Genetic markers for energy assessment in cattle

Abstract

The purpose of this study was to examine how intensive milk production technology (cold heifer rearing, early heifer insemination, high daily operating loads, etc.) affects the bioenergetic parameters of high-yielding Holstein breed cows by studying polymorphism of allelic variants of somatotropin GH genes and pituitary-specific transcription factor PIT-1. The PCR method was used to identify the cows' genotypes. The DNA in the blood was analyzed at a genetics lab. "Chelex-100" resin was used for the isolation of genomic DNA. The "Tertsyk" amplifier was used to carry out the reaction. Net maintenance energy (in MJ per day), net milk energy (in MJ per day), total net energy consumption (in MJ per day), energy index value (in % of energy released from milk), productivity index (in kilograms of 4% milk per 1 MJ), net energy consumption per 1 MJ of milk (in MJ), and energy released with milk per 1 kg of metabolic mass (in MJ) were all used for the energy assessment of young cows. The LL genotype of the GH gene, the AB genotype of the pituitary-specific transcription factor PIT-1, and the LL/AB and LL/BB paired genotypes all result in optimal energy output in cows. Compared to animals of the LV, BB, and LV/BB genotypes, these animals consistently had stronger bioenergetic markers during both the first and second lactational phases. Bioenergetic indices favor cows of the LL/AB genotype over those of the LV/BB genotype, however this advantage is much less during the first lactation period (3.9-15.2%) than it is during the second (1.8-7.4%). Genotype AB cows had higher bioenergetic characteristics than genotype BB cows did for the pituitary-specific transcription factor PIT-1. The larger lactotropic function of the L and A alleles, which results from a greater complementary influence on the functioning of the alleles of the linked genes in the complex genotype, explains the difference in bioenergetic parameters. The analysis of variance of one-factor complexes supported this finding, showing that genotypes had a greater effect on bioenergetic parameters during the first phase of breastfeeding compared to the second. However, regardless of lactation duration, the level of the paired genotype's impact on the GH and PIT-1 genes was consistently substantial, ranging from 8.9 to 20.9% (P 0.01-0.001). It will be interesting to see how polymorphisms in the GH and PIT-1 genes affect the outward appearance and internal make-up of various types of cows in the future.