Since rabbits are the most precocious animals, their raising is currently the promising livestock field to ensure population with high dietary meat.

Liver is the central organ, where all kinds of metabolism (carbohydrate, protein, fat) take place. Metabolic disorder in the liver leads to disfunction of the whole body, hormonal changes, disfunction of the body's antioxidant enzymes, free radical oxidation of lipids intensification process. Indicators of essential fatty acids deficiency in animals are: slow growth, the immune system weakening, dermatitis, increased water loss through the skin. Lipids together with proteins and carbohydrates form the main structural component of living cells. In a body the lipids are involved in depositing (triacylglycerols) and transportation (free fatty acids) of substances, which decay releases large amount of energy. Lipids are important structural components of cell membranes (phospholipids and free cholesterol), are involved in thermoregulation processes, act as barriers. Lipids protect vital organs and whole body against the thermal and mechanical influences and their destructive actions – injuries. Lipids may be the precursors of other biologically active substances, to serve as reserve energy material.

The literature describes the questions of lipid and protein metabolism study in white giant and gray giant rabbit breeds. However, little research is done on the indexes of lipid and protein metabolism in blood plasma and liver of different rabbit breeds and ages.

There were studied the features of lipid and protein metabolism in blood plasma and liver of new zealand rabbits breed in the period from birth to slaughter and there were established the breed features of the new zealand, california, soviet chinchilla, and silver in 90 days old rabbits. There were performed two stages of research, the first: the definition of age peculiarities was conducted on the new zealand breed, the biological material samples were taken at the age of 1, 15, 30, 45, 60, 75 and 90 days. For the second stage there were formed 4 rabbit groups of 90 days old new zealand, california, soviet chinchilla, silver breeds, each with five animals. The liver tissue and centrifugation separated plasma from stabilized blood were used for the experiment. The work was done in accordance with the "General ethic principles of animal experimentation" (Ukraine, 2006), consistent with the provisions of the "European Convention for the Protection of Vertebrate Animals used for experimental and other scientific purposes" (Strassbourg, 1985). The rabbits were kept in the same conditions during the whole research period.

The general lipid content, crude protein and creatinine content were tested in blood plasma and liver homogenate. The general lipids content was determined after sulfuric acid hydrolysis by the number of lipid decay products that interact with phosphovanillic reagent to form pink coloured complex with absorption maximum at λ = 530 nm. Determination of crude protein content was carried out by a method, based on the protein ability to react with Folin reagent. This reaction forms the dark blue compound. The creatinine content was determined by the method, when creatinine reacts with picric acid in alkaline environment with the formation of colored compounds. Statistical analysis was performed by the Microsoft Office Excel program. To determine the vallid differences between the average values we used the Student's t–test.

The study showed increase of the general lipids content in the blood plasma of 1–45 days old rabbits. The highest content of general lipids was observed in 15-days old rabbits, which was by 1.5 times higher than in the previous age. Starting from the 60-th till the 90-th day there was noted the possible decline of total lipids in the rabbits blood plasma. When determining the crude protein content in plasma it was found that from 1 till 60 days of age the figure increased and was higher by 21.2% in 60 days old rabbits, compared to the previous age. From 75 till 90 days of age its decrease was observed. The new zealand rabbit breed of 1–45 days age showed increase in creatinine content with the highest in 90-days old rabbits.

When exploring the general lipids content in liver, there was found a tendency to their growth in 15–60 days old rabbits. The 60-days old animals had the greatest lipid content – 33,8±2,71 mg / g tissue. When studying the liver crude protein content there were established valid changes in 15–30 days old rabbits compared to those of previous ages. The creatinine content in the rabbits’ liver tissue during the period from 1 to 30 days was characterized by a decrease trend, and later (from 30 till 90 days) it slightly increased.

There were identified breed features within the study of liver general lipids in the 90 days old rabbits. It was established that this value was in california breed higher by 26.6% as compared with new zealand one (Fig. 1a). The study has established that the highest value – of liver crude protein is registered in the new zealand breed rabbits, which was by 12.3% higher as compared to the california breed. The creatinine content was characterized by the highest value in the liver of silver breed rabbits and was 2 times higher as compared to the california species, which probably explains the energy formation increase during biochemical processes in the 90-days old rabbits.

The study of lipid metabolism parameters in animal organs within the age aspect is an important element in establishing the nature of changes in the intensity of the metabolism reactions. Determination of these parameters in animal body provides an opportunity to influence the physiological state and normalize it.

Thus, the conducted studies made it possible to establish, that in new zealand breed rabbits the highest value of general lipids in plasma was recorded in 15 days age, and the highest content of crude protein – in 60 days age, which can be associated with their body needs increase during the growth and development process. Increase of creatinine content in 90 days old rabbits may indicate the formation of energy, necessary for the functioning of muscle cells with meat productivity increase.

Indicators of general lipids in the liver tissue were characterized by the highest values –in the 60 days old animals of new zealand breed, crude protein content – in 15 daily content creatinine – a 90-day age.

The general lipids content in the liver of 90 days old rabbits was the highest in california breed, the crude protein content – in new zealand breed, and the creatinine content – in silver breed.

The further study of lipid and protein metabolism in the rabbit body during the use of vitamin and mineral supplements is very promising.

Key words: rabbits, blood plasma, liver, general lipids, crude protein, creatinine.