E. Yavuz, G. Ganchev, N. Todorov*
Department of Morphology, Physiology and Nutrition, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
Abstract. The objective of this paper was to review the literature on effects of different methods of processing of grain fraction of the starter feeds for young dairy calves, as well as providing another part of starter which is a source of protein, minerals and vitamins in different physical forms. The second aim was to discus the impact of the main protein sources for starter feeds on performance of preweaning and posteweaning dairy calves. The main criteria for assessment of physical form effect and sources of protein in the starter feeds were intake of dry feeds, daily live weight gain and frame size growth of calves, morphological and functional development of forestomachs, digestibility of feeds and health status of young calves. Data show big variations and lack of consistency of experimental results. Good results were achieved when calves were fed whole, ground, dry-rolled, pelleted and steam-flaked grains. It seemed that fineness of grinding and quantities of fine fraction were important for starter intake. Steam-flaking and grinding improved digestibility to the same extent, but whole grain stimulated chewing and improved rumen environment for bacteria growth. Soybean meal was the most palatable and ensured best performance of calves. Evidently, it is possible to replace soybean meal with rape seed, canola type meal, dry distillers grain with solubles (DDGS) and other protein sources which contain more fiber and are less digestible. However, it is difficult to appraise how much and at what conditions is it possible to replace completely or a maximum possible portion of soybean meal. Additional studies are needed to clarify interactions between physical form of starters, rumen fermentation environments and age of calves. Information for composition of diets is needed allowing inclusion of maximum amounts of canola meal, DDGS and sunflower meal, which are produced locally and are cheaper than soybean meal, without decreasing live weight gain and development of dairy calves.