Broilers chickens have very sensitive reaction to the number of nutrients, minerals and biologically active substances becouse of the high rate of growth. That’s why balanced diet is extremely important to them, especially at an early age
(on the first and second weeks of life), when the chicken is not adapted to the environment and is influenced by various stressors. As it is known, the enzymatic system of brolers digestive tract is formed during the first ten days. So, in this period chickens diet should contain digestible nutrients. Later, the chickens change their needs in energy, nutrients and bioactive substances, so it is necessary to feed them according to growing period (starting, growing and finishing). Each of these periods should be accompanied with feed with appropriate chemical composition and nutritional value.

Records about nutrition of complex feed additives, which were given for chickens in experimental groups during the first 14 days of the starting period with the addition of vegetable fats instead of the equivalent amount of soybean meal and soybean oil were not significantly different from the records in control group. The content of metabolizable energy in the fodder of second experimental group increased only by 1.6 %. And the content of critical amino acids such as lysine, methionine + cystine, histidine was at the same level.

It is very important to safe the initial number of chikens as their unpredictable rate can influence the profitability of broiler meat production. Our experiment showed low death rate of chickens. Survival in the control and second experimental group was 99 %, in the III and IV groups it was 100 %. So, included dried vegetable fat had a positive impact on chickens survival.

Addition of dry vegetable fats to diet of experimental groups had a positive impact not only on feed intake, but on the rate of chickens growth.

The results showed that live weight of chickens, which were fed with vegetable oils in different growth periods, increased more in the chickens of II and III experimental groups. Thus, live weight of chickens in II experimental group, which were fed with 5 % VAMZHK, increased by 2.8 % (P<0.95) during 7-day period, by 3.3 % (P>0.99) during 14 days, by 5.1% (P>0.999) during 21 days, by 4.3 % (P>0.999) at the end of growing period compared with control group. Chickens, which were fed with 7 % BZHK, had more intensive growing rate. During the first 7 days the difference in live weigh of chickens in experimental and control was not significant, just 0.5 %, but in other periods it was 2.4 % (P>0.95), 1.7 % (P>0.999), 6.6 and 5.6 % (P>0.999). The analysis of the chicken live weight increase in experimental groups showed that the optimal period for feeding with dry vegetable fat is the last phase of growth.

The liver is one of the most important glands, which provides a full existence and functioning of the whole organism. The study of its histological structure under the influence of different feed additives, makes it possible to determine the structural and functional condition of the body.

During our research we studied the efficiency of complex feed additives with palm oil in the broilers diet in the amount of 3 %, 5 % and 10 % instead of similar quantities of soybean meal and soybean oil.

Liver of chickens in control and experimental groups, which were fed with 3 % vitamin-amino-mineral complex, did not have any deviations in its structure. Lobular structure of the body was preserved. Dystrophic and degenerative changes in the parenchyma of the body were absent. In some parts of the liver there were some circulatory disorders that were presented with venous hyperemia of acini.

In the liver of birds, which were fed with forage mixture of 5 % protein and lipid, there were some signs of fatty degeneration. Beam structure was flat, hepatocytes were enlarged, with circular shape, they had void, vacuoles, formed in place of fat droplets. The nucleus in the cytoplasm were shifted to the periphery of the cell.

The liver of broilers, fed with 10 % protein and vitamin supplements, had  signs of protein malnutrition with disorders in hemodynamics. Hepatocytes increased in volume, the contours of the cells were not expressed, the cytoplasm was not clear, dull or with mild graininess. Some nucleus of hepatocytes had signs of pycnosis or rhexis.

Key words: broiler chickens, productivity, liver, morphology, histology.