Abstract
Abstract. Many researchers who have studied the relationships between milk protein polymorphisms and some yield traits in dairy cattle have reported incompatible results. In this study, in order to examine the overall relationships between milk protein genes known as major genes (CSN1S1, CSN2, CSN3, and BLG) and some yield traits (daily milk yield, lactation milk yield, fat yield, fat content, protein yield, and protein content), a meta-analysis was performed using some genetic models reported in the results of previous studies on cattle. The results suggest that the relationships of major milk protein genes with other factors should be studied using the codominant genetic model in general. Relationships among some CSN3 genotypes and fat yield, fat content, and protein content, and relationships between some BLG genotypes and daily milk yield, fat content, protein yield, and protein content were significant (P<0.05). No significant (P>0.05) relationships were found between these genotypes and other milk production traits. In addition, no significant (P>0.05) relationships between the CSN1S1 and CSN2 genotypes with the milk production traits examined were observed.
Highlights
For more than 50 years, many studies have reported alternative forms of milk protein genes and examined the relationships between these genetic variants and economic yield traits
Scientific journals were searched for published papers in English on genetic relationships between milk protein polymorphism and milk production traits in several databases (Web of Science, Science Direct, and Google Scholar), and 120 original publications from 1986 to 2016 were collected; the number of articles has been reduced for reasons such as suitability to criteria used and the presentation of results, and 40 papers were chosen
The meta-analysis demonstrated that the relationships of major milk protein genes with other factors should be examined using the codominant genetic model in general
Summary
For more than 50 years, many studies have reported alternative forms of milk protein genes and examined the relationships between these genetic variants and economic yield traits. Some authors reported the possibility of using milk protein as a polymorphic genetic marker (Eenennaam and Medrano, 1991; Chung et al, 1996; Kaygisiz and Dogan, 1999; Ikonen et al, 1999; Cardak, 2005; Alipanah et al, 2008; Heck et al, 2009; Mohammadi et al, 2013; Djedovic et al, 2015; Dyman et al, 2015). The conflicting results of these studies, which are performed and frequently repeated in various countries, do not benefit breeders
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