ABSTRACT
This chapter presents a step by step estimation of factors involved in energy requirements for pregnancy and lactation. Among domestic ruminants, energy requirements for pregnancy and lactation are proportional to the productive processes involved, that is synthesis of fetal, placental, uterine, and mammary tissue in pregnancy, and milk production in lactation. Calculation and comparison of the energy requirements for pregnancy by the factorial method requires an evaluation of fetal growth patterns, birth weights, energy deposition in fetal and associated tissues, and the energetic efficiency of these proceses. Pregnancy involves deposition of energy in associated supportive tissues as well as in the fetus. Mammary development during pregnancy involves accumulation of an additional energy increment equivalent to about 25 percent of the energy content of the gravid uterus in domestic sheep. Parturition terminates the rising energetic costs of pregnancy, but initiates an even more energy-demanding phase, lactation.
