Milk Yield Traits Research Articles

Genetic relationships of alternative somatic cell count traits with milk yield, composition and udder type traits in Italian Jersey cows.

The aim of this study was to estimate genetic associations between alternative somatic cell count (SCC) traits and milk yield, composition and udder type traits in Italian Jersey cows. Alternative SCC traits were test-day (TD) somatic cell score (SCS) averaged over early lactation (SCS_150), standard deviation of SCS of the entire lactation (SCS_SD), a binary trait indicating absence or presence of at least one TD SCC >400,000cells/ml in the lactation (Infection) and the ratio of the number of TD SCC >400,000 cells/ml to total number of TD in the lactation (Severity). Heritabilities of SCC traits, including lactation-mean SCS (SCS_LM), ranged from 0.038 to 0.136. Genetic correlations between SCC traits were moderate to strong, with very few exceptions. Unfavourable genetic associations between milk yield and SCS_SD and Infection indicated that high-producing cows were more susceptible to variation in SCC than low-producing animals. Cows with deep udders, loose attachments, weak ligaments and long teats were more susceptible to an increase of SCC in milk. Overall, results suggest that alternative SCC traits can be exploited to improve cow's resistance to mastitis in Italian Jersey breed.

Milk yield and quality traits in different lactation stages of Damascus goats: Concentrate and pasture based feeding systems

This study aimed to survey milk yield, lactation stages and milk quality traits of Damascus goats reared underdifferent feeding systems. Goats were divided according to feeding systems as pasture based and concentrate based. Feeding systemswere found to have significant effect on lactation milk yield but not on lactation duration. Although differences between feedingsystems were not found significant on pH, milk composition factors (fat, lactose, dry matter), somatic cell count and malondialdehyde(except for early lactation stage) for each lactation stage, significant effects were detected on same parameters among lactation stages.Calcium levels at early lactation stage in milk differed either between feeding systems or among lactation stages. Also, other mineralswere found to decrease with lactation. While most of the fatty acids were affected in any of the lactation stages by the feeding system,all of them were significantly altered by lactation stages. Pastured goats had a lower percentage of total saturated fatty acids, atherogenicindex, thrombogenic index and odour index ratios. In accordance with milk fatty acid composition, compared to the milk obtained fromgoats fed with concentrate, the milk obtained from the goats that pastured was healthier and early lactation stage was found to producehealthier milk than late lactation stage.

Linking first lactation survival to milk yield and components and lactation persistency in Tunisian Holstein cows.

Genetic parameters were estimated for first lactation survival defined as a binary trait (alive or dead to second calving) and the curve shape traits of milk yield, fat and protein percentages using information from 25 981 primiparous Tunisian Holsteins. For each trait, shape curves (i.e. peak lactation, persistency), level of production adjusted to 305 days in milk (DIMs) for total milk yield (TMY), and average fat (TF %) and protein (TP %) percentages were defined. Variance components were estimated with a linear random regression model under three bivariate animal models. Production traits were modelled by fixed herd test-day (TD) interaction effects, fixed classes of 25 DIMs age of calving season of calving interaction effects, fixed classes of pregnancy, random environment effects and random additive genetic effects. Survival was modelled by fixed herd year of calving interaction effects and age of calving season of calving interaction effects, random permanent environment effects, and random additive genetic effects. Heritability () estimates were 0.03 () for survival and 0.23 (), 0.31 () and 0.31 () for TMY, TF % and TP %, respectively. Genetic correlations between survival and TMY, TF % and TP % were 0.26 (), () and (), respectively. Genetic correlations between survival and persistency for fat and protein percentages were () and (), respectively. Cows that had higher persistencies for fat and protein percentages were more likely not to survive.

Short communication: Genetic aspects of milk differential somatic cell count in Holstein cows: A preliminary analysis

The aim of the present study was to assess genetic variation and heritability of a novel indicator of udder health, milk differential somatic cell count (DSCC), which represents the percentage of neutrophils plus lymphocytes in the total somatic cell count (SCC). Furthermore, we estimated genetic and phenotypic correlations of DSCC with other milk traits routinely measured in Italian Holstein cows. Besides DSCC, test-day data included milk yield, composition traits (i.e., fat, protein, casein, and lactose percentages), pH, milk urea nitrogen, and SCC. After editing, the final data set included 10,709 test-day records of 5,142 cows in 299 herds. Mean of DSCC was 62.07%, which means that macrophages were approximately 38% of total SCC. Comparing our results with the literature offered compelling evidence of the importance of acquiring information about the proportion of the different cell types in milk to better define the udder health status. In addition, our analysis revealed, for the first time, that DSCC is a heritable trait, and heritability (0.08 ± 0.02) was higher than that of traditional somatic cell score (0.04 ± 0.02). Nevertheless, heritability of DSCC is still low compared with milk yield and quality traits. Single-trait analysis within parity showed that DSCC was less heritable in primiparous than in multiparous cows, whereas bivariate analysis confirmed that DSCC and somatic cell score were 2 different traits, as their genetic and phenotypic correlations differed from unity. From a genetic point of view, the DSCC was positively weakly associated with milk yield, lactose percentage, and milk urea nitrogen, and negatively associated with pH. Our findings contributed to the understanding of the genetic background of DSCC and are a precursor to the potential use of DSCC in breeding programs to enhance cow resistance to mastitis. However, further research is needed to determine the weight this novel trait should receive in a selection program aimed to reduce udder health problems.

Genetic association of DDIT3, RPL23A, SESN2 and NR4A1 genes with milk yield and composition in dairy cattle.

Previously, we identified by RNA sequencing that DDIT3, RPL23A, SESN2 and NR4A1 genes were significantly differentially expressed between the mammary glands of lactating Holstein cows with extremely high and low milk protein and fat percentages; thus, these four genes are considered as promising candidates potentially affecting milk yield and composition traits in dairy cattle. In the present study, we further verified whether these genes have genetic effects on milk traits in a Chinese Holstein population. By re-sequencing part of the non-coding and the entire coding regions of the DDIT3, RPL23A, SESN2 and NR4A1 genes, a total of 35 SNPs and three insertions/deletions were identified, of which three were found in DDIT3, 12 in RPL23A, 16 in SESN2 and seven in NR4A1. Moreover, two of the insertions/deletions-g.125714860_125714872del and g.125714806delinsCCCC in SESN2-were novel and have not been reported previously. Subsequent single SNP analyses revealed multiple significant association with all 35 SNPs and three indels regressed against the dairy production traits (P-value=<0.0001-0.0493). In addition, with a linkage disequilibrium analysis, we found one, one, three, and one haplotype blocks in the DDIT3, RPL23A, SESN2 and NR4A1 genes respectively. Haplotype-based association analyses revealed that somehaplotypes were also significantly associated with milk production traits (P-value=<0.0001-0.0461). We also found that 12 SNPs and two indels (two in DDIT3, two in RPL23A, nine in SESN2 and one in NR4A1) altered the specific transcription factor binding sites in the promoter, thereby regulating promoter activity, suggesting that they might be promising potential functional variants for milk traits. In summary, our findings first determined the genetic associations of DDIT3, RPL23A, SESN2 and NR4A1 with milk yield and composition traits in dairy cattle and also suggested potentially causal variants, which require in-depth validation.

Relationship of udder morphometry with milk yield and body condition traits in Beetal goats

Present study was conducted to find the relationship of udder morphometry with milk yield and body condition traits in Beetal goats. Beetal goats (60) having 4 different parities were used. Udder (length, column width, row width, depth, circumference, volume) and teat (length, diameter, circumference, height from ground, inter teat distance) morphological traits were recorded just before morning milking at fortnightly interval up to 3 months post-kidding stage. Simultaneously, milk yield (morning and daily) and body condition parameters (body condition score (BCS), sternal and lumbar thickness) were also recorded. All the udder morphological traits were positively correlated with morning as well as daily milk yield. Similarly, teat morphological traits were also positively correlated with morning as well as daily milk yield except teat height from ground which had negative correlation. Whereas some of the udder and teat morphological traits showed positive correlation with body condition parameters. Milk yield had positive correlation with BCS, sternal and lumbar thickness. It can be concluded that the udder and teat morphological traits have direct relationship with milk yield and body condition parameters in Beetal goats.

Integrative Analysis of Transcriptome and GWAS Data to Identify the Hub Genes Associated With Milk Yield Trait in Buffalo.

The mammary gland is the production organ in mammals that is of great importance for milk production and quality. However, characterization of the buffalo mammary gland transcriptome and identification of the valuable candidate genes that affect milk production is limited. Here, we performed the differential expressed genes (DEGs) analysis of mammary gland tissue on day 7, 50, 140, and 280 after calving and conducted gene-based genome-wide association studies (GWAS) of milk yield in 935 Mediterranean buffaloes. We then employed weighted gene co-expression network analysis (WGCNA) to identify specific modules and hub genes related to milk yield based on gene expression profiles and GWAS data. The results of the DEGs analysis showed that a total of 1,420 DEGs were detected across different lactation points. In the gene-based analysis, 976 genes were found to have genome-wide association (P ≤ 0.05) that could be defined as the nominally significant GWAS geneset (NSGG), 9 of which were suggestively associated with milk yield (P < 10−4). Using the WGCNA analysis, 544 and 225 genes associated with milk yield in the turquoise module were identified from DEGs and NSGG datasets, respectively. Several genes (including BNIPL, TUBA1C, C2CD4B, DCP1B, MAP3K5, PDCD11, SRGAP1, GDPD5, BARX2, SCARA3, CTU2, and RPL27A) were identified and considered as the hub genes because they were involved in multiple pathways related to milk production. Our findings provide an insight into the dynamic characterization of the buffalo mammary gland transcriptome, and these potential candidate genes may be valuable for future functional characterization of the buffalo mammary gland.

Economic values and selection indices for production and reproduction traits of Iranian buffaloes (Bubalus bubalis)

Iranian buffalo plays a critical role in supplying a portion of the income and the necessities of the rural population. The first step to design a breeding program is difinition of breeding goal (BG), a linear combination of breeding values for various traits and their economic values (EV). The current study was aimed at determining EVs for important traits of Iranian buffaloes, namely milk yield (MY), milk fat (MF), age at the first calving (AFC), and calving interval (CI), as well as at estimating the genetic response of applying various types of selection indices. Economic and management data of 50 buffalo herds from various main regions of buffalo rearing in Iran were collected. The EVs were estimated using a simple profit function. Five selection indices were constructed by combining information on various traits. The EVs for BG traits of MY, MF, AFC, and CI were 0.18, 4.66, - 0.36, and - 1.87 US$, respectively. The highest predicted genetic gain in BG was 16.95 and came from applying the selection index that included all traits. The smallest genetic gain (4.93) was predicted for the index with only AFC included. Predicted genetic gain from an index that included production traits and AFC as a reproduction trait (16.9) was higher than that from the index with only production traits (16.15). Results showed that inclusion of reproductive traits in the selection index had a positive effect on genetic gain for breeding goal.

Multiple QTL underlie milk phenotypes at the CSF2RB locus

BackgroundOver many years, artificial selection has substantially improved milk production by cows. However, the genes that underlie milk production quantitative trait loci (QTL) remain relatively poorly characterised. Here, we investigate a previously reported QTL located at the CSF2RB locus on chromosome 5, for several milk production phenotypes, to better understand its underlying genetic and molecular causes.ResultsUsing a population of 29,350 taurine dairy cows, we conducted association analyses for milk yield and composition traits, and identified highly significant QTL for milk yield, milk fat concentration, and milk protein concentration. Strikingly, protein concentration and milk yield appear to show co-located yet genetically distinct QTL. To attempt to understand the molecular mechanisms that might be mediating these effects, gene expression data were used to investigate eQTL for 11 genes in the broader interval. This analysis highlighted genetic impacts on CSF2RB and NCF4 expression that share similar association signatures to those observed for lactation QTL, strongly implicating one or both of these genes as responsible for these effects. Using the same gene expression dataset representing 357 lactating cows, we also identified 38 novel RNA editing sites in the 3′ UTR of CSF2RB transcripts. The extent to which two of these sites were edited also appears to be genetically co-regulated with lactation QTL, highlighting a further layer of regulatory complexity that involves the CSF2RB gene.ConclusionsThis locus presents a diversity of molecular and lactation QTL, likely representing multiple overlapping effects that, at a minimum, highlight the CSF2RB gene as having a causal role in these processes.

Phenotypic analysis of milk composition, milk urea nitrogen and somatic cell score of Italian Jersey cattle breed

The present study aimed to assess the phenotypic variation of milk yield (MY) and quality traits in Italian Jersey (IJ) breed. Sources of variation were investigated through a linear mixed model, including the fixed effects of days in milk (DIM), parity, calving season, milking frequency, recording type, the interaction between DIM and parity, and the random effects of herd-test-day (HTD), cow and the residual. Results highlighted the high contents of milk fat (5.18%), protein (4.08%) and casein (3.16%) of IJ cows. Somatic cell score, averaging 3.35 units, should be lowered through specific managerial actions. Phenotypic variances of MY and milk quality traits were mainly due to cow effect, whereas phenotypic variance of milk urea nitrogen (MUN) content was mainly due to HTD effect, meaning that managerial conditions, especially feeding, are very important to explain the variation of MUN. In conclusion, the present study allowed to characterise milk of IJ cows at population level and to identify environmental factors associated with variation of MY and quality traits, which will be useful to adjust phenotypic records in genetic evaluation of Jersey breed.HighlightsFactors affecting milk quality traits of Italian Jersey cows have been investigated.Phenotypic variance of milk composition and SCS was mainly due to cow effect, and that of MUN was mainly driven by herd-test-day effect.Significant environmental factors identified in the present study will be used to adjust phenotypic records in genetic analysis.

Effect of Polymorphism in FGF2 Gene on First Lactation Milk Yield and Milk Composition Traits in Karan-Fries Cattle

The present study was performed to investigate the polymorphisms in the Fibroblast Growth Factor 2 (FGF2) gene and to reveal the association of different genotypes corresponding to gene with Breeding Value (BV) for first lactation milk yield and milk composition traits of Karan Fries (HF crossbred) cattle. The traits were adjusted against the significant effect of non-genetic factors. Blood samples were collected on vacutainer tubes supported with EDTA to prevent blood Clotting and DNA samples were isolated and purified using standard phenol chloroform method. Polymerase chain reactions were performed using specific primers for gene under study. FGF2 gene PCR products were subjected to cut them with specific restriction enzyme: Csp6I. Polymerase Chain Reaction – Restriction Fragment Length Polymorphism (PCR-RFLP) analysis of FGF2 (intron 1) gene revealed three genotypes; GG (171bp), AG (207bp and 171bp,) and AA (207bp). Genotypic frequencies of GG, AG and AA were 0.31, 0.52 and 0.17 whereas the allelic frequencies for G and A allele were 0.57 and 0.43, respectively. Breeding value of GG genotype was highest for ATDMY(kg) and 305MY (kg) (11.21 ± 0.67 and 3172.01 ± 51.33 ) whereas, AA genotype had highest breeding value for ATDFP and LFY (4.39 ± 0.16 and 137.41 ± 5.76). In addition, no significant effect of polymorphism on any of the traits was found. GG genotype was associated with a higher breeding value for 305MY, suggesting its further research in a large population and consequently its use in gene assisted selection for the genetic improvement of milk production.

Genetic polymorphisms at candidate genes affecting fat content and fatty acid composition in Modicana cows: effects on milk production traits in different feeding systems

Feeding greatly affects milk yield and composition. The research is highlighting the potential of genetic polymorphism at some loci to affect milk yield and quality traits. These loci can be up/down regulated depending on the production environment; therefore, we hypothesized that milk yield and composition could differ when cows with different genotype at SCD, DGAT1 and ABCG2 loci are reared in different feeding systems. The polymorphisms of SCD, DGAT1 and ABCG2 genes were investigated in Modicana breed. In all, three polymorphic sites, responsible for the genetic variation of quantitative trait loci and therefore defined quantitative trait nucleotides, were genotyped: the transition g.10329C>T in 5th exon determines a substitution p.A293V in the SCD, the dinucleotide mutation g.10433-10434AA>GC in 8th exon responsible for p.K232A substitution in the DGAT1 and the transition g.62569A>C in the 14th exon responsible for p.Y581S substitution in the ABCG2 gene. In the sample of 165 Modicana cows, SCD and DGAT1 genes resulted polymorphic; the alleles g.10329T and g.10433-10434GC were the most frequent in SCD and DGAT1 (0.73 and 0.91) respectively, whereas ABCG2 locus was monomorphic for allele A (p.581Y). Sequencing analysis was carried out on 14 samples with different genotypes to confirm the results of the PCR-RFLP protocols. Based on the genotypes at SCD locus, 47 Modicana cows were selected for the nutritional trial: 24 cows in a semi-intensive farm, with 2 h/day grazing on natural pasture, and 23 cows in an extensive farm, with 8 h/day grazing on natural pasture. Monthly, milk yield and composition were evaluated and individual milk samples were analyzed for fatty acids composition by gas chromatography. No differences in milk yield, fat, protein, lactose, casein and urea were associated to SCD genotype. Feeding systems affected milk yield and composition. No significant genotype×feeding system interaction was observed for milk yield and composition. Fatty acids composition was significantly affected only by the feeding system. Significant interactions were found between SCD genotype and feeding system for six fatty acids: 4:0, 6:0, 8:0, 10:0, 12:0 and t11 18:1. We concluded that the feeding system was the factor that mostly affected milk production and composition; moreover, our results do not confirm what reported in literature as regard the effect of the SCD polymorphism on milk fatty acid composition. The high amount of pasture seemed to have resized the SCD polymorphism effects because of the different fatty acids composition of the diet.

Effect of Non-Genetic Factors on Milk Yield and Composition Traits of Sahiwal Cattle at Organized Dairy Farm

Effect of Non-Genetic Factors on Milk Yield and Composition Traits of Sahiwal Cattle at Organized Dairy Farm

Genetic association of variations in the kappa-casein and β-lactoglobulin genes with milk traits in girolando cattle

SUMMARY In dairy farm animals, one the most important goal of the selection is the improvement of milk yield and composition. Several studies have demonstrated that the candidate genes of the kappa-casein (CSN3) and β - lactoglobulin (β-LG) are associated with milk yield, milk quality and health traits in dairy animals. Therefore the aim of this study was to detect polymorphisms in CSN3 and β-LG genes and its association with milk yield in up to 305 days (305MY) and predicted transmission capacity (PTA) for 305MY in Girolando cattle. Totally, 138 bulls and 729 cows (n=867) were sampled. The genotypes of both genes were obtained by the PCR-RFLP method using HinfI and HaeIII enzymes for CSN3 and β-LG genes, respectively. Statistical results revealed two alleles A and B for both genes. The genotypes and alleles more frequents for CSN3 and β-LG genes were respectively: AA (0.7324) and A (0.8558), and AB (0.4827) and A (0.5017). The x2 test revealed that the two loci were at Hardy-Weinberg equilibrium (p&lt;0.001). The allele substitution effects for the variants were not significant on 305MY and PTA for 305MY (p&gt;0.05). The allele variants of β-LG and CSN3 might be more investigated before include them into future breeding schemes designed for Girolando dairy cattle with objective of improving milk traits as milk yield in up to 305 days (305MY) and predicted transmission capacity (PTA) for 305MY..

Genetic Parameter Estimates for Milk Yield, Udder and Body Conformation Traits of Jersey Cattle in the New Derived Guinea Savannah Zone of Nigeria

Genetic Parameter Estimates for Milk Yield, Udder and Body Conformation Traits of Jersey Cattle in the New Derived Guinea Savannah Zone of Nigeria

A research on longevity, culling reasons and milk yield traits in between Holstein and Simmental cows

In recent years, dairy cattle breeders prefer Simental cows due to higher breeding time and lower incidence of disease, although they have lower milk yield than Holstein cows. Thus, the aim of the present study was to investigate longevity, the culling reason and some milk yield traits in between the two breeds to investigate the accuracy of this preference. All data that used were collected from herd (Bursa–Karacabey state farm) records belongs to culling cows in two years (2015-2016) and analysed. Longevity for Holstein and Simmental cows were determined 33.6±1.08 month and 33.7±1.21 month. Average lactation milk yield (LMY), 305 days milk yield (305-dMY) and days in milk (DIM), were found to be 8515.63±196.507 kg, 7517.98±148.289 kg and 403.75±9.575 days respectively for Holstein cows and 6079.75±163.126 kg, 5525.71±117.931 kg and 351.40±8.559 days for Simental cows. While the differences between two breeds in terms of longevity and culling reasons were not significant, Holstein cows had higher milk yield than Simmental cows. As a conclusion, it can be said that Holstein cows is the best choice for dairy breeders in local circumstances.

Effect of STAT1, OLR1, CSN1S1, CSN1S2 , and DGAT1 genes on milk yield and composition traits of Holstein breed

ABSTRACT The objectives of the study were to evaluate allelic frequencies and test the association between STAT1, OLR1, CSN1S1, CSN1S2 , and DGAT1 gene polymorphisms and milk production traits including lactation milk yield, 305 days milk yield, days before peak milk production, and peak milk yield. In addition, samples of milk were analysed for fat, protein, lactose, and total solid contents. A total of 168 purebred Holstein-Fresian cows were genotyped using polymerase chain reaction and restriction fragment length polymorphism methods. [...]

PRODUCTIVE AND REPRODUCTIVE PERFORMANCE OF FRIESIAN CATTLE UNDER ASSIUT ENVIRONMENTAL CONDITIONS

Environmental factors such as animal origin, parity, year of calving and season of calving affect productivity. This work focused on the study of the effect of these factors on milk yield and reproductive traits of Friesian cows raised under Upper Egypt conditions. Data used in this investigation were collected from 1975 lactation records of pure Friesian cows raised at the station of Abnoub Alhamam belonging to the project livestock development in Assiut Governorate. The records represented 49 sires and 427 dams during the period from 1987 to 2004. Least squire means and standard errors for the studied traits were estimated using SAS 9.13. The General Linear Model (GLM) was utilized for variance analyses of milk yield and reproductive traits. Duncan's multiple range test (DMRT) was used for multiple comparisons of each trait. Animal origin constituted a significant source of variation in lactation milk yield and 305-days milk yield, while did not have any significant effect on lactation length and dry period. Season of calving had no significant effect on lactation milk yield while it has significant effect on the 305-day milk yield, lactation length and dry period. Parity effect was found to be significant on lactation milk yield, 305-day milk yield and length of lactation period, while it does not have a significant effect on the dry period. Year of calving showed significant effects on lactation milk yield, 305- day milk yield, lactation length and dry period. For reproductive traits animal origin has not had any significant effect on the lactation milk yield. Animal origin had significant effect (P<0.01) on calving interval and the age at first calving. Season of calving had significant effect (P<0.01) on days open, calving interval and age at first calving (P<0.05). All reproductive traits under study were significantly affected by year of calving. The results indicated that Friesian cows born and raised in Egypt were better in some reproductive traits, while imported cows tended to have more total milk yield.

Polymorphisms of α-lactoalbumin, β-lactoglobulin and prolactin genes are highly associated with milk composition traits in Spanish Merino sheep

Traditionally, Merino Sheep has been used for wool and meat production. However, in Spain, it is used for manufacturing valuable artisanal cheeses. Therefore, milk production is becoming a very important trait to be considered. In this research, the effects of the different genetic variants of milk whey proteins α-lactoalbumin (LALBA) and β-lactoglobulin (LGB), and prolactin hormone (PRL) on milk quality traits have been estimated in 1114 lactations from 396 genotyped Merino ewes of an experimental flock. Nucleotide substitutions g.133C > T (A and B alleles) of LALBA gene and g.1617T > C (A and B alleles) of LGB gene and a deletion, g.460_483del, of PRL gene (A and B alleles) were analysed. Hardy-Weinberg Equilibrium (HWE) and fixation index (FIS) analyses detected that the genotyped Merino population have not been selected for the analyzed loci. Haplotype analyses of milk whey protein loci (LALBA and LGB) located at Ovis aries chromosome 3 (OAR3), indicate that alleles are independently inherited. So, we only studied the genetic effects of single genes on milk traits. Allele substitution and genotypes effects on milk yield and composition traits were estimated using a linear mixed model. Significant effects of LALBA *A (p. Ala27), LGB *A (p. Tyr38) and PRL *B (del24 bp) alleles on milk quality traits standardized to 120 days have been observed. LALBA *A allele is significantly associated with higher percentages of fat (FP; α = + 0.26%, P = 0.001), protein (PP; α = + 0.22%, P = 0.001), solids non fat (SNF; α = + 0.17%, P = 0.001) and total solids (TS; α = 0.42%, P = 0.0002). LGB *A allele shows significant positive effect on PP (α = + 0.136%, P = 0.032) and FP (α = + 0.140%, P = 0.070). PRL *B allele shows only a significant positive effect on PP (α = + 0.131%, P = 0.026). These positive effects could be of great interest for the cheese industry. Variants could be used as suitable markers to perform association analyses in commercial farms in order to implement a cheese yield selection program based on genotype information.

Jersey ve Holstein İneklerinde Buzağılama Yılının Süt Verimi ve Bileşenleri Üzerine Olan Etkisi

The aim of this study was to identify the effect of calving year on milk yield and milk composition traits in Holstein and Jersey cattle raised in Marmara and the Black Sea Regions of Turkey, respectively. The data set consisted of 582 dairy cows, which were 306 Holstein raised and 276 Jersey cows calving from 2011 to 2013. In this study, animals were identified and selected to be genotyped for the DGAT1 gene based on farm records. Except for fat yield, the effect of calving year on test day milk yield (TDMY), 305-day milk yield (305 DMY), fat percentage, protein percentage and protein yield of Jersey cows were affected by calving season. The effect of calving year on TDMY, 305 DMY, fat percentage, fat yield, protein percentage and protein yield of Holstein cows were found to be statically significant. In conclusion, in 2011 to 2013, milk yield and its composition in both Holstein and Jersey cows were significantly related to calving years.