A participatory animal-breeding program was applied to 9 commercial Awassi sheep flocks in Jordan. This study aimed to assess the influence of Beta-lactoglobulin (β-LG), Prolactin (PRL), and Kappa casein (CSN3) genes, genotypes and their interaction on milk production and composition traits of 167 genotyped Awassi ewes via Polymerase Chain Reaction (PCR) followed by sequencing. Allele frequencies for the two variants were 0.42 and 0.58 for β-LG, 0.82 and 0.18 for PRL, and 0.92 and 0.08 for CSN3. No association was found among β-LG and CSN3 polymorphic genotypes with milk production traits. However, ewes with PRL AA genotype showed higher milk production, β-LG AB was associated with lowest fat%, high solid not fat (SNF)%, protein%, and lactose%. β-LG BB was associated with highest milk density. PRL, β-LG, and CSN3 polymorphic genotypes were differentially associated with milk production and component traits. Furthermore, β-LG × PRL interaction showed the highest milk production and fat%; β-LG × PRL recorded the highest SNF%, protein%, lactose%, and milk density, while the PRL × CSN3 had the highest fat% and SNF%. The enhancing effects of these gene interactions can be incorporated in Awassi breeding programs to improve milk production and composition.

Simple SummaryThe Awassi sheep is a very important breed, and using molecular selection to enhance meat production is important. Following genotyping of Awassi sheep housed at two different research stations in Jordan, three genotypes were identified for the calpastatin Hha1 gene. Following a fattening trial, the polymorphic calpastatin gene affected final (marketing) body weight and longissimus muscle width. Hha1 restriction sites found in Calpastatin gene can be used for molecular marker-assisted selection in Awassi for meat purposes.AbstractAdvances in molecular genetics have allowed the identification of genes that can enhance livestock production. The aim of this study was to investigate possible relationships between the calpastatin (CAST) Hha1 gene polymorphisms and growth performance, carcass characteristics, and meat quality in Awassi sheep. A total of 87 blood samples were collected from two-week-old Awassi ram lambs. The amplification of the CAST Hha1 gene yielded a fragment of 622 bp. Three CAST genotypes were found in Awassi sheep: MM for two fragments (385 bp and 281 bp), MN for three fragments (622 bp, 385 bp, and 281 bp), and NN for only one fragment (622 bp). The M and N allele frequencies of the CAST Hha1 genotypes were 0.765 and 0.235, respectively, while the genotypic frequencies of MM, MN, and NN were 0.586, 0.356, and 0.057, respectively. Based on CAST Hha1 gene polymorphisms, three groups of lambs (MM: n = 8; MN: n = 6; and NN: n = 3 genotypes) were subjected to a fattening period of 70 days to investigate growth performance and meat characteristics. Only the final body weight and longissimus muscle width were significantly different between the three genotypes, while no significant differences were detected in any other carcass characteristics and meat quality parameters. In this study, new variants were observed in CAST using the Hha1 restriction site, potentially assisting in Awassi sheep breeding and selection programs to improve final body weight and longissimus muscle width.

Aim: This study was designed to introduce the callipyge (CLPG) and 50% of Rambouillet sheep genes to improve meat quality and quantity of Awassi (AW) sheep. Materials and Methods: The CLPG mutation was introduced into the AW sheep through frozen semen of homozygous Rambouillet rams for the CLPG mutation. Four ram lambs from the first-generation Rambouillet callipyge Awassi (F1-RCA) and five from pure AW were recruited for a fattening trial conducted in individual pens using standard ration, following which ram lambs were slaughtered for carcass and meat evaluation. Results: Final body weight, dry matter intake, average daily gain, and feed conversion ratio were significantly higher in F1-RCA than AW. Hot and cold carcass weights and the other carcass cuts' weights, except for the fat tail, were heavier in F1-RCA than AW. There was no difference in dressing percentage between the two genetic groups (p>0.05). All non-carcass components' weights, except spleen, kidney, and testis, were higher in F1-RCA. Total lean, total bone, and intermuscular fat weight were greater in F1-RCA, but bone-to-lean ratio was lower in F1-RCA when compared with AW (p<0.01). No differences (p>0.05) were observed in all meat quality parameters for muscle longissimus with the exception of pH, redness color, and tenderness that were lower (p<0.05) in F1-RCA than AW. F1-RCA lambs had larger longissimus muscle area (30.9 vs. 16.9 cm2) and less leg fat depth (11.1 vs. 17.4 mm). Conclusion: The implications of this research show the potential of 50% of Rambouillet genes and the CLPG mutation to improve growth and meat characteristics in AW-Rambouillet crosses and can be used further to develop a meat-type AW with improved productivity and muscle mass.

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.

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