1,720,965 research outputs found
Genetic parameters for functional longevity, type traits, SCS, milk flow and production in the Italian Brown Swiss
No full textThe aim of this study was to estimate genetic parameters for a set of new traits and to update values for production and morphological traits to be used in the selection index of Italian Brown Swiss dairy cattle. Longevity, milking speed and somatic cell scores (SCS) were considered for inclusion in the selection index, and (co)variances with all traits of the selection index were estimated. SCS was considered on a lactation basis while milk flow as the amount of milk (kg) released per time unit (minute) measured with a flowmeter. Cow functional longevity was the total herd life corrected for the production level. A total of 127,416 first lactation records of cows calving from 1985 to 2003 were considered. In order to maximize the number of records available for each combination of traits, 9 data sets were created. Estimates were obtained from multivariate linear sire models with equal design matrix in subsequent separated analysis. REML algorithms and canonical transformation were used to calculate (co)variance estimates among all traits: functional longevity, milking speed, SCS, 5 production traits (milk, fat and protein yields, fat and protein percent), and 19 type traits. Heritabilities estimated were 0.14 ± 0.02 for SCS, 0.33 ± 0.07 for milk flow, and 0.04 ± 0.01 for functional longevity. Genetic correlation values between SCS and milk yield, fat percent and protein percent resulted of 0.18 ± 0.09, -0.19 ± 0.08, and -0.22 ± 0.08 respectively. Functional longevity had a strong positive genetic correlation with udder depth (0.42 ± 0.10) while a negative correlation with rear legs set (-0.56 ± 0.10). Milk flow was positively correlated with most of the production measures: 0.30 ± 0.18 with milk yield, 0.24 ± 0.17 with fat yields 0.16 ± 0.20 with protein yield. Additionally milk flow resulted largely genetically correlated with some type traits (0.53 ± 0.14 rear udder width, 0.40 ± 0.16 hock quality, 0.32 ± 0.15 rump angle, -0.25 ± 0.19 with udder depth). The correlation between SCS and milk flow showed a value of 0.46 ± 0.26 indicating that faster cows are more susceptible to mastitis
Genetic evaluations for measures of the milk-flow curve in the Italian Brown Swiss population
No full textThe objective of this study was to estimate heritabilities and genetic correlations between milk-release parameters, somatic cell score, milk yield, and udder functional traits in the Italian Brown Swiss population. Data were available from 37,511 cows over a span of 12 yr (1997-2008) from 1,592 herds. Milking flows were recorded for each individual once during lactation. Three different analyses were performed to estimate variance components for all the traits of interest. The first analysis included single control data milk yield, somatic cell score, maximum milk flow, average milk flow, time of plateau, decreasing time, and total milking time, whereas the second analysis included milk-release parameters as well as total udder score, udder depth, and 305-d milk yield and somatic cell score as dependent variables. The third analysis included total milking time, 305-d milk yield and somatic cell score, total udder score, udder depth, and ratios of maximum milk flow over total milking time (R1), time of plateau (R2), and decreasing time (R3) to estimate the relationship between the shape of the milk-release curves and important milking traits. Results from the first and second analysis found similar heritabilities for milkability traits ranging from 0.05 to 0.41 with genetic correlations between production traits and flow traits ranging from low to moderate values. Positive genetic correlations were found among production, somatic cell score, and milkability traits. The third analysis showed that R1 had the greatest heritability of the ratio traits (0.37) with large genetic correlations with R2 and R3, a low correlation with 305-d somatic cell score, and no correlation with 305-d milk yield. Estimated responses to selection over 5 generations were also calculated using different indexes, which included either flow or ratio traits. The results of this study show that it is possible to use information collected through portable flowmeters to improve milkability traits. Using a set of variables or traits to describe the overall release of milk can be an advantageous selection strategy to decrease management costs while maintaining milk production
Bimodality and the genetics of milk flow traits in the Italian Holstein-Friesian breed
No full textThe overall goal of this study was to investigate milk flow traits in Italian Holstein-Friesian cows and, in particular, the bimodality of milk flow, defined as delayed milk ejection at the start of milking. Using a milkometer, 2,886 records were collected from 133 herds in northern Italy from 2001 to 2007. All records included 5 time-period measurements for milk flow, somatic cell score (SCS), milk yield, 8 udder type traits, and the presence or absence of bimodality in milk flow. Genetic parameters were estimated using linear animal models for continuous traits such as milk flow, udder type, SCS, and milk production, whereas bimodality was analyzed as a categorical trait. With the exception of decreasing time (which had a very small heritability value of 0.06), heritability values for milk flow traits were moderate, ranging from 0.10 (ascending time) to 0.41 (maximum milk flow). In addition, moderate to high genetic correlations were estimated between total milking time and other time measures (from 0.78 to 0.87), and among time flow traits (from 0.62 to 0.91). The decreasing time was the trait most genetically correlated with udder type traits, with correlation values of 0.92 with rear udder height, 0.85 with rear udder width, and 0.73 with teat placement. Large udders with strong attachments were also associated with greater milk production. Heritability estimated for bimodality was 0.43, and its genetic correlation with milk flow traits and SCS indicated a sizable genetic component underlying this trait. Bimodality was negatively associated with milk production; shorter milking times and greater peak milk levels were genetically correlated with more frequent bimodal flows, indicating that faster milk release would result in an increase in bimodal patterns. The negative genetic correlation of bimodality with SCS (-0.30) and the genetic correlation between milk flow traits and SCS suggest that the relationship between milkability and SCS is probably nonlinear and that intermediate flow rates are optimal with respect to mastitis susceptibility. Quicker milk flow over a shorter period would increase the frequency of bimodal curves in milking, whereas the correlation between bimodality and both ascending and descending time was less clear
Parametros geneticos de las caracteristicas morfologicas de ganado Carora
No full textSixteen (16) morphological traits from 3867 Carora cows in Venezuela were studied. Genetic parameters were analyzed using a multiple trait animal model. Fixed effects of herd- year of evaluation interaction, month evaluation, age, stage of lactation
classifier, within herd were considered, genetic parameters were obtained from REML estimates of covariance components.
The highest heritability was found for stature (0.47) and for body depth (0.27), whereas the lowest values were found for foot angle (0.03). Udder traits showed low heritability estimates ranging from 0.06 for rear with to 0.13 for de udder balance.
Higher estimations were found for tea placement side (0.16) and teat length (0.26). Genetic correlations among stature,
body depth, strength and rump width were high and ranged from 0.76 to 0.86. Fore udder attachment was positively associated with rear udder height (0.46), udder depth
(0.53), teat placement (0.17) and length (0.18) while a negative correlations with udder balance (-.028). Negative estimates genetic correlations were found between rump angle (-0.45), rear-legs rear view (-0.50), udder balance (-0.68), udder support
(-0.32) y la angularity. Angularity was positively associated with rear udder height 0.62. Small correlations were estimated between foot angle and most traits. Negative genetic correlations
between body development and udder traits suggested that selection to increase body size could not improve the udder conformation. Selection should be oriented towards animals
of medium size dairy characteristics
Relationship between milkability traits recorded with flowmeters and udder type traits in Italian Holstein Friesian cows
No full textInterfamiliar specific fertility in Italian Brown Swiss cattle
No full textThe aim of this study is to evaluate the effects of interaction between sire of cow and service sire on the success/unsuccess of inseminations. Data from insemination events of Italian Brown Swiss cows collected from January 1993 through August 2007 were restricted to repeat breeder cows. A cluster analysis was carried out to group herds with very few observations in clusters with at least 15 observations. The edited data set included 102,710 services of 10,708 cows, daughters of 1,716 sires and mated to 3,108 service sires. The success or unsuccess at each insemination was evaluated by a linear mixed model including the fixed effects of herd-year interaction, month of insemination, age, and the random effects of sire service-sire of cow interaction and residual. The distribution of bull combination estimates was bimodal. When the tails of distribution (best and worst 5% of estimates) were considered, 271 service sires were included in both tails. Results suggest that major gene can affect the survival of embryos and that positive or negative interactions between paternal and maternal genotype can affect this reproductive trait
Genetic correlation patterns between somatic cell score and protein yield in the Italian Holstein-Friesian Population
No full textGenetic parameters for somatic cell score (SCS) in the Italian Holstein-Friesian population were estimated addressing the pattern of genetic correlation with protein yield in different parities (first, second, and third) and on different days in milk within each parity. Three approaches for parameter estimation were applied using random samples of herds from the national database of the Italian Holstein Association. Genetic correlations for lactation measures (305-d protein yield and lactation SCS) were positive in the first parity (0.31) and close to zero in the second (0.01) and third (0.09) parities. These results indicated that larger values of SCS were genetically associated with increased production. The second and third sets of estimates were based on random regression test-day models, modeling the shape of lactation curve with the Wilmink function and fourth-order Legendre polynomials, respectively. Genetic correlations from both random regression models showed a specific pattern associated with days in milk within and across parities. Estimates varied from positive to negative in the first and second parity, and from null to negative in the third parity. Patterns were similar for both random regression models. The average overall correlation between SCS and protein yield was zero or slightly positive in the first lactation and ranged from zero to negative in later lactations. Correlation estimates differed by parity and stage of lactation. They also demonstrated the dubiousness of applying a single genetic correlation measure between SCS and protein in setting selection strategies. Differences in magnitude and the sign of genetic correlations between SCS and yields across and within parities should be accounted for in selection schemes
The QuaLAT Project : Mapping QTL for Milk Fatty Acid Content in the Italian Brown Population and in the Israel Holstein Friesian
No full textMilk contains a number of micro-components ("functional foods") having specific health promoting activities. Important among these compounds are the conjugated linoleic acids (CLAs) consistingof a mixture of isomers of C18:2 fatty acid with conjugated doublebonds. The predominant form in milk fat is the cis-9,trans-11 isomer, accounting for 75 to 90% of the total CLA content. Biomedical studies with animal models have demonstrated a variety of preventive health effects from CLA including anticarcinogenic, antiatherogenic, antiobesity, immune system enhancement and antidiabetic benefits. Linolenic acid does not form CLA as an intermediate in rumen biohydrogenation, but it does form vaccenic acid (C18:1,t11) that enters the bloodstream from the rumen, through the abomasum and intestine, and is transported to the mammary gland. Several investigations using direct and indirect approaches established that endogenous synthesis of CLA via Δ 9-desaturase action on vaccenic acid (VA, C18:1,t11) is the predominant source of the CLA found in milk fat across a range of diets. Thus, rumen VA production and mammary tissue Δ 9-desaturase (D9D) are of key importance in determining the CLA content of milk fat. Mammary tissue D9D activity is measured indirectly as the milk desaturase index (DI), calculated as the ratio of milk CLA to the sum of milk CLA and VA. The study is centered on the Italian Brown Swiss and Israeli Holstein dairy cattle populations. Objectives of the project are: i) to identify environmental and physiological factors (e.g., herd, season, parity and stage of lactation) affecting milk CLA content and DI, and determine appropriate correction factors, if needed; ii) to estimate heritability of milk CLA content and DI in the study populations; iii) to implement a total genome scan for QTL affecting milk CLA VA content and DI in the two study populations. using a selective DNA pooling approach based on milk samples for the initial scan, followed by individual genotyping to confirm suggestive QTL regions. For each of the studied populations,, the research includes determination of CLA,VA and DI for more than 2500 individuals of five large sire half-sib families (for the genome scan) and an additional 400 individuals of 20 small sire half-sib families for the heritability analysis. Milk fat is extracted and transmethylated according to Chouinard et al. (1999). Fatty acid methyl esters are analyzed by GC-FID with a highly polar 100 m SP-2560 column, using GLC-60 supplemented with CLA and VA as a standard. Based on the results obtained to date for the Italian Brown Swiss population, the mean (fatty acid composition over the total fatty acid) ±SD(minimum and maximum) are respectively: VA, 1.97±0.77 (0.63 - 5.40); CLA, 0.63±.0.47 (0.35 - 5.31); DI, 0.25±0.097 (0.063 - 0.64). The means for VA and CLA content found are similar to those reported by other studies (control treatment) and reviewed by Collomb et al (2006). The slightly larger variability here reported, anyhow within the limit of values found in literature, is possibly affected by the wide farming conditions of the individuals sampled
Estimates of missing heritability for complex traits in Brown Swiss cattle
Full text linkBackground: Genomic selection estimates genetic merit based on dense SNP (single nucleotide polymorphism) genotypes and phenotypes. This requires that SNPs explain a large fraction of the genetic variance. The objectives of this work were: (1) to estimate the fraction of genetic variance explained by dense genome-wide markers using 54 K SNP chip genotyping, and (2) to evaluate the effect of alternative marker-based relationship matrices and corrections for the base population on the fraction of the genetic variance explained by markers. Methods. Two alternative marker-based relationship matrices were estimated using 35 706 SNPs on 1086 dairy bulls. Both pedigree- and marker-based relationship matrices were fitted simultaneously or separately in an animal model to estimate the fraction of variance not explained by the markers, i.e. the fraction explained by the pedigree. The phenotypes considered in the analysis were the deregressed estimated breeding values (dEBV) for milk, fat and protein yield and for somatic cell score (SCS). Results: When dEBV were not sufficiently accurate (50 or 70%), the estimated fraction of the genetic variance explained by the markers was around 65% for yield traits and 45% for SCS. Scaling marker genotypes with locus-specific frequencies of heterozygotes slightly increased the variance explained by markers, compared with scaling with the average frequency of heterozygotes across loci. The estimated fraction of the genetic variance explained by the markers using separately both relationships matrices followed the same trends but the results were underestimated. With less accurate dEBV estimates, the fraction of the genetic variance explained by markers was underestimated, which is probably an artifact due to the dEBV being estimated by a pedigree-based animal model. Conclusions: When using only highly accurate dEBV, the proportion of the genetic variance explained by the Illumina 54 K SNP chip was approximately 80% for Brown Swiss cattle. These results depend on the SNP chip used and the family structure of the population, i.e. more dense SNPs and closer family relationships are expected to result in a higher fraction of the variance explained by the SNPs
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