Lactation energy requirements

One of the details omitted in the concept depicted in Figure 6.8 is the growth of the sulfate-reducing biomass. Characklis et al. (1990) proposed Equation (6.19) for determination of the stoichiometry for the sulfate reduction process using lactate as the carbon source for energy requirement and growth. This equation can be used to evaluate the importance of the simplification. 

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. 

Because the isotope method is noninvasive, nonrestrictive, and does not expose the subjects to radiation, the H2 0 method is considered the method of choice by the nutrition conununity for the estimation of energy requirements during infancy, growth, pregnancy, and lactation. 

When organisms (including humans) take in more nutrients than are needed for energy requirements, the excesses are not excreted they are converted first to fatty acids and then to body fat. Most of the conversion reactions take place in the liver, adipose tissue, and mammary glands. The mammary glands become especially active in the process during lactation. 

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. 

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