One of the main problems of poultry farms located in the industrially polluted area is environmentally friendly products production. Iodine supplements in the rations of laying hens have a positive effect on mineral metabolism and the elimination of heavy metals from their bodies. To conduct the research according to the group-analog method, 4 groups of laying hens of the UK-Kuban UK cross were formed – 123, at the age of 29 weeks, 40 animals each. One group served as a control and was treated with a general ration, and the other three groups were experimental and, in addition to the diet, received respectively 1.0, 1.5, 2.0, mg of iodine (as potassium iodide) per 1 kg of feed. Conducted scientific and management experiment and data analysis show that the content of heavy metals in the studied muscles is reduced due to an increase in iodine nutrition. In particular, the zinc content in the chest muscles decreased by 12.3 mg/kg or 35 %, and in the leg muscles by 12.4 mg/kg or 30.7 %. At the same time, an increase in iodine nutrition contributes to a decrease in the concentration of heavy metals in the internal organs, which undoubtedly improves the ecological status of laying hens and the products obtained from them.

Much attention when breeding dairy cattle is paid to the genetic potential of the livestock and the improvement of methods of its use. This is due to the fact that at present the number of crossbred animals with different parts of blood of Holstein breed has significantly increased, but there are no proven methods for determining the optimal part of Holstein blood, as a result of which the question of the association between the productivity of animals and their genotype remains very relevant. The research has been carried out under the conditions of JSC “ART” in the Right-bank district in the Republic of North Ossetia-Alania. For the purpose of conducting a scientific experiment, 3 groups of heifers of the line Reflection Sovereign 198998 have been formed with 10 heads in each. At the same time, the proportion of blood of the black-and-white Holstein breed in the experimental heifers was in the range from 50 to 75 %: 1st group – 1/2-blooded, 2nd group – 5/8-blooded and group 3rd – 3/4-blooded. The groups have been formed at the birth of young animals according to the method of analogues, taking into account the live weight and productivity of their ancestors. Accounting for the growth and development of heifers has been carried out by weighing at birth, at 3 and 6 months of age. The calculations made it possible to trace the dynamics of the variability of the live weight of experimental animals. The results obtained indicate the association between the indicators of live weight of heifers and their genotype. Against the background of the same conditions of maintenance and feeding in all age periods, the heifers of the 2nd group were superior in terms of live weight to the herdmates of the 1st and 3rd groups. So, with approximately the same live weight at birth with the herdmates of other groups, the heifers of the 2nd group at 3 months of age exceeded the half-blooded heifers from the 1st group by 3,2 kg or by 3,67 %, the 3rd group by 2,0 kg or by 2,26 %, at 6 months of age by 4,9 kg or by 3,27 % and by 3,3 kg or by 2,18, respectively. Heifers of the 3rd group slightly outstripped in the live weight of their herdmates from the 1st group. The fact that the heifers of the 2nd group (5/8-blooded according to Holstein) had better indicators of live weight compared to their herdmates of the 1st and 3rd groups (1/2-and 3/4-blooded), is proof of the influence of their genotype on the intensity of live weight gain.