The results of the investigations on the effect of the light of different intensity on the replacement rabbits of White Giant breed, Californian and New Zealand breeds have been presented in the article.

The objective of the investigation was to study the influence of light intensity on the protein content, calcium and phosphorus concentration in the blood serum and the state of natural resistance of the rabbits.

Materials and methods. The animals were kept in the rabbit house that was divided into three units, fresh air was provided from the calculation per 1 kg of live weight: in winter – 1m³/h, in spring and autumn – 2m³/h, in summer – 2,8 m³/h. Microclimate in the units was kept in the following parameters: air temperature – 14–16 ° C, relative humidity – 75–82 %, carbon dioxide concentration –1-1,2 l/m³, ammonia – 10–15 mg/m³, hydrogen sulphide – 5–10 mg/m³. The rabbits with the body weight 2,8–2,9 kg were used in the experiment. The conditional light threshold was 50 lc (control), in the experimental unit 1 – 70–75 lc, in the experimental unit 2 – 95–100lc. In order to assess the clinical and physiological state of the animals the amount of erythrocytes and leucocytes in the blood was determined in the chamber with Goryaev’s grid by A.A. Kudryavtsev et al.; the content of total protein in the serum was determined gefractometrically on IRF – 22, the amount of total calcium was determined complexonometrically with trilon – B and murexide, the content of inorganic phosphorus was determined colorimetrically with vanadatmolibden reagent. The activity of enzymes was determined by the analyzer made by the firm “BECMAN”, the content of mineral substances – by the atomadsorbtional spectra-photometer. To determine humoral parameters of natural resistance (bactericidal activity of blood serum – BASK) O.V. Smirnova et al.’s method was used, the lysozymic activity of blood serum – LASK was determined by V.T. Dorofeychuk et al., the cellular parameters (phagocytic activity of neutrophiles – PhAN and phagocytic index –PhI) were determined by S.I. Plyashchenko in the modification by V.F. Matusevich. The reproductive qualities were determined by the number of the young produced, the young rabbit growth and development, milking qualities of female rabbits.

Results of the research. It has been revealed that the animals kept under different light conditions showed different reactions to the abiotic factor- light. So, it has been found that

- there was the increase in the content of total protein in the rabbits kept under light intensity 70–75 lc by 22,5 %, under light intensity 95–100lc – by 25 %; albumin content increased by 14,9 %, alpha-globulin content – by 2,3 % , respectively; the rabbits of the White Giant breed surpassed the other breeds in the content of total protein and gamma-globulin and the rabbits of  New Zealand breed surpassed the other experimental breeds in the amount of beta-globulins and albumins.

- the content of inorganic phosphorus in the female rabbits of the White Giant breed decreased to the level – 7,4 %, Californian breed – to 18,3 % (p ≤ 0,05), the younger  the animals the higher content of inorganic phosphorus was in the blood of all experimental genotypes;

- bactericidal activity of blood serum increased in the rabbits of the above genotypes: in the rabbits of White Giant breed – up to 53,6±0,4 %, in the rabbits of the Californian breed – up to 51,3 %±0,2 %, in the rabbits of New Zealand breed – up to 52,4±0,3 %;

-the cellular parameters of immune defense, on the contrary, decreased with age but the above values were higher in the rabbits of the experimental groups as compared to the control one: phagocytic activity of neutrophils was higher in the animals of the experimental group 1 by 2,2 %, in the rabbits of the experimental group 2 – by 3.2 %;

- the rabbits kept under light intensity 100 lc had higher reproductive qualities (multiple fetus – 7,4 ±0,31, the number of the offspring from the number of fertilized females – 94,8%), they surpassed  the rabbits kept in the other units.

Key words: rabbits, microclimate, light intensity, resistance, total protein, determination, inorganic phosphorus, calcium, reproductive ability.