to estimate the net energy requirement for milk production. 

The French system provides tables of net energy values of some 149 foods for maintenance, which are considered applicable to lactation as well. The values are stated in terms of UFC (unite fouragere cheval) one UFC is equal to the net energy of standard barley, equal to 9.42 MJ/kg. 

For the Cornell net carbohydrate and protein system for predicting the requirements of cattle, the intake of lactating cows is predicted from the net energy content of the food and the milk yield and milk fat content of the animal. Predicted values are then adjusted for six other factors age, breed and body fat content of the cattle, the inclusion in the diet of any additives, the environmental temperature, and another component of the environment called mud . 

NET ENERGY FOR PHYSICAL ACTIVITY GROWTH PREGNANCY LACTATION COOLING THE BODY HEATING THE BODY... 

Andrew, S.M., H.F. Tyrrell, C.K. Reynolds and R.A. Erdman, 1991. Net energy value for lactation of a dietary fat, calcium salts of long chain fatty acids, for cows fed silage based diets. J. Dairy Sci. 74,2588-2600. 

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