Metabolisable energy milk production

Fig. 12.1 Relationship between milk energy derived from metabolisable energy intake (MJ/kg W° ) and metabolisable energy directed towards milk production (MJ/kg W°- 5).

Erom the calorimetric work of Forbes, Fries and Kellner, an efficiency of utilisation of metabolisable energy for milk production (kj) of about 0.70 is indicated. More recent estimates of k] have varied widely from 0.50 to 0.81, but the majority cluster around 0.60-0.65. There is considerable evidence that much of the variation is due to differences in the energy concentration of the diet. Van Es has suggested that the efficiency of utilisation of metabolisable energy for milk production is related to the metabolisability of the diet, defined as the ME (MJ/kg DM) at the maintenance level as a proportion of the gross energy (MJ/kg DM). His implied relationships for (a) Dutch and (b) American data are ... 

There is some evidence (Fig. 16.4) that the efficiency of utilisation of metabolisable energy for milk production is influenced by the proportion of acetate in the fatty acids produced during rumen fermentation. 

The requirement for metabolisable energy for milk production (Mi) may thus be calculated as ... 

Values for the efficiency of utilisation of metabolisable energy for maintenance and for milk production are related to the energy concentration of the diet and are very similar. 

Cohen, D.C., C.R. Stockdale and RT. Doyle, 2006. Feeding an energy supplement with white elover silage improves rumen fermentation, metabolisable protein utilisation, and milk production in dairy cows. AusL J. Agric. Sci. 57, 367-375. 

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