Single and combined effects of CSN1S1 and CSN2-casein genes on Awassi sheep milk quantity and quality

Abstract

Background and Aim: Milk produced from Awassi sheep is of high nutritive value; its production is relatively low in Awassi sheep, so the genetic improvement programs targeted milk production and its components are of high importance, especially when using genes that have an important signal to milk traits. This study was aimed at assessing the influence of alpha S1 (CSN1S1) and beta-casein (CSN2) genes genotypes interaction on Awassi ewes milk productivity. Materials and Methods: A total number of 391 milk yield and its composition records (taken through five consecutive years, 2007-2011) of 167 ewes were utilized for this study. DNA samples were extracted from the ewe's blood samples, then the polymerase chain reaction products of alpha S1 (CSN1S1) and beta-casein (CSN2) genes were sequenced. The obtained sequences were analyzed; thereafter, the detected variants were tested for their possible association with milk traits. Results: The CSN1S1 and CSN2 variants allelic frequencies were 0.85 and 0.15, and 0.95 and 0.05, respectively. Lactose and solid not fat (SNF) % were associated with TC CSN1S1 genotypes. No association was found among CSN1S1 polymorphic genotypes with milk production, lactose, and SNF % were associated with TC CSN1S1 genotypes. Ewes of CSN2 AC genotype showed higher milk production traits, while no association was found between milk composition traits and CNS2 genotypes. Nevertheless, CSN1S1∗CSN2 interaction showed the highest SNF, fat percentages, and milk production. Conclusion: The substantial interaction effects between CSN1S1×CSN2 genes were significantly affected the amount of milk, fat, and SNF% produced. The detected variants should be included in the breeding programs of Awassi sheep that are designed for improving their milk quantity and quality.

The implications of various gene variant combinations on breeding values for Awassi ewe milk production

“…According to our investigation, the interactions of the BLG|CSN3, BLG|CSN1S1, PRL|CSN2, PRL|CSN3, CSN2|CSN1S1, and PRL|CSN2|CSN1S1 genotypes significantly impacted the EBVs of milk production in Awassi sheep (Figures -2a-e and-3). Similarly, Jawasreh et al [14] and Al-Amareen and Jawasreh [21] both reported a significant effect of the BLG|PRL and CSN1S1|CSN2 genotypes on milk production in Awassi sheep.…”

“…Researchers worldwide have investigated different potential genes that substantially impact milk production in sheep [ 14 , 19 , 20 , 21 ]. These genes include CSN3 , CSN1S1 , CSN2 , BLG , and PRL .…”

“…Similarly, Jawasreh et al . [ 14 ] and Al-Amareen and Jawasreh [ 21 ] both reported a significant effect of the BLG | PRL and CSN1S1 | CSN2 genotypes on milk production in Awassi sheep.…”

“…We performed quantitative genetic analysis to generate EBVs, as described previously by Jawasreh et al [10], In a nutshell, the mixed model used in the ASreml program's Individual Animal Model was used to estimate phenotypic and genetic parameters, including estimated breeding values (EBVs).We performed DNA extraction, amplification procedure sequencing, and mutation detection using the protocols proposed by Jawasreh et al [14,21].…”