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Abstract
The paper surveys some problems related to ruminant nutrition in Eastern Europe. Monodiet feeding systems for beef and dairy cattle have been developed on the basis of highest yielding crops. By a favourable combination of a physical processing of feeds (grinding, pelleting, etc.) with methods of stimulating rumen bacterial activity and an appropriate method of feeding, very good results have been achieved with complete diets containing large amounts of waste roughages (corn stover, corn cobs and straw). In general the daily gain has been about the same as that with the intensive fattening methods using high concentrate levels. A kilogram of gain being obtained from 2 to 3 kg concentrate, waste roughages and a small quantity of alfalfa hay. The acreage needed for the production of 1 ton milk was considerably smaller than when more conventional forage systems were applied. Further increase in the use of waste roughages were achieved through combining pelleting and cubing with ammonia or sodium hydrate treatment which raises the digestibility and the feed consumption. The method was simple and highly efficient. Self-heating in the press accelerated the reactions and reduced the chemicals needed. A technique has been developed for the harvesting of whole plants of corn, barley, wheat and other crops as well as for their ensiling or dehydration. The effect of the two methods of conservation is discussed on the basis of the results obtained in a number of field trials with beef cattle and dairy cows. Extensive research has been carried out to test new NPN compounds and to find methods for the more efficient utilization of NPN. A special technique has been developed for using urea-mineral mixtures in the form of block licks, which was revealed an unexpected potential for this well-known principle of urea feeding. Due to the gradual influx of N and minerals into the rumen, high bacterial activity and comparatively low ammonia concentration are maintained. This apparently improves the N retention and, consequently, the animal performance compared to cases where urea is fed mixed with the concentrate. Good urea utilization has been observed when urea is included in the pelleted complete mixtures or in the corn silage fed ad libitum. Changes of urea 15N in the silage are determined. The urea breakdown and hence its effect on fermentation of the silage depend mainly on the length of time during which silage is under aerobic conditions. Only 2 to 3% of the urea-N are converted to protein. NPN also enhances the bacterial synthesis of fats in the rumen. When NPN was used as a sole N source in purified diets for sheep the ewes yielded over 80% of their potential production. In this case the activity of transaminases in the rumen content and the blood increased.
1 Presented as part of a Symposium, Animal Science Research in Some Eastern European Countries, July 31, 1974, during the 66th Annual Meeting of the A.S.A.S., at the University of Maryland, College Park.
2 Academy of Agriculture, Sofia, Bulgaria
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