Influence of inbreeding on living mass and own productivity of pigs of mirgorodic breed
It is generally recognized that inbreeding is a method of breeding individuals having common ancestors in the pedigree. Assessing the state of modern pig production, taking into account the number of breeds and imported livestock, we can conclude that the problem of inbreeding is relevant only for non-numerical local breeds, which are included in the category of so-called disappearing native populations. The main method of breeding animals in these populations is recognized pure-breed without the possibility of using crosses even with related breeds. In view of this, it remains only to observe and analyze the genetic situation in the rocks for the use of related breeding, as well as to determine the most successful options for selecting parental couples, which do not lead to the manifestation of inbred depression in descendants.
The purpose of the researchis to determine the level of growth of homozygosity (inbreeding rate) of pigs of Mirgorod breed for one generation, as well as to analyze the productivity of inbred swine and to establish the possibility of related breeding of pigs in a local non-large population.
The pigs of the Mirgorod breed are currently in the local, closed population, where it is impossible to avoid related breeding, and hence the use of inbred animals.
To determine the growth of homozygosity or loss of heterozygosity for one generation, we calculated the inbreeding rate (Fx), using the formula Fx = 1 / 2Ne. For its determination, the active part of the breed – 10 boars and 150 sows were taken into account. With the number of animals of the main herd, or those used to reproduce the herd and the selection of animals for the next generation, the inbreeding rate for one generation is 1,3%. This is not yet a critical limit for the local breed, but its further reduction can lead to irreversible consequences and degeneration of the population.
Our research has found that pigs of the Myrhorod breed with different inbreeding rates (Fx) in the process of growing from weaning in the 45 day to the age of nine months differed slightly in live weight, but this difference was not reliable. The most pronounced effect of inbreeding was shown on the live weight of the pigs during weaning, with animals with a higher inbreeding rate having a lower live weight than those of the first group whose inbreeding rate was at the level of Fx = 0,78–1,56%. At four months of age, inbred pigs had practically the same living weight, that is, the influence of related breeding on the development of this trait was virtually absent. But since 6 months of age there was a higher rate of inbreeding in the pigs, so their live weight was higher. Thus, mumps of group I (Fx = 0,78–1,56%), at the age of 6 months, had a live weight of 73,8 kg, group II (Fx = 2,34–4,68%) – 74,1 kg, and group III (Fx = 6,24–11,7%) – 75,8 kg. At 9 months of age, a similar tendency of greater live weight was observed in the pigs with a higher inbreeding rate, but also without a significant difference between the groups.
On the whole, it can be concluded that the in vitro adverse effect of inbreeding on the live weight of the pigs of the Mirgorod breed. Moreover, the related breeding was more effective provided that the inbreeding rate increased.
The estimation of inbred pigs according to their own productivity indicators made it possible to establish that, with an increase in the inbreeding rate from 2,34% to 11,7%, the age of achieving 100 kg live weight of animals during cultivation decreased by 11,4 days (P > 0,95), and the thickness of the pin, measured in vivo, respectively, at 2.7 mm. The pigs of the I group at 4 days later reached a live weight of 100 kg, compared to the animals of the second group (Fx = 2,34–4,68) and had a larger 2,3 mm fat thickness. Pigs II group inferior to representatives of the third group on the above indicators, respectively, for 7,4 days and 0,4 mm.
On the basis of the research carried out, the following general conclusions were made:
- In the presence of 150 main sows and 10 major kennels in the Mirgorod breed of pigs, an increase in inbreeding, or the loss of heterozygosity, for one generation is 1,3%, which is permitted in accordance with the biological law of animal survival in the natural population.
- In pure-breeding breeding of pigs of local breeds that are in the category of fading, a similar selection of parent pairs for the descendants, a complex inbreeding rate of no more than 11,7%, may be possible.
- The increase of the inbreeding rate in the pigs of the Mirgorod breed from 2,34% to 11,7% helps to reduce the thickness of the sphincter and reduce the age of reaching a live weight of 100 kg during growing, compared with the animals of the remote degree of inbreeding (Fx=0,78–1,56).
- The effect of the degree of inbreeding on the live weight of the pigs in the process of their cultivation in certain age periods, although it had a positive direction, but not reliably confirmed.
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