Effect and Interaction of β-Lactoglobulin, Kappa Casein, and Prolactin Genes on Milk Production and Composition of Awassi Sheep

Prolactin (PRL) is a lactogenic hormone that plays a significant role in milk production; its depletion in sheep provokes a severe reduction of milk secretion. Thus, PRL also could be used as a positional marker gene associated with milk production and composition traits. Therefore, the purpose of the study was to identify genotype frequencies of single nucleotide polymorphisms the intron 2 in ovine PRL gene and its possible association genotypes with milk traits in dairy sheep breeds. The genetic structures of ovine PRL gene were examined by PCR-RFLP and DNA sequencing methods in three sheep populations. Four hundred and fifty blood and milk samples were used in the study, which included 150 samples from each of Sakiz, Akkaraman and Awassi ewes respectively. As a result, PRL genotype AA showed a strong association with milk yields content, whereas the animals carrying BB genotype had a higher fat percentage value in the three sheep breeds. Haplotype analysis of the obtained sequences showed the presence of 12 haplotypes in the PRL intron 2 region. In the present study, we have reported for the first time 48 SNPs of the PRL gene for intron 2 in dairy sheep breeds. These preliminary results indicate that the identified SNPs lend themselves readily for further research regarding physiological impacts such as milk production and reproductive traits in other dairy sheep populations.

The aim of this study was to evaluate the effects of polymorphisms in the acylCoA diacylglycerol acyltransferase (DGAT1), fatty acid synthase (FASN) and prolactin (PRL) genes on milk production traits and the potential influence of the PRL gene on SCC of Simmental and crossbred Holstein cattle as well as comparatively among them. A total of eighty-three cows were genotyped by PCR-RFLP method. Crossbred Holsteins with DGAT1 genotype KA hadsignificantly higher fat content than cows with AA genotype and for FASN diplotype TW/AR had significantly higher fat content compared to diplotype AR/AR. In the observed group of animals, there was no association found between PRL SNP G8398A and milk production traits and SCC (SCS). For all three genes, cross bred Holstein hadsignificantly higher milk yield, fat and protein content in certain genotypes/diplotypes. The results of combined genotype analysis of the three SNPs showed that GG/TWAR/KK genotype combination had the lowest SCS.

ObjectiveThe purpose of this study was to compare intended and actual yearly genetic gains for milk production and conformation traits and to investigate the simple selection criterion practiced among milk production and conformation traits during the last two decades in Japan. Learning how to utilize the information on intended and actual genetic gains during the last two decades into the genomic era is vital.MethodsGenetic superiority for each trait for four paths of selection (sires to breed bulls [SB], sires to breed cows [SC], dams to breed bulls [DB], and dams to breed cows [DC]) was estimated. Actual practiced simple selection criteria were investigated among milk production and conformation traits and relative emphasis on milk production and conformation traits was compared.ResultsSelection differentials in milk production traits were greater than those of conformation traits in all four paths of selection. Realized yearly genetic gain was less than that intended for milk production traits. Actual annual genetic gain for conformation traits was equivalent to or greater than intended. Retrospective selection weights of milk production and conformation traits were 0.73:0.27 and 0.56:0.44 for intended and realized genetic gains, respectively.ConclusionSelection was aimed more toward increasing genetic gain in milk production than toward conformation traits over the past two decades in Japan. In contrast, actual annual genetic gain for conformation traits was equivalent to or greater than intended. Balanced selection between milk production and conformation traits tended to be favored during actual selection. Each of four paths of selection (SB, SC, DB, and DC) has played an individual and important role. With shortening generation interval in the genomic era, a young sire arises before the completion of sire’s daughters’ milk production records. How to integrate these four paths of selection in the genomic era is vital.

Growth hormone (GH) gene can be utilized as a major gene because its polymorphisms have been associated to milk traits in various livestock species. The aim of this present study was to investigate the polymorphism in the exon 1, 3 and 5 of gGH (goat GH) gene and to evaluate the possible associations with milk traits in Jamunapari goat, maintained at the ICAR-Central Institute for Research on Goats, Makhdoom, Uttar Pradesh, India.In this study, 100 primiparous lactating goats were randomlychosen, and their productive performances like 90-days, 140-days and total milk yield as well as milk compositional traits like fat %, SNF%, casein%, protein%, lactose% and ash % of three consecutive lactations were recorded. The exon 1, 3 and 5 of the gGH gene was PCR amplified and the resulting products wereanalyzed by Single-strand conformation polymorphism (SSCP).Two conformational patterns (A and B) for each the GH exon 3and 5 were detected but no polymorphism existed in exon 1 ofgrowth hormone gene.The frequency of the patterns varied from41.4 to 58.6% in these two fragments. Association studies ofSSCPs patterns at GH gene with milk production and milkcomposition traits in Jamunapari breed showed that onlypolymorphic patterns at exon 3 were positively associated with milk production traits, i.e., with 90-days milk yield, 140-days milk yield and total milk yield of animals but there was no significanteffect on milk composition traits. Animals with pattern A/A for exon 3 were significantly superior milk producers (P<0.01) than animals having B/B pattern for 90-days, 140-days and total milk yield of animals, whereas GH conformation patterns (A and B)for exon 3 didn’t have any impact on milk compositions. Further, in case of exon 5, the milk yields and milk compositions of animals didn’t vary significantly between animals having different GH conformation patterns (A and B).These findings may be used for preserving genetic diversity of the population and may be useful for marker assisted selection in order to improve milk production of this breed.

The present study investigates the genetic polymorphism of the kappa casein (CSN3) gene and its association with milk production and composition traits in Gir and Mulki cattle breeds from Narmadapuram Division of Madhya Pradesh state, India. A total of 256 cows, including 167 Mulki and 89 Gir, were analyzed. Genomic DNA was extracted from blood samples, and PCR-RFLP was employed to identify polymorphisms in the kappa casein gene. The study identified three genotypes-AA, AB, and BB—at the kappa casein locus. Allelic frequencies were found to be 0.83 (A) and 0.17 (B) in Gir cattle, and 0.89 (A) and 0.11 (B) in Mulki cattle. Statistical analysis revealed that Gir cattle exhibited significantly higher milk yield and daily milk yield across all genotypes compared to Mulki cattle. The BB genotype was associated with superior milk yield in both breeds. However, no significant associations were observed between kappa casein polymorphisms and milk composition traits such as fat percentage, protein content, SNF, density, pH, and freezing point. This study underscores the importance of kappa casein genetic variants in improving milk yield in indigenous cattle breeds, providing valuable insights for breed selection and dairy management practices.

Claw diseases and mastitis represent the most important disease traits in dairy cattle with increasing incidences and a frequently mentioned connection to milk yield. Yet, many studies aimed to detect the genetic background of both trait complexes via fine-mapping of quantitative trait loci. However, little is known about genomic regions that simultaneously affect milk production and disease traits. For this purpose, several tools to detect local genetic correlations have been developed. In this study, we attempted a detailed analysis of milk production and disease traits as well as their interrelationship using a sample of 34,497 50K genotyped German Holstein cows with milk production and claw and udder disease traits records. We performed a pedigree-based quantitative genetic analysis to estimate heritabilities and genetic correlations. Additionally, we generated GWAS summary statistics, paying special attention to genomic inflation, and used these data to identify shared genomic regions, which affect various trait combinations. The heritability on the liability scale of the disease traits was low, between 0.02 for laminitis and 0.19 for interdigital hyperplasia. The heritabilities for milk production traits were higher (between 0.27 for milk energy yield and 0.48 for fat-protein ratio). Global genetic correlations indicate the shared genetic effect between milk production and disease traits on a whole genome level. Most of these estimates were not significantly different from zero, only mastitis showed a positive one to milk (0.18) and milk energy yield (0.13), as well as a negative one to fat-protein ratio (-0.07). The genomic analysis revealed significant SNPs for milk production traits that were enriched on Bos taurus autosome 5, 6, and 14. For digital dermatitis, we found significant hits, predominantly on Bos taurus autosome 5, 10, 22, and 23, whereas we did not find significantly trait-associated SNPs for the other disease traits. Our results confirm the known genetic background of disease and milk production traits. We further detected 13 regions that harbor strong concordant effects on a trait combination of milk production and disease traits. This detailed investigation of genetic correlations reveals additional knowledge about the localization of regions with shared genetic effects on these trait complexes, which in turn enables a better understanding of the underlying biological pathways and putatively the utilization for a more precise design of breeding schemes.

Background: The exploration of milk production traits and prolactin gene polymorphisms in Sahiwal cattle has illuminated the genetic basis for their exceptional milk production process. These findings contribute to tailored breeding approaches aimed at augmenting milk yield, fat and protein content and reproductive efficiency of Sahiwal cattle. Amid evolving agricultural landscapes, this research plays a pivotal role in sustainable livestock production, boostering food security, and supporting rural economies, particularly in challenging climate regions. The selection of genetically superior animals at an early stage of life, the molecular markers are used along with traditional selection. The study was carried out to identify the genetic polymorphism in the exon3 region of the Prolactin and enumerate its effect on milk production performance in Sahiwal cattle. Methods: The study was conducted on various production traits and association of prolactin gene with the various traits under study on the herd of Sahiwal cattle maintained at the Sahiwal cattle farm, Livestock Farm Complex, College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati-22. Information from a total of 65 lactation records were utilized for the present study for Milk Production traits mainly Average daily milk yield, Lactation milk yield, Peak yield, Number of days to attain peak yield, Persistency of milk yield. A total of 382 milk samples were utilized to study the milk constituent traits. Milk samples were analysed using “Milk Quality Analyser Laktan 1-4” which includes Fat %, SNF (Solid Not Fat) %, Protein % and Density (kg/m3). Genomic DNA were extracted from the collected whole blood samples by using Nucleo-pore (Genetix Brand, India)Genomic DNA Purification Kit #DNASure®Blood Mini Kit (NP-61105) 50 preps. Results: The least-squares means with standard errors for milk production traits viz; average daily milk yield, lactation milk yield, peak yield, number of days to attain peak yield and persistency of milk yield were found to be 5.93±0.08 kg, 1609.36±31.21 kg, 13.20±0.16 kg, 47.39±0.88 days and 92.88±0.43 days, whereas, the Least Square means with standard errors for milk constituent traits viz; fat%, SNF%, Protein%, Density were found to be 4.34±0.04%, 8.41±0.03%, 3.34±0.07% and 29.28±0.12, respectively. PCR-RFLP was carried out using RsaI restriction endonuclease and revealed three genotypes AA, AB and BB, were 0.5, 0.312 and 0.188, the frequency of A and B allele of prolactin gene (exon 3) were 0.752 and 0.248, respectively. The result shows that cows with AA genotypes yielded most milk as compared to cows with genotype AB and BB.

Estimates of genetic parameters and genetic trends for growth, reproduction, milk production and milk composition traits of Awassi sheep

Milk fatty acids are essential for many dairy product productions, while intramuscular fat (IMF) is associated with the quality of meat. The triacylglycerols (TAGs) are the major components of IMF and milk fat. Therefore, understanding the polymorphisms and genes linked to fat synthesis is important for animal production. Identifying quantitative trait loci (QTLs) and genes associated with milk and meat production traits has been the objective of various mapping studies in the last decade. Consistently, the QTLs on chromosomes 14, 15, and 9 have been found to be associated with milk and meat production traits in cattle, goat, and buffalo and sheep, respectively. Diacylglycerol O-acyltransferase 1 (DGAT1) gene has been reported on chromosomes 14, 15, and 9 in cattle, goat, and buffalo and sheep, respectively. Being a key role in fat metabolism and TAG synthesis, the DGAT1 has obtained considerable attention especially in animal milk production. In addition to milk production, DGAT1 has also been a subject of interest in animal meat production. Several polymorphisms have been documented in DGAT1 in various animal species including cattle, buffalo, goat, and sheep for their association with milk production traits. In addition, the DGAT1 has also been studied for their role in meat production traits in cattle, sheep, and goat. However, very limited studies have been conducted in cattle for association of DGAT1 with meat production traits in cattle. Moreover, not a single study reported the association of DGAT1 with meat production traits in buffalo; thus, further studies are warranted to fulfill this huge gap. Keeping in view the important role of DGAT1 in animal production, the current review article was designed to highlight the major development and new insights on DGAT1 effect on milk and meat production traits in cattle, buffalo, sheep, and goat. Moreover, we have also highlighted the possible future contributions of DGAT1 for the studied species.

Preliminary genetic correlations of milk production and milk composition with reproduction, growth, wool traits and worm resistance in crossbred ewes

The aim of this study was to estimate allelic and genotypic frequencies of five DNA markers that are positional and functional candidates for milk production traits in Czech Fleckvieh cattle. In addition, we evaluated the association of these markers with milk production traits and breeding values for milk production traits and also estimated linkage disequilibrium (LD) between two markers within the prolactin (PRL) gene. As part of this study, 505 Czech Fleckvieh cows were genotyped. The markers in proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A), secreted phosphoprotein (SPP1), cytochrome P450 family 11 subfamily B hydroxylase (CYP11B1), and the two polymorphisms in the prolactin gene (PRL) showed evidence of segregation in our study. The PPARGC1A polymorphism was associated with milk yield, milk fat and protein traits. The polymorphism in SPP1 was significantly associated with milk protein percentage. The CYP11B1 polymorphism showed positive associations with milk composition traits and breeding values for milk yield, milk fat, and protein traits. Both polymorphisms within the PRL gene were associated with milk yield, milk fat and milk protein yield (individually and grouped). Linkage disequilibrium between the two polymorphisms in PRL was not observed. In conclusion, all markers examined in this study are important markers for milk production traits in Czech Fleckvieh cattle, and both markers within the PRL gene should be evaluated in future research.  

Associations between milk protein genetic polymorphisms and milk production traits in Merino sheep breed

<p><strong>Objective: </strong>The objective of this study was to analyze <em>CSN2</em> variants in Indonesian Friesian Holstein (FH) cow and their association with milk protein allergy and production traits.</p><p><strong>Methods: </strong>Genomic DNA was extracted from bloods of twelve Indonesian FH cow. Exon 7 of the <em>CSN2</em> was amplified using novel primer pair to produce 683 bp amplicon. The primers were 5’-ACCCCAATTTCTTAACCAAACCA-3’ as a forward primer and 5’-CATCAGAAGTTAAACAGCACAGT-3’ as a reverse primer. The PCR products were analyzed to determine the nucleotide sequence of <em>CSN2</em> using Bioedit version 7.2.5. Moreover, Hardy-Weinberg equilibrium (HWE) was calculated and one-way analysis of variance (ANOVA) was conducted to associate between <em>CSN2</em> variants and milk production traits.</p><p><strong>Results: </strong>Two polymorphisms, c.350A>C and c.516G>C, were identified in the <em>CSN2 </em>exon 7. Base substitution from adenine (A) to cytosine (C) of c.350A>C changed amino acid codon from histidine (CAU) to proline (CCU), and base substitution guanine (G) to cytosine (C) of c.516G>C changed amino acid codon from arginine (AGG) to serine (AGC). The CC genotype frequency for c.350A>C SNP was 33% and they were able to produce A2 <em>CSN2</em> variant which is favorable for preventing lactose intolerance. In addition, there were no association between c.350 A>C and c.516 G>C SNP of the <em>CSN2</em> with milk production traits.</p><p><strong>Conclusions: </strong>In conclusion, A1 and A2 variants of <em>CSN2</em> were identified in Indonesian FH population and they did not associate with milk production in Indonesian FH.</p><p> </p>

Prophet of POU1F1 (PROP1) plays direct or indirect important roles in the morphogen- esis of pituitary gonadotropes as well as lactotropes, somatotropes and caudomedial thyrotropes. It also controls the expression of growth hormone, prolactin and thyrotropin subunits through regula- tory PIT1 factor. These hormones have important influences on production traits in most animal species including the goat. Therefore, PROP1 gene could be considered as a candidate gene for milk production. The objective of this study was to determine the polymorphism of PROP1 gene and its association with milk yield and growth traits in Mahabadi goats. We investigated the mutation (Gen- Bank accession number: AY533708.1) within exon 2 of PROP1 gene by using the Hin6I PCR-RFLP method.This polymorphism alters the amino acid at codon 79 from alanine to valine in PROP1 pro- tein. Only two genotypes CC and CT (frequencies 0.9 and 0.1 respectively) were observed. Poly- morphism of PROP1-Hin6I locus showed significant relationship with milk production (P < 0.01), milk fat percentage (P < 0.05), milk protein percentage (P < 0.05), somatic cell count (P < 0.05) and daily weight gain (P < 0.05). Therefore, PROP1-Hin6I locus could be considered as a molecular marker for milk production and milk composition traits in Mahabadi goats. Keywords: Mahabadi goat, association analysis, PROP1 gene, production traits

Genetic parameters for beef and milk production in Dutch Red and White dual-purpose cattle and their implications for a breeding program