The effect of known CSN3, Pit-1 and LGB genes single nucleotide polymorphism (SNP) on milk performance traits (milk yield, protein, fat and lactose content, count of somatic cells) at the Czech Fleckvieh and the Holstein cattle breed was estimated. For more exact results, tested cows of each breed came from one source, and were selected into two groups according to their lactation. We tested around 100 animals at the first and 25 at the high (more than five) lactation of both breeds. Our attention was aimed particularly on combined genotypes of favourable alleles. We confirmed the positive tendention of the cheese yield valuable CSN3/BB with Pit-1/AA combined genotype for high milk production. By estimation of single gene effect, we found out significant association (P ≤ 0.01) between milk yield (kg) and Pit-1 genotypes at Holstein cows with the high lactation. This dependence was observed at the Czech Fleckvieh breed too, even it didn’t get conclusive value. Among all tested individuals, CSN3 genotypes significantly influenced milk yield (AA > BB, P ≤ 0.01), milk fat (BB > AA, P ≤ 0.01) and protein content (BB > AA, P ≤ 0.01). The genotypes AB and BB of the LGB gene at Holstein cows were joined with higher milk yield in selected cattle groups opposite to AA genotype (P ≤ 0.01, P ≤ 0.05). The influence of LGB on the somatic cell count in created cattle groups was not confirmed. Estimation of allele and genotype frequency according to lactation stage didn’t reveal higher differences at non of tested genes in both breeds.
Effects of first-lactation milk production and culling reasons on lifetime performance traits of Holstein cows culled from an intensive system in Egypt
