Сельскохозяйственная биология, 2010, № 4, с. 3-6.

УДК 636.4:636.064:636.082.12:577.2.08

BIOTECHNOLOGY IN THE BREEDING OF ANIMALS: BIOLOGICAL AND ECONOMIC IMPORTANT PARAMETERS OF TRANSGENIC PIGS

L.K. Ernst

The author discuss the results of experiments concerning the integration of human growth hormone releasing factor gene to pig genome and the estimation of its influence on biological and economic important parameters (growth rate, protein metabolism, hormonal status, fatty-acid composition of lipids, lard and pork mass ratio, indices of meat quality, immunity, productivity) in 12 generation of animals. The obtained results permit to initiates the work on a creation of new type of pigs, exceeded an existing breeds by the set of important determinants.

Key words: transgenic pigs, gene of releasing factor of human growth hormone, growth rate, protein metabolism, hormone status, fatty acid composition of lipids, ratio of the mass of fat and meat, meat quality, immunity, fertility.

From the very moment of discovery of genomic molecular structure, the creating of new types of plants and animals using genetic engineering has become in focus of many researches in the world. This process has already resulted in great success of agriculture: transgenic crops with various useful qualities now occupy the areas of many millions hectares.

Unfortunately, animal husbandry hasn’t yet obtained such results. The known studies involve mainly laboratorial animals and many investigations have certain shortcomings – for example, the fact that determinants are known to be studied in only one or two generations while the integrated  heterogeneous gene doesn’t manifest itself completely, which hinders the prediction of breeding prospects for integrating of such genes.

This study represents the data of experiments on the integration of human growth hormone releasing factor gene in pigs and evaluation of its impact on biological and economically valuable indicators. The investigations were carried out upon 12 generations (the first transgenic pigs of this type were obtained in 1994).

Endocrinology defines the releasing factor as an activator for cells producing growth hormone. However, the study of parameters of several animals’ generations showed the great impact on various biochemical and morphological traits provided by the integrated gene. Such a multiply effect has been established for mutations by the academician I.I. Shmalgausen, who proved that mutations lead to significant changes of correlation interconnections in an organism.

The study of transgenes in 12 generations of pigs has revealed significant biochemical and morphological changes. In several generations, it has been revealed the tendency to accelerated growth in late periods of feeding, as well as the trend to increased proportion of meat relative the weight of lard. The unexpected features of transgenic pigs were the increased immunogenicity and fertility. Though, it should be noted that the described changes were unstable, possibly, owing to a long-term nature of changes in certain indicators, including the stabilizing selection processes. Only in 11th and 12th generations, the stable differences in key indicators have been found, particularly, as the change in correlations between weights of individual parts of a carcass (Table 1).

Thus, the transgenic animal demonstrated markedly higher negative correlation between the content of meat and lard compared with control (see Table 1).

Table 2 shows the meaningful changes in most important protein characteristics (contents of total protein, albumin, globulin and creatinine) suggesting the significant shift in nature of protein metabolism.

The animals’ hormonal status significantly changed (Table 3), as well as the fatty acid composition of lard lipids (Table 4). The clear change in these correlations has led to the shift in such economically valuable characteristic as the ratio meat / lard (Table 5).

The 11th generation of transgenic pigs has shown 8,30% higher proportion of meat in total weight of a carcass compared with control, and the weight gain of meat in the middle part of a carcass equal to 20,81%.  In the 12th generation, these indices were respectively 11,19 and 22,22%. The average daily gain in live weight was 9,18% higher than in control.

This trend in the ratio meat / lard was confirmed by the analysis of pork from the animals (Table 6), which showed that the content of growth hormone in transgenic animals the 12th generation wasn’t raised and it remained at the level of control - 1,75%.

The thickness of a backfat (salo) layer sharply reduced in all studied points, while the observed tendency to reduce in carcass length promoted changes of an exterior.

These facts rise up a question - what was the reason for such a multiple effect on many indices of transgenic pigs while the growth hormone releasing factor has a highly specified action? The reduction of growth hormone content in the line of transgenic generations was most likely associated with increased incretion of somatostatin - the inhibitor of somatotropin release. Therefore, the transgenic animals have a high content of somatostatin providing a wide range of effects on body systems, which may explain the multiple changes of traits in transgenic pigs.

Thus, the obtained results allow the creation of new industrial type of pigs exceeding the existing varieties by a number of important features. This work has already started in the All-Russia Development and Research Institute of Livestock Husbandry (Dubrovitsy settlement, Moscow province), which helps the achievements of gene engineering to be for the first time realized in breeding practice.