[The energy requirement of heifers. 4. Comparison of the digestibility and rumen physiologic parameters in heifers and full-grown sheep]

[Proposal for the introduction of a metabolizable energy feed evaluation system based on unitary parameters and principles for all farm animals. 1. Energy feed evaluation for cattle]

The energy availability from the feedstuffs and the energy requirement of animals are characterized by the metabolizable energy. The metabolizable energy of the feed (feedstuff, ration) is interpreted as potential energy. For comparative analyses within and between animals species with regard to the energetic feed value of single feedstuffs the parameter "relative fat retention effect" is introduced. The metabolizable energy of a ration is estimated in consideration of energy level, live weight and protein production (protein in body gain and milk). The energy requirement is calculated factorial--as a rule by the partial utilization of metabolizable energy for partial performances (e.g. kf, kp, kl) in connection with the level and kind of partial performance; km is not used in the system. The proposed system of energetic feed evaluation is available as "computer variant" as well as "manual variant". The computer programme is fitted first of all to application in research and teaching. (The complete documentation of the proposal for energetic feed evaluation for cattle including a discette for using of the computer programme for scientific applications can be claimed in limited extend from the author.).

[The effect of starch sources barley, corn and potatoes and their ration proportions on nutrient digestibility and energy utilization in ruminants. 2. Fractions of ruminally and postruminally digested nutrients in cattle]

The investigations of this paper are part of a complex research project to develop energetic feed evaluation within the Net Energy Fat System. The aim was to obtain new results to estimate the relation between place as well as kind of nutrient digestion and energetic utilization of rations in cattle. The ruminal nutrient digestibility was measured in adult oxen on feeding level 1.7 by means of duodenal reentrant cannula for 9 rations including the starch sources barley, maize and potatoes and with their energy parts of 50, 25 and 10%. The intake of starch ranged from 484 to 2573 g/animal.d and the amounts of ruminal and postruminal digested starch from 444 to 2336 as well as 10 to 284 g/animal.d. For the organic matter, starch, water soluble carbohydrates and N free residual substances high relative parts of ruminal digested from apparent digested nutrients were measured with values between 78 and 88, 83 and 98, 93 and 97 as well as 88 and 100% respectively.

[Energy requirements of young female cattle. 5. Energy intake and energy expenditure]

From 6 experiments dealing with the development of young female cattle, partly from calf to calving, 660 metabolism periods were evaluated as to energy intake, live weight gain (LWG) and energy expenditure. Growth intensity was deliberately regulated through energy intake. In the experiment with the highest growth rate the average LWG was greater than 850 g/animal and day and in the experiment with the lowest growth rate at about 550 g/animal and day. Energy expenditure increased from 15 MJ net energy fatcattle/kg LWG at a live weight of 50 kg to 50-80 MJ NEFcattle/kg LWG in clear dependence on growth intensity. Comparative examinations of energy intake and energy requirement, estimated with equations forming the basis of recommendations for the energy supply of young female cattle in the framework of the GDR system of feed evaluation, lead to the conclusion that a new concept of identifying the energy requirement of young female cattle has to be developed.