الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Milk contains high-quality nutrients, energy supplements, and minerals essentials for human nutritional requirements. Nutritionally the fat is considered to be the primary source of energy. Milk protein contains a relatively high level of essential amino acids and a strong digestible quality. Milk synthesis and secretion in the mammary gland are regulated by several genes. thus, advanced research in the transcription of milk constituent-related genes could improve the effectiveness of the synthesis of milk components. Furthermore, the ABCG2 gene (ATP binding cassette subfamily G member 2) that produces ABCG2 protein occurs on chromosome 6 inside a linkage zone with Quantitative Trait Locus (QTL) for quantity and composition of milk. so, it is a practical candidate gene for milk production features in dairy cattle and situated on chromosome 7 in buffalo. The ABCG2 protein present in the alveolar epithelial cell membrane of the mammary gland is among the most active transport proteins, involved in the transmission of different cytostatic, xenobiotics drugs, in addition to cholesterol to milk through the cell membrane. So, the purpose of the research was a study the effect of lactation stage and animal species/strain on relative expression of the Lipoprotein lipase (LPL), K-Casein (CSN3), and glucose transporter 1(GLUT1) genes via qRTPCR and milk components. Via 72 milk samples were collected from 36 multiparous black-white and red-white HF cows and 22 milk samples from 11 Egyptian buffalo at the early and peak lactation stages using a non-invasive RNA isolation process. As well as ABCG2 gene polymorphism and its correlation with milk production traits using DNA sequencing. Through DNA extracted from blood samples from these animals. The results revealed that the expression of the LPL and CSN3 genes at an early stage was observed to be greater than the peak stage. But GLUT1 gene was noted at early lactation lower than the peak stage. This is associated with a rise in milk fat and protein percentages at an early stage and then decreased at the peak lactation stage. In contrast, lactose offers a low level at an early stage then elevated in the peak stage. Besides this, ABCG2 polymorphism, where (A/G) replacement at base NO 48 of intron 13 in red-white HF cow related to declining in milk quantity and rising in fat and protein %. C deletion at nucleotide NO 32 of intron 7, A/C replacement, and C deletion at nucleotide NO 290 and 358, respectively of intron 8 in black-white HF cow were found to be linked to a rise in milk quantity and reduction in fat and protein levels. As well G and A deletion at nucleotide NO 32 and 33 of intron 7, G/A, C/A, C/T, and G/T replacement at nucleotide NO 182, 191, 200, and 224 of exon 7, and A/T, C/G, A/G, and C/T at base NO 239, 316, 317, and 360 of intron 8 in Egyptian buffalo significantly linked to milk quantity, milk fat, and protein% compared to HF cow. Based on these findings, the LPL, CSN3, and GLUT1 gene expression profiles were identical to the differences in the percentage of milk fat, protein, and lactose, suggesting that the LPL and GLUT1 genes have a functional role in fatty acid and glucose absorption for fat and lactose synthesis, respectively in bovine mammary epithelial cells during lactation. It also helped to explain the pattern of LPL, CSN3, and GLUT1 gene expression in various stages of lactation in separate Holstein-Friesian strains of cattle and Egyptian buffalo. Moreover, the observed polymorphisms may be a possible genetic marker for improving the present population of Holstein-Friesian cow and Egyptian buffalo production.