Energy requirement of young female cattle. 3. Reproduction and products of conception

The results with regard to reproduction obtained from a study lasting several years of the energy requirement of young female cattle reared with different intensity are described. It becomes apparent that there are relations between feeding, rearing intensity and insemination expenditure. Age and weight at the time of conception in the individual test series averaged between 290 and 630 days and 270 and 430 kg respectively. The weight of the conceptional products of 31 calvings was registered and, according to Jakobsen (1956, 1957), the energy and N content of the conceptional products was proportionally assigned to the prenatal test periods. In the last 140 days of gravidity the N balance per animal and day increases from 16 to 23 g. N retention of the cows is low in the last days of gravidity. The utilization of metabolizable energy for the development of conceptional products is calculated as a conventional comparative value provided the maintenance requirement per unit metabolic body weight of the cows and the utilization of metabolizable energy for energy retention in the cows on an average of 156 individual values of 12 +/- 8% are the same and correspond in their magnitude to analogous findings of other authors, mainly compiled from dairy cows.